timing belts

95
T-3 THE WORLD OF TIMING BELTS SECTION 1 INTRODUCTION Timing belts are parts of synchronous drives which represent an important category of drives. Characteristically, these drives employ the positive engagement of two sets of meshing teeth. Hence, they do not slip and there is no relative motion between the two elements in mesh. Due to this feature, different parts of the drive will maintain a constant speed ratio or even a permanent relative position. This is extremely important in applications such as automatic machinery in which a definite motion sequence and/or indexing is involved. The positive nature of these drives makes them capable of transmitting large torques and withstanding large accelerations. Belt drives are particularly useful in applications where layout flexibility is important. They enable the designer to place components in more advantageous locations at larger distances without paying a price penalty. Motors, which are usually the largest heat source, can be placed away from the rest of the mechanism. Achieving this with a gear train would represent an expensive solution. Timing belts are basically flat belts with a series of evenly spaced teeth on the inside circumference, thereby combining the advantages of the flat belt with the positive grip features of chains and gears. There is no slippage or creep as with plain flat belts. Required belt tension is low, therefore producing very small bearing loads. Synchronous belts will not stretch and do not require lubrication. Speed is transmitted uniformly because there is no chordal rise and fall of the pitch line as in the case of roller chains. The tooth profile of most commonly known synchronous belts is of trapezoidal shape with sides being straight lines which generate an involute, similar to that of a spur gear tooth. As a result, the profile of the pulley teeth is involute. Unlike the spur gear, however, the outside diameter of a timing pulley is smaller than its pitch diameter, thus creating an imaginary pitch diameter which is larger than the pulley itself. This is illustrated in Figure 1. Backlash between pulley and belt teeth is negligible. The trapezoidal shape timing belt was superseded by a curvilinear tooth profile which exhibited some desirable and superior qualities. Advantages of this type of drive are as follows: Proportionally deeper tooth; hence tooth jumping or loss of relative position is less probable. Lighter construction, with correspondingly smaller centrifugal loss. Smaller unit pressure on the tooth since area of contact is larger. Pitch (circular pitch) Belt Pitch Line Sprocket Pitch Circle Curvilinear Tooth Profile Pitch (circular pitch) Trapezoidal Tooth Profile Pulley Pitch Circle Belt Pitch Line Fig. 1 Pulley and Belt Geometry NOTE: Credit for portions of this technical section are given to: Gates Rubber Co., Sales Engineering Dept., Rubber Manufacturers Association (RMA), International Organization for Standardization (ISO).

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Page 1: Timing belts

T-3

THE WORLD OF TIMING BELTS

SECTION 1 INTRODUCTION

Timing belts are parts of synchronous drives which represent an important category of drives.Characteristically, these drives employ the positive engagement of two sets of meshing teeth.Hence, they do not slip and there is no relative motion between the two elements in mesh.

Due to this feature, different parts of the drive will maintain a constant speed ratio or even apermanent relative position. This is extremely important in applications such as automatic machineryin which a definite motion sequence and/or indexing is involved.

The positive nature of these drives makes them capable of transmitting large torques andwithstanding large accelerations.

Belt drives are particularly useful in applications where layout flexibility is important. Theyenable the designer to place components in more advantageous locations at larger distanceswithout paying a price penalty. Motors, which are usually the largest heat source, can be placedaway from the rest of the mechanism. Achieving this with a gear train would represent an expensivesolution.

Timing belts are basically flat belts with a series of evenly spaced teeth on the insidecircumference, thereby combining the advantages of the flat belt with the positive grip features ofchains and gears.

There is no slippage or creep as with plain flat belts. Required belt tension is low, thereforeproducing very small bearing loads. Synchronous belts will not stretch and do not require lubrication.Speed is transmitted uniformly because there is no chordal rise and fall of the pitch line as in thecase of roller chains.

The tooth profile of most commonly known synchronous belts is of trapezoidal shape withsides being straight lines which generate an involute, similar to that of a spur gear tooth. As aresult, the profile of the pulley teeth is involute. Unlike the spur gear, however, the outsidediameter of a timing pulley is smaller than its pitch diameter, thus creating an imaginary pitchdiameter which is larger than the pulley itself. This is illustrated in Figure 1. Backlash betweenpulley and belt teeth is negligible.

The trapezoidal shape timing belt was superseded by a curvilinear tooth profile which exhibitedsome desirable and superior qualities. Advantages of this type of drive are as follows:• Proportionally deeper tooth; hence tooth jumping or loss of relative position is less probable.• Lighter construction, with correspondingly smaller centrifugal loss.• Smaller unit pressure on the tooth since area of contact is larger.

Pitch (circular pitch)

Belt Pitch Line

Sprocket Pitch Circle

Curvilinear ToothProfile

Pitch (circular pitch)

TrapezoidalTooth Profile

Pulley Pitch Circle

Belt Pitch Line

Fig. 1 Pulley and Belt Geometry

NOTE: Credit for portions of this technical section are given to: Gates Rubber Co., Sales Engineering Dept.,Rubber Manufacturers Association (RMA), International Organization for Standardization (ISO).

Page 2: Timing belts

T-4

Tension Member

CurvilinearTrapezoidalFig. 2 Stress Pattern in Belts

• Greater shear strength due to larger tooth cross section.• Lower cost since a narrower belt will handle larger load.• Energy efficient, particularly if replacing a "V" belt drive which incurs energy losses due to

slippage.• Installation tension is small, therefore, light bearing loads.

In Figure 2, the photoelastic pattern shows the stress distribution within teeth of differentgeometry. There is a definite stress concentration near the root of the trapezoidal belt tooth, withvery low strains elsewhere. For the curvilinear tooth, there is a uniform, nearly constant, straindistribution across the belt. The load is largest in the direction of the tension member to which it istransferred.

Because of their superior load carrying capabilities, the curvilinear belts are marketed underthe name of Gates' HTD drives. This is an abbreviation of High Torque Drives.

As a result of continuous research, a newer version of the curvilinear technology was developedby Gates, which was designated as Gates' PowerGrip GT belt drives.

SECTION 2 GATES POWERGRIP® GT BELT DRIVES

The PowerGrip GT Belt Drive System is an advance in product design over the Gates' older,standard HTD system. The PowerGrip GT System, featuring a modified curvilinear belt toothprofile, provides timing and indexing accuracy superior to the conventional PowerGrip TrapezoidalBelt System. Plus, PowerGrip GT Belts have a higher capacity and longer belt life than trapezoidalbelts.

It's difficult to make a true quantitative comparison between the backlash of a trapezoidal toothdrive and PowerGrip GT drive due to the difference in "pulley to belt tooth" fit (see Figure 3).Trapezoidal belts contact the pulley in the root radius-upper flank area only, while the PowerGripGT system permits full flank contact.

PowerGrip® Trapezoidal BeltTooth/Groove Contact

PowerGrip® HTD® BeltTooth/Groove Contact

PowerGrip® GT® BeltTooth/Groove Contact

Fig. 3 Comparison of Different Tooth Profiles

Page 3: Timing belts

T-5

The main stress line in a trapezoidal tooth timing belt is at the base of the teeth. Duringoperation, this stress greatly reduces belt life. The PowerGrip GT system overcomes this conditionwith its complete tooth flank contact which eliminates the tooth stress line area. This greatlyincreases belt life and prevents tooth distortion caused by drive torque. In addition, the conventionaltiming belt has a chordal effect as it wraps small pulleys. This is significantly reduced in thePowerGrip GT system because there is full tooth support along the pulley. Full support improvesmeshing, reduces vibration and minimizes tooth deformation.

On drives using a low installation tension, small pulleys, and light loads, the backlash of thePowerGrip GT system will be slightly better than the trapezoidal timing belt system. However, withincreased tension and/or loads and/or pulley sizes, the performance of the PowerGrip GT systembecomes significantly better than the trapezoidal timing belt system.

The PowerGrip GT system is an extension of the HTD system with greater load-carryingcapacity. HTD was developed for high torque drive applications, but is not acceptable for mostprecision indexing or registration applications. The HTD design requires substantial belt tooth topulley groove clearance (backlash) to perform.

As smaller diameter pulleys are used, the clearance required to operate properly is increased.HTD drive clearance, using small diameter pulleys, is approximately four times greater than anequivalent GT timing belt drive.

The PowerGrip GT system's deep tooth design increases the contact area which providesimproved resistance to ratcheting. The modified curvilinear teeth enter and exit the pulley groovescleanly, resulting in reduced vibration. This tooth profile design results in parallel contact with thegroove and eliminates stress concentrations and tooth deformation under load. The PowerGrip GTdesign improves registration characteristics and maintains high torque carrying capability.

PowerGrip GT belts are currently available in 2 mm, 3 mm and 5 mm pitches. Specificadvantages of the PowerGrip GT system can be summarized as follows:

• Longer belt lifeThe strong fiberglass tensile cords wrapped in a durable neoprene body provide the flexibilityneeded for increased service life. The deep tooth profile provides superior load-carryingstrength and greatly reduces ratcheting when used with pulleys provided by a licensed supplier.

• Precision registrationPowerGrip GT belts provide timing and synchronization accuracy that make for flawlessregistration, with no loss of torque carrying capacity.

• Increased load-carrying capacityLoad capacities far exceed HTD and trapezoidal belt capabilities making PowerGrip GT beltsthe choice for accurate registration, heavy loads and small pulleys.

• Quieter operationThe PowerGrip GT belt's specially engineered teeth mesh cleanly with pulley grooves toreduce noise and vibration. Clean meshing and reduced belt width result in significant noisereduction when compared to Trapezoidal and HTD belts.

• Precise positioningPowerGrip GT belts are specifically designed for applications where precision is critical, suchas computer printers and plotters, laboratory equipment and machine tools.

Some of the many applications of PowerGrip GT belts are:

• data storage equipment• machine tools• hand power tools• postage handling equipment• DC stepper/servo

applications• food processors

• centrifuges• printers• floor care equipment• money handling equipment• medical diagnostic equipment• sewing machines• automated teller machines

• ticket dispensers• plotters• copiers• robotics equipment• vending equipment• vacuum cleaners• office equipment

Page 4: Timing belts

T-6

20,0

00

10,0

00

5,00

04,

000

3,45

0

2,50

0

1,75

0

1,16

087

069

057

5

400

300

200

150

100

SECTION 3 COMPARISON GRAPHS

In order to provide comparison of performances of different pitch drives, several graphs havebeen developed.

Figure 4 shows numerical values, plotted in logarithmic scale, of Rated Horsepower vs.Speed (rpm) of faster shaft.

Fig

. 4

Co

mp

arat

ive

Bel

t P

itch

Sel

ecti

on

Gu

ide

Speed (rpm) of Faster Shaft

Rat

ed H

ors

epo

wer

.01

.01

5 .0

2 .0

3 .0

4 .0

5 .0

7

.1

.15

.2

.3

.5

.7

1

1

.5

2

3

4

5

7

10

1

5 2

0

30

40 5

0 7

0 1

00 1

50 2

00 3

00 4

00 5

00

MX

L=

.08

0" p

itch

XL

= .

200"

pit

chL

= .

375"

pit

chH

= .

500"

pit

chX

H=

.87

5" p

itch

XX

H=

1.25

0" p

itch

3 m

mG

T

2 m

mG

T

5 m

mG

T

H

XH

XX

H

XL

L

MX

L

Page 5: Timing belts

T-7

Fig. 5 Horsepower Ratings at High Speed

Figure 5 shows an illustrative graph representation of horsepower ratings over a wide speedrange of the belt types commonly used. The graph assumes that belt widths and pulley diametershave been chosen such that they provide realistic comparison of product capability.

Fig. 6 Horsepower Ratings at Low Speed

Figure 6 provides a comparison of the rated torque carrying capabilities of synchronous belts,on small diameter pulleys at low speeds. The pulley diameters and belt widths represent a realisticcomparison.

Ra

ted

Ho

rse

po

we

r

6

5

4

3

2

1

0

1 2 4 6 8 10 12 14 16 18 20Speed (x 1000 rpm)

0.38

0.30

0.23

0.15

0.08

0

10 20 40 60 100 200 300 500 700 1000Speed (rpm)

Ra

ted

Ho

rse

po

we

r

Page 6: Timing belts

T-8

SECTION 4 DRIVE COMPARATIVE STUDIES

The development of the PowerGrip GT belt has produced an impressive range of enhancedproperties and subsequent design opportunities for engineers.

Comparative studies, shown in Figures 7 through 10, allow designers to make quantitativeassessments and to highlight the most significant improvements and design opportunities. Particularlysignificant points from the comparative studies follow:

4.1 Durability

The greatly increased durability of the PowerGrip GT design has resulted in power capacitiesfar above those quoted for similar size belts of previous designs. The resulting small drive packageswill increase design flexibility, space utilization and cost effectiveness.

4.2 Tooth Jump Resistance

The very significant improvement in tooth jump resistance of PowerGrip GT when compared tosimilar belts has several important advantages.

1. Ratcheting resistance during high start-up torques.2. Reduced bearing loads, particularly in fixed-center drives. Lower average tensions can be

used without encountering tooth jump at the low tension end of the tolerance ranges.3. Reduced system losses result from lower pre-tensioning, with less potential for tooth

jumping.

Fig. 7 Comparison of Performance Ratios for Various Belts

Fig. 8 Comparison of Tooth Jump Torques for Various Belts

Test Stopped –––�

3 mm HTD Versus 3 mm PowerGrip GT

3 mm HTD 3 mm GTTEST CONDITIONS: Speed = 6000 rpm

Power = 1.00 lb⋅in/mm widthPulleys: Driver = 20 grooves

Driven = 20 grooves

Per

form

ance

Rat

io (

%) Test Stopped –––�

5 mm HTD Versus 5 mm PowerGrip GT

5 mm HTD 5mm GTTEST CONDITIONS: Speed = 2300 rpm

Power = 3.35 lb⋅in/mm widthPulleys: Driver = 20 grooves

Driven = 20 grooves

Per

form

ance

Rat

io (

%) 200

150

100

50

0

200

150

100

50

0

10

8

6

4

2

01 2 3 4 5

2 mm GT

MXL

2 mm PowerGrip GT Versus MXL

To

oth

Ju

mp

To

rqu

e (l

b⋅in

)

To

oth

Ju

mp

To

rqu

e (l

b⋅in

)

To

oth

Ju

mp

To

rqu

e (l

b⋅in

)

3 mm PowerGrip GT Versus 3 mm HTD 5 mm PowerGrip GT Versus 5 mm HTD

5 mm GT

5 mm HTD3 mm GT

3 mm HTD

60

50

40

30

20

10

0

450

375

300

225

150

75

02 4 6 8 10 15 30 45 60 75

Installed Tension (lb)TEST CONDITIONS:

Speed = 1130 rpmBelt Width = 4.8 mmPulleys: Driver = 20 grooves

Driven = 20 grooves

Installed Tension (lb)TEST CONDITIONS:

Speed = 750 rpmBelt Width = 6 mmPulleys: Driver = 30 grooves

Driven = 30 grooves

Installed Tension (lb)TEST CONDITIONS:

Speed = 2300 rpmBelt Width = 15 mmPulleys: Driver = 20 grooves

Driven = 20 grooves

Page 7: Timing belts

T-9

4.3 Noise

The smoother meshing action of the PowerGrip GT belt, with its optimized design, producessignificantly lower noise levels when compared with other similar sized belt types operating undersimilar speeds and tensions. These improvements are enhanced by the fact that narrower beltscan be used due to increased power capacities.

Fig. 9 Comparison of Noise Levels for Various Belts

Fig. 10 Comparison of Positioning Errors of Various Belts

2 mm GT MXL

APPLICATION: Motion TransferBelt: No. of teeth = 126

Width = 8 mmPulleys: Driver = 12 grooves

Driven = 40 groovesInstalled tension = 1.8 lbMotor = 200 steps/cycle

Po

siti

on

ing

Err

or

(in

)

3 mm GT 3 mm HTD

Po

siti

on

ing

Err

or

(in

)

.003

.002

.001

0

APPLICATION: Motion TransferBelt: No. of teeth = 92

Width = 6 mmPulleys: Driver = 20 grooves

Driven = 20 groovesInstalled tension = 6.6 lbMotor = 200 steps/cycle

.030

.020

.010

0

4.4 Positioning Accuracy

The PowerGrip HTD belt tooth forms were primarily designed to transmit high torque loads.This requirement increased tooth to groove clearances which resulted in increased backlash whencompared with the original trapezoidal designs.

PowerGrip GT has reversed this problem with power capacities now exceeding those ofPowerGrip HTD while giving equivalent or higher levels of positional accuracy than trapezoidaltiming belts.

3 mm HTD

3 mm GT

5 mm HTD

5 mm GT

110

100

90

80

70

60

50

40

110

100

90

80

70

60

50

40

3 mm PowerGrip GT Versus 3 mm HTD 5 mm PowerGrip GT Versus 5 mm HTD

Belt: No. of teeth = 188Width = 15 mm

Pulleys: Driver = 26 groovesDriven = 26 grooves

Microphone location midway betweenthe pulleys, 100 mm from the belt edge.

Belt: No. of teeth = 118Width = 30 mm

Pulleys: Driver = 20 groovesDriven = 20 grooves

Microphone location midway betweenthe pulleys, 100 mm from the belt edge.

1000 1500 2000 2500 3000 3500 4000 4500Speed (rpm)

1000 1500 2000 2500 3000 3500 4000 4500Speed (rpm)

dB

A

dB

A

Page 8: Timing belts

T-10

SECTION 5 DIFFERENT BELT CONFIGURATIONS

5.1 Double Sided Twin Power Belt Drives

Timing belts are also available in double sided designs, which offer an infinite number of newdesign possibilities on computer equipment, business machines, office equipment, textile machinesand similar light-duty applications. Belts with driving teeth on both sides make it possible to changethe direction of rotation of one or more synchronized pulleys with only one belt. The inside andoutside teeth are identical as to size and pitch and operate on standard pitch diameter pulleys.

If the belts have nylon facing on both sides, then the same design parameters can be used forthe drives on both sides of the belt. In case the outside teeth do not have nylon facing, thehorsepower rating of the outside teeth is only 45% of the total load.

For example: assuming the drive pulleyand belt are capable of transmitting 1horsepower, 0.55 hp can be transmitted fromthe inside teeth of the pulley (A), and 0.45hp can be transmitted by the outside teeth topulley (B) for a total of 1 hp, the rated capacityof the driver pulley.

5.2 Long Length Timing Belt Stock

These belts are an excellent solution for drivesthat require belt lengths longer than those produced inconventional endless form. Long length belting hasthe same basic construction as conventional timingbelts. These belts are usually produced by spiral cutof large diameter endless belts.

These belts are creatively used in:• reciprocating carriage drives• rack and pinion drives• large plottersAn example of application is shown in Figure 13.

A complete timing belt and a timing belt segment reducevibration and chatter in this oscillating drive for a surfacegrinder.

SECTION 6 BELT CONSTRUCTION

The load-carrying elements ofthe belts are the tension membersbuilt into the belts (see Figure 14).These tension members can bemade of:

1. Spirally wound steel wire.2. Wound glass fibers.3. Polyester cords.4. Kevlar.

Fig. 11 Double Sided Timing Belt

Pulley BOutside Teeth.45 hp

Pulley AInside Teeth

.55 hp

DriverOutput1 hp

�––––––––––––– Belt Direction

Fig. 13 Example of Timing Belt Stock Use

Fig. 14 Belt Construction

Curvilinear

Fig. 12 Timing Belt Stock

Trapezoidal

Page 9: Timing belts

T-11

The tension members are embedded in neoprene or polyurethane. The neoprene teeth areprotected by a nylon fabric facing which makes them wear resistant.

The contributions of the construction members of these belts are as follows:

1. Tensile Member – Provides high strength, excellent flex life and high resistance toelongation.

2. Neoprene Backing – Strong neoprene bonded to the tensile member for protection againstgrime, oil and moisture. It also protects from frictional wear if idlers are used on the backof the belt.

3. Neoprene Teeth – Shear-resistant neoprene compound is molded integrally with theneoprene backing. They are precisely formed and accurately spaced to assure smoothmeshing with the pulley grooves.

4. Nylon Facing – Tough nylon fabric with a low coefficient of friction covers the wearingsurfaces of the belt. It protects the tooth surfaces and provides a durable wearing surfacefor long service.

6.1 Characteristics Of Reinforcing Fibers

PolyesterTensile Strength 160,000 lbs/in2

Elongation at break 14.0%Modulus (approx.) 2,000,000 lbs/in2

One of the main advantages of polyester cord over higher tensile cords is the lower modulusof polyester, enabling the belt to rotate smoothly over small diameter pulleys. Also, the elasticproperties of the material enable it to absorb shock and dampen vibration.

In more and more equipment, stepping motors are being used. Polyester belts have provenfar superior to fiberglass or Kevlar reinforced belts in these applications.

High-speed applications with small pulleys are best served by polyester belts under low load.

KevlarTensile Strength 400,000 lbs/in2

Elongation at break 2.5%Modulus 18,000,000 lbs/in2

High tensile strength and low elongation make this material very suitable for timing beltapplications. Kevlar has excellent shock resistance and high load capacity.

FiberglassTensile Strength 350,000 lbs/in2

Elongation at break 2.5 – 3.5%Modulus 10,000,000 lbs/in2

The most important advantages are:1. High strength.2. Low elongation or stretch.3. Excellent dimensional stability.4. Excellent chemical resistance.5. Absence of creep, 100% elongation recovery.

Disadvantages:1. High modulus (difficult to bend).2. Brittleness of glass. Improper handling or installation can cause permanent damage.3. Poor shock resistance. No shock absorbing quality when used in timing belts.

Page 10: Timing belts

T-12

SteelTensile Strength 360,000 lbs/in2

Elongation at break 2.5%Modulus (approx.) 15,000,000 lbs/in2

Additional characteristics of tension members and their effect on the drive design are shown intabulated form in Table 1.

E

E

F

E

P

P

P

P

F

E

F

P

E

Fig. 16 Cord Twist

Fig. 15 Belt Cross Section

Nyl

on

Po

lyes

ter

Co

nt.

Fil.

Yar

n

Po

lyes

ter

Sp

un

Yar

n

Kev

lar-

Po

lyes

ter

Mix

Kev

lar

Co

nt.

Fil.

Yar

n

Kev

lar

Sp

un

Yar

n

Gla

ss

Sta

inle

ssS

teel

Po

lyes

ter

Film

Rei

nfo

rcem

ent

Operate over Small Pulley

High Pulley Speed

High Intermittent Shock Loading

Vibration Absorption

High Torque Low Speed

Low Belt Stretch

Dimensional Stability

High Temperature 200° FLow Temperature

Good Belt Tracking

Rapid Start/Stop Operation

Close Center-Distance Tolerance

Elasticity Required in Belt

G

E

G

G

P

P

P

P

G

G

G

P

G

E

E

G

E

P

P

P

P

G

E

E

P

E

F

F

E

G

F

P

F

P

G

G

G

P

G

P

P

E

F

G

G

G

E

G

F

P

G

P

F

F

E

F

F

F

G

E

E

G

G

F

P

P

P

P

P

E

E

E

E

E

F

P

E

P

P

P

G

P

E

E

E

E

E

P

E

E

P

G

G

F

F

F

G

G

F

G

E

G

G

P

* Courtesy of Chemiflex, Inc.

Table 1 Comparison of Different Tension Member Materials*E = Excellent G = Good F = Fair P = Poor

Belt Requirements

Continuously Applied Filament

Step of Helix

Spirally Applied Filament

6.2 Cord Twist And Its Effect On The Drive

There is a specific reason for notapplying the yarn directly in the form ofuntwisted filaments around the mold. Ifthe filament would be appliedcontinuously, the top and bottom of thebelt body would be prevented from beingproperly joined, and separation couldresult. See Figure 15.

Two strands each composed ofseveral filaments are twisted around eachother, thus forming a cord which issubsequently wound in a helical spiralaround the mold creating a space betweensubsequent layers, which corresponds tothe step of the helix. The two strands,however, can be twisted two ways in orderto create an "S" or a "Z" twist construction.See Figure 16.

Page 11: Timing belts

T-13

The "S" twist is obtained if we visualize the two strands being held stationary with our left handon one end, while a clockwise rotation is imparted by our right hand to the two strands, thuscreating a twisted cord. The "Z" twist is obtained similarly, if a counterclockwise rotation is impartedto the two strands.

Different types of cord twist will cause side thrust in opposite directions. The "S" twist willcause a lateral force direction which will obey the "Right Hand" rule as shown in Figure 17.

A "Z" type cord twist will produce a direction of lateral force opposite to that of "S" cord.Therefore, in order to produce a belt with minimum lateral force, standard belts are usually madewith "S" and "Z" twist construction, in which alternate cords composed of strands twisted in oppositedirections are wound in the belt. This is illustrated in Figure 18.

The lay of the cord is standard, asshown in Figure 18, and it is wound from leftto right with the cord being fed under themold. The smaller the mold diameter andthe fewer the strands of cord per inch, thegreater will be the helix angle, and the greaterthe tendency of the lay of the cord to makethe belt move to one side.

In general, a standard belt of "S" and"Z" construction, as shown in Figure 18, willhave a slight tendency to behave as apredominantly "S" twist belt, and will obeythe "Right Hand" rule accordingly.

6.3 Factors Contributing To Side Travel

The pulleys in a flat belt drive are crowned to keep the belt running true. Since crownedpulleys are not suitable for a timing belt, the belt will always track to one side. Factors contributingto this condition include:

I. In the Drive

1. Misalignment – A belt (any belt – any construction) will normally climb to the highend (or tight) side.

2. Tensioning – In general, lateral travel can be altered or modified by changingtension.

3. Location of plane – Vertical drives have a greater tendency to move laterally dueto gravity.

(a) Clockwise Rotation (b) Counterclockwise Rotation

Belt Travels AwayFrom Motor

Belt TravelsToward Motor

Fig. 17 Right Hand Rule Applicable to "S" Twist

Fig. 18 "S" and "Z" Cord Lay of the Mold

Page 12: Timing belts

T-14

4. Belt width greater than O.D. of pulley – This condition creates an abnormaldegree of lateral travel.

5. Belt length – The greater the ratio of length/width of the belt, the less the tendencyto move laterally.

II. In the Belt

1. Direction of the lay of the cords in the belt. See Figure 18.2. Twist of the strands in the cord. See Figure 16.

6.4 Characteristics Of Belt Body Materials

Basic characteristics of the three most often used materials are shown in Table 2. Thetabulated characteristics give rise to the following assessment of these materials:

Natural Rubber• High resilience, excellent compression set, good molding properties• High coefficient of friction; does not yield good ground finish• High tear strength, low crack growth• Can withstand low temperatures• Poor oil and solvent resistance; unable for ketones and alcohol• Ozone attacks rubber, but retardants can be added

Neoprene• High resilience• Flame resistant• Aging good with some natural ozone resistance• Oil and solvent resistance fair

Polyurethane• Excellent wear resistance, poor compression set• Low coefficient of friction• Oil and ozone resistance good• Low-temperature flexibility good• Not suitable for high temperatures

Table 2 Comparison of Different Belt Body Materials*Common Name Natural Rubber Neoprene Urethane, Polyurethane

Chemical DefinitionDurometer Range (Shore A)Tensile Range (p.s.i.)Elongation (Max. %)Compression SetResilience – ReboundAbrasion ResistanceTear ResistanceSolvent ResistanceOil ResistanceLow Temperature Usage (°F)High Temperature Usage (°F)Aging Weather – SunlightAdhesion to Metals

Polyisoprene20 – 100500 – 3500700ExcellentExcellentExcellentExcellentPoorPoor–20° to –60°to 175°PoorExcellent

Polychloroprene20 – 95500 – 3000600GoodExcellentExcellentGoodFairFair+10° to –50°to 185°GoodGood to Excellent

Polyester/Polyether Urethane35 – 100500 – 6000750PoorGoodExcellentExcellentPoorGood–10° to –30°to 175°ExcellentFair to Good

* Courtesy of Robinson Rubber Products

Page 13: Timing belts

T-15

Fig. 19a 0.080 Pitch MXL Fig. 19b 0.0816 Pitch 40 D.P. Fig. 19c 0.200 Pitch XL

Fig. 19d0.375 Pitch L

Fig. 19e 3 mm Pitch HTD Fig. 19f 5 mm Pitch HTD

Fig. 19g 2 mm Pitch GT Fig. 19h 3 mm Pitch GT Fig. 19i 5 mm Pitch GT

Fig. 19j T2.5 mm Pitch Fig. 19k T5 mm Pitch Fig. 19l T10 mm Pitch

Fig. 19 Belt Tooth Configuration Dimensions in ( ) are mm

Table 3 Allowable Working Tension of Different Belt ConstructionsAllowable Working Tension

Per 1 Inch of Belt Width

MXL40DP

XLLH

HTD

GT

T

2.032 2.07 5.08 9.52512.7 3 5 8 2 3 5 2.5 510

0.080 0.0816

0.2000.3750.5000.1180.1970.3150.0790.1180.197

–––

32 21.4

41 55140 64102138 25114160 32 41 55

142 95182244622285454614111507712142182244

Nlbs

BeltType

Inch mm

Pitch

19a19b19c19d

–19e19f–

19g19h19i19j19k19l

SECTION 7 BELT TOOTH PROFILES

There are several belt tooth profiles (Figure 19, Table 3) which are the result of differentpatented features, marketing and production considerations.

.005 R(0.13 R)TYP

.080(2.032)

.030 (0.76).018

(0.46)

.045 (1.14)

40° 60° 50°

.048(1.2)

.090 (2.3)

.0816(2.07264)

.024(0.6) .018

(0.46)

.200(5.08)

.054(1.4)

.050(1.3)

.015 R(0.4 R)TYP

.020 R(0.5 R)TYP

.128(3.25)

.075(1.9)

.140 (3.56)

.375(9.525)

40°

.095(2.41)

.11811(3)

.048(1.22)

.150(3.81)

.19685(5) .082

(2.08)

.060(1.52)

.07874(2)

.030(0.76)

.095(2.41)

.11811(3)

.045(1.14)

.150(3.81)

.19685(5)

.076(1.93)

.008 R(0.2 R)TYP

.09843(2.5)

.059(1.5) .028

(0.7)

.051(1.3)

40°

.016 R(0.4 R)TYP

.19685(5)

.047(1.2) .104

(2.65).087(2.2)

40°

.024 R(0.6 R)TYP

.3937(10)

.098(2.5)

.209(5.3)

.177(4.5)

40°

.003

Page 14: Timing belts

T-16

For the sake of completeness, the three additional belt profiles shown in Figure 19j, 19k and19l are used in Europe and are sometimes found on machinery imported from Europe and Japan.They are not produced in the U.S.A. and are not covered by RMA standards. The belts are madeof polyurethane, and steel is usually used as the tension member.

As described in previous sections, the presently known most advantageous belt toothconfiguration is the Gates PowerGrip GT. This is a result of continuous improvement of theprevious HTD tooth profile. The HTD profile is protected by U.S. Patent Number 4,337,056,whereas the GT profile is described in U.S. Patent Number 4,515,577.

Pulleys for these belt profiles are available only from manufacturers licensed by GatesRubber Company. Stock Drive Products is one of the licensees who can supply a full rangeof these pulleys as standards or specials, per customers' drawings.

SECTION 8 PULLEY PITCH AND OUTSIDE DIAMETERS

Pulley and belt geometry as indicated in Figure 1 shows reference to a Pitch Circle, which is largerthan the pulley itself. Its size is determined by the relationship:

P⋅Npd = ––––– (8-1) π

where P is the belt tooth spacing (pitch) and N is the number of teeth on the pulley. The reinforcingcord centerline will coincide with the pulley pitch diameter while the belt is in contact with the pulley. Atthe same time, the outside diameter of the pulley will be in contact with the bottom of the belt tooth.Hence, the distance “U ” between the reinforcing cord centerline and the bottom of the belt tooth willdetermine the outside diameters of pulleys for different pitches. See Table 4.

Distance from Pitch Lineto Belt Tooth Bottom “U”

Pulley O.D. O.D. = pd – 2U

.010 inches

.007 inches

.010 inches

.015 inches

.015 inches

.0225 inches

.027 inches

.010 inches

.015 inches

.0225 inches

0.3 millimeters0.5 millimeters1.0 millimeters

Minipitch 0.080" MXL40 D.P.1/5" XL3/8" L

3 mm HTD5 mm HTD8 mm HTD

2 mm GT3 mm GT5 mm GT

T2.5 (2.5 mm)T5 (5 mm)T10 (10 mm)

Common Description

Due to the particular geometry of the 8 mm HTD belts, some corrections are needed for small-sizepulleys only. Hence, consult pulley specifications tables given later in this text, pertaining to the 8 mmHTD pulley.

As previously noted, the pitch and the number of teeth will determine the pitch diameter of thepulley, whereas its outside diameter will depend on the “U” dimension (distance from tooth bottom tocenterline of cord) as shown in Table 4.

U

U

U

U

Table 4 Basic Belt Dimensions

Page 15: Timing belts

T-17

In order to provide fast reference, the following tables show pitch and outside diameters of differentpitch pulleys:

Table 5: 0.080" MXL Pitch

Table 6: 0.0816" (40 D.P.) Pitch

Table 7: 1/5" – XL Pitch

Table 8: 3/8" – L Pitch

Table 9: 3 mm Pitch HTD

Table 10: 5 mm Pitch HTD

Table 11: 8 mm Pitch HTD

Table 12: 2 mm Pitch GT

Table 13: 3 mm Pitch GT

Table 14: 5 mm Pitch GT

These tables enable the designer to judge immediately the space requirements for a particulardrive. In many instances, the torque transmission capability of the drive can be satisfied by a lessvoluminous solution. This is one of the excellent features of the GT profile; it facilitatesminiaturization. The size of the small pulley of the drive, however, is subject to some limitations.The suggested minimum size of the pulley related to a particular pitch and rpm is given in Table 15.

The "how to" textbook on practicalsmall mechanism design

784 page Stock Drive Products Data Book 757, Volume 2, containsselection and application data for designing with small gears, belt andchain drives, speed reducers, gear trains, motors, constant forcesprings, couplings, universal joints, shafts, bearings and vibrationmounts. Includes sections on Practical Design Hints, Shop Data andDesigners Data. Includes over 500 tables and illustrations.

Tel: 516-328-3300 Fax: 516-326-8827

Page 16: Timing belts

T-18

.255

.280

.306

.331

.357

.382

.407

.433

.458

.484

.509

.535

.560

.586

.611

.637

.662

.688

.713

.738

.764

.789

.815

.840

.866

.891

.917

.942

.968

.9931.0191.0441.0701.0951.1201.1461.1711.1971.2221.2481.2731.2991.3241.3501.3751.4011.4261.4511.4771.502

5.96 6.61 7.25 7.90 8.55 9.19 9.8410.4911.1311.7812.4313.0713.7214.3715.0215.6616.3116.9617.6018.2518.9019.5420.1920.8421.4822.1322.7823.4224.0724.7225.3626.0126.6627.3027.9528.6029.2529.8930.5431.1931.8332.4833.1333.7734.4235.0735.7136.3637.0137.65

38.3038.9539.5940.2440.8941.5342.1842.8343.4744.1244.7745.4246.0646.7147.3648.0048.6549.3049.9450.5951.2451.8852.5353.1853.8254.4755.1255.7656.4157.0657.7058.3559.0059.6460.2960.9461.5962.2362.8863.5364.1764.8265.4766.1166.7667.4168.0568.7069.3569.99

1.5281.5531.5791.6041.6301.6551.6811.7061.7321.7571.7831.8081.8331.8591.8841.9101.9351.9611.9862.0122.0372.0632.0882.1142.1392.1652.1902.2152.2412.2662.2922.3172.3432.3682.3942.4192.4452.4702.4962.5212.5462.5722.5972.6232.6482.6742.6992.7252.7502.776

38.8139.4640.1040.7541.4042.0442.6943.3443.9844.6345.2845.9246.5747.2247.8648.5149.1649.8050.4551.1051.7452.3953.0453.6854.3354.9855.6356.2756.9257.5758.2158.8659.5160.1560.8061.4562.0962.7463.3964.0364.6865.3365.9766.6267.2767.9168.5669.2169.8670.50

1.5081.5331.5591.5841.6101.6351.6611.6861.7121.7371.7631.7881.8131.8391.8641.8901.9151.9411.9661.9922.0172.0432.0682.0942.1192.1452.1702.1952.2212.2462.2722.2972.3232.3482.3742.3992.4252.4502.4762.5012.5262.5522.5772.6032.6282.6542.6792.7052.7302.756

6.47 7.11 7.76 8.41 9.06 9.7010.3511.0011.6412.2912.9413.5814.2314.8815.5216.1716.8217.4618.1118.7619.4020.0520.7021.3421.9922.6423.2923.9324.5825.2325.8726.5227.1727.8128.4629.1129.7530.4031.0531.6932.3432.9933.6334.2834.9335.5736.2236.8737.5138.16

.235

.260

.286

.311

.337

.362

.387

.413

.438

.464

.489

.515

.540

.566

.591

.617

.642

.668

.693

.718

.744

.769

.795

.820

.846

.871

.897

.922

.948

.973

.9991.0241.0501.0751.1001.1261.1511.1771.2021.2281.2531.2791.3041.3301.3551.3811.4061.4311.4571.482

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

60616263646566676869707172737475767778798081828384858687888990919293949596979899

100101102103104105106107108109

1011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859

.080" (2.03 mm) MXL Pitch Pulley Dimensions

Table 5

Continued on the next page

Page 17: Timing belts

T-19

2.8012.8272.8522.8782.9032.9282.9542.9793.0053.0303.0563.0813.1073.1323.1583.1833.2093.2343.2593.2853.310

70.6471.2971.9372.5873.2373.8774.5275.1775.8276.4677.1177.7678.4079.0579.7080.3480.9981.6482.2882.9383.58

71.1571.8072.4473.0973.7474.3875.0375.6876.3276.9777.6278.2678.9179.5680.2080.8581.5082.1482.7983.4484.08

2.7812.8072.8322.8582.8832.9082.9342.9592.9853.0103.0363.0613.0873.1123.1383.1633.1893.2143.2393.2653.290

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

110111112113114115116117118119120121122123124125126127128129130

131132133134135136137138139140141142143144145146147148149150

3.3363.3613.3873.4123.4383.4633.4893.5143.5403.5653.5913.6163.6413.6673.6923.7183.7433.7693.7943.820

84.7385.3886.0386.6787.3287.9788.6189.2689.9190.5591.2091.8592.4993.1493.7994.4395.0895.7396.3797.02

3.3163.3413.3673.3923.4183.4433.4693.4943.5203.5453.5713.5963.6213.6473.6723.6983.7233.7493.7743.800

84.2284.8785.5286.1686.8187.4688.1088.7589.4090.0490.6991.3491.9992.6393.2893.9394.5795.2295.8796.51

.080" (2.03 mm) MXL Pitch Pulley Dimensions

Table 5 (Cont.)

Drive Component LibraryThe most comprehensive source available

Features over 52,400 inch and metric, commercialand precision small drive components, availablefrom stock. These six catalogs include:• Technical specifications for over 13,000 gears(D190);• 7,900 shafts, bearings and couplings (D200);• 18,300 timing belt drives (D210);• 9,400 design components (D220) and• Fairloc® hub fastening components (D240).• NEMA and Bu-Ord size gearheads along withstepper and servo motors (D122).

Tel: 516-328-3300 Fax: 516-326-8827

See our Catalogs online at: http://www.sdp-si.com

Page 18: Timing belts

T-20

40 D.P. (2.07 mm) Pitch Pulley Dimensions

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99100101102103104105106107108109110111

101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

.246

.272

.298

.324

.350

.376

.402

.428

.454

.480

.506

.532

.558

.584

.610

.636

.662

.688

.714

.740 .766 .792 .818 .844 .870 .896 .922 .948 .9741.0001.0261.0521.0781.1041.1301.1561.1821.2081.2341.2601.2861.3121.3381.3641.3901.4161.4421.4681.4931.5201.546

6.24 6.90 7.56 8.22 8.88 9.5410.2010.8611.5212.1812.8613.5214.1814.8415.5016.1616.8217.4818.1418.8019.4620.1220.7821.4422.1022.7623.4224.0824.7425.4026.0626.7227.3828.0428.7029.3630.0230.6831.3432.0032.6633.3233.9834.6435.3035.9636.6237.2837.9338.6239.28

.260

.286

.312

.338

.364

.390

.416

.442

.468

.494

.520

.546

.572

.598

.624

.650

.676

.702

.728

.754 .780 .806 .832 .858 .884 .910 .936 .962 .9881.0141.0401.0661.0921.1181.1441.1701.1961.2221.2481.2741.3001.3261.3521.3781.4041.4301.4561.4821.5071.5341.560

6.60 7.26 7.92 8.58 9.24 9.9010.5611.2211.8812.5413.2213.8814.5415.2015.8616.5217.1817.8418.5019.1619.8220.4821.1421.8022.4623.1223.7824.4425.1025.7626.4227.0727.7328.3929.0529.7130.3731.0331.6932.3533.0133.6734.3334.9935.6536.3136.9737.6338.2938.9839.64

1.5861.6121.6381.6641.6901.7161.7421.7681.7941.8201.8461.8721.8981.9241.9501.9762.0022.0282.0542.0802.1062.1322.1582.1842.2102.2362.2622.2882.3142.3402.3662.3922.4182.4442.4702.4962.5222.5482.5742.6002.6262.6522.6782.7042.7302.7562.7822.8082.8342.8602.886

40.3040.9541.6142.2742.9343.5944.2544.9145.5746.2346.8947.5548.2148.8749.5350.1950.8551.5152.1752.8353.4954.1554.8155.4756.1356.7957.4558.1158.7759.4360.0960.7561.4162.0762.7363.3964.0764.7365.3966.0566.7167.3768.0368.6969.3570.0170.6771.3371.9972.6573.31

1.5721.5981.6241.6501.6761.7021.7281.7541.7801.8061.8321.8581.8841.9101.9361.9621.9882.0142.0402.0662.0922.1182.1442.1702.1962.2222.2482.2742.3002.3262.3522.3782.4042.4302.4562.4822.5082.5342.5602.5862.6122.6382.6642.6902.7162.7422.7682.7942.8202.8462.872

39.9440.6041.2641.9242.5843.2443.9044.5645.2245.8846.5447.2047.8648.5249.1849.8450.5051.1651.8152.4753.1353.7954.4555.1155.7756.4357.0957.7558.4159.0759.7360.3961.0561.7162.3763.0363.7264.3865.0465.6966.3567.0167.6768.3368.9969.6570.3170.9771.6372.2972.95

Table 6

Continued on the next page

Page 19: Timing belts

T-21

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

40 D.P. (2.07 mm) Pitch Pulley Dimensions

Table 6 (Cont.)

112113114115116117118119120121122123124125126127128129130131

132133134135136137138139140141142143144145146147148149150

2.9122.9382.9642.9903.0163.0423.0683.0943.1203.1463.1723.1983.2243.2503.2763.3023.3283.3543.3803.406

3.4323.4583.4843.5103.5363.5623.5883.6143.6403.6663.6923.7183.7443.7703.7963.8223.8483.8743.900

73.9774.6375.2975.9576.6177.2777.9378.5979.2579.9080.5681.2281.8882.5483.2083.8684.5285.1885.8486.50

87.1687.8288.4889.1489.8390.4991.1591.8192.4793.1393.7894.4495.1095.7696.4297.0897.7498.4099.06

2.8982.9242.9502.9763.0023.0283.0543.0803.1063.1323.1583.1843.2103.2363.2623.2883.3143.3403.3663.392

3.4183.4443.4703.4963.5223.5483.5743.6003.6263.6523.6783.7043.7303.7563.7823.8083.8343.8603.886

73.6174.2774.9375.5976.2576.9177.5778.2378.8979.5580.2180.8781.5382.1982.8583.5184.1784.8385.4986.15

86.8187.4788.1388.7989.4790.1390.7991.4592.1192.7793.4394.0994.7595.4196.0796.7397.3998.0598.71

Page 20: Timing belts

T-22

.637 .700 .764 .828 .891 .9551.0191.0821.1461.2101.2731.3371.4011.4641.5281.5921.6551.7191.7831.8461.9101.9742.0372.1012.1652.2282.2922.3552.4192.4832.5462.6102.6742.7372.8012.8652.9282.9923.0563.1193.1833.2473.3103.3743.4383.5013.5653.6293.6923.756

15.6617.2818.9020.5122.1323.7525.3626.9828.6030.2231.8333.4535.0736.6838.3039.9241.5343.1544.7746.3948.0049.6251.2452.8554.4756.0957.7059.3260.9462.5664.1765.7967.4169.0270.6472.2673.8775.4977.1178.7380.3481.9683.5885.1986.8188.4390.0491.6693.2894.90

3.8203.8833.9474.0114.0744.1384.2024.2654.3294.3934.4564.5204.5844.6474.7114.7754.8384.9024.9665.0295.0935.1575.2205.2845.3485.4115.4755.5395.6025.6665.7305.7935.8575.9215.9846.0486.1126.1756.2396.3036.3666.4306.4946.5576.6216.6846.7486.8126.8756.939

96.51 98.13 99.75101.36102.98104.60106.22107.83109.45111.07112.68114.30115.92117.53119.15120.77122.39124.00125.62127.24128.85130.47132.09133.70135.32136.94138.56140.17141.79143.41145.02146.64148.26149.87151.49153.11154.73156.34157.96159.58161.19162.81164.43166.04167.66169.28170.90172.51174.13175.75

16.1717.7919.4021.0222.6424.2625.8727.4929.1130.7232.3433.9635.5737.1938.8140.4342.0443.6645.2846.8948.5150.1351.7453.3654.9856.6058.2159.8361.4563.0664.6866.3067.9169.5371.1572.7774.3876.0077.6279.2380.8582.4784.0885.7087.3288.9490.5592.1793.7995.40

.617 .680 .744 .808 .871 .935 .9991.0621.1261.1901.2531.3171.3811.4441.5081.5721.6351.6991.7631.8261.8901.9542.0172.0812.1452.2082.2722.3352.3992.4632.5262.5902.6542.7172.7812.8452.9082.9723.0363.0993.1633.2273.2903.3543.4183.4813.5453.6093.6723.736

97.02 98.64100.25101.87103.49105.11106.72108.34109.96111.57113.19114.81116.42118.04119.66121.28122.89124.51126.13127.74129.36130.98132.59134.21135.83137.45139.06140.68142.30143.91145.53147.15148.76150.38152.00153.62155.23156.85158.47160.08161.70163.32164.94166.55168.17169.79171.40173.02174.64176.25

3.8003.8633.9273.9914.0544.1184.1824.2454.3094.3734.4364.5004.5644.6274.6914.7554.8184.8824.9465.0095.0735.1375.2005.2645.3285.3915.4555.5195.5825.6465.7105.7735.8375.9015.9646.0286.0926.1556.2196.2836.3466.4106.4746.5376.6016.6646.7286.7926.8556.919

1/5" (5.08 mm) XL Pitch Pulley Dimensions

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

60616263646566676869707172737475767778798081828384858687888990919293949596979899

100101102103104105106107108109

1011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859

Continued on the next page

Table 7

Page 21: Timing belts

T-23

7.0037.0667.1307.1947.2577.3217.3857.4487.5127.5767.6397.7037.7677.8307.8947.9588.0218.0858.1498.2128.2768.3408.4038.4678.5318.5948.6588.7228.7858.8498.9138.9769.0409.1049.1679.2319.2959.3589.4229.4869.5499.6139.6779.7409.8049.8689.9319.995

10.05910.122

177.87179.49181.11182.72184.34185.96187.57189.19190.81192.42194.04195.66197.28198.89200.51202.13203.74205.36206.98208.59210.21211.83213.45215.06216.68218.30219.91221.53223.15224.76226.38228.00229.62231.23232.85234.47236.08237.70239.32240.93242.55244.17245.79247.40249.02250.64252.25253.87255.49257.10

6.9837.0467.1107.1747.2377.3017.3657.4287.4927.5567.6197.6837.7477.8107.8747.9388.0018.0658.1298.1928.2568.3208.3838.4478.5118.5748.6388.7028.7658.8298.8938.9569.0209.0849.1479.2119.2759.3389.4029.4669.5299.5939.6579.7209.7849.8489.9119.975

10.03910.102

177.36178.98180.60182.21183.83185.45187.07188.68190.30191.92193.53195.15196.77198.38200.00201.62203.24204.85206.47208.09209.70211.32212.94214.56216.17217.79219.41221.02222.64224.26225.87227.49229.11230.73232.34233.96235.58237.19238.81240.43242.04243.66245.28246.90248.51250.13251.75253.36254.98256.60

258.21259.83261.45263.07264.68266.30267.92269.53271.15272.77274.38276.00277.62279.24280.85282.47284.09285.70287.32288.94290.55292.17293.79295.41297.02298.64300.26301.87303.49305.11306.72308.34309.96311.58313.19314.81316.43318.04319.66321.28322.90324.51326.13327.75329.36330.98332.60334.21335.83337.45

10.16610.23010.29310.35710.42110.48410.54810.61210.67510.73910.80310.86610.93010.99311.05711.12111.18411.24811.31211.37511.43911.50311.56611.63011.69411.75711.82111.88511.94812.01212.07612.13912.20312.26712.33012.39412.45812.52112.58512.64912.71212.77612.84012.90312.96713.03113.09413.15813.22213.285

258.72260.34261.96263.57265.19266.81268.42270.04271.66273.27274.89276.51278.13279.74281.36282.98284.59286.21287.83289.44291.06292.68294.30295.91297.53299.15300.76302.38304.00305.61307.23308.85310.47312.08313.70315.32316.93318.55320.17321.79323.40325.02326.64328.25329.87331.49333.10334.72336.34337.96

10.18610.25010.31310.37710.44110.50410.56810.63210.69510.75910.82310.88610.95011.01311.07711.14111.20411.26811.33211.39511.45911.52311.58611.65011.71411.77711.84111.90511.96812.03212.09612.15912.22312.28712.35012.41412.47812.54112.60512.66912.73212.79612.86012.92312.98713.05113.11413.17813.24213.305

1/5" (5.08 mm) XL Pitch Pulley Dimensions

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159

160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209

Table 7 (Cont.)

Page 22: Timing belts

T-24

3/8" (9.525 mm) L Pitch Pulley Dimensions

1.1941.3131.4321.5521.6711.7901.9102.0292.1492.2682.3872.5072.6262.7452.8652.9843.1043.2233.3423.4623.5813.7003.8203.9394.0584.1784.2974.4174.5364.6554.7754.8945.0135.1335.2525.3715.4915.6105.7305.8495.9686.0886.2076.3266.4466.5656.6846.8046.9237.043

29.56 32.59 35.62 38.65 41.68 44.72 47.75 50.78 53.81 56.84 59.88 62.91 65.94 68.97 72.00 75.04 78.07 81.10 84.13 87.16 90.19 93.23 96.26 99.29102.32105.35108.39111.42114.45117.48120.51123.55126.58129.61132.64135.67138.71141.74144.77147.80150.83153.86156.90159.93162.96165.99169.02172.06175.09178.12

1.1641.2831.4021.5221.6411.7601.8801.9992.1192.2382.3572.4772.5962.7152.8352.9543.0743.1933.3123.4323.5513.6703.7903.9094.0284.1484.2674.3874.5064.6254.7454.8644.9835.1035.2225.3415.4615.5805.7005.8195.9386.0586.1776.2966.4166.5356.6546.7746.893 7.013

30.32 33.35 36.38 39.41 42.45 45.48 48.51 51.54 54.57 57.61 60.64 63.67 66.70 69.73 72.77 75.80 78.83 81.86 84.89 87.92 90.96 93.99 97.02100.05103.08106.12109.15112.18115.21118.24121.28124.31127.34130.37133.40136.44139.47142.50145.53148.56151.59154.63157.66160.69163.72166.75169.79172.82175.85178.88

7.162 7.281 7.401 7.520 7.639 7.759 7.878 7.998 8.117 8.236 8.356 8.475 8.594 8.714 8.833 8.952 9.072 9.191 9.311 9.430 9.549 9.669 9.788 9.90710.02710.14610.26510.38510.50410.62410.74310.86210.98211.10111.22011.34011.45911.57811.69811.81711.93712.05612.17512.29512.41412.53312.65312.77212.89213.011

181.91184.95187.98191.01194.04197.07200.11203.14206.17209.20212.23215.26218.30221.33224.36227.39230.42233.46236.49239.52242.55245.58248.62251.65254.68257.71260.74263.77266.81269.84272.87275.90278.93281.97285.00288.03291.06294.09297.13300.16303.19306.22309.25312.29315.32318.35321.38324.41327.44330.48

7.132 7.251 7.371 7.490 7.609 7.729 7.848 7.968 8.087 8.206 8.326 8.445 8.564 8.684 8.803 8.922 9.042 9.161 9.281 9.400 9.519 9.639 9.758 9.877 9.99710.11610.23510.35510.47410.59410.71310.83210.95211.07111.19011.31011.42911.54811.66811.78711.90712.02612.14512.26512.38412.50312.62312.74212.86212.981

181.15184.18187.22190.25193.28196.31199.34202.37205.41208.44211.47214.50217.53220.57223.60226.63229.66232.69235.73238.76241.79244.82247.85250.89253.92256.95259.98263.01266.04269.08272.11275.14278.17281.20284.24287.27290.30293.33296.36299.40302.43305.46308.49311.52314.56317.59320.62323.65326.68329.71

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

60616263646566676869707172737475767778798081828384858687888990919293949596979899

100101102103104105106107108109

1011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859

Table 8

Continued on the next page

Page 23: Timing belts

T-25

13.13013.25013.36913.48813.60813.72713.84613.96614.08514.20514.32414.44314.56314.68214.80114.92115.04015.15915.27915.39815.51815.63715.75615.87615.99516.11416.23416.35316.47216.59216.71116.83116.95017.06917.18917.30817.42717.54717.66617.78617.90518.02418.14418.26318.38218.50218.62118.74018.86018.979

333.51336.54339.57342.60345.64348.67351.70354.73357.76360.80363.83366.86369.89372.92375.95378.99382.02385.05388.08391.11394.15397.18400.21403.24406.27409.31412.34415.37418.40421.43424.47427.50430.53433.56436.59439.62442.66445.69448.72451.75454.78457.82460.85463.88466.91469.94472.98476.01479.04482.07

13.10013.22013.33913.45813.57813.69713.81613.93614.05514.17514.29414.41314.53314.65214.77114.89115.01015.12915.24915.36815.48815.60715.72615.84615.96516.08416.20416.32316.44216.56216.68116.80116.92017.03917.15917.27817.39717.51717.63617.75617.87517.99418.11418.23318.35218.47218.59118.71018.83018.949

332.75335.78338.81341.84344.87347.91350.94353.97357.00360.03363.07366.10369.13372.16375.19378.22381.26384.29387.32390.35393.38396.42399.45402.48405.51408.54411.58414.61417.64420.67423.70426.74429.77432.80435.83438.86441.89444.93447.96450.99454.02457.05460.09463.12466.15469.18472.21475.25478.28481.31

19.09919.21819.33719.45719.57619.69519.81519.93420.05320.17320.29220.41220.53120.65020.77020.88921.00821.12821.24721.36721.48621.60521.72521.84421.96322.08322.20222.32122.44122.56022.68022.79922.91823.03823.15723.27623.39623.51523.63423.75423.87323.99324.11224.23124.35124.47024.58924.70924.82824.947

485.10488.14491.17494.20497.23500.26503.29506.33509.36512.39515.42518.45521.49524.52527.55530.58533.61536.65539.68542.71545.74548.77551.80554.84557.87560.90563.93566.96570.00573.03576.06579.09582.12585.16588.19591.22594.25597.28600.32603.35606.38609.41612.44615.47618.51621.54624.57627.60630.63633.67

19.06919.18819.30719.42719.54619.66519.78519.90420.02320.14320.26220.38220.50120.62020.74020.85920.97821.09821.21721.33721.45621.57521.69521.81421.93322.05322.17222.29122.41122.53022.65022.76922.88823.00823.12723.24623.36623.48523.60423.72423.84323.96324.08224.20124.32124.44024.55924.67924.79824.917

484.34487.37490.40493.44496.47499.50502.53505.56508.60511.63514.66517.69520.72523.76526.79529.82532.85535.88538.92541.95544.98548.01551.04554.07557.11560.14563.17566.20569.23572.27575.30578.33581.36584.39587.43590.46593.49596.52599.55602.59605.62608.65611.68614.71617.74620.78623.81626.84629.87632.90

3/8" (9.525 mm) L Pitch Pulley Dimensions

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159

160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209

Table 8 (Cont.)

Page 24: Timing belts

T-26Continued on the next page

3 mm Pitch HTD® Pulley Dimensions

2.2562.2932.3312.3692.4062.4442.4812.5192.5562.5942.6322.6692.7072.7442.7822.8202.8572.8952.9322.9703.0083.0453.0833.1203.1583.1963.2333.2713.3083.3463.3843.4213.4593.4963.5343.5723.6093.6473.6843.7223.7603.7973.8353.8723.9103.9483.9854.0234.0604.098

57.3058.2559.2160.1661.1262.0763.0363.9864.9465.8966.8467.8068.7569.7170.6671.6272.5773.5374.4875.4476.3977.3578.3079.2680.2181.1782.1283.0884.0384.9985.9486.9087.8588.8189.7690.7291.6792.6393.5894.5495.4996.4597.4098.3699.31

100.27101.22102.18103.13104.09

2.2262.2632.3012.3392.3762.4142.4512.4892.5262.5642.6022.6392.6772.7142.7522.7902.8272.8652.9022.9402.9783.0153.0533.0903.1283.1663.2033.2413.2783.3163.3543.3913.4293.4663.5043.5423.5793.6173.6543.6923.7303.7673.8053.8423.8803.9183.9553.9934.0304.068

56.5357.4958.4459.4060.3561.3162.2663.2264.1765.1366.0867.0467.9968.9569.9070.8671.8172.7773.7274.6875.6376.5977.5478.5079.4580.4181.3682.3283.2784.2385.1886.1487.0988.0589.0089.9690.9191.8792.8293.7894.7395.6996.6497.6098.5599.51

100.46101.42102.37103.33

.376 .414 .451 .489 .526 .564 .602 .639 .677 .714 .752 .790 .827 .865 .902 .940 .9771.0151.0531.0901.1281.1651.2031.2411.2781.3161.3531.3911.4291.4661.5041.5411.5791.6171.6541.6921.7291.7671.8051.8421.8801.9171.9551.9932.0302.0682.1052.1432.1812.218

9.5510.5011.4612.4113.3714.3215.2816.2317.1918.1419.1020.0521.0121.9622.9223.8724.8325.7826.7427.6928.6529.6030.5631.5132.4733.4234.3835.3336.2937.2438.2039.1540.1141.0642.0242.9743.9344.8845.8446.7947.7548.7049.6650.6151.5752.5253.4854.4355.3956.34

.346 .384 .421 .459 .496 .534 .572 .609 .647 .684 .722 .760 .797 .835 .872 .910 .947 .9851.0231.0601.0981.1351.1731.2111.2481.2861.3231.3611.3991.4361.4741.5111.5491.5871.6241.6621.6991.7371.7751.8121.8501.8871.9251.9632.0002.0382.0752.1132.1512.188

8.79 9.7410.7011.6512.6113.5614.5215.4716.4317.3818.3419.2920.2521.2022.1623.1124.0725.0225.9826.9327.8928.8429.8030.7531.7132.6633.6234.5735.5336.4837.4438.3939.3440.3041.2542.2143.1644.1245.0746.0346.9847.9448.8949.8550.8051.7652.7153.6754.6255.58

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

60616263646566676869707172737475767778798081828384858687888990919293949596979899

100101102103104105106107108109

1011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859

Table 9

Page 25: Timing belts

T-27

6.0156.0536.0906.1286.1666.2036.2416.2786.3166.3546.3916.4296.4666.5046.5426.5796.6176.6546.6926.7306.7676.8056.8426.8806.9186.9556.9937.0307.0687.1067.1437.1817.2187.2567.2947.3317.3697.4067.4447.4827.5197.5577.5947.6327.6697.7077.7457.7827.8207.857

152.79153.74154.70155.65156.61157.56158.52159.47160.43161.38162.34163.29164.25165.20166.16167.11168.07169.02169.98170.93171.89172.84173.80174.75175.71176.66177.62178.57179.53180.48181.44182.39183.35184.30185.26186.21187.17188.12189.08190.03190.99191.94192.90193.85194.81195.76196.72197.67198.62199.58

5.9856.0236.0606.0986.1366.1736.2116.2486.2866.3246.3616.3996.4366.4746.5126.5496.5876.6246.6626.7006.7376.7756.8126.8506.8886.9256.9637.0007.0387.0767.1137.1517.1887.2267.2647.3017.3397.3767.4147.4527.4897.5277.5647.6027.6397.6777.7157.7527.7907.827

152.03152.98153.94154.89155.85156.80157.76158.71159.67160.62161.58162.53163.49164.44165.40166.35167.31168.26169.22170.17171.12172.08173.03173.99174.94175.90176.85177.81178.76179.72180.67181.63182.58183.54184.49185.45186.40187.36188.31189.27190.22191.18192.13193.09194.04195.00195.95196.91197.86198.82

4.1364.1734.2114.2484.2864.3234.3614.3994.4364.4744.5114.5494.5874.6244.6624.6994.7374.7754.8124.8504.8874.9254.9635.0005.0385.0755.1135.1515.1885.2265.2635.3015.3395.3765.4145.4515.4895.5275.5645.6025.6395.6775.7155.7525.7905.8275.8655.9025.9405.978

105.04106.00106.95107.91108.86109.82110.77111.73112.68113.64114.59115.55116.50117.46118.41119.37120.32121.28122.23123.19124.14125.10126.05127.01127.96128.92129.87130.83131.78132.73133.69134.64135.60136.55137.51138.46139.42140.37141.33142.28143.24144.19145.15146.10147.06148.01148.97149.92150.88151.83

4.1064.1434.1814.2184.2564.2934.3314.3694.4064.4444.4814.5194.5574.5944.6324.6694.7074.7454.7824.8204.8574.8954.9334.9705.0085.0455.0835.1215.1585.1965.2335.2715.3095.3465.3845.4215.4595.4975.5345.5725.6095.6475.6855.7225.7605.7975.8355.8725.9105.948

104.28105.23106.19107.14108.10109.05110.01110.96111.92112.87113.83114.78115.74116.69117.65118.60119.56120.51121.47122.42123.38124.33125.29126.24127.20128.15129.11130.06131.02131.97132.93133.88134.84135.79136.75137.70138.66139.61140.57141.52142.48143.43144.39145.34146.30147.25148.21149.16150.12151.07

3 mm Pitch HTD® Pulley Dimensions

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159

160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209

Table 9 (Cont.)

Page 26: Timing belts

T-28

5 mm Pitch HTD® Pulley Dimensions

3.7603.8223.8853.9484.0104.0734.1364.1984.2614.3234.3864.4494.5114.5744.6374.6994.7624.8254.8874.9505.0135.0755.1385.2015.2635.3265.3895.4515.5145.5775.6395.7025.7655.8275.8905.9536.0156.0786.1416.2036.2666.3296.3916.4546.5176.5796.6426.7056.7676.830

95.49 97.08 98.68100.27101.86103.45105.04106.63108.23109.82111.41113.00114.59116.18117.77119.37120.96122.55124.14125.73127.32128.92130.51132.10133.69135.28136.87138.46140.06141.65143.24144.83146.42148.01149.61151.20152.79154.38155.97157.56159.15160.75162.34163.93165.52167.11168.70170.30171.89173.48

3.7153.7773.8403.9033.9654.0284.0914.1534.2164.2784.3414.4044.4664.5294.5924.6544.7174.7804.8424.9054.9685.0305.0935.1565.2185.2815.3445.4065.4695.5325.5945.6575.7205.7825.8455.9085.9706.0336.0966.1586.2216.2846.3466.4096.4726.5346.5976.6606.7226.785

.627 .689 .752 .815 .877 .9401.0031.0651.1281.1911.2531.3161.3791.4411.5041.5661.6291.6921.7541.8171.8801.9422.0052.0682.1302.1932.2562.3182.3812.4442.5062.5692.6322.6942.7572.8202.8822.9453.0083.0703.1333.1963.2583.3213.3843.4463.5093.5723.6343.697

15.9217.5119.1020.6922.2823.8725.4627.0628.6530.2431.8333.4235.0136.6138.2039.7941.3842.9744.5646.1547.7549.3450.9352.5254.1155.7057.3058.8960.4862.0763.6665.2566.8468.4470.0371.6273.2174.8076.3977.9979.5881.1782.7684.3585.9487.5489.1390.7292.3193.90

.582 .644 .707 .770 .832 .895 .9581.0201.0831.1461.2081.2711.3341.3961.4591.5211.5841.6471.7091.7721.8351.8971.9602.0232.0852.1482.2112.2732.3362.3992.4612.5242.5872.6492.7122.7752.8372.9002.9633.0253.0883.1513.2133.2763.3393.4013.4643.5273.5893.652

14.7716.3617.9619.5521.1422.7324.3225.9127.5029.1030.6932.2833.8735.4637.0538.6540.2441.8343.4245.0146.6048.1949.7951.3852.9754.5656.1557.7459.3460.9362.5264.1165.7067.2968.8970.4872.0773.6675.2576.8478.4380.0381.6283.2184.8086.3987.9889.5891.1792.76

94.35 95.94 97.53 99.12100.72102.31103.90105.49107.08108.67110.27111.86113.45115.04116.63118.22119.81121.41123.00124.59126.18127.77129.36130.96132.55134.14135.73137.32138.91140.50142.10143.69145.28146.87148.46150.05151.65153.24154.83156.42158.01159.60161.19162.79164.38165.97167.56169.15170.74172.34

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

60616263646566676869707172737475767778798081828384858687888990919293949596979899

100101102103104105106107108109

1011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859

Continued on the next page

Table 10

Page 27: Timing belts

T-29

5 mm Pitch HTD® Pitch Pulley Dimensions

6.8936.9557.0187.0807.1437.2067.2687.3317.3947.4567.5197.5827.6447.7077.7707.8327.8957.9588.0208.0838.1468.2088.2718.3348.3968.4598.5228.5848.6478.7108.7728.8358.8988.9609.0239.0869.1489.2119.2749.3369.3999.4629.5249.5879.6509.7129.7759.8379.9009.963

175.07176.66178.25179.84181.44183.03184.62186.21187.80189.39190.99192.58194.17195.76197.35198.94200.53202.13203.72205.31206.90208.49210.08211.68213.27214.86216.45218.04219.63221.22222.82224.41226.00227.59229.18230.77232.37233.96235.55237.14238.73240.32241.91243.51245.10246.69248.28249.87251.46253.06

6.8486.9106.9737.0357.0987.1617.2237.2867.3497.4117.4747.5377.5997.6627.7257.7877.8507.9137.9758.0388.1018.1638.2268.2898.3518.4148.4778.5398.6028.6658.7278.7908.8538.9158.9789.0419.1039.1669.2299.2919.3549.4179.4799.5429.6059.6679.7309.7929.8559.918

173.93175.52177.11178.70180.29181.88183.48185.07186.66188.25189.84191.43193.03194.62196.21197.80199.39200.98202.57204.17205.76207.35208.94210.53212.12213.72215.31216.90218.49220.08221.67223.26224.86226.45228.04229.63231.22232.81234.41236.00237.59239.18240.77242.36243.96245.55247.14248.73250.32251.91

10.02510.08810.15110.21310.27610.33910.40110.46410.52710.58910.65210.71510.77710.84010.90310.96511.02811.09111.15311.21611.27911.34111.40411.46711.52911.59211.65511.71711.78011.84311.90511.96812.03112.09312.15612.21912.28112.34412.40712.46912.53212.59412.65712.72012.78212.84512.90812.97013.03313.096

254.65256.24257.83259.42261.01262.61264.20265.79267.38268.97270.56272.15273.75275.34276.93278.52280.11281.70283.30284.89286.48288.07289.66291.25292.84294.44296.03297.62299.21300.80302.39303.99305.58307.17308.76310.35311.94313.53315.13316.72318.31319.90321.49323.08324.68326.27327.86329.45331.04332.63

9.98010.04310.10610.16810.23110.29410.35610.41910.48210.54410.60710.67010.73210.79510.85810.92010.98311.04611.10811.17111.23411.29611.35911.42211.48411.54711.61011.67211.73511.79811.86011.92311.98612.04812.11112.17412.23612.29912.36212.42412.48712.54912.61212.67512.73712.80012.86312.92512.98813.051

253.50255.10256.69258.28259.87261.46263.05264.65266.24267.83269.42271.01272.60274.19275.79277.38278.97280.56282.15283.74285.34286.93288.52290.11291.70293.29294.88296.48298.07299.66301.25302.84304.43306.03307.62309.21310.80312.39313.98315.57317.17318.76320.35321.94323.53325.12326.72328.31329.90331.49

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159

160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209

Table 10 (Cont.)

Page 28: Timing belts

T-30

8 mm Pitch HTD® Pulley Dimensions

2.2062.3062.4062.5062.6072.7072.8072.9073.0083.1083.2083.3083.4093.5093.6093.7093.8103.9104.0104.1104.2114.3114.4114.5114.6124.7124.8124.9125.0135.1135.2135.3145.4145.5145.6145.7155.8155.9156.0156.1166.2166.3166.4166.5176.617

56.0258.5761.1263.6666.2168.7571.3073.8576.3978.9481.4984.0386.5889.1391.6794.2296.7799.31

101.86104.41106.95109.50112.05114.59117.14119.68122.23124.78127.32129.87132.42134.96137.51140.06142.60145.15147.70150.24152.79155.34157.88160.43162.97165.52168.07

2.1522.2522.3522.4522.5532.6532.7532.8532.9543.0543.1543.2543.3553.4553.5553.6553.7563.8563.9564.0564.1574.2574.3574.4574.5584.6584.7584.8584.9595.0595.1595.2605.3605.4605.5605.6615.7615.8615.9616.0626.1626.2626.3626.4636.563

54.6557.2059.7462.2964.8467.3869.9372.4875.0277.5780.1282.6685.2187.7690.3092.8595.3997.94

100.49103.03105.58108.13110.67113.22115.77118.31120.86123.41125.95128.50131.05133.59136.14138.68141.23143.78146.32148.87151.42153.96156.51159.06161.60164.15166.70

170.61173.16175.71178.25180.80183.35185.89188.44190.99193.53196.08198.63201.17203.72206.26208.81211.36213.90215.45219.00221.54224.09226.64229.18231.73234.28236.82239.37241.92244.46247.01249.55252.10254.65257.19259.74262.29264.83267.38269.93272.47275.02277.57280.11282.66

6.6636.7636.8646.9647.0647.1647.2657.3657.4657.5657.6667.7667.8667.9668.0678.1678.2678.3678.4688.5688.6688.7688.8698.9699.0699.1699.2709.3709.4709.5709.6719.7719.8719.972

10.07210.17210.27210.37310.47310.57310.67310.77410.87410.97411.074

169.24171.79174.34176.88179.43181.97184.52187.07189.61192.16194.71197.25199.80202.35204.89207.44209.99212.53215.08217.63220.17222.72225.27227.81230.36232.90235.45238.00240.54243.09245.64248.18250.73253.28255.82258.37260.92263.46266.01268.56271.10273.65276.19278.74281.29

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

676869707172737475767778798081828384858687888990919293949596979899

100101102103104105106107108109110111

222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566

6.7176.8176.9187.0187.1187.2187.3197.4197.5197.6197.7207.8207.9208.0208.1218.2218.3218.4218.5228.6228.7228.8228.9239.0239.1239.2239.3249.4249.5249.6249.7259.8259.925

10.02610.12610.22610.32610.42710.52710.62710.72710.82810.92811.02811.128

Continued on the next page

Table 11

Page 29: Timing belts

T-31

8 mm Pitch HTD® Pulley Dimensions

11.22911.32911.42911.52911.63011.73011.83011.93012.03112.13112.23112.33112.43212.53212.63212.73212.83312.93313.03313.13313.23413.33413.43413.53413.63513.73513.83513.93514.03614.13614.23614.33614.43714.53714.63714.73714.83814.93815.03815.13915.23915.33915.43915.54015.640

285.21287.75290.30292.85295.39297.94300.48303.03305.58308.12310.67313.22315.76318.31320.86323.40325.95328.50331.04333.59336.14338.68341.23343.77346.32348.87351.41353.96356.51359.05361.60364.15366.69369.24371.79374.33376.88379.43381.97384.52387.06389.61392.16394.70397.25

11.17511.27511.37511.47511.57611.67611.77611.87611.97712.07712.17712.27712.37812.47812.57812.67812.77912.87912.97913.07913.18013.28013.38013.48013.58113.68113.78113.88113.98214.08214.18214.28214.38314.48314.58314.68314.78414.88414.98415.08515.18515.28515.38515.48615.586

283.83286.38288.93291.47294.02296.57299.11301.66304.21306.75309.30311.85314.39316.94319.48322.03324.58327.12329.67332.22334.76337.31339.86342.40344.95347.50350.04352.59355.14357.68360.23362.77365.32367.87370.41372.96375.51378.05380.60383.15385.69388.24390.79393.33395.88

399.80402.34404.89407.44409.98412.53415.08417.62420.17422.72425.26427.81430.35432.90435.45437.99440.54443.09445.63448.18450.73453.27455.82458.37460.91463.46466.01468.55471.10473.65476.19478.74481.28483.83486.38488.92491.47494.02496.56499.11501.66504.20506.75509.30511.84

15.68615.78615.88715.98716.08716.18716.28816.38816.48816.58816.68916.78916.88916.98917.09017.19017.29017.39017.49117.59117.69117.79117.89217.99218.09218.19218.29318.39318.49318.59318.69418.79418.89418.99419.09519.19519.29519.39519.49619.59619.69619.79719.89719.99720.097

398.43400.97403.52406.07408.61411.16413.70416.25418.80421.34423.89426.44428.98431.53434.08436.62439.17441.72444.26446.81449.36451.90454.45456.99459.54462.09464.63467.18469.73472.27474.82477.37479.91482.46485.01487.55490.10492.65495.19497.74500.28502.83505.38507.92510.47

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201

112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156

15.74015.84015.94116.04116.14116.24116.34216.44216.54216.64216.74316.84316.94317.04317.14417.24417.34417.44417.54517.64517.74517.84517.94618.04618.14618.24618.34718.44718.54718.64718.74818.84818.94819.04819.14919.24919.34919.44919.55019.65019.75019.85119.95120.05120.151

Table 11 (Cont.)

Page 30: Timing belts

T-32

2 mm Pitch GT® Pulley Dimensions

.251

.276

.301

.326

.351

.376

.401

.426

.451

.476

.501

.526

.551

.576

.602

.627

.652

.677

.702

.727

.752

.777

.802

.827

.852

.877

.902

.927

.952

.9771.0031.0281.0531.0781.1031.1281.1531.1781.2031.228

6.377.017.648.288.919.55

10.1910.8211.4612.1012.7313.3714.0114.6415.2815.9216.5517.1917.8318.4619.1019.7420.3721.0121.6522.2822.9223.5524.1924.8325.4626.1026.7427.3728.0128.6529.2829.9230.5631.19

.231

.256

.281

.306

.331

.356

.381

.406

.431

.456

.481

.506

.531

.556

.582

.607

.632

.657

.682

.707

.732

.757

.782

.807

.832

.857

.882

.907

.932

.957

.9831.0081.0331.0581.0831.1081.1331.1581.1831.208

5.866.507.137.778.409.049.6810.3110.9511.5912.2212.8613.5014.1314.7715.4116.0416.6817.3217.9518.5919.2319.8620.5021.1421.7722.4123.0523.6824.3224.9625.5926.2326.8727.5028.1428.7829.4130.0530.69

1.2531.2781.3031.3281.3531.3791.4041.4291.4541.4791.5041.5291.5541.5791.6041.6291.6541.6791.7041.7291.7541.7801.8051.8301.8551.8801.9051.9301.9551.9802.0052.0302.0552.0802.1052.1302.1552.1812.2062.231

31.8332.4733.1033.7434.3835.0135.6536.2936.9237.5638.2038.8339.4740.1140.7441.3842.0242.6543.2943.9344.5645.2045.8446.4747.1147.7548.3849.0249.6650.2950.9351.5752.2052.8453.4854.1154.7555.3956.0256.66

1.2331.2581.2831.3081.3331.3591.3841.4091.4341.4591.4841.5091.5341.5591.5841.6091.6341.6591.6841.7091.7341.7601.7851.8101.8351.8601.8851.9101.9351.9601.9852.0102.0352.0602.0852.1102.1352.1612.1862.211

31.3231.9632.6033.2333.8734.5135.1435.7836.4237.0537.6938.3338.9639.6040.2440.8741.5142.1542.7843.4244.0644.6945.3345.9746.6047.2447.8848.5149.1549.7950.4251.0651.6952.3352.9753.6054.2454.8855.5156.15

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

50515253545556575859606162636465666768697071727374757677787980818283848586878889

10111213141516171819202122232425262728293031323334353637383940414243444546474849

Continued on the next page

Table 12

Page 31: Timing belts

T-33

2 mm Pitch GT® Pulley Dimensions

3.1583.1833.2083.2333.2583.2833.3083.3333.3593.3843.4093.4343.4593.4843.5093.5343.5593.5843.6093.6343.6593.6843.7093.7353.7603.7853.8103.8353.8603.8853.9103.9353.9603.9854.010

80.2180.8581.4982.1282.7683.4084.0384.6785.3185.9486.5887.2287.8588.4989.1389.7690.4091.0491.6792.3192.9593.5894.2294.8695.4996.1396.7797.4098.0498.6899.3199.95

100.59101.22101.86

3.1383.1633.1883.2133.2383.2633.2883.3133.3393.3643.3893.4143.4393.4643.4893.5143.5393.5643.5893.6143.6393.6643.6893.7153.7403.7653.7903.8153.8403.8653.8903.9153.9403.9653.990

2.2562.2812.3062.3312.3562.3812.4062.4312.4562.4812.5062.5312.5572.5822.6072.6322.6572.6822.7072.7322.7572.7822.8072.8322.8572.8822.9072.9322.9582.9833.0083.0333.0583.0833.1083.133

57.3057.9358.5759.2159.8460.4861.1261.7562.3963.0363.6664.3064.9465.5766.2166.8567.4868.1268.7569.3970.0370.6671.3071.9472.5773.2173.8574.4875.1275.7676.3977.0377.6778.3078.9479.58

2.2362.2612.2862.3112.3362.3612.3862.4112.4362.4612.4862.5112.5372.5622.5872.6122.6372.6622.6872.7122.7372.7622.7872.8122.8372.8622.8872.9122.9382.9632.9883.0133.0383.0633.0883.113

56.7957.4258.0658.7059.3359.9760.6161.2461.8862.5263.1563.7964.4365.0665.7066.3466.9767.6168.2568.8869.5270.1670.7971.4372.0772.7073.3473.9874.6175.2575.8976.5277.1677.8078.4379.07

79.7180.3480.9881.6282.2582.8983.5384.1684.8085.4486.0786.7187.3587.9888.6289.2689.8990.5391.1791.8092.4493.0893.7194.3594.9995.6296.2696.8997.5398.1798.8099.44

100.08100.71101.35

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

90919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125

126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160

Table 12 (Cont.)

Page 32: Timing belts

T-34

3 mm Pitch GT® Pulley Dimensions

2.2562.2932.3312.3692.4062.4442.4812.5192.5562.5942.6322.6692.7072.7442.7822.8202.8572.8952.9322.9703.0083.0453.0833.1203.1583.1963.2333.2713.3083.3463.3843.4213.4593.4963.5343.5723.6093.6473.6843.7223.7603.7973.8353.8723.9103.9483.9854.0234.0604.098

57.3058.2559.2160.1661.1262.0763.0363.9864.9465.8966.8467.8068.7569.7170.6671.6272.5773.5374.4875.4476.3977.3578.3079.2680.2181.1782.1283.0884.0384.9985.9486.9087.8588.8189.7690.7291.6792.6393.5894.5495.4996.4597.4098.3699.31

100.27101.22102.18103.13104.09

2.2262.2632.3012.3392.3762.4142.4512.4892.5262.5642.6022.6392.6772.7142.7522.7902.8272.8652.9022.9402.9783.0153.0533.0903.1283.1663.2033.2413.2783.3163.3543.3913.4293.4663.5043.5423.5793.6173.6543.6923.7303.7673.8053.8423.8803.9183.9553.9934.0304.068

56.5357.4958.4459.4060.3561.3162.2663.2264.1765.1366.0867.0467.9968.9569.9070.8671.8172.7773.7274.6875.6376.5977.5478.5079.4580.4181.3682.3283.2784.2385.1886.1487.0988.0589.0089.9690.9191.8792.8293.7894.7395.6996.6497.6098.5599.51

100.46101.42102.37103.33

.376 .414 .451 .489 .526 .564 .602 .639 .677 .714 .752 .790 .827 .865 .902 .940 .9771.0151.0531.0901.1281.1651.2031.2411.2781.3161.3531.3911.4291.4661.5041.5411.5791.6171.6541.6921.7291.7671.8051.8421.8801.9171.9551.9932.0302.0682.1052.1432.1812.218

9.5510.5011.4612.4113.3714.3215.2816.2317.1918.1419.1020.0521.0121.9622.9223.8724.8325.7826.7427.6928.6529.6030.5631.5132.4733.4234.3835.3336.2937.2438.2039.1540.1141.0642.0242.9743.9344.8845.8446.7947.7548.7049.6650.6151.5752.5253.4854.4355.3956.34

.346 .384 .421 .459 .496 .534 .572 .609 .647 .684 .722 .760 .797 .835 .872 .910 .947 .9851.0231.0601.0981.1351.1731.2111.2481.2861.3231.3611.3991.4361.4741.5111.5491.5871.6241.6621.6991.7371.7751.8121.8501.8871.9251.9632.0002.0382.0752.1132.1512.188

8.79 9.7410.7011.6512.6113.5614.5215.4716.4317.3818.3419.2920.2521.2022.1623.1124.0725.0225.9826.9327.8928.8429.8030.7531.7132.6633.6234.5735.5336.4837.4438.3939.3440.3041.2542.2143.1644.1245.0746.0346.9847.9448.8949.8550.8051.7652.7153.6754.6255.58

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

60616263646566676869707172737475767778798081828384858687888990919293949596979899

100101102103104105106107108109

1011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859

Continued on the next page

Table 13

Page 33: Timing belts

T-35

Table 13 (Cont.)

3 mm Pitch GT® Pulley Dimensions

6.0156.0536.0906.1286.1666.2036.2416.2786.3166.3546.3916.4296.4666.5046.5426.5796.6176.6546.6926.7306.7676.8056.8426.8806.9186.9556.9937.0307.0687.1067.1437.1817.2187.2567.2947.3317.3697.4067.4447.4827.5197.5577.5947.6327.6697.7077.7457.7827.8207.857

152.79153.74154.70155.65156.61157.56158.52159.47160.43161.38162.34163.29164.25165.20166.16167.11168.07169.02169.98170.93171.89172.84173.80174.75175.71176.66177.62178.57179.53180.48181.44182.39183.35184.30185.26186.21187.17188.12189.08190.03190.99191.94192.90193.85194.81195.76196.72197.67198.62199.58

5.9856.0236.0606.0986.1366.1736.2116.2486.2866.3246.3616.3996.4366.4746.5126.5496.5876.6246.6626.7006.7376.7756.8126.8506.8886.9256.9637.0007.0387.0767.1137.1517.1887.2267.2647.3017.3397.3767.4147.4527.4897.5277.5647.6027.6397.6777.7157.7527.7907.827

152.03152.98153.94154.89155.85156.80157.76158.71159.67160.62161.58162.53163.49164.44165.40166.35167.31168.26169.22170.17171.12172.08173.03173.99174.94175.90176.85177.81178.76179.72180.67181.63182.58183.54184.49185.45186.40187.36188.31189.27190.22191.18192.13193.09194.04195.00195.95196.91197.86198.82

4.1364.1734.2114.2484.2864.3234.3614.3994.4364.4744.5114.5494.5874.6244.6624.6994.7374.7754.8124.8504.8874.9254.9635.0005.0385.0755.1135.1515.1885.2265.2635.3015.3395.3765.4145.4515.4895.5275.5645.6025.6395.6775.7155.7525.7905.8275.8655.9025.9405.978

105.04106.00106.95107.91108.86109.82110.77111.73112.68113.64114.59115.55116.50117.46118.41119.37120.32121.28122.23123.19124.14125.10126.05127.01127.96128.92129.87130.83131.78132.73133.69134.64135.60136.55137.51138.46139.42140.37141.33142.28143.24144.19145.15146.10147.06148.01148.97149.92150.88151.83

4.1064.1434.1814.2184.2564.2934.3314.3694.4064.4444.4814.5194.5574.5944.6324.6694.7074.7454.7824.8204.8574.8954.9334.9705.0085.0455.0835.1215.1585.1965.2335.2715.3095.3465.3845.4215.4595.4975.5345.5725.6095.6475.6855.7225.7605.7975.8355.8725.9105.948

104.28105.23106.19107.14108.10109.05110.01110.96111.92112.87113.83114.78115.74116.69117.65118.60119.56120.51121.47122.42123.38124.33125.29126.24127.20128.15129.11130.06131.02131.97132.93133.88134.84135.79136.75137.70138.66139.61140.57141.52142.48143.43144.39145.34146.30147.25148.21149.16150.12151.07

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159

160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209

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T-36Continued on the next page

Table 14

5 mm Pitch GT® Pulley Dimensions

3.7603.8223.8853.9484.0104.0734.1364.1984.2614.3234.3864.4494.5114.5744.6374.6994.7624.8254.8874.9505.0135.0755.1385.2015.2635.3265.3895.4515.5145.5775.6395.7025.7655.8275.8905.9536.0156.0786.1416.2036.2666.3296.3916.4546.5176.5796.6426.7056.7676.830

95.49 97.08 98.68100.27101.86103.45105.04106.63108.23109.82111.41113.00114.59116.18117.77119.37120.96122.55124.14125.73127.32128.92130.51132.10133.69135.28136.87138.46140.06141.65143.24144.83146.42148.01149.61151.20152.79154.38155.97157.56159.15160.75162.34163.93165.52167.11168.70170.30171.89173.48

3.7153.7773.8403.9033.9654.0284.0914.1534.2164.2784.3414.4044.4664.5294.5924.6544.7174.7804.8424.9054.9685.0305.0935.1565.2185.2815.3445.4065.4695.5325.5945.6575.7205.7825.8455.9085.9706.0336.0966.1586.2216.2846.3466.4096.4726.5346.5976.6606.7226.785

.627 .689 .752 .815 .877 .9401.0031.0651.1281.1911.2531.3161.3791.4411.5041.5661.6291.6921.7541.8171.8801.9422.0052.0682.1302.1932.2562.3182.3812.4442.5062.5692.6322.6942.7572.8202.8822.9453.0083.0703.1333.1963.2583.3213.3843.4463.5093.5723.6343.697

15.9217.5119.1020.6922.2823.8725.4627.0628.6530.2431.8333.4235.0136.6138.2039.7941.3842.9744.5646.1547.7549.3450.9352.5254.1155.7057.3058.8960.4862.0763.6665.2566.8468.4470.0371.6273.2174.8076.3977.9979.5881.1782.7684.3585.9487.5489.1390.7292.3193.90

.582 .644 .707 .770 .832 .895 .9581.0201.0831.1461.2081.2711.3341.3961.4591.5211.5841.6471.7091.7721.8351.8971.9602.0232.0852.1482.2112.2732.3362.3992.4612.5242.5872.6492.7122.7752.8372.9002.9633.0253.0883.1513.2133.2763.3393.4013.4643.5273.5893.652

14.7716.3617.9619.5521.1422.7324.3225.9127.5029.1030.6932.2833.8735.4637.0538.6540.2441.8343.4245.0146.6048.1949.7951.3852.9754.5656.1557.7459.3460.9362.5264.1165.7067.2968.8970.4872.0773.6675.2576.8478.4380.0381.6283.2184.8086.3987.9889.5891.1792.76

94.35 95.94 97.53 99.12100.72102.31103.90105.49107.08108.67110.27111.86113.45115.04116.63118.22119.81121.41123.00124.59126.18127.77129.36130.96132.55134.14135.73137.32138.91140.50142.10143.69145.28146.87148.46150.05151.65153.24154.83156.42158.01159.60161.19162.79164.38165.97167.56169.15170.74172.34

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

60616263646566676869707172737475767778798081828384858687888990919293949596979899

100101102103104105106107108109

1011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859

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T-37

5 mm Pitch GT® Pulley Dimensions

6.8936.9557.0187.0807.1437.2067.2687.3317.3947.4567.5197.5827.6447.7077.7707.8327.8957.9588.0208.0838.1468.2088.2718.3348.3968.4598.5228.5848.6478.7108.7728.8358.8988.9609.0239.0869.1489.2119.2749.3369.3999.4629.5249.5879.6509.7129.7759.8379.9009.963

175.07176.66178.25179.84181.44183.03184.62186.21187.80189.39190.99192.58194.17195.76197.35198.94200.53202.13203.72205.31206.90208.49210.08211.68213.27214.86216.45218.04219.63221.22222.82224.41226.00227.59229.18230.77232.37233.96235.55237.14238.73240.32241.91243.51245.10246.69248.28249.87251.46253.06

6.8486.9106.9737.0357.0987.1617.2237.2867.3497.4117.4747.5377.5997.6627.7257.7877.8507.9137.9758.0388.1018.1638.2268.2898.3518.4148.4778.5398.6028.6658.7278.7908.8538.9158.9789.0419.1039.1669.2299.2919.3549.4179.4799.5429.6059.6679.7309.7929.8559.918

173.93175.52177.11178.70180.29181.88183.48185.07186.66188.25189.84191.43193.03194.62196.21197.80199.39200.98202.57204.17205.76207.35208.94210.53212.12213.72215.31216.90218.49220.08221.67223.26224.86226.45228.04229.63231.22232.81234.41236.00237.59239.18240.77242.36243.96245.55247.14248.73250.32251.91

10.02510.08810.15110.21310.27610.33910.40110.46410.52710.58910.65210.71510.77710.84010.90310.96511.02811.09111.15311.21611.27911.34111.40411.46711.52911.59211.65511.71711.78011.84311.90511.96812.03112.09312.15612.21912.28112.34412.40712.46912.53212.59412.65712.72012.78212.84512.90812.97013.03313.096

254.65256.24257.83259.42261.01262.61264.20265.79267.38268.97270.56272.15273.75275.34276.93278.52280.11281.70283.30284.89286.48288.07289.66291.25292.84294.44296.03297.62299.21300.80302.39303.99305.58307.17308.76310.35311.94313.53315.13316.72318.31319.90321.49323.08324.68326.27327.86329.45331.04332.63

9.98010.04310.10610.16810.23110.29410.35610.41910.48210.54410.60710.67010.73210.79510.85810.92010.98311.04611.10811.17111.23411.29611.35911.42211.48411.54711.61011.67211.73511.79811.86011.92311.98612.04812.11112.17412.23612.29912.36212.42412.48712.54912.61212.67512.73712.80012.86312.92512.98813.051

253.50255.10256.69258.28259.87261.46263.05264.65266.24267.83269.42271.01272.60274.19275.79277.38278.97280.56282.15283.74285.34286.93288.52290.11291.70293.29294.88296.48298.07299.66301.25302.84304.43306.03307.62309.21310.80312.39313.98315.57317.17318.76320.35321.94323.53325.12326.72328.31329.90331.49

Pitch Diameter Outside DiameterNo. ofGrooves Inch mm Inch mm

No. ofGrooves Inch mm Inch mm

Pitch Diameter Outside Diameter

110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159

160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209

Table 14 (Cont.)

Page 36: Timing belts

T-38

Minimum Pulley Diameters

BeltType

Pitch

Inch mm

rpmMax.

Suggested Minimum*

No. ofGrooves

Pitch Diameter

10000750050003500350017501160350017501160350017501160350017501160350017501160350017501160

1400075005000500028001600200014001000360018001200

< 1200360018001200

< 1200360018001200

< 1200

14121110121110161412201816201817302622322824161412201816222018

14

16

14

16

16

18

.357

.306

.280

.255

.764

.700

.6371.9101.6711.4323.1822.8652.546.752.677.639

1.8801.6291.3793.2082.8072.406.401.351.301.752.677.602

1.3791.2531.128

.417

.480

.844

.969

1.931

2.183

2.03

5.08

9.525

12.7

3

5

8

2

3

5

2.5

5

10

0.080

0.200

0.375

0.500

0.118

0.197

0.315

0.079

0.118

0.197

.0984

.19685

.3937

MXL

XL

L

H

HTD

GT

"T"Series

* Smaller pulleys than shown under "Suggested Minimum" may be used if a corresponding reduction in belt life issatisfactory. Use of pulleys smaller than those shown will be at customers' own responsibility for performance and belt life.

Table 15

inch mm 9.07 7.77 7.11 6.4819.4117.7816.1848.5142.4436.3780.8272.7764.6719.117.216.2347.7541.3835.0381.4871.361.1110.19 8.92 7.6519.117.215.2935.0331.8328.65

10.6

12.2

21.45

24.6

49.05

55.45

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T-39

SECTION 9 DESIGN AND INSTALLATION SUGGESTIONS

There are some general guidelines which are applicable to all timing belts, including miniatureand double sided belts:

1. Drives should always be designed with ample reserve horsepower capacity. Use ofoverload service factors is important. Belts should be rated at only 1/15th of theirrespective ultimate strength.

2. For MXL pitch belts, the smallest recommended pulley will have 10 teeth. For otherpitches, Table 15 should be used.

3. The pulley diameter should never be smaller than the width of the belt. 4. Belts with Fibrex-glass fiber tension members should not be subjected to sharp bends or

rough handling, since this could cause breakage of the fibers. 5. In order to deliver the rated horsepower, a belt must have six or more teeth in mesh with

the grooves of the smaller pulley. The number of teeth in mesh may be obtained byformula given in SECTION 24 TIMING BELT DRIVE SELECTION PROCEDURE. Theshear strength of a single tooth is only a fraction of the belt break strength.

6. Because of a slight side thrust of synchronous belts in motion, at least one pulley in thedrive must be flanged. When the center distance between the shafts is 8 or more timesthe diameter of the smaller pulley, or when the drive is operating on vertical shafts, bothpulleys should be flanged.

7. Belt surface speed should not exceed 5500 feet per minute (28 m/s) for larger pitch beltsand 10000 feet per minute (50 m/s) for minipitch belts. For the HTD belts a speed of6500 feet per minute (33 m/s) is permitted, whereas for GT belts the maximum permittedspeed is 7500 feet per minute (38 m/s).

8. Belts are, in general, rated to yield a minimum of 3000 hours of useful life if all instructionsare properly followed.

9. Belt drives are inherently efficient. It can be assumed that the efficiency of a synchronousbelt drive is greater than 95%.

10. Belt drives are usually a source of noise. The frequency of the noise level increasesproportionally with the belt speed. The higher the initial belt tension, the greater thenoise level. The belt teeth entering the pulleys at high speed act as a compressor andthis creates noise. Some noise is the result of a belt rubbing against the flange, which inturn may be the result of the shafts not being parallel. As shown in Figure 9 (page T-9),the noise level is substantially reduced if the PowerGrip GT belt is being used.

11. If the drive is part of a sensitive acoustical or electronics sensing or recording device, it isrecommended that the back surfaces of the belt be ground to assure absolutely uniformbelt thickness.

12. For some applications, no backlash between the driving and the driven shaft is permitted.For these cases, special profile pulleys can be produced without any clearance betweenthe belt tooth and pulley. This may shorten the belt life, but it eliminates backlash.Figure 10 (page T-9) shows the superiority of PowerGrip GT profile as far as reduction ofbacklash is concerned.

13. Synchronous belts are often driven by stepping motors. These drives are subjected tocontinuous and large accelerations and decelerations. If the belt reinforcing fiber, i.e.,tension member, as well as the belt material, have high tensile strength and no elongation,the belt will not be instrumental in absorbing the shock loads. This will result in shearedbelt teeth. Therefore, take this into account when the size of the smallest pulley and thematerials for the belt and tension member are selected.

14. The choice of the pulley material (metal vs. plastic) is a matter of price, desired precision,inertia, color, magnetic properties and, above all, personal preference based onexperiences. Plastic pulleys with metal inserts or metal hubs represent a good compromise.

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T-40

The following precautions should be taken when installing all timing belt drives: 1. Timing belt installation should be a snug fit, neither too tight nor too loose. The positive grip

of the belt eliminates the need for high initial tension. Consequently, a belt, when installedwith a snug fit (that is, not too taut) assures longer life, less bearing wear and quieteroperation. Preloading (often the cause of premature failure) is not necessary.When torque is unusually high, a loose belt may "jump teeth" on starting. In such a case, thetension should be increased gradually, until satisfactory operation is attained. A good rule ofthumb for installation tension is as shown in Figure 20, and the corresponding tensioningforce is shown in Table 16, both shown in SECTION 10 BELT TENSIONING. For widthsother than shown, increase force proportionally to the belt width. Instrumentation for measuringbelt tension is available. Consult the product section of this catalog.

2. Be sure that shafts are parallel and pulleys are in alignment. On a long center drive, it issometimes advisable to offset the driven pulley to compensate for the tendency of the belt torun against one flange.

3. On a long center drive, it is imperative that the belt sag is not large enough to permit teeth onthe slack side to engage the teeth on the tight side.

4. It is important that the frame supporting the pulleys be rigid at all times. A nonrigid framecauses variation in center distance and resulting belt slackness. This, in turn, can lead tojumping of teeth – especially under starting load with shaft misalignment.

5. Although belt tension requires little attention after initial installation, provision should be madefor some center distance adjustment for ease in installing and removing belts. Do not forcebelt over flange of pulley.

6. Idlers, either of the inside or outside type, are not recommended and should not be usedexcept for power takeoff or functional use. When an idler is necessary, it should be on theslack side of the belt. Inside idlers must be grooved, unless their diameters are greater thanan equivalent 40-groove pulley. Flat idlers must not be crowned (use edge flanges). Idlerdiameters must exceed the smallest diameter drive pulley. Idler arc of contact should be heldto a minimum.

In addition to the general guidelines enumerated previously, specific operating characteristics ofthe drive must be taken into account. These may include the following:

9.1 Low Speed Operation

Synchronous drives are especially well suited for low speed, high torque applications. Theirpositive driving nature prevents potential slippage associated with V-belt drives , and even allowssignificantly greater torque carrying capability. Small pitch synchronous drives operating at speeds of50 ft/min (0.25 m/s) or less are considered to be low speed. Care should be taken in the drive selectionprocess as stall and peak torques can sometimes be very high. While intermittent peak torques canoften be carried by synchronous drives without special considerations, high cyclic peak torque loadingshould be carefully reviewed.

Proper belt installation tension and rigid drive bracketry and framework is essential in preventingbelt tooth jumping under peak torque loads. It is also helpful to design with more than the normalminimum of 6 belt teeth in mesh to ensure adequate belt tooth shear strength.

Newer generation curvilinear systems like PowerGrip GT and PowerGrip HTD should be used inlow speed, high torque applications, as trapezoidal timing belts are more prone to tooth jumping, andhave significantly less load carrying capacity.

9.2 High Speed Operation

Synchronous belt drives are often used in high speed applications even though V-belt drives aretypically better suited. They are often used because of their positive driving characteristic (no creep or

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T-41

slip), and because they require minimal maintenance (don't stretch significantly). A significant drawbackof high speed synchronous drives is drive noise. High speed synchronous drives will nearly alwaysproduce more noise than V-belt drives. Small pitch synchronous drives operating at speeds in excessof 1300 ft/min (6.6 m/s) are considered to be high speed.

Special consideration should be given to high speed drive designs, as a number of factors cansignificantly influence belt performance. Cord fatigue and belt tooth wear are the two most significantfactors that must be controlled to ensure success. Moderate pulley diameters should be used toreduce the rate of cord flex fatigue. Designing with a smaller pitch belt will often provide better cordflex fatigue characteristics than a larger pitch belt. PowerGrip GT is especially well suited for highspeed drives because of its excellent belt tooth entry/exit characteristics. Smooth interactionbetween the belt tooth and pulley groove minimizes wear and noise. Belt installation tension isespecially critical with high speed drives. Low belt tension allows the belt to ride out of the drivenpulley, resulting in rapid belt tooth and pulley groove wear.

9.3 Smooth Running

Some ultrasensitive applications require the belt drive to operate with as little vibration aspossible, as vibration sometimes has an effect on the system operation or finished manufacturedproduct. In these cases, the characteristics and properties of all appropriate belt drive productsshould be reviewed. The final drive system selection should be based upon the most critical designrequirements, and may require some compromise.

Vibration is not generally considered to be a problem with synchronous belt drives. Low levelsof vibration typically result from the process of tooth meshing and/or as a result of their high tensilemodulus properties. Vibration resulting from tooth meshing is a normal characteristic of synchronousbelt drives, and cannot be completely eliminated. It can be minimized by avoiding small pulleydiameters, and instead choosing moderate sizes. The dimensional accuracy of the pulleys alsoinfluences tooth meshing quality. Additionally, the installation tension has an impact on meshingquality. PowerGrip GT drives mesh very cleanly, resulting in the smoothest possible operation.Vibration resulting from high tensile modulus can be a function of pulley quality. Radial run outcauses belt tension variation with each pulley revolution. V-belt pulleys are also manufactured withsome radial run out, but V-belts have a lower tensile modulus resulting in less belt tension variation.The high tensile modulus found in synchronous belts is necessary to maintain proper pitch underload.

9.4 Drive Noise

Drive noise evaluation in any belt drive system should be approached with care. There aremany potential sources of noise in a system, including vibration from related components, bearings,and resonance and amplification through framework and panels.

Synchronous belt drives typically produce more noise than V-belt drives. Noise results fromthe process of belt tooth meshing and physical contact with the pulleys. The sound pressure levelgenerally increases as operating speed and belt width increase, and as pulley diameter decreases.Drives designed on moderate pulley sizes without excessive capacity (over designed) are generallythe quietest. PowerGrip GT drives have been found to be significantly quieter than other systemsdue to their improved meshing characteristic (see Figure 9, page T-9). Polyurethane belts generallyproduce more noise than neoprene belts. Proper belt installation tension is also very important inminimizing drive noise. The belt should be tensioned at a level that allows it to run with as littlemeshing interference as possible.

Drive alignment also has a significant effect on drive noise. Special attention should be givento minimizing angular misalignment (shaft parallelism). This assures that belt teeth are loadeduniformly and minimizes side tracking forces against the flanges. Parallel misalignment (pulleyoffset) is not as critical of a concern as long as the belt is not trapped or pinched between opposite

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T-42

flanges (see the special section dealing with drive alignment). Pulley materials and dimensionalaccuracy also influence drive noise. Some users have found that steel pulleys are the quietest,followed closely by aluminum. Polycarbonates have been found to be noisier than metallic materials.Machined pulleys are generally quieter than molded pulleys. The reasons for this revolve aroundmaterial density and resonance characteristics as well as dimensional accuracy.

9.5 Static Conductivity

Small synchronous rubber or urethane belts can generate an electrical charge while operatingon a drive. Factors such as humidity and operating speed influence the potential of the charge. Ifdetermined to be a problem, rubber belts can be produced in a conductive construction to dissipatethe charge into the pulleys, and to ground. This prevents the accumulation of electrical chargesthat might be detrimental to material handling processes or sensitive electronics. It also greatlyreduces the potential for arcing or sparking in flammable environments. Urethane belts cannot beproduced in a conductive construction.

RMA has outlined standards for conductive belts in their bulletin IP-3-3. Unless otherwisespecified, a static conductive construction for rubber belts is available on a made-to-order basis.Unless otherwise specified, conductive belts will be built to yield a resistance of 300,000 ohms orless, when new.

Nonconductive belt constructions are also available for rubber belts. These belts are generallybuilt specifically to the customers conductivity requirements. They are generally used in applicationswhere one shaft must be electrically isolated from the other.

It is important to note that a static conductive belt cannot dissipate an electrical chargethrough plastic pulleys. At least one metallic pulley in a drive is required for the charge to bedissipated to ground. A grounding brush or similar device may also be used to dissipate electricalcharges.

Urethane timing belts are not static conductive and cannot be built in a special conductiveconstruction. Special conductive rubber belts should be used when the presence of an electricalcharge is a concern.

9.6 Operating Environments

Synchronous drives are suitable for use in a wide variety of environments. Specialconsiderations may be necessary, however, depending on the application.

Dust: Dusty environments do not generally present serious problems to synchronous drivesas long as the particles are fine and dry. Particulate matter will, however, act as an abrasiveresulting in a higher rate of belt and pulley wear. Damp or sticky particulate matter deposited andpacked into pulley grooves can cause belt tension to increase significantly. This increased tensioncan impact shafting, bearings, and framework. Electrical charges within a drive system cansometimes attract particulate matter.

Debris: Debris should be prevented from falling into any synchronous belt drive. Debriscaught in the drive is generally either forced through the belt or results in stalling of the system. Ineither case, serious damage occurs to the belt and related drive hardware.

Water: Light and occasional contact with water (occasional wash downs) should not seriouslyaffect synchronous belts. Prolonged contact (constant spray or submersion) results in significantlyreduced tensile strength in fiberglass belts, and potential length variation in aramid belts. Prolongedcontact with water also causes rubber compounds to swell, although less than with oil contact.Internal belt adhesion systems are also gradually broken down with the presence of water. Additivesto water, such as lubricants, chlorine, anticorrosives, etc. can have a more detrimental effect on the

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belts than pure water. Urethane timing belts also suffer from water contamination. Polyestertensile cord shrinks significantly and experiences loss of tensile strength in the presence of water.Aramid tensile cord maintains its strength fairly well, but experiences length variation. Urethaneswells more than neoprene in the presence of water. This swelling can increase belt tensionsignificantly, causing belt and related hardware problems.

Oil: Light contact with oils on an occasional basis will not, generally damage synchronous belts.Prolonged contact with oil or lubricants, either directly or airborne, results in significantly reduced beltservice life. Lubricants cause the rubber compound to swell, breakdown internal adhesion systems,and reduce belt tensile strength. While alternate rubber compounds may provide some marginalimprovement in durability, it is best to prevent oil from contacting synchronous belts.

Ozone: The presence of ozone can be detrimental to the compounds used in rubbersynchronous belts. Ozone degrades belt materials in much the same way as excessive environmentaltemperatures. Although the rubber materials used in synchronous belts are compounded to resistthe effects of ozone, eventually chemical breakdown occurs and they become hard and brittle andbegin cracking. The amount of degradation depends upon the ozone concentration and duration ofexposure. For good performance of rubber belts, the following concentration levels should not beexceeded: (parts per hundred million)

Standard Construction: 100 pphmNon Marking Construction: 20 pphmConductive Construction: 75 pphmLow Temperatures Construction: 20 pphm

Radiation: Exposure to gamma radiation can be detrimental to the compounds used in rubberand urethane synchronous belts. Radiation degrades belt materials much the same way excessiveenvironmental temperatures do. The amount of degradation depends upon the intensity of radiationand the exposure time. For good belt performance, the following exposure levels should not beexceeded:

Standard Construction: 108 radsNon Marking Construction: 104 radsConductive Construction: 106 radsLow Temperatures Construction: 104 rads

Dust Generation: Rubber synchronous belts are known to generate small quantities of finedust, as a natural result of their operation. The quantity of dust is typically higher for new belts, asthey run in. The period of time for run in to occur depends upon the belt and pulley size, loadingand speed. Factors such as pulley surface finish, operating speeds, installation tension, andalignment influence the quantity of dust generated.

Clean Room: Rubber synchronous belts may not be suitable for use in clean roomenvironments, where all potential contamination must be minimized or eliminated. Urethane timingbelts typically generate significantly less debris than rubber timing belts. However, they arerecommended only for light operating loads. Also, they cannot be produced in a static conductiveconstruction to allow electrical charges to dissipate.

Static Sensitive: Applications are sometimes sensitive to the accumulation of static electricalcharges. Electrical charges can affect material handling processes (like paper and plastic filmtransport), and sensitive electronic equipment. Applications like these require a static conductivebelt, so that the static charges generated by the belt can be dissipated into the pulleys, and to

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ground. Standard rubber synchronous belts do not meet this requirement, but can be manufacturedin a static conductive construction on a made-to-order basis. Normal belt wear resulting from longterm operation or environmental contamination can influence belt conductivity properties.

In sensitive applications, rubber synchronous belts are preferred over urethane belts sinceurethane belting cannot be produced in a conductive construction.

9.7 Belt Tracking

Lateral tracking characteristics of synchronous belts is a common area of inquiry. While it isnormal for a belt to favor one side of the pulleys while running, it is abnormal for a belt to exertsignificant force against a flange resulting in belt edge wear and potential flange failure. Belttracking is influenced by several factors. In order of significance, discussion about these factors isas follows:

Tensile Cord Twist: Tensile cords are formed into a single twist configuration during theirmanufacture. Synchronous belts made with only single twist tensile cords track laterally with asignificant force. To neutralize this tracking force, tensile cords are produced in right and left handtwist (or "S" and "Z" twist) configurations. Belts made with "S" twist tensile cords track in theopposite direction to those built with "Z" twist cord. Belts made with alternating "S" and "Z" twisttensile cords track with minimal lateral force because the tracking characteristics of the two cordsoffset each other. The content of "S" and "Z" twist tensile cords varies slightly with every belt that isproduced. As a result, every belt has an unprecedented tendency to track in either one direction orthe other. When an application requires a belt to track in one specific direction only, a single twistconstruction is used. See Figures 16 & 17, previously shown, on pages T-12 and T-13.

Angular Misalignment: Angular misalignment, or shaft nonparallelism, cause synchronousbelts to track laterally. The angle of misalignment influences the magnitude and direction of thetracking force. Synchronous belts tend to track "downhill" to a state of lower tension or shortercenter distance.

Belt Width: The potential magnitude of belt tracking force is directly related to belt width.Wide belts tend to track with more force than narrow belts.

Pulley Diameter: Belt operating on small pulley diameters can tend to generate highertracking forces than on large diameters. This is particularly true as the belt width approaches thepulley diameter. Drives with pulley diameters less than the belt width are not generally recommendedbecause belt tracking forces can become excessive.

Belt Length: Because of the way tensile cords are applied on to the belt molds, short beltscan tend to exhibit higher tracking forces than long belts. The helix angle of the tensile corddecreases with increasing belt length.

Gravity: In drive applications with vertical shafts, gravity pulls the belt downward. Themagnitude of this force is minimal with small pitch synchronous belts. Sag in long belt spansshould be avoided by applying adequate belt installation tension.

Torque Loads: Sometimes, while in operation, a synchronous belt will move laterally fromside to side on the pulleys rather than operating in a consistent position. While not generallyconsidered to be a significant concern, one explanation for this is varying torque loads within thedrive. Synchronous belts sometimes track differently with changing loads. There are many potentialreasons for this; the primary cause is related to tensile cord distortion while under pressure againstthe pulleys. Variation in belt tensile loads can also cause changes in framework deflection, and

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angular shaft alignment, resulting in belt movement.

Belt Installation Tension: Belt tracking is sometimes influenced by the level of belt installationtension. The reasons for this are similar to the effect that varying torque loads have on belttracking.

When problems with belt tracking are experienced, each of these potential contributing factorsshould be investigated in the order that they are listed. In most cases, the primary problem willprobably be identified before moving completely through the list.

9.8 Pulley Flanging

Pulley guide flanges are necessary to keep synchronous belts operating on their pulleys. Asdiscussed previously in Section 9.7 on belt tracking, it is normal for synchronous belts to favor oneside of the pulleys when running.

Proper flange design is important in preventing belt edge wear, minimizing noise and preventingthe belt from climbing out of the pulley. Dimensional recommendations for custom-made or moldedflanges are included in tables dealing with these issues.

Proper flange placement is important so that the belt is adequately restrained within its operatingsystem. Because design and layout of small synchronous drives is so diverse, the wide variety offlanging situations potentially encountered cannot easily be covered in a simple set of rules withoutfinding exceptions. Despite this, the following broad flanging guidelines should help the designer inmost cases:

Two Pulley Drives: On simple two pulley drives, either one pulley should be flanged on bothsides, or each pulley should be flanged on opposite sides.

Multi Pulley Drives: On multiple pulley (or serpentine) drives, either every other pulleyshould be flanged on both sides, or every pulley should be flanged on alternating sides around thesystem.

Vertical Shaft Drives: On vertical shaft drives, at least one pulley should be flanged on bothsides, and the remaining pulleys should be flanged on at least the bottom side.

Long Span Lengths: Flanging recommendations for small synchronous drives with long beltspan lengths cannot easily be defined due to the many factors that can affect belt trackingcharacteristics. Belts on drives with long spans (generally 12 times the diameter of the smallerpulley or more) often require more lateral restraint than with short spans. Because of this, it isgenerally a good idea to flange the pulleys on both sides.

Large Pulleys: Flanging large pulleys can be costly. Designers often wish to leave largepulleys unflanged to reduce cost and space. Belts generally tend to require less lateral restraint onlarge pulleys than small and can often perform reliably without flanges. When deciding whether ornot to flange, the previous guidelines should be considered. The groove face width of unflangedpulleys should also be greater than with flanged pulleys. See Table 34, on page T-65 forrecommendations.

Idlers: Flanging of idlers is generally not necessary. Idlers designed to carry lateral sideloads from belt tracking forces can be flanged if needed to provide lateral belt restraint. Idlers usedfor this purpose can be used on the inside or backside of the belts. The previous guidelines shouldalso be considered.

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9.9 Registration

The three primary factors contributing to belt drive registration (or positioning) errors are beltelongation, backlash, and tooth deflection. When evaluating the potential registration capabilities ofa synchronous belt drive, the system must first be determined to be either static or dynamic interms of its registration function and requirements.

Static Registration: A static registration system moves from its initial static position to asecondary static position. During the process, the designer is concerned only with how accuratelyand consistently the drive arrives at its secondary position. He/she is not concerned with anypotential registration errors that occur during transport. Therefore, the primary factor contributing toregistration error in a static registration system is backlash. The effects of belt elongation and toothdeflection do not have any influence on the registration accuracy of this type of system.

Dynamic Registration: A dynamic registration system is required to perform a registeringfunction while in motion with torque loads varying as the system operates. In this case, thedesigner is concerned with the rotational position of the drive pulleys with respect to each other atevery point in time. Therefore, belt elongation, backlash and tooth deflection will all contribute toregistrational inaccuracies.

Further discussion about each of the factors contributing to registration error is as follows:

Belt Elongation: Belt elongation, or stretch, occurs naturally when a belt is placed undertension. The total tension exerted within a belt results from installation, as well as working loads.The amount of belt elongation is a function of the belt tensile modulus, which is influenced by thetype of tensile cord and the belt construction. The standard tensile cord used in rubber synchronousbelts is fiberglass. Fiberglass has a high tensile modulus, is dimensionally stable, and has excellentflex-fatigue characteristics. If a higher tensile modulus is needed, aramid tensile cords can beconsidered, although they are generally used to provide resistance to harsh shock and impulseloads. Aramid tensile cords used in small synchronous belts generally have only a marginallyhigher tensile modulus in comparison to fiberglass. When needed, belt tensile modulus data isavailable from our Application Engineering Department.

Backlash: Backlash in a synchronous belt drive results from clearance between the belt teethand the pulley grooves. This clearance is needed to allow the belt teeth to enter and exit thegrooves smoothly with a minimum of interference. The amount of clearance necessary dependsupon the belt tooth profile. Trapezoidal Timing Belt Drives are known for having relatively littlebacklash. PowerGrip HTD Drives have improved torque carrying capability and resist ratcheting,but have a significant amount of backlash. PowerGrip GT Drives have even further improvedtorque carrying capability, and have as little or less backlash than trapezoidal timing belt drives. Inspecial cases, alterations can be made to drive systems to further decrease backlash. Thesealterations typically result in increased belt wear, increased drive noise and shorter drive life.Contact our Application Engineering Department for additional information.

Tooth Deflection: Tooth deformation in a synchronous belt drive occurs as a torque load isapplied to the system, and individual belt teeth are loaded. The amount of belt tooth deformationdepends upon the amount of torque loading, pulley size, installation tension and belt type. Of thethree primary contributors to registration error, tooth deflection is the most difficult to quantify.Experimentation with a prototype drive system is the best means of obtaining realistic estimationsof belt tooth deflection.

Additional guidelines that may be useful in designing registration critical drive systems are asfollows:

• Select PowerGrip GT or trapezoidal timing belts.

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• Design with large pulleys with more teeth in mesh.• Keep belts tight, and control tension closely.• Design frame/shafting to be rigid under load.• Use high quality machined pulleys to minimize radial runout and lateral wobble.

SECTION 10 BELT TENSIONING

10.1 What Is Proper Installation Tension

One of the benefits of small synchronous belt drives is lower belt pre-tensioning in comparisonto comparable V-belt drives, but proper installation tension is still important in achieving the bestpossible drive performance. In general terms, belt pre-tensioning is needed for proper belt/pulleymeshing to prevent belt ratcheting under peak loading, to compensate for initial belt tension decay,and to prestress the drive framework. The amount of installation tension that is actually needed isinfluenced by the type of application as well as the system design. Some general examples of thisare as follows:

Motion Transfer Drives: Motion transfer drives, by definition, are required to carry extremelylight torque loads. In these applications, belt installation tension is needed only to cause the belt toconform to and mesh properly with the pulleys. The amount of tension necessary for this isreferred to as the minimum tension (Tst). Minimum tensions on a per span basis are included inTable 16, on page T-48. Some motion transfer drives carry very little torque, but have rightregistration requirements. These systems may require additional static (or installation) tension inorder to minimize registration error.

Normal Power Transmission Drives: Normal power transmission drives should be designedin accordance with published torque ratings and a reasonable service factor (between 1.5 and 2.0).In these applications, belt installation tension is needed to allow the belt to maintain proper fit withthe pulleys while under load, and to prevent belt ratcheting under peak loads. For these drives,proper installation tension can be determined using two different approaches. If torque loads areknown and well defined, and an accurate tension value is desired, Equation (10-1) or Equation(10-2) should be used. If the torque loads are not as well defined, and a quick value is desired foruse as a starting point, values from Table 17 can be used. All static tension values are on a perspan basis.

0.812 DQTst = –––––––– + mS 2 (lb) (10-1)

d(For drives with a Service Factor of 1.3 or greater)

1.05 DQTst = –––––––– + mS 2 (lb) (10-2)

d(For drives with a Service Factor less than 1.3)

where: Tst = Static tension per span (lbs)DQ = Driver design torque (lb⋅in)d = Driver pitch diameter (in)S = Belt speed/1000 (ft/min)

where Belt speed = (Driver pitch diameter x Driver rpm)/3.82m = Mass factor from Table 16

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Belt 4 mm 6 mm 9 mm 12 mm 15 mm 20 mm 25 mm2 mm GT3 mm GT5 mm GT

3 mm HTD5 mm HTD

MXLXL

1/8" 3/16" 1/4" 5/16" 3/8" 7/16" 1/2"

2————

22

38—5—

33

41118 913

34

515221218

45

—19271624

56

—25352233

—8

——43—43

—9

Minimum Tst (lbs)Per Span

BeltWidth

Belt m Y

4 mm 6 mm 9 mm12 mm 6 mm 9 mm12 mm15 mm 9 mm15 mm20 mm25 mm 6 mm 9 mm15 mm 9 mm15 mm25 mm

1/8"3/16"1/4"1/4"3/8"

2 mm GT

3 mm GT

5 mm GT

3 mm HTD

5 mm HTD

MXL

XL

0.0260.0390.0580.0770.0770.1200.1500.1900.1700.2800.3800.4700.0680.1020.1700.1630.2720.4530.0030.0040.0050.0100.015

1.372.053.084.103.224.836.458.0614.924.933.241.53.815.719.5214.924.941.51.402.112.813.304.94

1.32.03.04.02.23.34.45.58.4

14.118.723.42.54.37.86.3

12.021.31.01.72.33.25.1

Table 16 Belt Tensioning Force

Registration Drives: Registration drives are required to register, or position accurately.Higher belt installation tensions help in increasing belt tensile modulus as well as in increasingmeshing interference, both reducing backlash. Tension values for these applications should bedetermined experimentally to confirm that desired performance characteristics have been achieved.As a beginning point, use values from Table 17 multiplied by 1.5 to 2.0.

Table 17 Static Belt Tension, Tst (lbs) Per Span – General Values

NOTE: Y = constant used in Equations (10-4) and (10-5).

Most synchronous belt applications often exhibit their own individual operating characteristics.The static installation tensions recommended in this section should serve as a general guideline indetermining the level of tension required. The drive system should be thoroughly tested to confirmthat it performs as intended.

10.2 Making Measurements

Belt installation tension is generally, measured in the following ways:

Force/Deflection: Belt span tension can be measured by deflecting a belt span 1/64" per

Belt

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inch (0.4 mm per 25 mm) of span length at midspan, with a known force (see Figure 20). Thismethod is generally convenient, but not always very accurate, due to difficulty in measuring smalldeflections and forces common in small synchronous drives. The force/deflection method is mosteffective on larger drives with long span lengths. The static (or installation) tension (Tst) can eitherbe calculated from Equation (10-1) or Equation (10-2), or selected from Table 16 or Table 17.The deflection forces can be calculated from Equation (10-4) and Equation (10-5). The spanlength can either be calculated from Equation (10-3), or measured. If the calculated static tensionis less than the minimum Tst values in Table 16, use the minimum values.

–––––––––––––––––––PD – pd 2

t = √ CD2 – (––––––––) (10-3) 2

where: t = Span length (in)CD = Drive center distance (in)PD = Large pitch diameter (in)pd = Small pitch diameter (in)

t Tst + (––) Y

LDeflection force, Min. = –––––––––––– (lbs) (10-4)

16 t

1.1 Tst + (––) Y L

Deflection force, Max. = –––––––––––––– (lbs) (10-5) 16

where: Tst = Static tension (lbs)t = Span length (in)L = Belt pitch length (in)Y = Constant, from Table 16

Shaft Separation: Belt installationtension can be applied directly byexerting a force against either the driveror driven shaft in a simple 2-point drivesystem (see Figure 21). The resultingbelt tension will be as accurate as theforce applied to driver or driven shaft.This method is considerably easier toperform than the force/deflection methodand, in some cases, more accurate.

In order to calculate the requiredshaft separation force, the proper statictension (on a per span basis) shouldfirst be determined as previouslydiscussed. This tension value will bepresent in both belt spans as tension isapplied. The angle of the spans withrespect to the movable shaft should thenbe determined. The belt spans shouldbe considered to be vectors (force withdirection), and be summed into a singletension vector force (see Figure 22).Refer to SECTION 14 BELT PULLAND BEARING LOADS for furtherinstructions on summing vectors.

Fig. 20 Force/Deflection Method

Deflection 1/64" per inch of span

Fig. 21 Shaft Separation Method

Fig. 22 Single Tension Vector Force

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Idler Force: Belt installationtension can also be applied by exertinga force against an idler pulley within thesystem that is used to take up belt slack(see Figure 23). This force can beapplied manually, or with a spring.Either way, the idler should be lockeddown after the appropriate tension hasbeen applied.

Calculating the required force willinvolve a vector analysis as describedabove in the shaft separation section.

Sonic Tension Meter: The SonicTension Meter (Figure 24) is anelectronic device that measures thenatural frequency of a free stationarybelt span and instantly computes thestatic belt tension based upon the beltspan length, belt width, and belt type.This provides accurate and repeatabletension measurements while using anonintrusive procedure (themeasurement process itself doesn'tchange the belt span tension). Ameasurement is made simply byplucking the belt while holding thesensor close to the vibrating belt span.

The unit is about the size of a portable phone (8-1/8" long x 3-3/4" wide x 1-3/8" thick or206mm long x 95mm wide x 35mm thick) so it can be easily handled. The sensor is about 1/2"(13mm) in diameter for use in cramped spaces, and the unit is either battery operated for portabilityor AC operated for production use. The unit measures virtually all types of light power andprecision belts. A gain adjustment allows measurements to be made in environments with highnoise levels. Data can also be collected through an IBM Compatible RS-232 serial port, if desired.For additional details, see the product section of this handbook.

SECTION 11 DRIVE ALIGNMENT

11.1 Angular And Parallel

Drive misalignment is one of the most common sources of drive performance problems.Misaligned drives can exhibit symptoms such as high belt tracking forces, uneven belt tooth wear,high noise levels, and tensile cord failure. The two primary types of drive misalignment are angularand parallel. Discussion about each of these types are as follows:

Angular: Angular misalignmentresults when the drive shafts are notparallel (see Figure 25). As a result,the belt tensile cords are not loadedevenly, resulting in uneven tooth/landpressure and wear. The edge cords onthe high tension side are often

Fig. 23 ldler Forces

Fig. 24 Sonic Tension Meter

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overloaded which may cause an edgecord failure that propagates across theentire belt width. Angular misalignmentoften results in high belt-tracking forcesas well which cause accelerated beltedge wear, sometimes leading to flangefailure or belts tracking off of the pulleys.

Parallel: Parallel misalignmentresults from pulleys being mounted outof line from each other (see Figure 26).Parallel misalignment is generally more of a concern with V-type belts than with synchronous beltsbecause V-type belts run in grooves and are unable to free float on the pulleys. Synchronous beltswill generally free float on the pulleys and essentially self-align themselves as they run. This self-aligning can occur as long as the pulleys have sufficient groove face width beyond the width of thebelts. If not, the belts can become trapped between opposite pulley flanges causing seriousperformance problems. Parallel misalignment is not generally a significant concern with synchronousdrives as long as the belts do not become trapped or pinched between opposite flanges. Forrecommendations on groove face width, see Table 34, on page T-65.

Allowable Misalignment: In order to maximize performance and reliability, synchronousdrives should be aligned closely. This is not, however, always a simple task in a productionenvironment. The maximum allowable misalignment, angular and parallel combined, is 1/4°.

11.2 Practical Tips

Angular misalignment is not always easy to measure or quantify. It is sometimes helpful touse the observed tracking characteristics of a belt, to make a judgment as to the system's relativealignment. Neutral tracking "S" and "Z" synchronous belts generally tend to track "down hill" or to astate of lower tension or shorter center distance when angularly misaligned. This may not alwayshold true since neutral tracking belts naturally tend to ride lightly against either one flange or theother due to numerous factors discussed in the section on belt tracking. This tendency willgenerally hold true with belts that track hard against a flange. In those cases, the shafts will requireadjustment to correct the problem.

Parallel misalignment is not often found to be a problem in synchronous belt drives. Ifclearance is always observable between the belt and all flanges on one side, then parallelmisalignment should not be a concern.

SECTION 12 INSTALLATION AND TAKE-UP

12.1 Installation Allowance

When designing a drive system for a manufactured product, allowance for belt installationmust be built into the system. While specific installation allowances could be published, as they arefor larger industrial belt drives, small synchronous drive applications are generally quite diverse,making it nearly impossible to arrive at values that apply in all cases. When space is at a premium,the necessary installation allowance should be determined experimentally using actual productionparts for the best possible results.

12.2 Belt Installation

During the belt installation process, it is very important that the belt be fully seated in the

Fig. 26 Parallel Misalignment

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pulley grooves before applying final tension. Serpentine drives with multiple pulleys and drives withlarge pulleys are particularly vulnerable to belt tensioning problems resulting from the belt teethbeing only partially engaged in the pulleys during installation. In order to prevent these problems,the belt installation tension should be evenly distributed to all belt spans by rotating the system byhand. After confirming that belt teeth are properly engaged in the pulley grooves, belt tensionshould be rechecked and verified. Failure to do this may result in an under-tensioned conditionwith the potential for belt ratcheting.

12.3 Belt Take-up

Synchronous belt drives generally require little if any retensioning when used in accordancewith proper design procedures. A small amount of belt tension decay can be expected within thefirst several hours of operation. After this time, the belt tension should remain relatively stable.

12.4 Fixed Center Drives

Designers sometimes attempt to design synchronous belt drive systems without any means ofbelt adjustment or take-up. This type of system is called a Fixed Center Drive. While this approachis often viewed as being economical, and is simple for assemblers, it often results in troublesomereliability and performance problems in the long run.

The primary pitfall in a fixed center design approach is failure to consider the effects of systemtolerance accumulation. Belts and pulleys are manufactured with industry accepted productiontolerances. There are limits to the accuracy that the center distance can be maintained on aproduction basis as well. The potential effects of this tolerance accumulation is as follows:

Low Tension:Long Belt with Small Pulleys on a Short Center Distance

High Tension:Short Belt with Large Pulleys on a Long Center Distance

Belt tension in these two cases can vary by a factor of 3 or more with a standard fiberglasstensile cord. This potential variation is great enough to overload bearings and shafting, as well asthe belts themselves. The probability of these extremes occurring is a matter of statistics, buthowever remote the chances may seem, they will occur in a production setting. In power transmissiondrives, the appearance of either extreme is very likely to impact drive system performance in anegative manner.

The most detrimental aspect of fixed center drives is generally the potentially high tensioncondition. This condition can be avoided by adjusting the design center distance. A commonapproach in these designs is to reduce the center distance from the exact calculated value by somesmall fraction. This results in a drive system that is inherently loose, but one that has much lessprobability of yielding excessively high shaft loads. NOTE: This approach should not be used forpower transmission drives since the potentially loose operating conditions could result in acceleratedwear and belt ratcheting, even under nominal loading.

There are times when fixed center drive designs can't be avoided. In these cases, thefollowing recommendations will maximize the probability of success.

1. Do not use a fixed center design for power transmission drives. Consider using a fixedcenter design only for lightly loaded or motion transfer applications.

2. Do not use a fixed center design for drives requiring high motion quality or registrationprecision.

3. When considering a fixed center design, the center distance must be held as accurately aspossible, typically within 0.002" – 0.003" (0.05 mm – 0.08 mm). This accuracy oftenrequires the use of stamped steel framework. Molding processes do not generally havethe capacity to maintain the necessary accuracy.

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4. Pulleys for fixed center systems should be manufactured with a process that is capable ofproducing the required O.D. tolerances accurately enough.

5. The performance capabilities of the drive system should be verified by testing belts producedover their full length tolerance range on drive systems representing the full potential center-distance variation.

SECTION 13 IDLER USAGE

Idlers in synchronous belt drives are commonly used to take up belt slack, apply installationtension or to clear obstructions within a system. While idlers cause additional belt bending,resulting in fatigue, this effect is generally not significant as long as proper design procedures arefollowed. Synchronous belts elongate very little over time, making them relatively maintenancefree. All idlers should be capable of being locked down after being adjusted and should requirelittle additional attention. Specific guidelines and recommendations are given below.

13.1 Inside/Outside

Inside idlers are generally preferred over backside idlers from a belt fatigue standpoint. Bothare commonly used with good success. Inside idlers should be pulleys, but can be flat, if the O.D.is equivalent to the pitch diameter of a 40-groove pulley. Backside idlers should be flat anduncrowned.

13.2 Tight Side/Slack Side

Idlers should be placed on the slack (or nonload-carrying) side, if possible. Their effect on beltfatigue is less on the slack side than on the tight (or load-carrying) side. If spring loaded idlers areused, they should never be placed on the tight side (see Spring Loaded Idlers). Also, note thatdrive direction reversals cause the tight and slack spans to reverse, potentially placing the idler onthe tight side.

13.3 Idler Placement

In synchronous belt drives, idlers can be placed nearly anywhere they are needed. Synchronousdrives are much less sensitive to idler placement and belt wrap angles than V-belt drives. Thedesigner should make sure that at least 6 belt teeth are in mesh on load-carrying pulleys. Forevery tooth in mesh less than this (with a minimum of 2), 20% of the belt torque rating must besubtracted. In order to minimize the potential for belt ratcheting, each loaded pulley in the systemshould also have a wrap angle of at least 60°. If a loaded pulley has less than 6 teeth in mesh and60° of wrap, idlers can often be used to improve this condition. Nonloaded idler pulleys do nothave tooth meshing or wrap angle restriction.

13.4 Spring Loaded Idlers

Using a spring to apply a predetermined force against a tensioning idler to obtain proper beltinstallation tension is acceptable as long as the idler can be locked down after belt installation.

Dynamic spring loaded idlers are generally not recommended for synchronous belt drives. Ifused, spring loaded belt idlers should never be used on the tight (or load-carrying) side. Tight sidetensions vary with the magnitude and type of load carried by the system. High tight side tensionscan overcome the idler spring force allowing the belt to ratchet. In order to prevent this fromoccurring, an excessively high spring force is required. This high spring force can result in highshaft/bearing loads and accelerated belt wear.

If dynamic spring loaded idlers are to be used, they should be used on the slack (or nonload-carrying) side of the drive. Potential drive loading variations in the system will have the leastpossible impact on idler movement due to spring compression with the idler placed in this way. Besure to note that the tight and slack spans shift as the direction of drive rotation reverses. Thiscould place the spring loaded idler on the tight side. In some cases, drive vibration and harmonicproblems may also be encountered with the use of spring loaded idlers.

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13.6 Specifying Shaft Locations In Multipoint Drive Layouts

When collecting geometrical layout data for multiple pulley drive layouts, it is important to usea standard approach that is readily understood and usable for drive design calculations. This is ofparticular importance when the data will be provided to our Application Engineering Department foranalysis.

2-Point DriveWhen working with a simple 2-point drive (driver/driven only) it is sufficient to specify the

desired distance between shaft centers for belt length calculations.

3-Point DriveWhen working with a 3-point drive (driver/driven/idler), X-Y coordinates are desirable. It is

sufficient, however, to specify desired center distances between each of the three shaft centers toform a triangle. In either case, pulley/idler movement details for belt tensioning and take up arealso necessary.

Multi-Point DriveWhen working with a drive system having more

than 3 shafts, the geometrical layout data must becollected in terms of X-Y coordinates for analysis.For those unfamiliar with X-Y coordinates, the X-YCartesian coordinate system is commonly used inmathematical and engineering calculations andutilizes a horizontal and vertical axis as illustrated inFigure 27.

The axes cross at the zero point, or origin.Along the horizontal, or "X" axis, all values to theright of the zero point are positive, and all values tothe left of the zero point are negative. Along thevertical, or "Y" axis, all values above the zero pointare positive, and all values below the zero point arenegative. This is also illustrated in Figure 27.

13.5 Size Recommendations

Inside idler pulleys can be used in the minimum recommended size for each particular beltpitch. Inside flat idlers can be used on the tooth side of synchronous belts as long as they are of adiameter equivalent to the pitch diameter of a 40-groove pulley in the same pitch. Drives withinside flat idlers should be tested, as noise and belt wear may occur. Flat backside idlers should beused with diameters at least 30% larger than the minimum recommended inside pulley size.

Table 18 summarizes our idler size recommendations.

Fig. 27 Cartesian Coordinate System

Minimum InsideFlat Idler O.D.

Minimum BacksideIdler O.D.Minimum

Inside IdlerBelt Type

MXLXL

3 mm HTD5 mm HTD2 mm GT3 mm GT5 mm GT

12 grooves12 grooves12 grooves14 grooves12 grooves12 grooves14 grooves

0.501.000.751.250.500.751.25

1.002.501.502.501.001.502.50

Table 18 Idler Size Recommendations

inch mm inch mm

12.725.419.131.812.719.131.8

25.463.538.163.525.438.163.5

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When identifying a shaft center location, each X-Y coordinate is specified with a measurementin the "X" as well as the "Y" direction. This requires a horizontal and vertical measurement for eachshaft center in order to establish a complete coordinate. Either English or Metric units of measurementmay be used.

A complete coordinate is specified as follows:

(X, Y) (13-1)

where: X = measurement along X-axis (horizontal)Y = measurement along Y-axis (vertical)

In specifying X and Y coordinates for each shaft center, the origin (zero point) must first bechosen as a reference. The driver shaft most often serves this purpose, but any shaft center canbe used. Measurements for all remaining shaft centers must be taken from this origin or referencepoint. The origin is specified as (0, 0).

An example layout of a 5-pointdrive system is illustrated in Figure 28.Here, each of the five shaft centers arelocated and identified on the X-Ycoordinate grid.

When specifying parameters for themovable or adjustable shaft (for beltinstallation and tensioning), the followingapproaches are generally used:

Fixed Location: Specify thenominal shaft location coordinate with amovement direction.

Slotted Location: Specify alocation coordinate for the beginning ofthe slot, and a location coordinate forthe end of the slot along its path of linearmovement.

Pivoted Location: Specify theinitial shaft location coordinate along witha pivot point location coordinate and thepivot radius.

Performing belt length and idlermovement/positioning calculations byhand can be quite difficult and timeconsuming. With a completegeometrical drive description, we canmake the drive design and layoutprocess quite simple for you.

SECTION 14 BELT PULL AND BEARING LOADS

Synchronous belt drives are capable of exerting lower shaft loads than V-belt drives in somecircumstances. If pre-tensioned according to SDP/SI recommendations for a fully loaded steady

Fig. 28 Example of 5-Point Drive System

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state condition, synchronous and V-belt drives will generate comparable shaft loads. If the actualtorque loads are reduced and the level of pre-tension remains the same, they will continue to exertcomparable shaft loads. In some cases, synchronous belts can be pre-tensioned for less than fullloads, under nonsteady state conditions, with reasonable results. Reduced pre-tensioning insynchronous belts can be warranted in a system that operates with uniform loads most of the time,but generates peak loads on an intermittent basis. While V-belt drives require pre-tensioningbased upon peak loads to prevent slippage, synchronous drive pre-tensioning can be based uponlower average loads rather than intermittent peak loads, as long as the belt does not ratchet underthe peak loads. When the higher peak loads are carried by the synchronous drive, the belt will self-generate tension as needed to carry the load. The process of self-tensioning results in the beltteeth riding out of the pulley grooves as the belt enters the driven pulley on the slack side, resultingin increased belt tooth and pulley wear. As long as peak loads occur intermittently and belts do notratchet, reduced installation tension will result in reduced average belt pull without serious detrimentaleffects. Synchronous belts generally require less pretension than V-belts for the same load. Theydo not require additional installation tension for belt wrap less than 180 degrees on loaded pulleysas V-belt drives do. In most cases, these factors contribute to lower static and dynamic shaft loadsin synchronous belt drives.

Designers often wish to calculate how much force a belt drive will exert on the shafting/bearings/framework in order to properly design their system. It is difficult to make accurate belt pullcalculations because factors such as torque load variation, installation tension and pulley runout allhave a significant influence. Estimations, however, can be made as follows:

14.1 Motion Transfer Drives

Motion transfer drives, by definition, do not carry a significant torque load. As a result, the beltpull is dependent only on the installation tension. Because installation tensions are provided on aper span basis, the total belt pull can be calculated by vector addition.

14.2 Power Transmission Drives

Torque load and installation tension both influence the belt pull in power transmission drives.The level of installation tension influences the dynamic tension ratio of the belt spans. The tensionratio is defined as the tight side (or load carrying) tension TT divided by the slack side (or nonloadcarrying) tension TS. Synchronous belt drives are generally pre-tensioned to operate dynamicallyat a 5:1 tension ratio in order to provide the best possible performance. After running for a shorttime, this ratio is known to increase somewhat as the belt runs in and seats with the pulleys,reducing tension. Equations (14-1) and (14-2) can be used to calculate the estimated TT and TS

tensions assuming a 5:1 tension ratio. TT and TS tensions can then be summed into a single vectorforce and direction.

2.5 (Q)TT = –––––– (lb) (14-1)

Pd 0.5 (Q)

TS = –––––– (lb) (14-2) Pd

where: TT = Tight side tension (lbs)TS = Slack side tension (lbs)Q = Torque Load (lb⋅in)Pd = Pitch diameter (in)

If both direction and magnitude of beltpull are required, the vector sum of TT andTS can be found by graphical vector additionas shown in Figure 29. TT and TS vectorsare drawn parallel to the tight and slack sidesat a convenient scale. The magnitude anddirection of the resultant vector, or belt pull,can then be measured graphically. The same

Fig. 29 Belt Pull Vector Diagram

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procedures can be used for finding belt pull on the driven shaft. This method can also be used fordrives using three or more pulleys or idlers.

For two pulley drives, belt pull on the driver and driven shafts is equal but opposite in direction.For drives using idlers, both magnitude and direction may be different. If only the magnitude of thebelt pull is needed in a two pulley drive, use the following procedure:

1. Add TT and TS

2. Using the value of (D – d )/C for thedrive, find the vector sum correctionfactor using Figure 30. Or, use theknown arc of contact on the smallpulley, where: D = large diameter

d = small diameterC = center distance

3. Multiply the sum of TT and TS by thevector sum correction factor to findthe vector sum, or belt pull.

For drives using idlers, either use thegraphical method or contact our ApplicationEngineering Department for assistance.

14.3 Registration Drives

Synchronous belt drives used for purposes of accurate registration or synchronization generallyrequire the use of higher than normal installation tensions (see section on Belt Tensioning). Thesedrives will operate with higher belt pulls than normal power transmission drives. Belt pull values forthese types of applications should be verified experimentally, but can be estimated by adding theinstallation tension in each belt span vectorially.

14.4 Bearing Load Calculations

In order to find actual bearing loads, it is necessary to know the weights of machine componentsand the value of all other forces contributing to the load. However, sometimes it helps to know thebearing load contributed by the belt drive alone. The resulting bearing load due to belt pull can becalculated if both bearing spacing with respect to the pulley center and the belt pull are known. Forapproximate bearing load calculations, machine designers use belt pull and ignore pulley weightforces. If more accurate bearing load calculations are needed, or if the pulley is unusually heavy,the actual shaft load (including pulley weight) should be used.

A. Overhung Pulleys (See Figure 31)

Shaft Load x (a + b)Load at B = ––––––––––––––––– (14-3)

a

Shaft Load x bLoad at A = ––––––––––––– (14-4)

a

B. Pulley Between Bearings (See Figure 32)

Shaft Load x cLoad at D = ––––––––––––– (14-5)

(c + d)

Shaft Load x dLoad at C = ––––––––––––– (14-6)

(c + d)

Fig. 31 Overhung Pulley

Fig. 32 Pulley Between Bearings

Fig. 30 Vector Sum Correction Factor

Pulley

Pulley

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SECTION 15 HANDLING AND STORAGE

The following has been condensed from RMA Bulletin No. IP-3-4: "Storage of PowerTransmission Belts":

Recommendations for proper belt storage is of interest to designers as well as to users.Under favorable storage conditions, high quality belts maintain their performance capabilities andmanufactured dimensions. Good storage conditions and practices will result in the best value frombelt products.

Power transmission belts should ideally be stored in a cool and dry environment. Excessweight against belts resulting in distortion should be avoided. Avoid storing belts in environmentsthat may allow exposure to sunlight, moisture, excessive heat, ozone, or where evaporating solventsor other chemicals are present. Belts have been found to be capable of withstanding storage,without changing significantly, for as long as 8 years at temperatures less than 85° F (30° C) andrelative humidity below 70 percent without direct contact with sunlight.

Proper handling of synchronous belts is also important in preventing damage that couldreduce their performance capabilities. Synchronous belts should never be crimped or tightly bent.Belts should not be bent tighter than the minimum recommended pulley size specified for each beltsection, or pitch. Belt backside bending should be limited to the values specified in Table 18 for aminimum diameter backside idler.

SECTION 16 STANDARDS APPLICABLE TO BELTS

Different belt tooth configurations are shown in Figure 19 and their characteristics are describedin Table 3, both on page T-15. Since synchronous belts are manufactured by several manufacturers,each has established individual standards. Subsequently, the following general standards havebeen published:

1. Specifications by the Rubber Manufacturers Association for Drives using SynchronousBelts.

2. Synchronous Belt Drives – specification by the International Organization for Standardization.

Based on these, as well as standards developed by belt manufacturers, the following informationis presented in this handbook:

Recommended Tension for Length Measurement ........................................Table 19Belt Width Tolerances .................................................................................... Table 20Pitch Length Tolerances ................................................................................Table 21Center Distance Tolerances .......................................................................... Table 22Overall Belt Thickness dimensions ................................................................Table 23Overall Belt Thickness Tolerances ................................................................Table 24

Length MeasurementThe pitch length of a synchronous belt is determined

by placing the belt on a measuring fixture comprisingtwo pulleys of equal diameter, applying tension andmeasuring the center distance between the two pulleys.One of the pulleys is fixed in position, while the other ismovable along a graduated scale.

The fixture is shown schematically in Figure 33.Any pair of equal-diameter pulleys of the proper pitchand manufactured to specifications may be used formeasuring. The measuring tension is given in Table 19. Fig. 33 Length Measuring Fixture

NB = Number ofTeeth of Belt

Np = Number of Groovesof Pulley

CenterDistance

TotalMeasuring

Force

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0 to 33"(0 to 838 mm)

Belt LengthOver 66"

(Over 1676 mm)33.01" to 66"

(839 to 1676 mm)Belt Width

in mm in mm in mm in mm From 0.125 To 0.438 Over 0.438 To 1.500 Over 1.500 To 2.000

From 3 To 11 Over 11 To 38.1 Over 38.1 To 50.8

+0.016–0.031+0.031–0.031+0.031–0.047

+0.016–0.031+0.031–0.047+0.047–0.047

——

+0.031–0.047+0.047–0.063

+0.4–0.8+0.8–0.8+0.8–1.2

+0.4–0.8+0.8–1.2+1.2–1.2

——

+0.8–1.2+1.2–1.6

Table 20 Belt Width Tolerances

In measuring the length of a synchronous belt,the belt should be rotated at least two revolutions toseat it properly and to divide the tension equallybetween the two spans.

The pitch length is calculated by adding the pitchcircumference of one pulley to twice the centerdistance:

Belt Pitch Length = 2 C + 2 ( 1/2 NPulley x Pitch)

Pitch (NBelt – NPulley)C = ––––––––––––––––– 2

where C is the Center Distance expressed in sameunits as the Pitch.

Total Measuring TensionBelt Width Measuring Force

mmin Nlbf 6.4 7.9 9.512.719.125.4

0.250.310.370.500.751.00

36 44 53105180245

81012244055

Table 19 Recommended Tension forLength Measurement

Belt Pitch LengthPermissible Deviation

from Standardmmin mmin

Belt Pitch LengthPermissible Deviation

from Standardmmin mmin

Table 21 Pitch Length Tolerances

From 1778 To 2032 From 2032 To 2286 From 2286 To 2540 From 2540 To 3084 From 3084 To 3556 From 3556 To 4064 From 4064 To 4318 From 4318 To 4572

Up to254

From 254 To 381 From 381 To 508 From 508 To 762 From 762 To 1016 From 1016 To 1270 From 1270 To 1524 From 1524 To 1778

Up to10

From 10 To 15 From 15 To 20 From 20 To 30 From 30 To 40 From 40 To 50 From 50 To 60 From 60 To 70

From 70 To 80 From 80 To 90 From 90 To 100 From 100 To 120 From 120 To 140 From 140 To 160 From 160 To 170 From 170 To 180

±0.40

±0.46

±0.51

±0.61

±0.66

±0.76

±0.81

±0.86

±0.016

±0.018

±0.020

±0.024

±0.026

±0.030

±0.032

±0.034

±0.91

±0.96

±1.02

±1.12

±1.22

±1.32

±1.37

±1.47

±0.036

±0.038

±0.040

±0.044

±0.048

±0.052

±0.054

±0.058

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SECTION 17 STANDARDS APPLICABLE TO PULLEYS AND FLANGES

Pulleys are components manufactured to close tolerances in order to achieve best performanceand long belt life. They are available in finished form or as bar stock which can be used for in-housemanufacture of prototypes or smaller quantities.

For an uninitiated observer, a pulley may appear simply as a component with some trapezoidalor curvilinear grooves. In fact, the efficiency and integrity of a belt drive is closely attributed to thequality of pulleys involved. The pulleys, therefore, should be supplied by qualified and licensedsuppliers. In case of HTD and GT drives, the suppliers must be licensed by the Gates RubberCompany. Stock Drive Products is one of such licensed full line suppliers.

To achieve the reproduction of the correct pulley profile, licensed hobs are used. The followinginspection and design aids are used as well:

Master Profile: A scaled line drawing of the ideal groove profile with tolerance bands plottedon dimensionally stable translucent material. Suitable for groove inspection purposes on an opticalcomparator.

Dimensional Profile Drawing: A line drawing of the ideal groove profile with all arcs and radiidefined. Suitable for mold design.

Digitized Points: A series of X and Y coordinates defining the ideal groove profile. Availablein printed form or on a floppy disk. Suitable for mold design.

Table 22 Center Distance Tolerances

inches mm inches

Center DistanceToleranceBelt Length

Up to 10

Over 10To 15Over 15To 20

Over 20To 30Over 30To 40Over 40To 50

Over 50To 60Over 60To 70Over 70To 80

Over 80To 90Over 90To 100Over 100To 110

Over 110To 120

Up to 254

Over 254To 381Over 381To 508

Over 508To 762Over 762To 1016Over 1016To 1270

Over 1270To 1524Over 1524To 1778Over 1778To 2032

Over 2032To 2286Over 2286To 2540Over 2540To 2794

Over 2794To 3048

±.008

±.009

±.010

±.012

±.013

±.015

±.016

±.017

±.018

±.019

±.020

±.021

±.022

mm

±.20

±.23

±.25

±.30

±.33

±.38

±.41

±.43

±.46

±.48

±.51

±.53

±.56

Table 23 Overall Belt Thickness Dimensions

inches mm

Overall Thickness(ref.)Belt Type Belt Pitch

MXL40 D.P.

XL3 mm HTD5 mm HTD2 mm GT3 mm GT5 mm GT

.080".0816"

.200"3 mm5 mm2 mm3 mm5 mm

.045

.045

.090

.095

.150

.060

.095

.150

1.141.14

2.292.413.811.522.413.81

Table 24 Overall Belt Thickness TolerancesStandard Class 2 Class 1±0.015"±0.38 mm

±0.010"±0.25 mm

±0.005"±0.13 mm

NOTE 1: Belts with pitch lengths greater than 5.5"(140 mm) are furnished with a Class 2grind unless otherwise specified. Beltswith pitch lengths less than 5.5" (140mm) are unground and produced tostandard tolerances.

NOTE 2: A Class 1 grind is available at additionalcost for finished belts only.

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Tolerancing/Inspection Procedure: Atypical pulley groove tolerance band is illustratedin Figure 34. Groove inspection must be madeon an optical comparator at a specifiedmagnification. The actual pulley groove profilemust fit within the specified tolerance bandswithout any sharp transition or undercuts.

17.1 Pulley Tolerances

Stock Drive Products has accepted, as aminimum requirement, the Engineering Standardsrecommended by the Mechanical PowerTransmission Association. The RubberManufacturers Association, Inc. (RMA), the RubberAssociation of Canada and the Gates RubberCompany standards are approved by the TechnicalCommittee of the above associations. Thesestandards are in substantial compliance withstandards developed by the InternationalOrganization for Standardization (ISO).

Requirements of some belt manufacturers exceed those of RMA and ISO. Whenever practicable,Stock Drive Products adheres to those specifications which are more stringent.

The following tables contain the applicable tolerances:

Fig. 34 Typical Pulley GrooveTolerance Band

inches mm inches mm

PulleyO.D. TollerancesPulley O.D.

Up to 1

Over 1To 2Over 2

To 4Over 4To 7Over 7To 12Over 12

To 20

Over 20

+.002–.000+.003

–.000+.004–.000+.005–.000+.006

–.000+.007–.000+.008–.000

+.05–.00+.08

–.00+.10–.00+.13–.00+.15

–.00+.18–.00+.20–.00

Up to 25.4

Over 25.4To 50.8Over 50.8

To 101.6Over 101.6To 177.8Over 177.8To 304.8Over 304.8

To 508.0

Over 508.0

Table 25 Pulley O.D. Tolerances

inches mm inches mm

Total EccentricityTotal Indicator ReadingOutside Diameter

Up to 2

Over 2To 4Over 4

To 8

Over 8

0.0025

0.003

0.004

.0005"/inchO.D. > 8"

Table 26 Pulley Eccentricity

Up to 50

Over 50To 100Over 100

To 200

Over 200

0.06

0.08

0.10

.013/mm O.D.O.D.> 200mm

(may not exceedface diameter tolerance)

The following definitions are being used when considering quality of pulleys:

Eccentricity: The allowable amount of radial run out from the pulley bore to the O.D. isshown in Table 26.

Helix Angle: Grooves should be parallel to the axis of the bore within 0.001" per inch (0.025mm per 25.4 mm) of pulley groove face width.

Draft: The maximum permissible draft on the groove form is 0.001" per inch (0.025 mm per25.4 mm) of face width and must not exceed the O.D. tolerance.

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Parallelism: The bore of the pulleyis to be perpendicular to the verticalfaces of the pulley within 0.001" per inch(0.025 mm per 25.4 mm) of diameterwith a maximum of 0.020" (0.51 mm)total indicator reading.

Pitch Accuracy: Adequate pitchto pitch accuracy is generally moredifficult to achieve with molded pulleysthan with machined pulleys.Recommended tolerances are listed inTable 28.

Balancing: Balancing is often notrequired on machined metal pulleys. Allpulleys should be statically balanced to1/8 oz (3.5 grams) in all sizes. Drivesexceeding 6500 ft/min (33m/s) mayrequire special materials, and should bedynamically balanced to 1/4 oz⋅in (1.78N⋅mm).

Production pulleys should be madeas closely to these tolerances aspossible in order to maximize driveperformance.

In addition to the Tables 26, 27and 28 which define the tolerancesrelated to pulleys manufactured by SDP/SI, Tables 29 through 32 are given forreference only, as published by ISO(International Organization forStandardization) and RMA (RubberManufacturers Association).

Table 28 Pulley Pitch Accuracy

in mm

To 1

1 to 2

2 to 3

3 up

Bore

Table 27 Bore Tolerance for Pulleys

in mm

Up to 1.0

Over 1.0

To 2.0Over 2.0To 4.0Over 4.0To 7.0Over 7.0

To 12.0Over 12.0To 20.0

Over 20.0

Bore

Up to 25.4

Over 25.4

To 50.8Over 50.8To 101.6Over 101.6To 177.8Over 177.8

To 304.8Over 304.8To 508.0

Over 508.0

* Over 90°

in mm+.0010

–.0000+.0015–.0000+.0020–.0000+.0025

–.0000

+0.025

– 0.000+0.038– 0.000+0.051– 0.000+0.064

– 0.000

Bore Tolerance

in mmPitch to Pitch Accumulative*

±.001

±.001

±.001

±.001

±.001

±.001

±.001

±0.025

±0.025

±0.025

±0.025

±0.025

±0.025

±0.025

in mm

±.001

±.001

±.001

±.001

±.001

±.001

±.001

±0.025

±0.025

±0.025

±0.025

±0.025

±0.025

±0.025

To 2.54

25.4 to 50.8

50.8 to 76.2

76.2 up

Outside Diameter Range Total Indicator Reading (max.)

in mm in mm

≤ 4.000

> 4.000 … ≤ 10.000

> 10.000

≤ 101.60

> 101.60 … ≤ 254.00

> 254.00

.004

.001/in of O.D.

.010 + .0005/in of O.D.over 10.000"

0.10

0.001/mm of O.D.

0.25 + 0.0005/mm of O.D.over 254.00 mm

Outside Diameter Range Total Indicator Reading (max.)

in mm in mm

≤ 8.000

> 8.000

≤ 203.20

> 203.20

.005

.005 + .0005/in of O.D.over 8.000

0.13

0.13 + 0.0005/mm of O.D.over 203.20 mm

Table 29 ISO Axial Pulley Runout

Table 30 ISO Radial Pulley Runout

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Outside Diameter Tolerances

in mm in mm

≤ 1.000

> 1.000 … ≤ 2.000

> 2.000 … ≤ 4.000

> 4.000 … ≤ 7.000

> 7.000 … ≤ 12.000

> 12.000 … ≤ 20.000

> 20.000

≤ 25.40

> 25.40 … ≤ 50.80

> 50.80 … ≤ 101.60

> 101.60 … ≤ 177.80

> 177.80 … ≤ 304.80

> 304.80 … ≤ 508.00

> 508.00

+.002 /–.000

+.003 /–.000

+.004 /–.000

+.005 /–.000

+.006 /–.000

+.007 /–.000

+.008 /–.000

+0.05 / 0

+0.08 / 0

+0.10 / 0

+0.13 / 0

+0.15 / 0

+0.18 / 0

+0.20 / 0

Table 31 ISO Pulley O.D. Tolerances

Up thru.75 (19)

Over .75(19)

to andincluding1.00 (25.4)

Over 1.00(25.4)to and

including1.25 (31.8)

Over 1.25(31.8)to and

including1.50 (38.1)

Over 1.50(38.1)to and

including2.00 (50.8)

Over 2.00(50.8)to and

including2.50 (63.5)

Over 2.50(63.5)to and

including3.00 (76.2)

Length

+.0015+.0005+0.038( )+0.013

+.0015+.0005+0.038( )+0.013

+.0015+.0005+0.038( )+0.013

+.0015+.0005+0.038( )+0.013

+.0015+.0005+0.038( )+0.013

+.0015+.0005+0.038( )+0.013

+.0015+.0005+0.038( )+0.013

+.0015+.0005+0.038( )+0.013

+.0020+.0005+0.051( )+0.013

+.0015+.0005+0.038( )+0.013

+.0015+.0005+0.038( )+0.013

+.0015+.0005+0.038( )+0.013

+.0020+.0005+0.051( )+0.013

+.0020+.0005+0.051( )+0.013

+.0015+.0005+0.038( )+0.013

+.0020+.0005+0.051( )+0.013

+.0020+.0010+0.051( )+0.025

+.0025+.0010+0.064( )+0.025

+.0025+.0010+0.064( )+0.025

+.0020+.0005+0.051( )+0.013

+.0020+.0010+0.051( )+0.025

+.0025+.0010+0.064( )+0.025

+.0025+.0010+0.064( )+0.025

+.0020+.0005+0.051( )+0.013

+.0020+.0010+0.051( )+0.025

+.0025+.0010+0.064( )+0.025

+.0025+.0010+0.064( )+0.025

Up thru0.50 (12.7)

Over 0.50(12.7)to and

including1.00 (25.4)

Over 1.00(25.4)to and

including1.50 (38.1)

Over 1.50(38.1)to and

including2.00 (50.8)

Over 2.00(50.8)to and

including2.50 (63.5)

Diameterof Bore Tolerances

Table 32 RMA Pulley Bore Tolerances

NOTE: Dimensions in ( ) are in mm, all others are in inches

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17.2 Pulley Materials

There is a wide variety of materials and manufacturing processes available for the productionof synchronous belt pulleys. In selecting an appropriate material and production process, thedesigner should consider dimensional accuracy, material strength, durability and production quantity.Some broad guidelines and recommendations are as follows:

1. MachiningExcellent dimensional accuracy. Economical for low to moderate production quantities.

Typical materials:Steel – Excellent Wear Resistance.Aluminum – Good Wear Resistance; pulleys for power transmission drives should be

hard anodized.

2. Powdered Metal and Die CastingGood dimensional accuracy. Economical for moderate to high production quantities.

Typical materials:Sintered Iron – Excellent Wear Resistance.Sintered Aluminum – Good Wear Resistance; Light Weight and Corrosion Resistant.Zinc Die Cast – Good Wear Resistance.

3. Plastic MoldingGood dimensional accuracy. Economical for high production quantities. Best suited for light

to moderate torque loads. Fiber loading improves overall material strength and dimensional stability.However, increased belt wear can result from the presence of sharp abrasive fiber ends on thefinished surface.

Assistance for total drive system design is available. Please contact our Application EngineeringDepartment.

17.3 Flange Design And Face Width Guidelines

Figure 35 illustrates the expressions used in flange and pulley design. Tables 33 and 34pertain to flange dimensions and pulley face widths respectively.

Fig. 35 Expressions Used in Flange and Pulley Design

Face Width Face Width

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17.4 Guidelines For PowerGrip GT Flange Design

In some instances, special pulleys are used whch are made from pulley stock. The followingguidelines are given to establish the design parameters for flanges which would fit these specialpulleys. If possible, standard available flanges should be used to avoid tooling charges associatedwith production of special sized flanges.

Table 33 Nominal Flange Dimensions for Molding,Sintering, Casting, etc.

Table 34 Additional Amount of Face WidthRecommended over Nominal Belt Width*

inches mm inches mmMinimum Flange Height Nominal Flange HeightBelt

Type

MXLXL

2 mm GT3 mm GT & HTD5 mm GT & HTD

0.0400.0600.0430.0670.091

——

1.101.702.20

0.0500.0800.0590.0980.150

——

1.502.503.80

inches mm inches mmMinimum Flange Height Nominal Flange HeightBelt

Type

MXLXL

2 mm GT3 mm GT & HTD

5 mm GT & HTD

+0.125+0.190+0.118+0.157

+0.197

——

+3.00+4.00

+5.00

+0.040+0.060+0.039+0.049

+0.059

——

+1.00+1.25

+1.50* Add Table Values to Nominal Belt Width for Nominal Face Width

Steps:1. Determine pulley size and finished O.D. (See Tables 12 through 14 on pages T-32 thru T-37).2. Determine root diameter (Root Diameter = Finished O.D. – 2 x Nominal Groove Depth). See

Figure 19, page T-15.3. Determine maximum flange seat diameter

(Maximum Flange Seat Diameter = Root Diameter – Pitch Factor).4. Select flange with inside diameter less than maximum flange seat diameter (see available

flange sizes in the product section).5. Determine flange seat diameter (Flange Seat Diameter = Flange I.D. +.000" –.003")6. Determine flange seat width (Flange Seat Width = Flange Gauge + .020" ±.005"; see

available flange sizes).7. Flanges can be rolled, staked or punched on.

Figure 36 Terms Used for Timing Pulley Flange Design

Nominal PowerGrip GTGroove Depths

2 mm — .030" (0.76 mm)3 mm — .045" (1.14 mm)5 mm — .076" (1.93 mm)

PowerGrip GT Pitch Factors

2 mm — .016" (0.41 mm)3 mm — .050" (1.27 mm)5 mm — .070" (1.78 mm)

Page 64: Timing belts

T-66

SECTION 18 DOUBLE SIDED TWIN POWER BELT TOLERANCES

This type of belt was introduced briefly in Section 5.1, page T-10. As previously described,this type of belt has teeth on both sides to provide synchronization from both driving surfaces. Thisspecial feature makes possible unique drive designs, such as multipoint drives, rotation reversalwith one belt, serpentine drives, etc. It may also provide solutions to other difficult design problems.

Twin Power Belts are similar in construction to regular synchronous belts, including nylon-faced teeth on both sides. This construction uses essentially the same design parameters asstandard synchronous belts. Their torque ratings are the same as conventional PowerGrip Belts ofidentical pitch and width.

Twin Power Belts are available in trapezoidal configurations from stock and HTD configurationson a made-to-order basis in lengths from 15" (381mm) through 180" (4572mm).

Twin Power ConstructionTensile members of the PowerGrip Twin

Power Belt are helically-wound fiberglass cordsproviding the same load-carrying capacity as singlesided PowerGrip belts. The body is Neoprenerubber providing oil and weather resistance andprotection for the fiberglass cords. Both sides ofthe belt have a specially treated nylon tooth facingthat provides a tough wear-resistant surface withminimal friction.

Twin Power TolerancesSince Twin Power Belts are manufactured

and cut to the required width by the same methodas standard PowerGrip belts, the samemanufacturing tolerances apply, except for thethickness and center distance tolerances listed inTables 35 and 36.

Overall thickness, opposing teeth symmetryand pitch line symmetry are closely controlledduring Twin Power Belt manufacture.

Specifying Twin Power BeltsThe available Twin Power Belts and other

double sided belts from stock can be found fromthe Timing Belt Locator Chart, on page 1-2 of theproduct section.

Twin Power Drive SelectionTwin Power Belts can transmit 100% of their

maximum rated load from either side of the belt or incombination where the sum of the loads exerted onboth sides does not exceed the maximum rating ofthe belt. For example, a Twin Power Belt rated at 6lb⋅in could be used with 50% of the maximum ratedon one side, and 50% on the other; or 90% on oneside, and 10% on the other.

BeltXL (.200")3 mm HTD5 mm HTD

Table 35 Belt Thickness Tolerances

Fig. 37 Twin Power Belt Tolerances

T (in).120 ± .007.126 ± .006.209 ± .007

W (in) Ref..020.030.045

15 to 2020.01 to 3030.01 to 4040.01 to 5050.01 to 6060.01 to 70

over 70

± .020± .024± .026± .030± .032± .034

To be specified

Table 36 Center Distance Tolerances

Fig. 38 Twin Power Belt Application

Belt Length(in)

Center DistanceTolerances (in)

Page 65: Timing belts

T-67

Drive selection procedures for drives using Twin Power Belts are much the same as for drivesusing conventional belting. Refer to the appropriate product and engineering sections in thiscatalog for drive torque ratings, engineering information, pulley details, belt tension recommendations,etc.

Some manufacturers, however, are producing double sided belts which have nylon faced teethon one side only. For those belts, the limitations given in Section 5.1, page T-10 apply.

SECTION 19 LONG LENGTH TIMING BELT STOCK SPECIFICATIONS

Brief mention of this type of belt was given in Section 5.2, page T-10. As previously indicated,long length belting is produced in spiral form. Spiral cut belting is produced from a belt sleeve bymoving the slitter laterally while the belt sleeve is rotating.

The resulting belting does not have continuous tensile cords, and the teeth are not perfectlyperpendicular to the longitudinal axis of the belt. As long as the belt width is narrow, theseproperties have been found to contribute little if any detrimental effects to belt performance. Themaximum belt width available using this process is 1/2" (12 mm). Tensile modulus and strengthare equivalent to conventional endless and long length belting.

This innovative prod-uct is available in all typesof PowerGrip belting in allpitches. Reciprocating car-riage drives requiring theuse of higher performancecurvilinear tooth belt prod-ucts in long length form cannow be easily handled.

This type of belt iscalled belt stock, and itsavailability from stock is in-dicated on the Timing BeltLocator Chart, on page 1-2, at the beginning of thebelt product section.

Drive Selection WithPowerGrip Long-Length BeltingDrive selection proce-

dures for drives usingLong-Length Belting aremuch the same as fordrives using conventionalendless belting. Refer tothe appropriate productand engineering sections inthis catalog for drive torqueratings, engineering infor-mation, pulley details, belt tension recommendations etc. Table 37 includes rated belt workingtension data, for those applications for which it could be helpful, as well as maximum lengthavailable in each pitch. For drive design selection assistance with belt stock, contact our Applica-tion Engineering Department.

BeltType

StockWidth

MXL (.080")

5 mm HTD

5 mm GT

1/83/161/43/81/43/81/21/23/41

.236

.354

.984

.236

.354

.512

.984

.236

.354

.472

.236

.354

.472

.354

.472

Table 37 PowerGrip Long-Length Belting Specifications

XL (.200")

L (.375")

3 mm HTD

2 mm GT

3 mm GT

in mm

Rated WorkingTension, Ta

MaximumAvailable Length

3 4.5

6 9.5

6 9.5

13131925 6 925 6 91325 6 912 6 912 912

1.8 3.2

5 8 7 11 16 24 39 55 11 18 60 18 30 42100 6 9 12 27 40 54 56 75

lb N 8 14 22 35 31 49 71106173245 49 80267 80133187449 27 40 53120178240249334

65 65450300350250150100100100450290100250275200100250170125375250180250180

ft m 19 19150 90120 80 50 30 30 30150 97 30 80 92 60 30 80 57 42125 80 60 80 60

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T-68

SECTION 20 COMPANION CD-ROM — BRIEF DESCRIPTION

A companion CD-ROM is made available in conjunction with the publication of Handbook D260. Itactually represents a complete computerized catalog containing all the product information presented inthis book. In addition, it provides computerized Drive Ratio and Center Distance calculations. TheCenter Distance Designer program on the CD-ROM computes belt lengths for various center distancesand checks for the number of teeth in mesh for both pulleys. It calculates pulley drive ratios and theminimal center distance for a designated pulley pair.

It searches and retrieves all pulleys and belts shown in the Handbook that fit within thecustomer criteria. Once the design is completed, the part numbers can be instantly retrieved fromthe database with each part number linked to an electronic catalog page which is viewable and canbe printed.

The CD-ROM is presented in an interactive format with the navigator program residing on theCD itself. The user can design a drive in a most efficient manner since the program describedabove presents available alternatives as well as direct reference to catalog page numbers and partnumbers involved.

Included with the CD-ROM is a short manual introducing the user step-by-step to the sequenceof the operations of this disc.

It is assumed, however, that not all users of this Handbook have access to a computer.Therefore, the Drive Ratio and Center Distance Tables are presented in this Handbook also, inprinted format.

SECTION 21 DRIVE RATIO TABLES

In the design of belt drives, we usually know the speed ratio (transmission ratio) and we needto determine pulley sizes, center distance and belt length. These quantities are shown in Figure39, for an open (uncrossed) belt.

The Drive Ratio Tables (Table 38, starting on page T-70) are designed to facilitate thedetermination of these quantities. They list the following information:

N1/N2 = the transmission ratio obtained when the larger pulley (N1 teeth) is the input andsmaller pulley (N2 teeth) is the output. Given to 3 decimal places.

N2/N1 = the transmission ratio obtained when the larger pulley (N1 teeth) is the output andthe smaller pulley (N2 teeth) is the input. Given to 3 decimal places.(Note that N1/N2 is the reciprocal of N2/N1)

N1 = number of teeth on larger pulley.N2 = number of teeth on smaller pulley.N1 – N2 = difference between number of teeth on larger and smaller pulleys. This number is

useful in center-distance determination.C MIN = The minimum center distance between pulleys for a belt of unit pitch. If the pitch

is denoted by p, the actual minimum center distance is a product of C MIN and p.The minimum center distance is determined from the condition that at the minimumcenter distance, the pitch circles of the pulleys can be assumed to touch. Thiswill generally give a satisfactory approximation to the practical minimum centerdistance. The table is based on the equation:

N1 + N2C MIN = –––––––– x Belt Pitch (21-1)

2πAt the beginning of the table, a list of standard pulley sizes is shown. The smallest pulley has

10 teeth and the largest, 156 teeth. A standard size will be the most economical. If a nonstandardsize is needed, however, please contact Stock Drive Products for assistance.

Page 67: Timing belts

T-69

N1/N21.067

N2/N10.938

N11632

N21530

N1/N22.250

2.273

N2/N10.444

0.440

N1367225

N1 – N212

C MIN4.9349.868

N2163211

N1 – N2204014

The use of the tables is best illustrated by means of examples.

Example 1: For a transmission ratio of 1.067, find the number of teeth of the pulleys and theminimum center distance for a belt of 5 mm pitch.

When the transmission ratio is greater than unity, the larger pulley is the input and the smallerpulley is the output. That is to say, the transmission ratio is equal to N1/N2. The table is organizedin order of increasing values of N1/N2 and decreasing values of N2/N1. Referring to the table atthis value of N1/N2, we find the following entries:

Fig. 39 Belt Nomenclature

Hence, there are 2 different pulley combinations for the given transmission ratio of 1.067. For eachof these, the minimum center distance is 5 x (C MIN) in mm. If the smaller pulley were driving, thetransmission ratio would have been 0.938. The quantity (N1 – N2) is needed in center-distancecalculations, as described in the next section.

Example 2: Given a transmission ratio of 0.680, determine the pulley sizes.Since the transmission ratio is less than one, the smaller pulley is the input and the transmission

ratio is given by N2/N1 = 0.680. Looking up this ratio in the table, we find N1 = 25, N2 = 17,N1 – N2 = 8. In this case, only one pulley combination is available.

Example 3: Given a driving pulley of 48 teeth and a driven pulley of 19 teeth, find theminimum center distance for a belt pitch of 3 mm.

The transmission ratio is N1/N2 = 48/19 = 2.526. Looking up this ratio in the table, we findC MIN = 10.663. The minimum center distance, therefore, is given by 3 x 10.663 or 31.989 mm.

Example 4: Given a transmission ratio of 2.258, find the pulley sizes.Looking through the table, there is no entry at this value of the transmission ratio. The nearest

entries are:

Page 68: Timing belts

T-70

Since the difference between the desired ratio and the nearest available ratios is only about0.008, it is likely that the 2.250 or 2.273 ratios will be acceptable. If this is not the case, however,the design may require review, or a nonstandard pulley combination may be considered.

Table 38

Definition:

Drive Ratio (Transmission Ratio) is the ratio of number of teeth of the input andoutput pulleys. If the input pulley is larger than the output, the Drive Ratio will belarger than one and we have a step-up drive. If the input pulley is smaller than theoutput pulley, the Drive Ratio will be smaller than one and we have a step-downdrive.

Nomenclature Used:

N1 = Number of teeth of large pulleyN2 = Number of teeth of small pulleyN1/N2 = Step-up Drive RatioN2/N1 = Step-down Drive RatioN1 – N2 = Pulley tooth differential needed for Table 39 – Center Distance Factor

TableC MIN = Minimum center distance for particular pulley combination expressed

in belt pitches

Pulley Sizes Included:

10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 24, 25,28, 30, 32, 36, 40, 48, 60, 72, 84, 96, 120, 156

Note:

These pulley sizes reflect the preferred sizes per ISO Standard 5294 for synchronousbelt drives – Pulleys (First edition – 1979-07-15). Many other sizes are offered inthis catalog. The availability of stock sizes varies depending on the particular choiceof pitch, material and configuration. Nonstandard sizes are available as custommade specials. Please submit your requirement for us to quote.

Continued on the next page

Drive Ratio Tables

Page 69: Timing belts

T-71

1.000

1.0421.0531.0561.0591.0631.067

1.071

1.0771.0831.091

1.100

1.111

1.118

1.000

0.9600.9500.9470.9440.9410.938

0.933

0.9290.9230.917

0.909

0.900

0.895

101112131415161718192022242528303236404860728496

120156252019181716321530141312241122204019

101112131415161718192022242528303236404860728496

120156241918171615301428131211221020183617

00000000000000000000000000111111212111212242

3.1833.5013.8204.1384.4564.7755.0935.4115.7306.0486.3667.0037.6397.9588.9139.549

10.18611.45912.73215.27919.09922.91826.73830.55838.19749.6567.7996.2075.8895.5705.2524.9349.8684.6159.2314.2973.9793.6617.3213.3426.6856.048

12.0965.730

1.1201.125

1.1331.1361.143

1.1541.1581.167

1.1761.1821.1881.200

1.2141.2221.2311.250

1.2631.2671.273

1.2801.286

1.2941.300

1.308

0.8930.889

0.8820.8800.875

0.8670.8640.857

0.8500.8460.8420.833

0.8240.8180.8130.800

0.7920.7890.786

0.7810.778

0.7730.769

0.765

2818361725163296152214288420131912182430364872172216152025304060

120241914283218362213

15617

251632152214288413191224721711161015202530406014181312162024324896191511222514281710

12013

3242324

122324

12323234568

1234334568

1224543674853

364

8.4355.411

10.8235.0937.4804.7759.549

28.6484.4566.5254.1388.276

24.8285.8893.8205.5703.5015.2527.0038.754

10.50414.00621.0084.9346.3664.6154.2975.7307.1628.594

11.45917.18934.3776.8445.4113.9797.9589.0725.093

10.1866.2073.661

43.9274.775

N1/N2 N2/N1 N1 N2 N1-N2 C MIN N1/N2 N2/N1 N1 N2 N1-N2 C MIN

Table 38 (Cont.)

Continued on the next page

Drive Ratio Tables

Page 70: Timing belts

T-72

1.3161.333

1.3571.364

1.3751.3851.3891.400

1.4121.4171.429

1.4401.455

1.4621.4671.4711.4741.500

1.5381.5451.5561.5631.5711.5791.583

0.7600.750

0.7370.733

0.7270.7220.7200.714

0.7080.7060.700

0.6940.688

0.6840.6820.6800.6790.667

0.6500.6470.6430.6400.6360.6330.632

251620243240489619153022182514288424172040

12036163219222528151824303648607220172825223019

1912151824303672141122161318102060171214288425112213151719101216202432404813111816141912

64568

10122454865748

24756

1236115

106789568

101216202476

1098

117

7.0034.4565.5706.6858.913

11.14113.36926.7385.2524.1388.2766.0484.9346.8443.8207.639

22.9186.5254.6155.411

10.82332.4689.7084.2978.5945.0935.8896.6857.4803.9794.7756.3667.9589.549

12.73215.91519.0995.2524.4567.3216.5255.7307.7994.934

4.1386.2078.276

10.34512.41424.82840.1074.6159.2317.1625.0936.3667.639

10.18615.27930.5588.1175.5704.2976.048

12.0964.7757.003

21.0087.4807.9586.2074.4568.913

17.8254.9349.8685.4115.889

38.1976.8447.321

14.6427.7998.7544.615

11.6186.0484.775

69

12151836607

14118

10121624481397

10208

12361314118

16329

1810117213142815179

231210

1015202530609611221712151824367219131014281116481718141020401122121384151632171910251310

162432404896

1561836282025304060

120322217244819288430322518367220402224

156283060323619482520

0.625

0.6150.611

0.6070.600

0.5940.5910.5880.583

0.5790.571

0.5670.5630.5600.556

0.550

0.5450.5420.5380.5360.533

0.5310.5280.5260.5210.5200.500

1.600

1.6251.636

1.6471.667

1.6841.6921.7001.714

1.7271.750

1.7651.7781.7861.800

1.818

1.8331.8461.8571.8671.875

1.8821.8951.9001.9201.9232.000

N1/N2 N2/N1 N1 N2 N1-N2 C MIN N1/N2 N2/N1 N1 N2 N1-N2 C MIN

Continued on the next page

Table 38 (Cont.)

Drive Ratio Tables

Page 71: Timing belts

T-73

2.000

2.0832.1002.1052.1182.1332.1432.1432.1542.1672.182

2.2002.2222.250

2.2732.2862.3082.333

2.3532.400

2.4622.500

0.500

0.4800.4760.4750.4720.4690.4670.4670.4640.4620.458

0.4550.4500.444

0.4400.4380.4330.429

0.4250.417

0.4060.400

2224283032364048607296

1202584403632306028

1562448224036722532302884402436486072963225304060

1112141516182024303648601240191715142813721122101816321114131236171015202530401310121624

1112141516182024303648601344211917163215841326122220401418171648231421283542561915182436

5.2525.7306.6857.1627.6398.5949.549

11.45914.32417.18922.91828.6485.889

19.7359.3908.4357.4807.003

14.0066.525

36.2875.570

11.1415.0939.2318.276

16.5525.7307.3216.8446.366

19.0999.0725.4118.117

10.82313.52816.23421.6457.1625.5706.6858.913

13.369

26.73810.6636.2077.958

15.91534.37718.4627.0038.754

10.50421.0086.525

13.0517.7996.048

18.14410.3458.594

15.4386.8446.3667.639

10.18612.73215.27917.82520.37225.4658.435

12.5736.685

10.02720.05432.4687.480

14.9618.276

12.41424.82817.3489.868

19.73517.18912.255

722917224496522025306019382318543126472120243240485664802741223366

10825502842845934686043

4819111428603212151836112213103017142511101216202428324013191015304811221218362514282417

12048283672

156843240489630603628844840723230364860728496

1204060324896

15636724060

1208448968460

0.4000.3960.3930.389

0.3850.3810.375

0.367

0.3610.357

0.3540.3500.3470.3440.333

0.3250.3170.313

0.3080.306

0.300

0.2980.292

0.2860.283

2.5002.5262.5452.571

2.6002.6252.667

2.727

2.7692.800

2.8242.8572.8802.9093.000

3.0773.1583.200

3.2503.273

3.333

3.3603.429

3.5003.529

N1/N2 N2/N1 N1 N2 N1-N2 C MIN N1/N2 N2/N1 N1 N2 N1-N2 C MIN

Continued on the next page

Table 38 (Cont.)

Drive Ratio Tables

Page 72: Timing belts

T-74

3.600

3.6363.6923.750

3.7893.8183.8403.9004.000

4.2004.2354.286

4.3334.364

4.4214.5004.6154.6674.800

4.8754.9415.000

5.0535.1435.2005.2505.3335.455

5.5385.571

0.278

0.2750.2710.267

0.2640.2620.2600.2560.250

0.2380.2360.233

0.2310.229

0.2260.2220.2170.2140.208

0.2050.2020.200

0.1980.1940.1920.1900.1880.183

0.1810.179

3672404860

120728496

1564048607296

120847260

120156489684726084487296

1201568460

1209672

156849660

12072

156

1020111316321922254010121518243020171428361122191613181015202532171224191430161811221328

265229354488536271

11630364554729064554692

12037746556476638577695

1246748967758

1266878499859

128

7.32114.642 8.117 9.70812.09624.19214.48316.87019.25831.194 7.958 9.54911.93714.32419.09923.87316.55214.16511.77723.55530.558 9.39018.78016.39314.00611.61816.234 9.23113.84618.46223.07729.92116.07511.45922.91818.30313.68729.60315.91518.14411.30022.60013.52829.285

15.75617.98511.14113.36915.59717.82522.28228.80722.12317.66615.43828.64813.21021.96317.50715.27921.80428.33013.05117.34821.64515.12028.01117.18921.48627.85214.96121.32727.69317.03027.53421.16816.87027.37521.00827.21520.84927.05620.69026.89726.73826.57926.420

697950607080

100131101

8171

13261

1028272

103134

6283

10473

13684

105137

74106138

85139107

86140108141109142110143144145146

15171012141620251915132411181412172210131611201215191014181117131016121511141013121110

849660728496

120156120

9684

15672

1209684

120156

7296

12084

15696

120156

84120156

96156120

96156120156120156120156156156156

0.1790.1770.167

0.1600.1580.1560.1550.1540.1530.1500.1460.1430.1420.1410.1390.1350.1330.1310.1280.125

0.1220.1190.1170.1150.1150.1090.1080.1040.1030.1000.0960.0920.0900.083

0.0770.0710.064

5.6005.6476.000

6.2406.3166.4006.4626.5006.5456.6676.8577.0007.0597.0917.2007.3857.5007.6367.8008.000

8.2118.4008.5718.6678.7279.1769.2319.6009.750

10.00010.40010.90911.14312.000

13.00014.18215.600

N1/N2 N2/N1 N1 N2 N1-N2 C MIN N1/N2 N2/N1 N1 N2 N1-N2 C MIN

Table 38 (Cont.)

Drive Ratio Tables

Page 73: Timing belts

T-75

SECTION 22 CENTER DISTANCE FORMULAS

22.1 Nomenclature And Basic Equations

Figure 40 illustrates the notation involved.The following nomenclature is used:

C = Center Distance (in)L = Belt Length (in) = p⋅NBp = Pitch of Belt (in)NB = Number of Teeth on belt = L/pN1 = Number of Teeth (grooves) on larger pulleyN2 = Number of Teeth (grooves) on smaller pulleyφ = one half angle of wrap on smaller pulley (radians)θ = π/2 – φ = angle between straight portion of belt and line of centers (radians)R1 = Pitch Radius of larger pulley (in) = (N1) p/2πR2 = Pitch Radius of smaller pulley (in) = (N2) p/2ππ = 3.14159 (ratio of circumference to diameter of circle)

Figure 40 Belt Geometry

The basic equation for the determination of center distance is:

2C sinφ = L – π(R1 + R2) – (π – 2φ) (R1 – R2) (22-1)

where C cosφ = R1 – R2 (22-2)

These equations can be combined in different ways to yield various equations for thedetermination of center distance. We have found the formulations which follow useful.

22.2 Exact Center Distance Determination – Unequal Pulleys

The exact equation is as follows:

C = (1/2)p [(NB – N1) + k(N1 – N2)] (22-3)

1 π φwhere k = (––) [tan(–– – ––) + φ] (22-4)

π 4 2

and φ is determined from: 1 (NB – N1)(––) (tanφ – φ) = –––––––––– = Q (say) (22-5) π (N1 – N2)

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T-76

The value of k varies within the range (1/π, 1/2) depending on the number of teeth on the belt.All angles in Equations (22-4) through (22-5) are in radians.

The procedure for center distance determination is as follows:

1. Select values of N1, N2 (in accordance with desired transmission ratio) and NB.

2. Compute Q = (NB – N1)/(N1 – N2).

3. Compute φ by solving Equation (22-5) numerically.

4. Compute k from Equation (22-4).

5. Compute C from Equation (22-3).

22.3 Exact Center Distance Determination – Equal Pulleys

For equal pulleys, N1 = N2 and Equation (22-3) becomes:

p (NB – N1)C = ––––––––––– (22-6)

2

22.4 Approximate Center Distance Determination

Approximate formulas are used when it is desirable to minimize computation time and whenan approximate determination of center distance suffices.

An alternative to Equation (22-1) for the exact center distance can be shown to be the following: _________________________________

p (N1 + N2) (N1 + N2) 2 2 (N1 – N2) 2

C = –– {NB – ––––––––– + �[NB – –––––––––] – –––––––––– (1 + S) } (22-7) 4 2 2 π2

where S varies between 0 and 0.1416, depending on the angle of wrap of the smaller pulley. Thevalue of S is given very nearly by the expression:

(cos2φ)S = –––––– (22-8) 12

In the approximate formulas for center distance, it is customary to neglect S and thus to obtainfollowing approximation for C:

____________________________ p (N1 + N2) (N1 + N2) 2 2 (N1 – N2) 2

C = –– {NB – ––––––––– + �[NB – –––––––––] – ––––––––––– } (22-9) 4 2 2 π 2

The error in Equation (22-9) depends on the speed ratio and the center distance. Theaccuracy is greatest for speed ratios close to unity and for large center distances. The accuracy isleast at minimum center distance and high transmission ratios. In many cases, the accuracy of theapproximate formula is acceptable.

22.5 Number Of Teeth In Mesh (TIM)

It is generally recommended that the number of teeth in mesh be not less than 6. Thenumber, TIM, teeth in mesh is given by:

TIM = λ ⋅ N2 (22-10) φ

where λ = –– when φ (see Equation (22-5)) is given in radians (see also the derivation given for π

TIM in this Handbook).

Page 75: Timing belts

T-77

22.6 Determination Of Belt Size For Given Pulleys And Center Distance

Occasionally, the center distance of a given installation is prescribed and the belt length is tobe determined. For given pitch, number of teeth on pulleys and center distance, the number ofteeth of the belt can be found from the equation:

_______________ (N1 + N2) (N1 – N2) (N1 – N2)p 2C 2 N1 – N2 2

NB = ––––––––– + ––––––––– sin –1 [––––––––––] + �(–––) – (––––––––) (22-11) 2 π 2 π C p π

where the arcsin is given in radians and lies between 0 and π/2. Since NB, in general, will not be awhole number, the nearest whole number less than NB can be used, assuming a slight increase inbelt tension is not objectionable.

An approximate formula can be used to obtain the belt length:

(D1 – D2)2

L = 2C + ––––––––––– + 1.57 x (D1 + D2) (22-12)4C

SECTION 23 CENTER DISTANCE FACTOR TABLES (TABLE 39)

TABLE 39

Definition:

The center distance factor is the center distance between two pulleys expressed in adimensionless unit, which corresponds to the pitch of the pulley and the belt used.

How To Use:

Multiply the center distance factor by the pitch of the belt expressed in inch or metric unit.The number obtained will be the center distance expressed in the same (inch or metric)unit.

Nomenclature Used:

N1 = Number of teeth of larger pulleyN2 = Number of teeth of smaller pulleyNB = Number of teeth of belt used

Example:

From the Transmission Ratio Table, for N1/N2 = 1.750, N1 = 28 and N2 = 16 are chosen.From the same table we also note that N1 – N2 = 12 and C MIN = 7.003. Assume thatNB = 80. Then, NB – N1 = 52. Refer to the Center Distance Factor Table for N1 – N2 =12 and NB – N1 = 52 and obtain the center distance factor of 28.937 which is larger thanthe required minimum (C MIN = 7.003). Assuming the pitch of the belt to be 5 mm, theactual center distance in mm is 28.937 x 5 = 144.685 mm.If 3 mm pitch belt is used, the center distance factor 28.937 has to be multiplied by 3,and a center distance of 86.811 mm is obtained.

Note:For the Center Distance Finder Formular please visit www.sdp-si.com. The printedbook continues with 64 pages representing the exact solutions of Equation (22-3) dividedby the pitch, p, for various values of (N1 – N2) and (NB – N1).

Page 76: Timing belts

T-142

SECTION 24 TIMING BELT DRIVE SELECTION PROCEDURE

Step 1 Determination of design load

Drives consist of a driver and a driven pulley. In general, both pulleys are not of the samesize; therefore, a speed reduction or increase occurs. Both convey the same power; however, thetorque on each pulley is different. Drive designs should be based on the smaller pulley which willbe subject to higher speed.

The peak design load must be taken into account, and it is obtained by multiplying the torqueby a service factor. Service factors between 1.5 and 2.0 are generally recommended whendesigning small pitch synchronous drives. Knowledge of drive loading characteristics should influencethe actual value selected. A higher service factor should be selected for applications with highpeak loads, high operating speeds, unusually severe operating conditions, etc. Lower servicefactors can be used when the loading is smooth, well defined, etc. and the reliability is less critical.Some designs may require service factors outside the 1.5 to 2.0 range, depending upon the natureof the application.

If a stall torque of the driver is not given but the nameplate horsepower or kW power consumptionis known, the torque can be obtained from:

63.025 x Shaft HPT (lb•in) = ––––––––––––––––– (24-1) Shaft rpm

T (lb•in) = 8.85 x T (N•m) or (24-2)

T (oz•in) = 16 x T (lb•in) (24-3)

Tpeak = T x Service Factor (24-4)

1 kW = 1.341 HP (24-5)

Step 2 Choice of belt pitch

As shown in Figure 4, (page T-6) different belt pitches can satisfy the same horsepowerrequirements, also taking into account the speed of the faster shaft. The choice is somewhatindividual and may take into account, among others, the following factors:

• compatibility with previous designs• superiority of GT drives as far as noise, backlash, positioning accuracy, etc. is concerned• local availability for replacement• size limitations; i.e. the size of pulleys and of the entire drive will be optimized if GT or HTD

pitches are used

Step 3 Check belt pitch selection based on individual graphs

Graphs shown on Figures 41 through 43 show the peak torque, Tpeak computed previously,plotted against the speed of faster shaft. Since the belt pitch was chosen in Step 2, reference tothese graphs will confirm the validity of the selection.

As an example, assume that the following data was obtained: Tpeak = 0.5 N•m and 1000 rpm.The potential choices are: 2 mm GT, 3 mm HTD, or XL. The 2 mm drive will be substantiallysmaller than the other choices.

Step 4 Determine speed ratio

Use CD-ROM or Drive Ratio Tables shown in SECTION 21, starting at page T-68, andestablish the number of teeth of the small and large pulley based on the chosen speed ratio.Attempt to use available stock sizes for best economy. Use of the CD-ROM will immediately guideyou to the appropriate catalog page and part number. Make note of the Pitch Diameter (PD) of thesmall pulley.

Page 77: Timing belts

T-143

Fig. 41 GT Belt Selection Guide

1 2 3 4 5 7 10 20 30 40 50 70 100 200 300 400 500 (lb⋅in)0.11 0.23 0.34 0.45 0.57 0.79 1.1 2.3 3.4 4.5 5.7 7.9 11 23 34 45 57 (N⋅m)

14,000

12,000

10,0009,0008,000

7,000

6,000

5,000

4,000

3,000

2,000

1,000900800700

600

500

400

300

200

100

rpm

of

Fas

ter

Sh

aft

2 mm GT 3 mm GT 5 mm GT

Design Torque (Tpeak)

Page 78: Timing belts

T-144

Fig. 42 HTD Belt Selection Guide

0 50 100 150 200 250 300 350 (lb⋅in) 5.7 11 17 23 28 34 40 (N⋅m)

rpm

of

Fas

ter

Sh

aft

30,000

20,000

10,000

8,000

6,000

5,000

4,000

3,000

2,000

1,000

800

600

500

400

300

200

100

3,450 rpm

1,750 rpm

1,160 rpm

870 rpm

3 mm HTD 5 mm HTD

Design Torque (Tpeak)

Page 79: Timing belts

T-145

Fig. 43 Trapezoidal Belt Selection Guide

0 2 4 6 8 10 12 14 (lb⋅in) 32 64 96 128 160 192 224 (oz⋅in) 0.23 0.45 0.68 0.9 1.13 1.35 1.58 (N⋅m)

rpm

of

Fas

ter

Sh

aft

30,000

20,000

10,000

8,000

6,000

5,000

4,000

3,000

2,000

1,000

800

600

500

400

300

200

100

3,450 rpm

1,750 rpm

1,160 rpm

870 rpm

MXL(.080" & .0816") XL (.200")

Design Torque (Tpeak)

Page 80: Timing belts

T-146

Step 5 Check belt speed

Belt speeds up to 6,500 fpm (33.02 m/s) do not require special pulleys. Speeds higher thanthese require special pulley materials and dynamic balancing.

Speed is computed using the following equations:

V(fpm) = 0.262 x pulley PD (in) x pulley rpm (24-5)

V(m/s) = 0.0000524 x pulley PD (mm) x pulley rpm (24-6)

where: m/s = 0.00508 x fpm (24-7)

Step 6 Determine belt length

The design layout may govern the determination of the belt length. Since the pulley sizes areknown, use of Center Distance Factor Tables shown in SECTION 23 (starting on page T-77) willyield NB – the number of teeth of the belt. If a fractional number is obtained, the closest integernumber should be chosen, and the calculation must be repeated to obtain the new center distancefor the design.

It is worthwhile to check if a belt with the chosen number of teeth is available in this Handbook.If it is not available, the closest fitting belt size must be chosen, and the calculation must berepeated to establish the center distance to which the layout must be corrected to accommodatethe available choice of belt.

Step 7 Determine the belt width

The number of grooves of the small pulley as well as the rpm of the faster shaft on which thispulley is located are known. Tables 40 through 47 show the torque and/or horsepower or kilowattratings for the base width of particular belt pitches.

For the HTD and GT drives, the torque ratings shown in these tables must be multiplied by thelength correction factor. This factor is a number smaller than 1 for shorter length and higher forlonger belts. This reflects the fact that a longer belt will be less prone to wear and tear as opposedto a shorter belt.

When the given torque from the table is multiplied by the length correction factor, this figuremay be smaller or larger than the previously computed peak torque Tpeak. If it is smaller, a beltnarrower than the base width can be used. Alternatively, if Tpeak is larger, a wider belt must bespecified. In order to finalize the belt width, the width multiplier given on the particular table itselfmust be used. Also, consult the appropriate belt product page for availability of standard widths.We are able to supply nonstandard width belts as well as nonstandard width pulleys, if desired.

In any event, the torque ratings given in the table multiplied by the length factor and by thewidth multiplier must yield a torque greater than the Tpeak computed previously.

The torque or horsepower ratings are based on 6 or more teeth in mesh for the smaller pulley.

Step 8 Check the number of teeth in mesh

The arc of contact on the smaller pulley in degrees can be found as follows:

60 (PD – pd )Arc of Contact = 180 – (––––––––––––) (degrees) (24-8)

C

where: PD = Large pitch diameter, inchespd = Small pitch diameter, inchesC = Drive center distance, inches

Page 81: Timing belts

T-147

The number of teeth in mesh on the smaller pulley can be found as follows:

(Arc) (n)Teeth in Mesh = –––––––– (24-9)

360

where: Arc = Arc of contact; small pulley, degreesn = number of grooves, small pulley

Drop any fractional part and use only the whole number as any tooth not fully engaged cannotbe considered a working tooth.

If the teeth in mesh is less than 6, correct the belt torque rating with the following multiplicationfactors:

5 teeth in mesh .............. multiply by 0.84 teeth in mesh .............. multiply by 0.63 teeth in mesh .............. multiply by 0.42 teeth in mesh .............. suggest redesign1 tooth in mesh .............. suggest redesign

Step 9 Determine proper belt installation tension

Procedure to calculate proper belt installation tension for specific applications are included inSECTION 10, on page T47.

Step 10 Check availability of all components

For the specified parts, both pulleys and belt, obtain part numbers from the Handbook or CD-ROM. In case special sizes or alterations are needed, contact SDP/SI Application EngineeringDepartment.

Free CD-ROM companion diskThis CD-ROM, which will run on any IBM or compatible PC, will contain theprograms to compute center distances, belt lengths, number of teeth inmesh, etc., as well as give the appropriate selection of our catalog partsbased on the parameters supplied by the designer.To obtain your copy see page 1-0.

Tel: 516-328-3300 Fax: 516-326-8827

See our Catalogs online at: http://www.sdp-si.com

Page 82: Timing belts

127.64

0.3010.900.890.870.860.850.830.820.810.800.800.790.790.780.780.780.770.770.760.760.760.750.750.750.740.730.730.720.72

148.91

0.3511.091.071.051.031.021.000.990.980.970.970.960.950.940.940.940.930.930.920.920.920.910.910.900.900.890.880.880.87

1610.190.4011.271.251.221.211.191.171.151.141.141.131.121.111.111.101.101.091.091.081.081.071.071.061.061.051.041.031.031.02

1811.460.4511.451.421.401.381.361.341.321.311.301.291.281.271.271.261.261.251.251.241.231.231.221.221.211.201.191.181.181.17

10 20 40 60 100 200 300 400 500 600 800 1000 1200 1400 1600 1800 2000 2400 2800 3200 3600 4000 5000 6000 8000100001200014000

rpmof

FastestShaft

Table 40 Rated Torque (lb⋅in) for Small Pulleys — 6 mm Belt Width

2012.730.5011.631.601.571.551.531.501.491.471.461.461.441.431.431.421.411.411.411.401.391.391.381.381.371.361.351.341.331.32

2415.280.6021.991.961.921.901.881.841.821.811.791.781.771.761.751.741.731.731.721.711.711.701.691.691.681.671.651.641.631.62

2817.830.7022.352.312.272.252.222.172.152.132.122.112.092.082.072.062.052.042.042.032.022.012.002.001.981.971.951.941.931.92

3220.370.8022.712.662.622.592.552.512.482.462.442.432.412.402.382.372.362.362.352.342.332.322.312.302.292.272.252.242.222.21

3622.920.9023.073.012.962.932.892.842.812.782.772.752.732.712.702.692.682.672.662.652.632.622.622.612.592.582.552.532.522.51

4025.461.0033.433.373.313.273.233.173.143.113.093.083.053.033.023.002.992.982.972.962.952.932.922.912.902.882.852.832.822.80

4830.561.2034.134.063.993.953.903.833.793.763.733.723.693.663.643.633.623.603.593.573.563.543.533.523.503.483.453.423.403.38

5635.651.4044.844.764.684.634.574.494.444.404.384.354.324.294.274.254.244.224.214.194.174.154.144.134.104.084.044.013.983.96

6440.741.6045.555.455.365.305.235.145.085.045.014.994.954.924.894.874.854.844.824.804.784.764.744.734.704.674.634.594.564.53

7245.841.8056.256.146.045.985.905.795.735.685.655.625.585.545.525.495.475.455.445.415.385.365.355.335.295.265.215.175.14—

8050.932.0056.956.836.716.646.566.446.376.326.286.256.206.166.136.116.086.066.056.015.995.965.945.925.885.855.795.755.70—

Belt Width (mm)Width Multiplier

40.67

61.00

91.50

122.00

100 50104 520.70Length Correction Factor

106 53122 610.75

124 62144 720.80

146 73168 840.85

170 85196 980.90

198 992301150.95

2321162701351.00

2721363161581.05

3181593701851.10

3721864342171.15

4362185082541.20

5102555962981.25

5982996963481.30

6983498004001.35

For BeltLength

From

To

Length (mm)# of teeth

Length (mm)# of teeth

The following table represents the torque ratings for each belt in its base width atthe predetermined number of grooves, pitch diameters and rpm's. These ratingsmust be multiplied by the appropriate width factor and applicable belt length factorto obtain the corrected torque rating (see Step 7 of SECTION 24, on page T-146).

2 mm Pitch PowerGrip® GT® Belts

Continued on the next page

Number of GroovesPitchDiameter

mminches

Page 83: Timing belts

127.64

0.3010.100.100.100.100.100.090.090.090.090.090.090.090.090.090.090.090.090.090.090.090.090.080.080.080.080.080.080.08

148.91

0.3510.120.120.120.120.120.110.110.110.110.110.110.110.110.110.110.110.100.100.100.100.100.100.100.100.100.100.100.10

1610.190.4010.140.140.140.140.130.130.130.130.130.130.130.130.120.120.120.120.120.120.120.120.120.120.120.120.120.120.120.12

1811.460.4510.160.160.160.160.150.150.150.150.150.150.140.140.140.140.140.140.140.140.140.140.140.140.140.140.130.130.130.13

10 20 40 60 100 200 300 400 500 600 800 1000 1200 1400 1600 1800 2000 2400 2800 3200 3600 4000 5000 6000 8000100001200014000

2012.730.5010.180.180.180.180.170.170.170.170.170.160.160.160.160.160.160.160.160.160.160.160.160.160.150.150.150.150.150.15

2415.280.6020.230.220.220.210.210.210.210.200.200.200.200.200.200.200.200.200.190.190.190.190.190.190.190.190.190.190.180.18

2817.830.7020.270.260.260.250.250.250.240.240.240.240.240.230.230.230.230.230.230.230.230.230.230.230.220.220.220.220.220.22

3220.370.8020.310.300.300.290.290.280.280.280.280.270.270.270.270.270.270.270.270.260.260.260.260.260.260.260.250.250.250.25

3622.920.9020.350.340.330.330.330.320.320.310.310.310.310.310.310.300.300.300.300.300.300.300.300.290.290.290.290.290.280.28

4025.461.0030.390.380.370.370.360.360.350.350.350.350.340.340.340.340.340.340.340.330.330.330.330.330.330.330.320.320.320.32

4830.561.2030.470.460.450.450.440.430.430.420.420.420.420.410.410.410.410.410.410.400.400.400.400.400.400.390.390.390.380.38

5635.651.4040.550.540.530.520.520.510.500.500.490.490.490.490.480.480.480.480.480.470.470.470.470.470.460.460.460.450.450.45

6440.741.6040.630.620.610.600.590.580.570.570.570.560.560.560.550.550.550.550.540.540.540.540.540.530.530.530.520.520.520.51

7245.841.8050.710.690.680.680.670.650.650.640.640.640.630.630.620.620.620.620.610.610.610.610.600.600.600.590.590.580.58—

8050.932.0050.790.770.760.750.740.730.720.710.710.710.700.700.690.690.690.690.680.680.680.670.670.670.660.660.660.650.64—

rpmof

FastestShaft

Table 40 (Cont.) Rated Torque (N⋅m) for Small Pulleys — 6 mm Belt Width

Belt Width (mm)Width Multiplier

40.67

61.00

91.50

122.00

100 50104 520.70Length Correction Factor

106 53122 610.75

124 62144 720.80

146 73168 840.85

170 85196 980.90

198 992301150.95

2321162701351.00

2721363161581.05

3181593701851.10

3721864342171.15

4362185082541.20

5102555962981.25

5982996963481.30

6983498004001.35

For BeltLength

From

To

Length (mm)# of teeth

Length (mm)# of teeth

The following table represents the torque ratings for each belt in its base width atthe predetermined number of grooves, pitch diameters and rpm's. These ratingsmust be multiplied by the appropriate width factor and applicable belt length factorto obtain the corrected torque rating (see Step 7 of SECTION 24, on page T-146).

2 mm Pitch PowerGrip® GT® Belts

Number of GroovesPitchDiameter

mminches

Page 84: Timing belts

924 3081089 3631.35

To

1615.280.60214.0212.8211.6210.9110.03 8.83 8.12 7.63 7.24 6.92 6.43 6.04 5.72 5.46 5.22 5.02 4.84 4.52 4.25 4.02 3.81 3.63 3.24 2.91 2.40 1.99 1.64 1.34

1817.190.67716.2714.9213.5712.7811.7810.43 9.64 9.08 8.65 8.29 7.73 7.30 6.94 6.64 6.38 6.15 5.94 5.59 5.28 5.02 4.79 4.58 4.14 3.77 3.19 2.72 2.32 1.98

Number of GroovesPitchDiameter

mminches

10 20 40 60 100 200 300 400 500 600 800 1000 1200 1400 1600 1800 2000 2400 2800 3200 3600 4000 5000 6000 8000100001200014000

Table 41 Rated Torque (lb⋅in) for Small Pulleys — 6 mm Belt Width

2019.100.75218.5017.0015.5014.6213.5112.0111.1410.5110.03 9.64 9.01 8.53 8.14 7.80 7.51 7.26 7.03 6.63 6.29 6.00 5.74 5.51 5.02 4.61 3.95 3.42 2.97 2.57

2422.920.90222.8921.0919.2918.2416.9115.1114.0613.3212.7412.2611.5210.9410.4610.06 9.71 9.40 9.13 8.65 8.25 7.90 7.58 7.30 6.71 6.21 5.40 4.74 4.17 3.66

3028.651.12829.3827.1324.8823.5621.9019.6518.3417.4016.6816.0915.1514.4313.8313.3312.8912.5112.1611.5611.0510.6110.22 9.86 9.10 8.46 7.41 6.53 5.75 5.03

3432.471.27833.6131.0628.5127.0225.1422.5921.1020.0419.2218.5517.4916.6715.9915.4214.9314.4914.1013.4212.8412.3311.8811.4810.60 9.86 8.63 7.59 6.64 5.75

3836.291.42937.8234.9732.1230.4528.3525.5023.8322.6521.7320.9819.7918.8718.1217.4816.9316.4416.0015.2314.5814.0113.5013.0412.0511.20 9.77 8.55 7.41 6.33

4442.021.65444.0040.7037.4135.4833.0429.7427.8126.4425.3824.5123.1422.0721.2020.4619.8119.2418.7317.8417.0816.4115.8115.2714.0913.0711.33 9.78 8.32 6.89

5047.751.88050.1346.3842.6340.4437.6733.9231.7330.1728.9627.9726.4125.2024.2023.3622.6221.9721.3920.3719.4918.7218.0317.4016.0214.8112.7010.79 8.93

5653.482.10556.1551.9547.7545.3042.2038.0035.5433.8032.4531.3429.5928.2327.1126.1625.3424.6023.9422.7921.8020.9320.1419.4117.8116.4013.8911.54

——

6461.122.40664.1059.3054.5051.6948.1543.3540.5438.5537.0035.7333.7332.1730.8929.8028.8528.0127.2525.9124.7623.7422.8121.9520.0418.3215.1712.13

——

7268.752.70771.9366.5361.1357.9854.0048.6045.4343.1941.4540.0237.7636.0034.5633.3232.2531.2930.4328.9027.5826.4025.3224.3222.0519.9816.09

———

8076.393.00879.6773.6867.6864.1759.7453.7450.2347.7345.7944.2141.6939.7338.1236.7435.5434.4633.4931.7730.2728.9227.6826.5223.8621.3916.64

———

Belt Width (mm)Width Multiplier

61.00

91.50

122.00

120 40126 420.70Length Correction Factor

129 43150 500.75

153 51177 590.80

180 60210 700.85

213 71249 830.90

252 84291 970.95

294 983451151.00

3481164051351.05

4081364771591.10

4801605641881.15

5671896632211.20

6662227832611.25

7862629213071.30

For BeltLength

FromLength (mm)

# of teethLength (mm)

# of teeth

The following table represents the torque ratings for each belt in its base width atthe predetermined number of grooves, pitch diameters and rpm's. These ratingsmust be multiplied by the appropriate width factor and applicable belt length factorto obtain the corrected torque rating (see Step 7 of SECTION 24, on page T-146).

152.50

2624.830.97725.0623.1121.1620.0218.5916.6415.5014.6914.0613.5512.7412.1111.6011.1610.7810.4510.15 9.64 9.20 8.81 8.48 8.17 7.52 6.98 6.09 5.36 4.73 4.15

2221.010.82720.7019.0517.4016.4415.2213.5712.6111.9211.3910.9610.27 9.74 9.31 8.94 8.62 8.34 8.09 7.65 7.28 6.96 6.67 6.42 5.87 5.42 4.69 4.10 3.59 3.13

1092 3641200 4001.40

rpmof

FastestShaft

3 mm Pitch PowerGrip® GT® Belts

Continued on the next pageShaded area indicates drive conditions where reduced service life can be expected.

Page 85: Timing belts

1615.280.6021.581.451.311.231.131.000.920.860.820.780.730.680.650.620.590.570.550.510.480.450.430.410.370.330.270.220.190.15

1817.190.6771.841.691.531.441.331.181.091.030.980.940.870.820.780.750.720.690.670.630.600.570.540.520.470.430.360.310.260.22

2019.100.7522.091.921.751.651.531.361.261.191.131.091.020.960.920.880.850.820.790.750.710.680.650.620.570.520.450.390.340.29

2422.920.9022.592.382.182.061.911.711.591.501.441.391.301.241.181.141.101.061.030.980.930.890.860.830.760.700.610.540.470.41

3028.651.1283.323.062.812.662.472.222.071.971.881.821.711.631.561.511.461.411.371.311.251.201.151.111.030.960.840.740.650.57

3432.471.2783.803.513.223.052.842.552.382.262.172.101.981.881.811.741.691.641.591.521.451.391.341.301.201.110.970.860.750.65

3836.291.4294.273.953.633.443.202.882.692.562.452.372.242.132.051.971.911.861.811.721.651.581.531.471.361.271.100.970.840.72

4442.021.6544.974.604.234.013.733.363.142.992.872.772.612.492.402.312.242.172.122.021.931.851.791.731.591.481.281.110.940.78

5047.751.8805.665.244.824.574.263.833.583.413.273.162.982.852.732.642.562.482.422.302.202.122.041.971.811.671.441.221.01—

5653.482.1056.345.875.405.124.774.294.023.823.673.543.343.193.062.962.862.782.712.582.462.362.282.192.011.851.571.30——

6461.122.4067.246.706.165.845.444.904.584.364.184.043.813.633.493.373.263.163.082.932.802.682.582.482.262.071.711.37——

7268.752.7078.137.526.916.556.105.495.134.884.684.524.274.073.903.773.643.543.443.273.122.982.862.752.492.261.82———

8076.393.0089.008.327.357.256.756.075.685.395.174.994.714.494.314.154.023.893.783.593.423.273.133.002.702.421.88———

Belt Width (mm)Width Multiplier

61.00

91.50

122.00

The following table represents the torque ratings for each belt in its base width atthe predetermined number of grooves, pitch diameters and rpm's. These ratingsmust be multiplied by the appropriate width factor and applicable belt length factorto obtain the corrected torque rating (see Step 7 of SECTION 24, on page T-146).

152.50

2624.830.9772.832.612.392.262.101.881.751.661.591.531.441.371.311.261.221.181.151.091.041.000.960.920.850.790.690.610.530.47

2221.010.8272.342.151.971.861.721.531.421.351.291.241.161.101.051.010.970.940.910.860.820.790.750.730.660.610.530.460.410.35

924 3081089 3631.35

To

Table 41 (Cont.) Rated Torque (N⋅m) for Small Pulleys — 6 mm Belt Width

120 40126 420.70Length Correction Factor

129 43150 500.75

153 51177 590.80

180 60210 700.85

213 71249 830.90

252 84291 970.95

294 983451151.00

3481164051351.05

4081364771591.10

4801605641881.15

5671896632211.20

6662227832611.25

7862629213071.30

For BeltLength

FromLength (mm)

# of teethLength (mm)

# of teeth

1092 3641200 4001.40

10 20 40 60 100 200 300 400 500 600 800 1000 1200 1400 1600 1800 2000 2400 2800 3200 3600 4000 5000 6000 8000100001200014000

rpmof

FastestShaft

3 mm Pitch PowerGrip® GT® Belts

Shaded area indicates drive conditions where reduced service life can be expected.

Number of GroovesPitchDiameter

mminches

Page 86: Timing belts

1960 3922000 4001.30

To

1828.651.12878.2472.3866.5363.1158.8052.9449.5247.0945.2043.6641.2239.3337.7836.4735.3334.3233.4131.8430.4929.3128.2627.3125.2323.4520.4317.7715.2912.88

2031.831.25393.6187.1180.6076.8072.0165.5161.7059.0056.9155.1952.4950.3848.6647.2045.9344.8043.7942.0340.5339.2038.0236.9434.5832.5529.0325.8822.8819.91

10 20 40 60 100 200 300 400 500 600 800 1000 1200 1400 1600 1800 2000 2400 2800 3200 3600 4000 5000 6000 8000100001200014000

Table 42 Rated Torque (lb⋅in) for Small Pulleys — 15 mm Belt Width (See Table 43 for hp or kW ratings)

2235.011.379109.00101.80 94.69 90.51 85.23 78.08 73.89 70.92 68.61 66.73 63.74 61.43 59.53 57.92 56.51 55.27 54.16 52.20 50.53 49.06 47.74 46.53 43.88 41.56 37.50 33.79 30.19 26.56

2641.381.629139.30130.90122.40117.50111.20102.80 97.83 94.31 91.59 89.36 85.83 83.09 80.83 78.92 77.25 75.77 74.44 72.10 70.09 68.31 66.70 65.21 61.91 58.98 53.67 48.63 43.57 38.34

3250.932.005184.30173.90163.50157.50149.80139.40133.30129.00125.60122.90118.50115.10112.30109.90107.90106.00104.30101.40 98.84 96.54 94.45 92.50 88.07 84.01 76.33 68.66 60.63

3657.302.256

214.10202.40190.70183.90175.20163.50156.70151.80148.00144.90140.00136.20133.00130.30128.00125.90124.00120.60117.60115.00112.50110.20104.90 99.93 90.27 80.34

——

4063.662.506243.60230.60217.60209.90200.40187.40179.70174.30170.10166.70161.20156.90153.40150.40147.80145.40143.20139.40136.00132.90130.10127.40121.10115.10103.10

———

4470.032.757

272.90258.60244.30235.90225.40211.10202.70196.70192.10188.30182.30177.60173.70170.30167.40164.70162.30158.00154.20150.70147.40144.30136.90129.70115.00

———

4876.393.008302.10286.50270.90261.80250.30234.70225.50219.00213.90209.80203.20198.00193.70190.10186.80183.90181.20176.40172.10168.10164.30160.70152.10143.50125.60

———

5689.133.509

359.90341.70323.50312.90299.50281.20270.60263.00257.00252.20244.40238.30233.30228.90225.00221.50218.20212.30206.90201.80197.00192.30180.60168.70

————

64101.864.010417.20396.40375.60363.40348.10327.30315.10306.40299.60294.00285.10278.00272.10267.00262.40258.20254.40247.20240.60234.20228.10222.00206.70190.60

————

72114.594.511

474.10450.60427.20413.50396.30372.80359.10349.30341.60335.30325.20317.20310.40304.50299.20294.30289.70281.10273.10265.30257.60249.80230.00

—————

80127.325.013530.60504.60478.50463.30444.10418.10402.80391.80383.30376.20364.90355.90348.20341.40335.30329.60324.20314.10304.40294.90285.30275.70

——————

Belt Width (mm)Width Multiplier

90.60

151.00

201.33

200 40210 420.65Length Correction Factor

215 43255 510.70

260 52310 620.75

315 63370 740.80

375 75445 890.85

450 905351070.90

5401086451290.95

6501307751551.00

7801569301861.05

935 1871125 2251.10

1130 2261350 2701.15

1355 27116203241.20

1625 3251955 3911.25

For BeltLength

FromLength (mm)

# of teethLength (mm)

# of teeth

The following table represents the torque ratings for each belt in its base width atthe predetermined number of grooves, pitch diameters and rpm's. These ratingsmust be multiplied by the appropriate width factor and applicable belt length factorto obtain the corrected torque rating (see Step 7 of SECTION 24, on page T-146).

251.67

2844.561.754154.30145.20136.10130.80124.10115.00109.70105.90103.00100.60 96.76 93.80 91.37 89.31 87.50 85.90 84.46 81.92 79.73 77.79 76.02 74.39 70.74 67.46 61.43 55.06 49.67 43.46

2438.201.504124.20116.40108.60104.00 98.27 90.46 85.90 82.65 80.14 78.08 74.83 72.30 70.22 68.46 66.93 65.57 64.34 62.20 60.36 58.73 57.27 55.93 52.96 50.35 45.69 41.35 37.07 32.69

rpmof

FastestShaft

5 mm Pitch PowerGrip® GT® Belts

Continued on the next pageShaded area indicates drive conditions where reduced service life can be expected.

Number of GroovesPitchDiameter

mminches

Page 87: Timing belts

The following table represents the torque ratings for each belt in its base width atthe predetermined number of grooves, pitch diameters and rpm's. These ratingsmust be multiplied by the appropriate width factor and applicable belt length factorto obtain the corrected torque rating (see Step 7 of SECTION 24, on page T-146).

5 mm Pitch PowerGrip® GT® Belts

1960 3922000 4001.30

To

1828.651.1288.848.187.527.136.645.985.595.325.114.934.664.444.274.123.993.883.783.603.453.313.193.092.852.652.312.011.731.45

2031.831.25310.58 9.84 9.11 8.68 8.14 7.40 6.97 6.67 6.43 6.24 5.93 5.69 5.50 5.33 5.19 5.06 4.95 4.75 4.58 4.43 4.30 4.17 3.91 3.68 3.28 2.92 2.59 2.25

10 20 40 60 100 200 300 400 500 600 800 1000 1200 1400 1600 1800 2000 2400 2800 3200 3600 4000 5000 6000 8000100001200014000

2235.011.37912.3211.5110.7010.23 9.63 8.82 8.38 8.01 7.75 7.54 7.20 6.94 6.73 6.54 6.39 6.24 6.12 5.90 5.71 5.54 5.39 5.26 4.96 4.70 4.24 3.82 3.41 3.00

2641.381.62915.7414.7813.8313.2712.5711.6111.0510.6610.3510.10 9.70 9.39 9.13 8.92 8.73 8.56 8.41 8.15 7.92 7.72 7.54 7.37 7.00 6.66 6.06 5.49 4.92 4.33

3250.932.00520.8319.6518.4817.7916.9215.7515.0614.5714.1913.8813.3913.0112.6912.4212.1911.9811.7911.4611.1710.9110.6710.45 9.95 9.49 8.627.766.85 —

3657.302.25624.1922.8721.5520.7719.8018.4817.7017.1516.7216.3715.8215.3915.0314.7314.4614.2214.0113.6213.2912.9912.7112.4511.8511.2910.20 9.08

——

4063.662.50627.5226.0524.5823.7222.6421.1720.3119.7019.2218.8318.2117.7317.3316.9916.6916.4316.1815.7515.3715.0214.7014.4013.6813.0111.65

———

4470.032.75730.8429.2227.6026.6625.4723.8522.9022.2321.7121.2820.6020.0619.6219.2418.9118.6118.3417.8517.4217.0216.6516.3015.4614.6512.99

———

4876.393.00834.1432.3730.6129.5828.2826.5125.4824.7424.1723.7022.9622.3721.8921.4721.1120.7820.4719.9319.4418.9918.5718.1617.1816.2114.20

———

5689.133.50940.6738.6136.5535.3533.8331.7830.5729.7129.0428.4927.6226.9326.3625.8625.4225.0224.6523.9823.3822.8022.2621.7220.4119.06

————

64101.864.01047.1444.7942.4441.0639.3336.9835.6034.6133.8533.2232.2131.4130.7530.1729.6529.1828.7427.9327.1826.4725.7725.0823.3521.54

————

72114.594.51153.5650.9248.2746.7244.7742.1340.5739.4638.6037.8836.7435.8435.0734.4033.8033.2532.7331.7630.8529.9729.1028.2325.99

—————

80127.325.01359.9557.0154.0752.3550.1847.2445.5144.2743.3142.5141.2340.2139.3438.5837.8937.2436.6335.4934.3933.3232.2431.15

——————

Belt Width (mm)Width Multiplier

90.60

151.00

201.33

200 40210 420.65Length Correction Factor

215 43255 510.70

260 52310 620.75

315 63370 740.80

375 75445 890.85

450 905351070.90

5401086451290.95

6501307751551.00

7801569301861.05

935 1871125 2251.10

1130 2261350 2701.15

1355 27116203241.20

1625 3251955 3911.25

For BeltLength

FromLength (mm)

# of teethLength (mm)

# of teeth

251.67

2844.561.75417.4416.4115.3814.7814.0212.9912.3911.9611.6311.3610.9310.6010.3210.09 9.89 9.71 9.54 9.26 9.01 8.79 8.59 8.41 7.99 7.62 6.94 6.28 5.61 4.91

2438.201.50414.0313.1512.2711.7511.1010.22 9.71 9.34 9.05 8.82 8.45 8.17 7.93 7.73 7.56 7.41 7.27 7.03 6.82 6.64 6.47 6.32 5.98 5.69 5.16 4.67 4.19 3.69

rpmof

FastestShaft

Table 42 (Cont.) Rated Torque (N⋅m) for Small Pulleys — 15 mm Belt Width (See Table 43 for hp or kW ratings)

Shaded area indicates drive conditions where reduced service life can be expected.

Number of GroovesPitchDiameter

mminches

Page 88: Timing belts

1960 3922000 4001.30

To

1828.651.1280.010.020.040.060.090.170.240.300.360.420.520.620.720.810.900.981.061.211.351.491.611.732.002.232.592.822.912.86

2031.831.2530.010.030.050.070.110.210.290.370.450.530.670.800.931.051.171.281.391.601.801.992.172.342.743.103.694.114.364.42

10 20 40 60 100 200 300 400 500 600 800 1000 1200 1400 1600 1800 2000 2400 2800 3200 3600 4000 5000 6000 8000100001200014000

Table 43 Rated Horsepower for Small Pulleys — 15 mm Belt Width

2235.011.3790.020.030.060.090.140.250.350.450.540.640.810.971.131.291.431.581.721.992.242.492.732.953.483.964.765.365.755.90

2641.381.6290.020.040.080.110.180.330.470.600.730.851.091.321.541.751.962.162.362.753.113.473.814.144.915.626.817.728.308.52

3250.932.005 0.03 0.06 0.10 0.15 0.24 0.44 0.63 0.82 1.00 1.17 1.50 1.83 2.14 2.44 2.74 3.03 3.31 3.86 4.39 4.90 5.40 5.87 6.99 8.00 9.6910.8911.54 —

3657.302.256 0.03 0.06 0.12 0.18 0.28 0.52 0.75 0.96 1.17 1.38 1.78 2.16 2.53 2.90 3.25 3.59 3.93 4.59 5.23 5.84 6.43 6.99 8.32 9.5111.4612.75

——

4063.662.506 0.04 0.07 0.14 0.20 0.32 0.59 0.86 1.11 1.35 1.59 2.05 2.49 2.92 3.34 3.75 4.15 4.55 5.31 6.04 6.75 7.43 8.09 9.6110.9613.09

———

4470.032.757 0.04 0.08 0.16 0.22 0.36 0.67 0.96 1.25 1.52 1.79 2.31 2.82 3.31 3.78 4.25 4.71 5.15 6.02 6.85 7.65 8.42 9.1610.8612.3414.59

———

4876.393.008 0.05 0.09 0.17 0.25 0.40 0.74 1.07 1.39 1.70 2.00 2.58 3.14 3.69 4.22 4.74 5.25 5.75 6.72 7.64 8.53 9.3910.2012.0613.6615.95

———

5689.133.509 0.06 0.11 0.21 0.30 0.48 0.89 1.29 1.67 2.04 2.40 3.10 3.78 4.44 5.08 5.71 6.32 6.92 8.08 9.1910.2511.2512.2014.3316.06

————

64101.864.010 0.07 0.13 0.24 0.35 0.55 1.04 1.50 1.94 2.38 2.80 3.62 4.41 5.18 5.93 6.66 7.38 8.07 9.4110.6911.8913.0314.0916.4018.15

————

72114.594.511 0.08 0.14 0.27 0.39 0.63 1.18 1.71 2.22 2.71 3.19 4.13 5.03 5.91 6.76 7.60 8.40 9.1910.7012.1313.4714.7115.8618.25

—————

80127.325.013 0.08 0.16 0.30 0.44 0.70 1.33 1.92 2.49 3.04 3.58 4.63 5.65 6.63 7.58 8.51 9.4110.2911.9613.5214.9716.3017.50

——————

Belt Width (mm)Width Multiplier

90.60

151.00

201.33

200 40210 420.65Length Correction Factor

215 43255 510.70

260 52310 620.75

315 63370 740.80

375 75445 890.85

450 905351070.90

5401086451290.95

6501307751551.00

7801569301861.05

935 1871125 2251.10

1130 2261350 2701.15

1355 27116203241.20

1625 3251955 3911.25

For BeltLength

FromLength (mm)

# of teethLength (mm)

# of teeth

The following table represents the horsepower ratings for each belt in its basewidth at the predetermined number of grooves, pitch diameters and rpm's. Theseratings must be multiplied by the appropriate width factor and applicable belt lengthfactor to obtain the corrected horsepower rating (see Step 7 of SECTION 24, onpage T-146). See Table 42 for torque ratings.

251.67

2438.201.5040.020.040.070.100.160.290.410.520.640.740.951.151.341.521.701.872.042.372.682.983.273.554.204.795.806.567.067.26

rpmof

FastestShaft

5 mm Pitch PowerGrip® GT® Belts

Continued on the next page

2844.561.7540.020.050.090.120.200.360.520.670.820.961.231.491.741.982.222.452.683.123.543.954.344.725.616.427.808.829.469.65

Shaded area indicates drive conditions where reduced service life can be expected.

Number of GroovesPitchDiameter

mminches

Page 89: Timing belts

1960 3922000 4001.30

To

1828.651.1280.010.020.030.040.070.130.180.220.270.310.390.470.540.600.670.730.790.901.011.111.201.291.491.671.932.102.172.13

2031.831.2530.010.020.040.050.090.160.220.280.340.390.500.600.690.780.870.951.041.191.341.481.621.752.052.312.753.063.253.30

10 20 40 60 100 200 300 400 500 600 800 1000 1200 1400 1600 1800 2000 2400 2800 3200 3600 4000 5000 6000 8000100001200014000

Table 43 (Cont.) Rated Kilowatts for Small Pulleys — 15 mm Belt Width

2235.011.3790.010.020.040.060.100.180.260.340.410.470.600.730.850.961.071.181.281.481.671.862.032.202.602.953.554.004.294.40

2641.381.6290.020.030.060.080.130.240.350.450.540.630.810.981.151.311.461.611.762.052.322.592.843.093.664.195.085.756.196.35

3250.932.0050.020.040.080.110.180.330.470.610.740.871.121.361.591.822.042.262.472.883.273.664.024.385.215.967.238.128.61 —

3657.302.2560.030.050.090.130.210.390.560.720.881.031.331.611.892.162.422.682.933.423.904.354.795.226.217.098.549.51——

4063.662.5060.030.050.100.150.240.440.640.831.011.181.531.862.182.492.803.103.393.964.515.035.546.037.168.179.76———

4470.032.757 0.03 0.06 0.12 0.17 0.27 0.50 0.72 0.93 1.14 1.34 1.73 2.10 2.47 2.82 3.17 3.51 3.84 4.49 5.11 5.71 6.28 6.83 8.10 9.2010.88

———

4876.393.008 0.04 0.07 0.13 0.19 0.30 0.56 0.80 1.04 1.27 1.49 1.92 2.34 2.75 3.15 3.54 3.92 4.29 5.01 5.70 6.36 7.00 7.61 9.0010.1911.89

———

5689.133.509 0.04 0.08 0.15 0.22 0.35 0.67 0.96 1.24 1.52 1.79 2.31 2.82 3.31 3.79 4.26 4.72 5.16 6.03 6.85 7.64 8.39 9.1010.6811.98

————

64101.864.010 0.05 0.09 0.18 0.26 0.41 0.77 1.12 1.45 1.77 2.09 2.70 3.29 3.86 4.42 4.97 5.50 6.02 7.02 7.97 8.87 9.7210.5112.2313.53

————

72114.594.511 0.06 0.11 0.20 0.29 0.47 0.88 1.27 1.65 2.02 2.38 3.08 3.75 4.41 5.04 5.66 6.27 6.85 7.98 9.0510.0410.9711.8213.61

—————

80127.325.013 0.06 0.12 0.23 0.33 0.53 0.99 1.43 1.85 2.27 2.67 3.45 4.21 4.94 5.66 6.35 7.02 7.67 8.9210.0811.1612.1513.05

——————

Belt Width (mm)Width Multiplier

90.60

151.00

201.33

200 40210 420.65Length Correction Factor

215 43255 510.70

260 52310 620.75

315 63370 740.80

375 75445 890.85

450 905351070.90

5401086451290.95

6501307751551.00

7801569301861.05

935 1871125 2251.10

1130 2261350 2701.15

1355 27116203241.20

1625 3251955 3911.25

For BeltLength

FromLength (mm)

# of teethLength (mm)

# of teeth

251.67

2438.201.5040.010.030.050.070.120.210.300.390.470.550.710.861.001.131.271.401.521.772.002.222.442.653.133.574.324.895.265.42

rpmof

FastestShaft

5 mm Pitch PowerGrip® GT® Belts

2844.561.7540.020.030.060.090.150.270.390.500.610.710.921.111.301.481.661.832.002.332.642.953.243.524.184.795.816.587.057.20

The following table represents the horsepower ratings for each belt in its basewidth at the predetermined number of grooves, pitch diameters and rpm's. Theseratings must be multiplied by the appropriate width factor and applicable belt lengthfactor to obtain the corrected horsepower rating (see Step 7 of SECTION 24, onpage T-146). See Table 42 for torque ratings.

Shaded area indicates drive conditions where reduced service life can be expected.

Number of GroovesPitchDiameter

mminches

Page 90: Timing belts

To

109.55.3763.33.33.33.33.33.33.02.82.72.62.52.42.42.32.22.12.02.01.91.91.81.71.61.41.3

1211.46.4514.04.04.04.04.04.03.73.43.33.13.02.92.92.82.72.62.52.52.42.32.22.11.91.71.6

10 20 40 60 100 200 300 400 500 600 700 800 870 1000 1160 1450 1600 1750 2000 2500 3000 3500 5000 800010000

Table 44 Rated Torque (lb⋅in) for Small Pulleys — 6 mm Belt Width

1413.37.5264.84.84.84.84.84.84.44.13.93.73.63.53.43.33.23.03.02.92.82.72.62.52.32.01.9

1817.19.6776.56.56.56.56.56.55.95.55.25.04.84.74.64.44.34.03.93.93.73.53.43.33.02.62.5

2624.83.97710.210.210.210.210.210.2 9.2 8.6 8.1 7.7 7.4 7.2 7.0 6.8 6.5 6.2 6.0 5.9 5.7 5.4 5.1 4.9 4.5 3.9 3.6

3028.651.12812.312.312.312.312.312.311.110.3 9.7 9.2 8.9 8.6 8.4 8.1 7.8 7.3 7.2 7.0 6.7 6.4 6.1 5.8 5.2 4.5 4.1

3432.471.27814.514.514.514.514.514.513.012.011.310.810.410.0 9.8 9.4 9.1 8.5 8.3 8.1 7.8 7.4 7.0 6.7 6.0 5.1 4.6

3836.291.42916.816.816.816.816.816.815.013.913.112.411.911.511.210.810.4 9.8 9.5 9.3 8.9 8.4 8.0 7.6 6.8 5.7 5.1

4442.021.65420.520.520.520.520.520.518.316.915.815.014.413.913.513.012.511.711.411.110.710.0 9.4 9.0 8.0 6.6 5.7

5047.751.88024.624.624.624.624.624.621.820.018.817.817.016.315.915.314.613.713.312.912.411.611.010.4 9.2 7.3 6.3

5653.482.10527.727.727.727.727.727.724.622.621.220.119.218.418.017.216.515.415.014.614.013.012.311.710.2 8.0 6.6

6259.212.33130.730.730.730.730.730.727.325.023.422.221.220.419.919.118.217.116.516.115.414.413.512.811.1 8.5 6.8

7268.752.70735.735.735.735.735.735.731.629.127.225.824.623.723.122.121.219.819.218.717.916.615.614.812.7 9.1—

Belt Width (mm)Width Multiplier

61.00

91.66

152.97

144 48195 650.80Length Correction Factor

198 66261 870.90

264 884051351.00

4081365971991.10

600200

603 & up201 & up

1.20

For BeltLength

FromLength (mm)

# of teethLength (mm)

# of teeth

The following table represents the torque ratings for each belt in its base width atthe predetermined number of grooves, pitch diameters and rpm's. These ratingsmust be multiplied by the appropriate width factor and applicable belt length factorto obtain the corrected torque rating (see Step 7 of SECTION 24, on page T-146).

1615.28.6025.65.65.65.65.65.65.14.84.54.34.24.14.03.93.73.53.43.43.33.13.02.92.62.32.2

rpmof

FastestShaft

3 mm Pitch PowerGrip HTD Belts

Continued on the next page

2221.01.8278.38.38.38.38.38.37.57.06.66.36.15.95.85.65.45.15.04.94.74.44.24.13.73.33.0

8076.393.00839.639.639.639.639.639.635.232.330.228.627.426.325.624.623.522.021.320.719.818.417.316.313.8 9.3—

Shaded area indicates drive conditions where reduced service life can be expected.

Number of GroovesPitchDiameter

mminches

Page 91: Timing belts

3028.651.1281.41.41.41.41.41.41.21.21.11.01.01.00.90.90.90.80.80.80.80.70.70.70.60.50.5

2624.83.9771.21.21.21.21.21.21.01.00.90.90.80.80.80.80.70.70.70.70.60.60.60.60.50.40.4

2221.01.8270.90.90.90.90.90.90.80.80.70.70.70.70.70.60.60.60.60.50.50.50.50.50.40.40.3

1817.19.6770.70.70.70.70.70.70.70.60.60.60.50.50.50.50.50.50.40.40.40.40.40.40.30.30.3

1615.28.6020.60.60.60.60.60.60.60.50.50.50.50.50.40.40.40.40.40.40.40.40.30.30.30.30.2

1413.37.5260.50.50.50.50.50.50.50.50.40.40.40.40.40.40.40.30.30.30.30.30.30.30.30.20.2

1211.46.4510.50.50.50.50.50.50.40.40.40.40.30.30.30.30.30.30.30.30.30.30.20.20.20.20.2

109.55.3760.40.40.40.40.40.40.30.30.30.30.30.30.30.30.20.20.20.20.20.20.20.20.20.20.2

To

10 20 40 60 100 200 300 400 500 600 700 800 870 1000 1160 1450 1600 1750 2000 2500 3000 3500 5000 800010000

Table 44 (Cont.) Rated Torque (N⋅m) for Small Pulleys — 6 mm Belt Width

3432.471.2781.61.61.61.61.61.61.51.41.31.21.21.11.11.11.01.00.90.90.90.80.80.80.70.60.5

3836.291.4291.91.91.91.91.91.91.71.61.51.41.31.31.31.21.21.11.11.01.00.90.90.90.80.60.6

4442.021.6542.32.32.32.32.32.32.11.91.81.71.61.61.51.51.41.31.31.31.21.11.11.00.90.70.6

5047.751.8802.82.82.82.82.82.82.52.32.12.01.91.81.81.71.71.51.51.51.41.31.21.21.00.80.7

5653.482.1053.13.13.13.13.13.12.82.62.42.32.22.12.01.91.91.71.71.61.61.51.41.31.20.90.7

6259.212.3313.53.53.53.53.53.53.12.82.62.52.42.32.22.22.11.91.91.81.71.61.51.51.31.00.8

7268.752.707

4.04.04.04.04.04.03.63.33.12.92.82.72.62.52.42.22.22.12.01.91.81.71.41.0—

Belt Width (mm)Width Multiplier

61.00

91.66

152.97

144 48195 650.80Length Correction Factor

198 66261 870.90

264 884051351.00

4081365971991.10

600200

603 & up201 & up

1.20

For BeltLength

FromLength (mm)

# of teethLength (mm)

# of teeth

The following table represents the torque ratings for each belt in its base width atthe predetermined number of grooves, pitch diameters and rpm's. These ratingsmust be multiplied by the appropriate width factor and applicable belt length factorto obtain the corrected torque rating (see Step 7 of SECTION 24, on page T-146).

rpmof

FastestShaft

3 mm Pitch PowerGrip HTD Belts

8076.393.0084.54.54.54.54.54.54.03.63.43.23.13.02.92.82.72.52.42.32.22.11.91.81.61.1—

Shaded area indicates drive conditions where reduced service life can be expected.

Number of GroovesPitchDiameter

mminches

Page 92: Timing belts

1422.28.87719.019.019.019.019.019.017.316.215.314.714.213.713.513.012.612.011.911.711.411.311.110.510.0 9.6 8.8 7.8 7.2

To

Table 45 Rated Torque (lb⋅in) for Small Pulleys — 9 mm Belt Width

Belt Width (mm)Width Multiplier

91.00

151.89

253.38

350 70435 870.80Length Correction Factor

440 885501100.90

5551118401681.00

845 1691090 2181.10

1095 219

1100 & up220 & up

1.20

For BeltLength

FromLength (mm)

# of teethLength (mm)

# of teeth

The following table represents the torque ratings for each belt in its base width atthe predetermined number of grooves, pitch diameters and rpm's. These ratingsmust be multiplied by the appropriate width factor and applicable belt length factorto obtain the corrected torque rating (see Step 7 of SECTION 24, on page T-146).

5 mm Pitch PowerGrip HTD Belts

Continued on the next page

1625.461.00322.322.322.322.322.322.320.218.917.917.216.516.015.715.214.714.013.913.613.313.212.912.211.711.110.2 8.9 8.2

10 20 40 60 100 200 300 400 500 600 700 800 870 1000 1160 1400 1450 1600 1750 1800 2000 2500 3000 3600 5000 800010000

1828.651.12825.725.725.725.725.725.723.321.820.619.719.018.418.017.416.816.115.915.615.215.114.713.913.312.711.610.1 9.2

2235.011.37933.033.033.033.033.033.029.927.826.325.124.223.422.922.121.320.420.219.719.219.118.617.616.715.914.512.311.0

2641.381.62940.940.940.940.940.940.936.934.332.430.929.728.728.127.126.124.924.624.023.523.322.721.320.319.317.414.412.7

2844.561.75445.145.145.145.145.145.140.637.735.633.932.631.530.829.728.627.227.026.325.625.524.723.322.121.018.915.413.4

3250.932.00553.853.853.853.853.853.848.344.842.240.238.637.236.435.133.732.031.730.930.129.929.027.325.824.421.817.314.5

3657.302.25663.163.163.163.163.163.156.552.349.246.844.943.342.340.739.137.136.735.734.834.533.531.429.727.924.719.015.3

4063.662.50673.073.073.073.073.073.065.260.256.553.751.549.648.446.544.642.341.940.739.639.338.135.633.531.527.620.4—

4470.032.75783.583.583.583.583.583.574.468.564.361.058.356.154.852.650.447.747.245.844.644.242.839.937.535.130.421.5—

4876.393.00894.594.594.594.594.594.584.077.272.368.565.563.061.458.956.453.252.751.149.749.247.644.241.538.633.122.3—

5689.133.509113.3113.3113.3113.3113.3113.3100.4 92.2 86.2 81.7 78.0 74.9 73.0 70.0 66.9 63.1 62.4 60.4 58.7 58.2 56.2 51.9 48.5 44.8 37.4

——

64101.864.010129.5129.5129.5129.5129.5129.5114.8105.3 98.5 93.3 89.1 85.5 83.4 79.9 76.3 71.9 71.1 68.9 66.8 66.2 63.9 58.8 54.6 50.1 40.6

——

2031.831.25329.329.329.329.329.329.326.524.723.422.421.620.920.419.819.118.218.017.617.217.116.615.715.014.313.111.210.1

rpmof

FastestShaft

2438.201.50436.936.936.936.936.936.933.331.029.328.026.926.025.524.623.722.622.421.821.321.220.619.418.517.615.913.411.9

72114.594.511145.7145.7145.7145.7145.7145.7129.1118.5110.8104.9100.1 96.2 93.7 89.8 85.7 80.7 79.8 77.2 74.9 74.1 71.4 65.5 60.5 55.0 43.0

——

Shaded area indicates drive conditions where reduced service life can be expected.

Number of GroovesPitchDiameter

mminches

Page 93: Timing belts

1422.28.8772.12.12.12.12.12.12.01.81.71.71.61.61.51.51.41.41.31.31.31.31.31.21.11.11.00.90.8

To

Table 45 Rated Torque (N⋅m) for Small Pulleys — 9 mm Belt Width

Belt Width (mm)Width Multiplier

91.00

151.89

253.38

350 70435 870.80Length Correction Factor

440 885501100.90

5551118401681.00

845 1691090 2181.10

1095 219

1100 & up220 & up

1.20

For BeltLength

FromLength (mm)

# of teethLength (mm)

# of teeth

The following table represents the torque ratings for each belt in its base width atthe predetermined number of grooves, pitch diameters and rpm's. These ratingsmust be multiplied by the appropriate width factor and applicable belt length factorto obtain the corrected torque rating (see Step 7 of SECTION 24, on page T-146).

5 mm Pitch PowerGrip HTD Belts

1625.461.0032.52.52.52.52.52.52.32.12.01.91.91.81.81.71.71.61.61.51.51.51.51.41.31.31.21.00.9

10 20 40 60 100 200 300 400 500 600 700 800 870 1000 1160 1400 1450 1600 1750 1800 2000 2500 3000 3600 5000 800010000

1828.651.1282.92.92.92.92.92.92.62.52.32.22.12.12.02.01.91.81.81.81.71.71.71.61.51.41.31.11.0

2235.011.3793.73.73.73.73.73.73.43.13.02.82.72.62.62.52.42.32.32.22.22.22.12.01.91.81.61.41.2

2641.381.6294.64.64.64.64.64.64.23.93.73.53.43.23.23.13.02.82.82.72.72.62.62.42.32.22.01.61.4

2844.561.754

5.15.15.15.15.15.14.64.34.03.83.73.63.53.43.23.13.03.02.92.92.82.62.52.42.11.71.5

3250.932.0056.16.16.16.16.16.15.55.14.84.54.44.24.14.03.83.63.63.53.43.43.33.12.92.82.52.01.6

3657.302.256

7.17.17.17.17.17.16.45.95.65.35.14.94.84.64.44.24.14.03.93.93.83.53.43.22.82.11.7

4063.662.5068.38.38.38.38.38.37.46.86.46.15.85.65.55.35.04.84.74.64.54.44.34.03.83.63.12.3—

4470.032.757

9.49.49.49.49.49.48.47.77.36.96.66.36.25.95.75.45.35.25.05.04.84.54.24.03.42.4—

4876.393.00810.710.710.710.710.710.7 9.5 8.7 8.2 7.7 7.4 7.1 6.9 6.7 6.4 6.0 6.0 5.8 5.6 5.6 5.4 5.0 4.7 4.4 3.7 2.5—

5689.133.50912.812.812.812.812.812.811.310.4 9.7 9.2 8.8 8.5 8.2 7.9 7.6 7.1 7.0 6.8 6.6 6.6 6.3 5.9 5.5 5.1 4.2——

64101.864.01014.614.614.614.614.614.613.011.911.110.510.1 9.7 9.4 9.0 8.6 8.1 8.0 7.8 7.6 7.5 7.2 6.6 6.2 5.7 4.6——

2031.831.2533.33.33.33.33.33.33.02.82.62.52.42.42.32.22.22.12.02.01.91.91.91.81.71.61.51.31.1

rpmof

FastestShaft

2438.201.5044.24.24.24.24.24.23.83.53.33.23.02.92.92.82.72.62.52.52.42.42.32.22.12.01.81.51.3

72114.594.51116.516.516.516.516.516.514.613.412.511.911.310.910.610.1 9.7 9.1 9.0 8.7 8.5 8.4 8.1 7.4 6.8 6.2 4.9——

Shaded area indicates drive conditions where reduced service life can be expected.

Number of GroovesPitchDiameter

mminches

Page 94: Timing belts

106.48.2554.614.614.614.614.614.614.614.614.604.594.59

Table 46 Rated Torque (oz⋅in) for Small Pulleys — 1/8" Top Width

Belt Width (in)Width Multiplier

3/83.50

7/164.18

1/24.86

The following table represents the torque ratings for each belt in its base width atthe predetermined number of grooves, pitch diameters and rpm's. These ratingsmust be multiplied by the appropriate width factor to obtain the corrected torquerating (see Step 7 of SECTION 24, on page T-146).

MXL (.080 in) Belts

No. of GroovesPitchDiameter

mmin

10 100 1000 2000 2500 3000 3500 5000 80001000012000

rpmof

FastestShaft

117.11.2805.065.065.065.065.065.065.065.065.055.045.03

127.77.3065.535.535.535.535.535.535.535.535.525.515.49

149.07.3576.456.456.456.456.456.456.456.446.436.416.39

159.70.3826.916.916.916.906.906.906.906.896.876.856.83

1610.34.4077.367.367.367.367.357.357.357.347.327.307.27

1811.63.4588.288.288.288.288.288.278.278.268.228.198.15

2012.93.5099.209.209.209.209.209.199.199.179.129.089.03

2113.59.5359.679.679.679.679.669.669.669.649.589.539.47

2214.22.560

10.1010.1010.1010.1010.1010.1010.1010.1010.00 9.96 9.98

2415.52.61111.011.011.011.011.011.011.011.010.910.810.7

2818.11.71312.912.912.912.912.912.912.812.812.712.612.4

3019.41.76413.813.813.813.813.813.813.813.713.513.413.2

3220.70.81514.714.714.714.714.714.714.714.614.414.214.0

3623.29.91716.616.616.616.616.516.516.516.416.115.915.5

4025.881.01918.418.418.418.418.418.318.318.217.817.417.0

4227.181.07019.319.319.319.319.319.219.219.118.618.217.7

4428.451.12020.220.220.220.220.220.120.119.919.418.918.4

4831.041.22222.122.122.122.022.021.921.921.721.020.419.6

6038.811.52827.627.627.627.527.427.327.226.825.524.322.8

5/162.84

1/42.33

3/161.66

1/81.00

Page 95: Timing belts

1016.18.6372.322.322.322.322.322.312.312.312.312.312.312.312.302.272.24

Table 47 Rated Torque (lb⋅in) for Small Pulleys — 1/4" Top Width

Belt Width (in)Width Multiplier

1/22.20

The following table represents the torque ratings for each belt in its base width atthe predetermined number of grooves, pitch diameters and rpm's. These ratingsmust be multiplied by the appropriate width factor to obtain the corrected torquerating (see Step 7 of SECTION 24, on page T-146).

XL (.200 in) Belts

Number of GroovesPitchDiameter

mminches 10 100 500 1000 1160 1450 1600 1750 2000 2500 3000 3500 5000 800010000

rpmof

FastestShaft

1117.78.7002.552.552.552.542.542.542.542.542.542.542.542.532.522.482.45

1219.41.7642.782.782.782.782.782.782.782.772.772.772.772.762.752.702.65

1422.63.8913.243.243.243.243.243.243.243.233.233.233.223.223.193.113.04

1524.26.9553.473.473.473.473.473.473.473.473.463.463.453.443.413.323.23

1625.881.0193.713.713.703.703.703.703.703.703.693.693.683.673.633.523.41

1829.111.1464.174.174.174.164.164.164.164.154.154.144.134.124.063.903.75

2032.331.2734.634.634.634.624.624.624.614.614.614.594.584.564.484.264.05

2133.961.3374.864.864.864.864.854.854.844.844.844.824.804.784.694.434.19

2235.591.4015.095.095.095.095.085.085.075.075.065.055.035.004.904.604.32

2438.811.5285.565.565.555.555.545.545.535.535.525.495.475.435.314.924.56

2845.291.7836.486.486.486.476.466.456.446.446.426.386.346.296.095.474.89

3048.511.9106.956.956.946.936.926.906.906.896.876.826.776.716.465.704.99

7/161.89

3/81.59

5/161.29

1/41.00