GEAR DRIVE DESIGN JONATHAN BUNIE

APRIL 26 2012

PROJECT SUMMARY

This gear drive was designed for Titan Industries for the purpose of powering coal

transfer conveyers. As requested, it was designed using a Baldor CEM3769T-5 three phase

electric motor rated at 7.5 horse power at 3525 rpm. The drive consists of three shafts, two

pinions, two gears, three different types of bearings, and other support accessories as well.

The motor is mounted directly to the gear housing with the shaft entering the housing

through the back. The shaft must be reduced to a ¾ inch diameter due to the small size of the

pinion. The motor’s shaft is supported by a bearing to resist stress resulting from bending

moment. The input pinion is mounted directly to the motor shaft using a key to transmit torque

and a retaining ring for pinion positioning on the shaft. There are also three identical spacers

located in a row between the inner bearing race and the pinion also for the purpose of axial

location on the shaft.

The intermediate shaft has a nominal diameter of 1.25 inches but has and enlarged

diameter section located against the inner race of the rear bearing and is used for resisting

thrust loads on the shaft thus maintaining shaft position. The rear intermediate gear is placed

against the opposite side of the enlarged section and is constrained using a key for

transmitting torque followed by a spacer to separate the gear and the pinion on the same

shaft. The rear end of the shaft is threaded to receive a nut which secures the shaft to the

bearing. The front of the shaft contains a retaining ring and groove before entering the bearing.

This combination prevents any axial shaft translation.

The output shaft is slightly longer than the intermediate shaft for the acceptance of the

chain sprocket however they share the same nominal diameter. Similar to the intermediate

shaft, there is also a section of the output shaft with a larger diameter to prevent axial

movement of the gears. The rear end is threaded for fixation to the bearing. The gear is

constrained using a key for torque transfer as well as a retaining ring to prevent axial

APRIL 26 2012

GEAR DRIVE DESIGN

APRIL 26 2012

PROJECT SUMMARY (CONT.)

movement. The front end of the output shaft is splined and threaded in order to attach the

chain sprocket using a large nut. All shafts are manufactured using 1040 cold drawn steel

incorporating a safety factor of four.

The housing is constructed using quarter inch thick 1040 cold drawn steel. All joints are

welded with the exception of the cover plate which is secured using bolts. The cover plate

provides easy access for assembly and disassembly and provides support for the shaft and

bearings.

The following standard parts were incorporated into the design: Four high load, double

sealed bearings for 1.25 inch shaft diameter and one high load, double sealed bearing for ¾

inch shaft diameter, one #6799K26 Stainless steel machinable-bore sprocket for #80 roller

chain, several various size stainless steel shims, aluminum washers, and ½-13 grade 8 steel

hex nuts and 1.75 inch bolts. The retaining rings used are external type rings with a black

finish. Finally, Buna-N O-ring cord stock must be used as an oil seal between the cover plate

and housing.

Using the provided fill ports, add 5.25 US Quarts of API GL-3 Gear oil for proper gear

lubrication.

APRIL 26 2012

GEAR DESIGN

MOTOR SHAFT

The motor shaft contains one pinion with a key to transmit torque. The pinion is constrained axially with a retaining ring and a spacer to separate the pinion from the bearing. The pinion has a diametral pitch of 8 and with a 2.25 inch diameter, the number of teeth total 18. The pinion is manufactured using .20 carbon steel giving an allowable bending stress of 20000lb. The total bending stress was calculated to be 12151 lb. The pinion was designed to slide freely onto the shaft with an RC1 tolerance. All gears in the unit were designed with a 1 inch face width.

INTERMEDIATE SHAFT

Contains two gears, one receiving power from the motor

pinion, and one transmitting power to the output shaft.

Both gears transmit torque with a 1 inch long by .25 inch

square key.

Both have a diametral pitch of 8. The larger gear has a

diameter of 8.28 inches and has 66 teeth. The smaller

pinion has a diameter of 2.25 inches and has 18 teeth.

Both gears are designed to slide freely over the shaft

using an RC1 tolerance.

The two gears are constrained between the enlarged

diameter shaft section and a retaining ring before the front

bearing. One spacer separates the gear from the pinion.

The gear and pinion are manufactured using .20 carbon

steel giving an allowable bending stress of 20000lb. The

total bending stress was calculated to be 12151 lb for the

gear and 19452.7 lb for the pinion

OUTPUT SHAFT

Contains one gear receiving power from the intermediate

shaft.

The gear has a diametral pitch of 8. It has a diameter of

8.28 inches and has 66 teeth.

It transmits torque through a 1 inch long by .25 inch

square key.

The chain sprocket located outside the gearbox receives

torque through the splines and is constrained between the

bearing and a large nut.

The gear and pinion are manufactured using .20 carbon

steel giving an allowable bending stress of 20000lb. The

total bending stress was calculated to be 19452.7 lb.

The gears and chain sprocket designed to slide freely

over the shaft using an RC1 tolerance.

APRIL 26 2012

SHAFT DESIGN

MOTOR SHAFT

The motor is manufactured with a shaft with a 1.375 inch diameter. The shaft needs to be reduced to a 0.75 inch diameter to receive the pinion. The keyway on the motor shaft is designed to be 0.19 inch in width and height by 0.945 inch long. Directly after the keyway is a retaining ring groove with a 0.7 inch diameter and a 0.046 inch width. This shaft enters the gearbox through a bearing using a force fit class FN2.

INTERMEDIATE SHAFT Rear threaded end to accept large constraint nut.

Nominal diameter is 1.25 inches with a .188 inch long

section of diameter 1.55 inches.

2 gear keyways separated by a spacer. Recommended

key length of .239 inches was adjusted to 1 inch.

Designed to accept .25 inch square key.

Retaining ring groove immediately following keyways

toward front of shaft. Accepts 1/8’’ thick type 316

stainless steel external retaining rings.

The overall length is 4.056 inches with a chamfer on the

back end and a fillet on the front end.

Both ends are supported by bearings using a force fit

class FN2.

OUTPUT SHAFT Threaded on both ends to accept a large shaft constraint

nut as well as to constrain the chain sprocket to the shaft.

Rear threaded end to accept large constraint nut.

Nominal diameter is 1.25 inches with a 1.313 inch long

section of diameter 1.55 inches.

1 gear keyway immediately after enlarged shaft section.

Recommended key length of .881 inches was adjusted to

1 inch. Designed to accept .25 inch square key.

Retaining ring groove immediately following keyway

toward front of shaft. Accepts 1/8’’ thick type 316

stainless steel external retaining rings.

The overall length is 6.256 inches with a chamfer on both

ends.

Both ends are supported by bearings using a force fit

class FN2.

Torque is transmitted from the chain sprocket through 8

splines. The sprocket is separated from the bearing using

3 identical spacers and is secured axially with a large nut.

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june

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ACCESSORIES

The gears transmit torque in the shaft through the use of keys and keyways. The standard size is .25 inch

square of the intermediate and output shafts and 0.188 inch quare for the motor shaft. They have design

lengths of .881 inches of the output shaft, .239 inches for the intermediate shaft, and .087 inches for the motor

shaft.

The shafts are supported by high load, double sealed bearing and use a class 2 force fit for the shaft mount

and a class 1 clearance fit for the bearings mounted to the housing. All bearing have a maximum of 5000 rpm

and are design for 20000 hr of life.

The 6799K26 Chain Sprocket is a stainless steel machinable bore sprocket for ANSI #80 Roller Chain. The

hub has a 4 inch diameter and the overall width is 1.5 inches. The overall diameter is 5.95 inches with a tooth

pitch of 1 inch. The bore needs to be 1.25 inches with class 1 clearance fit and 8 splines .05x.1 inches.

The shaft components consist of spacers and retaining rings. The spacers are 1/8 inch thick stainless steel

shims for a 1.25 inch and ¾ inch diameters. The

retaining rings are black finish, magnetic, external

retaining rings. The motor shaft receives a .042 inch

thick ring for ¾ inch diameter. The drive shafts receive

a .05 inch thick ring for 1.25 inch diameter.

A large nut is used on the back of the intermediate

shaft and on both ends of the output shaft. It is a 1.75

inch hexagonal nut with 1 ¼ - 7 threads.

Housing

The housing is composed of .25 inch carbon steel

with welded seams.

To assist in maintenance, an access cover was

added for easy assembly and disassembly.

The bearings rest on the access cover and rear of the

housing and are constrained between extruded

portions in the face of the housing.

The access cover is held in place using 16 bolts and

washer assemblies. The bolts are 1.75 inches long

and have ½ - 13 threads and a head width of ¾

inches. The washers are .05 inch thick lightweight

aluminum for a bolt diameter of .5 inches.

The access cover is oil sealed with Buna-N 1/8 inch

O-ring cord stock. The O-ring stock fits into a groove

behind the access cover.

Drain and fill ports were added on the top and left

side for easy maintenance.

A filler cap is manufactured using 1.5 inch hexagonal

stock and is bored with 1 ¼ - 7 threads that are .5

inches deep.

For added strength, the base of the housing

supporting the electric motor is manufactured using ½

inch thick steel.

APRIL 26 2012