Finnl Report

el nopt Feusibility Study

al, LIGHTWEIGHT, HIGH MOBILITY TRACK

Contract DAAEO7-67-C-3847 ','

Army Tank Automotive Command

Ordnance Management Strecture Cede No.

5521.12.26900

Department Of The Army Project No.

D D C I..S5.21801.D.263

R" A 16 197

B r 9 FEBRUARY 1968

Distribution of this document is unlimited.

S T T AApproved for public reeaie"

Dio.riution u rth'mIted "

DEFENSE OPERATIONS DIVISION 1 CHRYSLERCORPORATION

Defense EngineeringDetroit, Michigan

Reproduced by

NATIONAL TECHNICALINFORMATION SERVICE

5pInqf.Id. Va 22151

BestAvailable

Copy

[i

Concopt rFeasiuuiuy

LIGHTWEIGHT, HIGH MOBILITY TRACK

(ontract BAAE7-67-C-fl47

H Army Taut Aetemetlve (summed

Ordnance Memegemeus Strutter. Cud. No.

5521.12.26900

H ~w'&~eDepoutment Of The Army Project No.it? ~ 1 -S -21801-1-263

C' r9 1f31VA1Y 19U8

DIFENSE OPERATIONS8 DMIIO CHRYSLERWCORPORATION

Defense lEngineering

Detroit, Michigan P-0. &o. 757 Detroit, Mich., 48231

DELIVERED BY CHRYSLER CORPORATION, PURSUANT TO CONTRACTDAJW07-67-C-3847. GOVERNENT USE CONTROLLED BY GENERALPRO ISION ENTITLED "RIGHTS IN TECHNICAL DATA" OF THECONTRACT 4I CH IS ASPR 9-203(b), FEBRUARY i9465.

ABSTRACT

This report presents Chrysler's concept feasibility study of the Lightweight

High Mobility Track, performed under Contract DAAEO7-67-C-3847, effective

10 May 1967. The subject track consists of a fiber glass reinforced belt

with guide tooth projections on its inside surface and pneumatic pads on

its outside surface. This part icuiar track vwo intended tor use on o

vehicle with a gross weight of 3000 pounds. The resultant concept is 12

Inches wide, welahs 5.83 pounds per foot, and is 110.7 percent buoyant. in

addition, the inharent advantages of the design Include a smooth roadwheel

path, the ability to absorb road shocks, quiet operation, and expected iong

life.

The concept was analyze=. fron, a nmiber of standpoints Including weight,

buoyancy, tensile streng n, and feesibility of manufacture. it was con-

cluded that the concept 's feasible and that it would be applicable to

lightweight cargo and rtconnaltsance vehicles. Recommendations for future

activity on thts projety are iftso presented.

4f

LIGT IHT H-IG1 MILITY TRACK

TYKE BUOYANT RWSER BELT WIThN PNEUMATIC ROAiD PADS

WOTH 12 INC4ES

WEIGHT 2.75 IN4O4S tROADI4EL T1 GROUND

PITCH 6 iNCHES

MAIN TENISlON, AR FIBER GLASS CORDS

MEIQHT PER FOOT 9.83 LB

BUOYANCY I 0l

CONTENTS

1.0 INTROOUCTION

2.0 TECHNICAL REQUIREAENTS 2-1

3.0 CONCEPT !M STGATION 3-!

5.1 Reinforced Belt 3-1_

3.1.1 Functional Requiremnts 3-1

3.1.2 Concept Developeent 3-1

3.1.3 Manufacturing Tecbnques 3-6

3.1.3.1 Open-Side Press 3-8

3.1.3.2 Positive-Drive Type CIrcular Mold 3-8

3.1.3.3 Rot--Cur. 3-9

3.2 Road Pad

3.2.1 Functional Requirennts 3-10

3.2.2 Concept Deve loptnt 3-I0

3.3 Sprocket 3-17

3.3.1 Functional Requiremnts 3-17

3.5.2 Concept Oevelopm nt 3-19

4.0 CONCEPT DESCRIPTION 4-I

4.J General 4-.1

4.2 , I nforced BoIt 4-I

4.3 Road Pads 4-4

4.4 Sprocke t

LIST OF ALSTWRATIO$

F I ure Lim_

3-i Proposal Concept - Front View 3-2

3-2 Lightlght High AMbllity Track - Latera. l-5Cross-Sct ion

3-3 Lightweight High Mobility Track - Side Vew 3-7

1-4 Proposel Cofcept - Sid* afvd Bottom Viii 3-1i

3-5 LightWeight High Mobility Track - Croes- 3-14Section Through Attachments and Valve

3-6 Tire Valve Mounting 3-15

3-7 Lightweight High Mobility Track - Bottom View 3t-18

3-8 Sprocket - Side View 3-20

3-9 Sprocket - Cross-Section --21

4-1 Light eight High #ability Track - Plan View 4-5

5-I Track Pad Wear Rates Versus Footprint 5-5Pressure (Graeph)

5-2 Track Pad Wear Rates Versus Average Footprint 5-6Presssw f~raion I

TABLES

Table I Comarison of Lightweight Track end )S71 5-10Track

1.0 INTRODUCTION

F This report presents a concept feasibility study of the Lightweight High

Mobility Track conducted under Contract DAAEO7-67-C-3847, wcin became

effective on 10 May 1967. The scope of work included the development and

1pfintion of the track concept and its drive sprocket end the analyses

necesa-ry to establlsh feas!biifty.

The project originafed as a result of Chryslerls proposal i.t response to

Request for Quotation 0AAE07-67--Q-W72, which was Issued on t2 October i6

by the U. S. Army Tank Automoti ve Comnmand. The technical requirements of

thls RFQ were formulated by the Mobility Systems Laboratory at ATAC, which

also prov!ded technical administration for the feasibility study. Chrysler

proposed a buoyant track consisting of a continuous fiber glass-reinforced

bait with rubber guide teeth on Its tnside surface and pneumatic track pads

on Its outer surfocia. This unique approach was adopted because of require-

ments for buoyancy, light weight, shock absorption, and smoothness of

operottono

The requirement that the track be buoyant enough to support itself In vater

was perhaps the most difficult, especially In light of the other require-

ments. The first tracks concepted in preparing the proposal were much more

conventional, having pins or bands, and compartments to Increase volume and

buoyancy. Each of these concepts achieved buoyancy only by Increasing

weight In comparison to existing track designs. Furthermore, these concepts

were quite unwiidy and subject to easy dage from a number of standpoints.

i-I

Ii

F1

!t thus teca.e tvi d~t that the ealsred track mwst be unlque In many

respects. First, a buoyant track would require that metallic parts be

held to an absolute minirMun. Second, to provide a truly "satisfactory"

cushion against road shock, vlbrat;on, and noise wt-uld require a degree

of materlal flexibility m're typical of el astomers thart of metals.

The idea of eitminatlng metallic parts at much as possible was reinforced

by an amnknent to the RFQ, dated 14 0c-tber 196. The amendment Indicated

that the rack should be applicable to a vehicle with a gross weight of

3,000 to 9,000 pounds. Chrysler interpreted this as Indicative of a desire

for a track of extrew%-ly I ght weight.

Following a review of the technical requirements for the track, this report

discusses the concept Investigation and presents a description of the

resulting concept. The various analyses used to deter-nir* feasibility and

compatibility w!th the specifications ore then presented, as well as con-

cluslons and recontendations.

1-2

2.0 TECHNICAL REJIURJENTS

The following technical re. iremerts were listed In the RF, and the concept

presented In the propos l was directed toward meeting them. These require-

mtwhts were also state4 |In the feasibility study contract under Section 8,

Description or Specificatlons. The track was to have th e following capabi!l-

t Ies:

1. High flotation abTilty sufficient to make it better than self-

supporting In water.

2. Cepablilty of traversing the following terrain spectrum at the

&verago Indicated speeds.

PERCENT REQUIRED NPH DESIRED MPH

(a) Dry, hard cross 16.6 35 50country

(b) Dry, mild cross 33.6 20 28.5country (Includ-Ing level culti-voted field andtell grass)

(c) Dry, r"ogh cross 16.6 12 17country lInclud-Ing uncultivatedlend, smell trees,brusht, and steepgrades)

(di Wet mal lnel 16.6 17.5 25cross countryI Including mud,peddles, svnM,muskag, and snow)

(Wi Inland waterways 16.6 7 12fincluding river,lakes, and canalscontilning sharpobstacles andsteep banks)

2-I

LLA

5. Capability of negotiating a 60 percent dry cross country grade,

a 40 percent dry side slope, and climb wet, soft 60 percent slopes

et the water's edge.

4. The track shall be easily maintained In the field.

5. High rellab;ilty of operation for a life of 5,000 m;loz (long

range goat 8,000 to 10,000 rritesl at low cost per vehicle mite.

6. A satisfactory cushion against vibration, road shock, and noise.

7. Operational capability within an eftlent trawarature range of -65OF

to ±1 25F.

8. Low propulsive power loss throughout the operating speed range ano

terrain spectrum.

9. Maximum use of, but not limited to, coomercially available materials.

Proposed use of promising new materials to obtain the desired off I-

clency, economy, and life Is deslrable.

In addition to the above requirements, the contract listed target goals ard

parameters, which wire ormulated by ATAC and agreed to by Chrysler during

contract negotletions:

I) Target Track Width - 12 Inches

(b) Gross Vehicle Weight IGVW) - 3,000 lbs.

1) Curh Weight - 2,000 lbs.

(d) Target Track Weight - 12.0 lbs/ft. maxilum

(el Target Buoyancy - 100 percent minimum

2-2

3.0 CONCEPT INVESTIGATION

This section describes the concept investigation and the evolution of the

design from ;ts inceptioA to its finai form. A review of the functional

requirements for each part is also given to further explain the selection

of certain design characteristics.

3.1 Reinforced Belt

3.1.1 Functional Requirements

It is essential that tl e belt possess the following characteristics in order

for it to function properly:

a. Adequate strength in tension

b. Provide smooth roadwheel path

c. Lateral stability

d. Torsional stability

e. Low weight

f. Suitable for attachment of road pads

g. Provide guiding surfaces

h. Provide driving and braking surfaces

I Minimum stretch under tension

3.1.2 Concept DevelplMent

The belt portion of the track initially proposed was 20 inches wide, one-half

inch thick, and had two rows of teeth for guiding on the outboard edges of

the roadwheels, es shown In Figure 3-1, page 3-2. A segmented construction

was envisioned as the best approach rather then an endless construction. The

3-f

FIgur* 3-1 Proposal Concept -Front Vlew

belt was reinforced only Ny the fiber glass cord. Meetings with ATAC

personnel and the establishment of target parameters indicated that the

concept would have to be altered at the beginning of the feasibility study.

First, the width of the belt was changed to 12 inches. Second, it was

recoamended that a centar gulde/center drive arrangeant be used instead of

the double row of guide teeth.

The investigation began with layout studies te determine the overall con-

figuration of the concept based upon the target speclfik.ations. Simultaneously,

the strength requirements for the belt were determined and research on rein-

forcing materials was begun. The properties of fiber glass were examined, and

it was concluded that this materii waulo make en excellent reinforcement for

carrying belt tension loads. Specific properties whicit sujpor' this conclusion

include the following (I):

o High tensile strength: 25,000-315,000 psi

o Complete recovery from strain up to about three percent

a Not affected by age

o Not affected by moisture

0 Not attacked by most acids, weak alkalies, or organic solvents

o Compatible with track operating temperature requirements

0 Not attacked by micro-organisms

Discuasir with manufacturers of fiber glass confirmed these properties. In

addition, It was recommendec that the fiber glass not be loaded in shear, but

only in tension. For this reason, it was decided to make the belt an endless

construction rather than attempting to segment it. This construction eliminates

Numbers in parentheses indicate references listed on page 7-1.

3 -3

shear loads introduced by attaching one segment to another end offers the

greatest strength capability In tension. It provides an uninterrupted path

for the roadwheels and allows uniform sprocket engagtint at any point on

the belt. A weight savings is a!so realized In the endless construction.

The restriction on shear loading for the fiber glass Indicated that, by

itself, it would not furnish a suitable base for ettachment of road pads.

Therefore, some other type of InternaJ belt relnforceient would be required

in addition to the fiber glass. A fabric such as iylon or rayon was selected

because of success in similar applications and because It Is extrerely tough.

In addition to providing strength in the attachment area, the fabric increases

the tors~onal and lateral stability of the track. It was decided to p lace the

layer of fabric between the fiber glass and the inner (roadwheel) surfac, of

the beit, closest to the point of attachment load application (Figure 3-2,

page 3-5). In this location, the fabric also protects the fiber glass from

impact loads caused by the interaction of the roadwheeIs with debris on the

inner surface of the belt. This "cushioning" effect occurs because the fabric

has a high ultimate elongation and thus can deform locally to distribute con-

centrated loads. In this way, the material converts impact energy into strain

energy vAich is in part dissipated by :nternai friction or stored and subse-

quently released as the material regains its original shape. The study of

Internal reinforcements for the belt revealed that the belt thickness could

be reduced from one-half inch to three-eighths Inch, thereby reducing the

weight of the flat portion of the belt by 25 percent.

Following the reconmendation for a center guide/center drive arrangwment for

the track guide toeth, a preliminary design for the teeth was concepted on

3-4

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-5

layout drawings. An attweat was mae to provide the teeth with the largest

bases oosslble within reason In order to produce adequate strength to with-

stand guiding, driving, and braking loads. The front and rear surfaces of

the teeth ere then developed by a layout study In vehlch the belt was graph-

ically wrapped and unwrapped around the sprocket. A tooth height of three

Inche was conidcered adequate for guiding purposes, especially In view of

the ,erge area of the tooth sides IFlgure 3-3, page 3-7). For roadwheets

greater than 14 inches In diameter, at least two teeth are In contact with a

radwheel At all times.

3,.3 .nufacturing rachnioums

In order to establish the feasibility of the belt, it was necessary to deter-

mine the problem Inherent to its manufac'sre and If, .inded, It could be

manufactured. During the nitt i stages of the Investigation, handbooks on

rubber products and processes were first reviewed to provide background infor-

mation in preparation fcr discussions with suppliers. A basic method for

manufacturIng the belt was also formulated. Following the changes in the

concept pronpted by the contract target specifications, a number of suppliers

with experience in manufacturing fiber glass reinforced belts were cntbcte"W.

Saw of the discussIons vA ich followed pro"pted minor change. In the belt cc"n

cept. Chrysler's original IC*a on manufacturing wers also generally confirmed,

with the addition of details In nomenclature, processes, end sequence of opera-

tions. The pararaphs below describe three methods of manufacturing and the

advantages Of ech.

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3-7

1.,3,1 Onon-Side Pro'ns

This process If Saggeaseld as the least expensive method for producing proto-

type belts In small quantlties. Uncured shoet rubber stock Is first laid

over a round mandrel. The Inside dameter of the eubbet on the mandrel is

equal to the length of the Inside surface of the f!nlshed track. The fiber

glass tension masc- Is wound around the mandrel wile under tension. Another

sheet of uncured rubber Is then laid ovr the tansIon member and secured with

a curable adhesive. The "roW' belt Is suspended on two rtllers, one on each

side of the press. A mold In the press is loaded with uncured rubber stock

which has been pre-cut to the approximate shape of the guide teth. The bel t

Is put under tension by a hydrautl cylinder which Is con-iectd to one of the

rollers. The press Is then cloned upon the belt, subjecting .it to het and

pr-essure Thus, the belt Is cured (vulcunized) In increments (typically 3-

feet) and Is indexed when the cure of one incumenrO : complete. The control of

tempwature and temperature gradients along tW, po - !n being cured is

extremely Important to prevent overcure or undor_.-ure In overlap areas betwe n

Increments. This method may be used to cure a bolt of ny anticipated length,

but a specific mandrel Is required for a g3ven belt length.

3.1.3.2 Posit ive-Drty. TyI CIrcular Mold

Like te open-side press method, the circular mold method requIres a mndrtel

for establishing the belt length. The raw belt Is placed In an autoclave

which contains a circular moid. Pressure Is applied by a sleeve tnd a bag

which Is pressurized with steam which surrounds the belt and the mold. When

the bag Is pressurized, the belt Is pressed against the mold. The production

rate of tnis process Is approximately 6-7 times that of the open side press

method, but a specific mold is required for a given belt length. The mol

would be much more costly than that required for the open-51de press. The

circular mold process would, the.efore, be best suited for production of

large quantities at belts of a specific iengtn ana would offer a maximur

prodjct!on r~tq in co~narison to other methods.

As with the above processes, the rota-cure method requires a mandrel for a

specific belt length. Rather than curing in increments or in one step, the

rota-cure machine feeds the raw belt through a series of rollers, one of

which Is a heated mld. Pressure is applied by a stainless steel band which

Is also wrapped around the rollirs. The use of this steel band requires that

one side of the belt be smooth. A singular advantage of Vhis pr-ocess is that

It can cure belts of various lengths, provided the width, pitcr, etc. are the

same. The rotc-cure process is not as fast as the circuizr !r1t prnocess, bt

it Is expected t!hat two belts could be handled per riacnire, thjs sh-owing an

advantage over the open-side press.

All of the above processes can be appied t., an endless belt construction,

wherein the tension meembrs do not have to te spi iced or conrected ,echan -

ically. This type of construction is consider-ed essential for a aximurn eit

life and strength. It wes, therefore, canclucea that ali -: these processcs

could be used to manufacture the helt portlon of the 'ightmigiht track, with

a reasonable probability of success, owin9 tPa "to previous experience of

H suppliers with similar items.

3.2 RanttPt

I,-

,2, I fumt nn Rsgurw~nts

The following charecterlstics were considered of major importence in the

design of the pneumatic road pads:

A. High buoyarcy

b. Low might

c. Longitudinal flexib lity

d. Satisfeactory c¢shion ageinst road *hocks

o. Nn-directional tread to avoid rcessity of right- and left-hand

parts

f. Low "footprint" pressure

g. Adequate heat dissipation

h. Adequate attachment strength

1. Resistance to penetration

j. Valve requiring a minimum of time and effort to fill air chamber

t.2.2 Co j roXfa. Tei ostnt

heds of icl vore Inside the air cel cavity (Figure 3-4, page lgly The

air valve wase Integral with one of the studs. The road tontact surfe was

chevron-shae .

At the outset of the feasibility study, the road pad concept mas first reduced

in width froi 20 Inches to 12 Inche. The first aree to be Investigated was

the otttchment to the be lt Various types of retnforcemnts were concepted

for the interior of the air cavity. The overall pad design ws lIso discL4sed

with rubber cVcanlee, ad It w, decided that major changes would be necessary

3-10

A

Figure 3-4 Proposal Concept - ide and £otton Views

to facilitate manufacturing. Fi-st, having the attaching studs enter the

air cavity p-osented Sealing problem as well as manufacturing problems.

Second, placing reinforcements inside the cavity required that access to the

cavity be provided. The overall shape of the pad also made It extremely

difficult to place fabric reinforcements in the cavity walls, and the pad

would not tlex properly oecause its wails were straight-uided and had rather

sharD cornersE. Thus, it becarm evident that a complete redesign would have

to be made to overcome these problems.

A basically oval shape was selected to allow the placement of the fab.-ic

reinforcements and to allow flexing by eliminating corners. The top surface

of the pad remained rectangular. The pad would consist of a rectangular

upper (belt sida) piece and an ovai-shaped lower piece containing the air

cavity. The lower piece would have a flange matching the periphery of the

upper piece. The two pieces would be Joined by applying heat and pressure to

the flange area. A heat-sensitive cement would be used in the Joining piocess.

Prior to joining, each piece would be molded separately and partially vulcan-

ized in the flange area. Vulcanization would be completed In the joining

process.

Following the above approach, the configuration for the road pad concept was

re-established. Detalled study of certain areas and discussions with sup-

pliers established the correct corner radii, d-aft angles, and material

thickness.

The attachment area was further inve'12ated once the basic configuration of

the pad had been estabitshed. In addition to facilitating closure of the

3-12

ar cell during manufacturing, the flange around the top of fhe pad pro-

vided a means of making the attachment without violating the air cell

cavity. The corners of the flange offered an excellent place to make the

attachment with three-eighths i3/8) bolts and flat washers. As with the

belt, a steel sleeve was used to line the bolt hole to aid in distributing

the lateral attaching loads and to prevent the threads of the bolt from

working against the rubber (Figure 3-5, page 3-14)- The sleeve also pre-

vents the rubber from being compressed due to bolt tension. The front and

rear edges and corners of the pad flange were also reinforced with steel

clips. These clips protect the edges from tearing and keep the top of the

pad flat against the track.

The decision to make the attachment with boits outside the air cavity elin.i-

nated the Idea of using one of the bolts as a valve. A review of the pad

design Indicated that the valve should be located in the top portion of the

pad, where the surface Is subjected to a minimum of flexing and where the

valve would receive the least abuse during operation. A small valve such

as used with tubeless tire rim was first considered. The valve would extend

from he top of the pad through a hole in the track. Since these valves are

designed for mounting In m*tal wheel rims, It was decided to reinforce the

hole in the top of the pad with a steel ring as shown In Figure 3-6, page 3-15.

This ring would be boneed to the rubber and would provide a sealing surface

against which the body of the valve could expand following insertion. It

would also prevent localized ilexIng In the area of the valve. This type of

valve requires a cap which prevents the build-up of debris around the valve

stem and alds in sealin;. The plac.rent of this valve Is critical because

t3-13

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CAP

TOP O PAD-RETAINING RING

Figure 3-6 Tire Valve Mount ing

F I 3-15

uOL , L, un nr uddwhhel wId the ro a .heel must pSS b tween

rne gUije reetnl an 'm e rcw of valves. 1he valve is also qui re vulnerable

due to tne fact fht it projects from the inside surface of the irack close

to the outboard edge.

When the above pr.)t .s ecmaro nvident, a search for a valve requiring less

conplexity, weighr. space, and ef*ort to use was initiated. Since this is a

low pressure application "pp-oximately (i psi static), other types of valves

typically useo tc. 1-,:, pressues were examined, It was founo that the valves

connoniy used in tootoal's, bOsketb-!,s, etc. would meet the requirements.

These valves are c~omnonty called "inflaters" or "needie valves" because they

are tilled with a hollow needle.

This type of valve has several advantages over the tire valve originally

selected. The weignt of tne inifater is almost negigibie (approximately

1.9 grams); no cap is required; the valve will not ex*end beyond the Inner

sirface of the belt nc, therefore, will not be as vulnerable lFigure 3-5,

page 3-i4". In addition, the rime required to fill the pad with this valve

is expected to be less, and a pre-set ai- pressure source may be used to

great advantage. It is also expecred that the valve may e Inserred directly

into the to-p portion of the pad 8nd bondel With an ;)dheslve, thus eliminating

the metal seating ring required with the fire valve.

In developing the pneuriatic pad concept, the idea of a chevron-shaped

grouser was carried over from the proposal concept. With a grouser of this

shape and the fact that the valve would have to be locatea near the ourboard

edge of the pad, it would have Deen necessary to have left- and right-hand

3-16

pads f-.r uFe on opposite sides of the vehicle. Also, the area of contact

of this p d on the ground was rather small. Therefore, an attempt was made

to design a grouser which would be non-dIre,.tional and provide a large

"foipr iai" area to reduce ihe unit prosk-o on th rubber for greater iear

and to ioer the pad inflation pressure requirement.

The grou,:6r fnally selected gives mra.imum protection and support to the pad

air cell. It also presents gripping edges in toth longitudinal and lateral

directions (Figure 3-7. page 3-18). A iot-Crl slot in the grouser prevents

excessive stiffness when bending around the roadwheels and sprocket. The

thickness of the grouser was established as 5/8 inch, based upon weight and

buoyancy requirements.

3.3 5grocket

3.3.1 Functional ReqMIrgMnts

Because of the somewhat unorthodox design of the track and its rubi or guide

teeth, It was necessary to design a sprocket specifically suited to this

application. The following characterlstics were considered in the develop-

ment of the concept:

a. Smooth engagement and disengagement with track guide teeth

b. Light Wolght

c. Self-cleaning

d. Ease of manufacture

e. Adequate support of track

f, Ease of attac.hment to final drive hub

3)-17

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3-1-'

3.3.2 Concept DeV*;Qpment

The sprocket concept presented In the proposal consisted of twelve hollow

steel drive pins welded on each end to circular plates. In view of the

cIanges made to the trA-ck concept at the outset of t-" fe~ibilify study, it

wm n-.-essary to revise the sprocket concept and provide additional detail

to *grob with the track and the hypothetical vehicle application.

Beginning with the basic loea of a pin-type sprocket, It was first decided

to reduce ttve number of pir-s to ten In order to reduce size and weight. This

was considered advisable because the vvhicle application envisioned was

extremely light. The first step in designing the sprock~et was to determine

the correct location of the drive pins. Thls was done by considering the

Inside surf- :Ff the belt as the pitch line of the track and arranging the

drive pins to be targent to the inside of a diameter co nsisting of ten arc

lengths of o.00 lnchs. The pitch dliamter. therefore, was found to be 19.10

Inches (Figure 3-8, page 3-20).

WIth the dlametrai locations of the drive p;ns establ ished, attention was

next centered on providing support for the pinls while all ing clearance

for the track guide teeth. it was also desired to support the track belt

outboard of the pins. Two Identical deep-dish formfed sections were thus

developed to the desired shope. It was reasoned that thIs method would

facilitate manufacturing and would minimize the number of parts required

(Figure 3-9, page 3-21).

The formed sections were then perforated to cradle the pins prior to welding.

In this way, accurate positioning of the pins was assured. Additional

3-49

Figure 3-8 Sprocket -Side View

3-20

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P1gw-s 3.S Spiocket - Cress-Sect Ion

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3-21

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perfoirations were included to allo debris to fail free of the sprocket and

to reduce weight.

The attachnnt of the aprocket to the final drive hub was the next area to

e nvestgated. in thu absence of definition in this area, an M116 final

trive tuo was used as :. giide. The variou;s parts Inicluding bearings, drive

shaft, hut, and support housing were re rranged and revised to suit the n*w

sprocket design WiThOUt charging the basic concept. S[nce fin-| drive hub

definition was beyond the scope of this project, no further study wfts per-

iormed in this area. A hole in the center of the sprocket assembly was made

to pilot on a diameter of the final drive hub, and the sprocket was held In

place by studs and by nuts, in a manner similar to automobile wheei mounting.

3-22

4.0 CONCEPT DESCRIPTION

4.1 General

The Lightweliht High Mobility Track is essentially an endless reinforced

rubber belt havIn9 guide teeth molded to its inner surface and rubber

pneumatic road pads bolted to its outer surface, The track is 12 inches

wide and h" a "pitch" of 6 inches. One guide tooth and one road pad are

located oxn each p 1tch. Due to te !lexlbi!ity of th-is track, the term

"pitch" takes on implIcatio is different from the same term applied to p n-

type tracks or conventlon~l band tracks using rigio shoes; as the track

travels arojnd roadwheels, sprocket, and return rollers, it will bend suff1-

ciently to partially conform to these objects rather than forming distinct

chords.

The track weighs approximately 9.83 pounds per foot and is 1l0.7 percent

buoyant in water. The envelope length envisioned for the theoret~cal vehicle

applical ion is 22.5 ieet, and each track will weigh 210 pounds. Each pitch

of track displaces .0874 cubic feet of water when submerged.

ItThe sprocket engages the guide teeth on the inside surface of the belt. The

sprocket teeth are cylindrical hollo pins which are welded to two deep-dish

formed wteel sections which bolt to the sprocket hub. The formed sections

are perforated to prevent the colection of debris around the Pins and are

shaped to guide the track by forming a groove for the guide reeth. The track

is supported outboard of the pIns by flanges on each of the formed wheel

sections.

4--

4.2 ~inforced Belt

The reinforced rubber belt section of the track resembles a cogged positive-

drive belt, except that the teeth do not extend across the entire width. The

thickness of the belt is 3/8 Inch and the guide toeth extend throe inzhes from

the Inside surface. The teeth serve not only as driving surfaces, but also as

track guides; the dual roadwheels straddle the teeth and or* presented with a

smooth, uninterrupted path.

The tension iembei-s of the track are located In the thin belt section. Tension

losds are carried by strands of fiber gless cord. The ultimate tensile

strength of th* belt Is expected to Pe approximately 66,000 pounds. The fiber

glass cord consists 0~ one strand wrapped many times around the. track envelope

and located at the center of the 3/6 Inch thick section. This reinforcement

extends across the full wid'sh of the belt (Fgure 3-2, page 3-5). Only one

layer of the cord Is required. Two or more layers could not be used In this

application because of the rigidity of the fiber glass cord In tension. Bend-

Ing around a roaduheel or sprocket could set up enough stress in the cord to

cause failure of tlhe rubbr or of the cord Itself.

The fiber glaes cord Is made from cortt nuous fil aments grouped Into strands.

The strands are twisted together to produce the cord, It is Important that

the direction of tWit be reversed at the center of the belt. For example,

the portion of the belt from the longitudinal centerline to the right edge

would contain cord with a right or left-hand "Ist. The portion of the belt

on the opposite side of the centerline would contain cord of the opposite

twist. This arrangemient elIminates the tendency for the bell, to twist under

tension.

Indivicuai *ioers are treated wittl an organic or- Inorganic lubricant which

keeps them apart and minimilzes the abrasive act ion of glass on glass. With-

out this lubricant, the fibers would scratch each other and cause fracture.

The selection of he lubricant largely depends upon its conpatibilIty with

the rubber In which the cord wi lt be encased. The lubricant is permanent

becau&6 It Is completely enclosed In rubber and not subject to dilution or

attack by environmental influences. The fiber glass cord to be used will be

similar to that descrlbed in MIL-Y-1140 E, Yarn, Cord, Cloth and Tape-Gfass,

Section 3.3.2, page 5, 30 December 1943.

In addition to the fiber glass cord, the belt is reinforced wth cme ply of

nylon or rayon fabric, located between the fiber glass ccrd and the Inside

surface of the belt. The fabric reinforcement gives lateral and torsional

strength to the track and Increases the shear strength of the belt for the

road pod attachment. The fabric material has a much lower modulus of e!as-

ticity than the fiber glass and a higher ultimato elongation. Therefore, the

fabric does not carry normal belt tension loads, but serves to protect the

fiber glass from concentrated shear or point loads. It also adds to the

overall toughness of the belt section.

The guide teeth on the inner surface of the belt are Integral with the belt

and are molded from the same rubber as the belt. They are prismoidal In

shape, tapering on all sides toward the top. Large radii are located at the

Junction cf the front and rear surfaces of the tooth and the Inner surface

of the belt. The sprocket pins engage the teeth at these radii. The ares

of the base of each tooth Is quite large in order to provide adequate shear

strength to withstand driving and guiding loads.

4-3

The road pedj are !oceted on the outer surface of the belt and each Is heal

in place by four bolts. The belt has four steel-reinforced holes per pitch

to accommodate the attaching bolts (Figure 4-1, page 4-.5). This steel rein-

forcement allows the attachment to be made without locally compressing the

belt as the nut is tightened and helps di.tribute lateral forces to the belt

during operation. Access to the road pad air valve is through an additional

hole In the belt, located near Its outetde edge.

4.3 Road Pads

The pneumatic road pads serve two primary purposes in addition to providing

tractlve surfaces: they add buoyancy and serve to absorb shocks. Each pad

consists of a pressurized air cell and a rubber grouser which Is Integral with

the cell. The air cell Is ovai-shaped (Figure 3-7, page 3-18) and Is con-

structed of two pieces. The upper piece is a flat sheet of rubber which Is

reinforced with fabric. This piece Is adjacent to the outside surface of the

belt when the pad Is Installed. The lower piece contains the air cell cavity.

The two pieces are joined at a flinge which encompasses the upper surface of

the pad assembly. The leading and trailing edges of this flange are rein-

forced with steel clips to prevent tearing of the rubber during operation.

The attaching bolts extend through the flange at the corners, and the holes

for the bolts are reinforced with steel sleeves.

The flat upper surface of the pad contains an inflater, a valve similar to

those used In athletic equipment. A "needle" Is used to fill or deflate the

air cell. This type of valve has no moving parts and is made entirely of a

highly resilient grade of rubber. Due to this resiliency, the hole for the

"needle" closes and forms a seal whmen the needle Is not Inserted.

4-4

-- ............ !00 ---

/ -ATTACRtWNT

:..-GUIDE TOOTH

,,-VALVE

- -- - - - -- -

Figure 4-I LlghtwIght High MobiI ty Treck - Plan View

4-5

The liwer portion of the pad is reinforced with two plies of fabric along

the sides and above the grouser. The fabric gives the pad lateral and

longitudinal stability as well as resistance to penetration. It also pro-

vides strength In the area of the attachnent. The grouser Is non-directional

anu has an area of 32.9 square 1nchtes. A lateral slot in the grouser aids in

bending around the roadwheels and sprocket.

4.4 Sprocks t

The sprocket Is a fabricated construction consisting of ten hollow cylindrical

pins end two formed sections similar to an automotive wheel. The pins are

welded to these sections at each and (Figure 3-6, page 3-20, and Figure 3-9,

page 5-21).

The pins engage the guide teeth on the track for driving and braking. The

track Is supported as It travels around the sprocket by the pins and by

flanges on the outboard edges of the formed wheel sections. The driving and

gulding interfaces are all rubber to metal, providing quiet operation. The

sprocket Is self-cleaning because the formed sections are perforated to

I permit the expulsion of debris. The pitch dieter of the sprocket is

19.10 inches; the overall width Is 8.65 inches.

The sprocket is attached to the final drive hub by StudS end nuts. The

st4d are pressed Into the hub mounting flange. A pilot diameter on the

hub guides the formed sections of the sprocket to assure accurate mounting.

H

5.0 FEASIBILITY ANALYSES

Throughout the duration of the concept feasibility study, it was necessary

to evaluate the lightweight track from several standpoints at each stage of

t"o concepi evolution. These evaluations not only provided incresed cocept

definition, but In many cases also indicated areas for improvenent of the

designs. This section presents the analyses used to determine certain design

requirements and to evaluate tho finol concept.

5.1 Track Tension Requirements

Since the ability of the track to carry axial loads is extremely important,

the first analysis was performed to determine the magnitudes of these foads.

The calculations (page A-1) were based upon the hypothetical vehicle appilca-

tion having a gross weight of 3000 pound4. Mtaximum operating tension was

letermined by considering the vehicle operating on a surface with a traction

coefficient of 0.80, thus maktng this tension equal to 40 percent of the gross

weight or 1200 pounds.

4Maximum potential tension Is usualiy based upon sprocket torque data. In

the absence of these data, however, ATAC recomnendsd that the maximum poten-

tial tension be equal to the gross vehicle weight multiplied by 1.25 or 3750

pounds.

Studies of the properties of fiber glss and discussions with suppliers of

fiber glaes-reinforced belts Indicated that the ultimate strength of the belt

should be 15 to 20 times as great aG the maximwm operating tension. It was

also noted that such belts are currently being manufactured with strengths of

approximately 6000 pounds per inch of width. With a track width of 12 Inches,

5-I

less a total of one inch to allow for attachmnts, it was found that the belt

portion of the track could be manufactured with an ultimate strength of 66,000

pounds. The strength potential of the belt, therefore, far exceeded the

suggested ultimate strength; the ultimate strength of the bolt could be as

high as 55 times the maximum operating tension and 17.6 times as high as the

maximum potentlt tension, as shown on psge A-S.

5.2 Weight and Buoyancy

An analysis of the weight and buoyancy of the concept was performed as soon

as the final configuration was determined. in performing the analysis, the

material and displaced volumes were computed for each geometrical section of

the belt and the pneumatic road pad, as shown In the calculations beginning on

page A-J. The specific weight of rubber used was 0.0415 pounds per cubic inch,

as provided by suppliers. This figure was found to agree with other data on

rubber 12). It was assumed that the effective specific weights of tue fiber

glass cord and fabric would be the same as that of rubber. The weights of

attachments were either calculated or, when poslbte, determined directly with

a scale. The analysis showed that the track would weigh 9.83 pounds per foot

and would have a buOyancy In water of 110.7 percent. The weight of the

sprocket was calculated to be 56.2 pounds (page A-7).

5.3 Lenoth Chane due to Temeratur. Variation

Dimensional stability, especially in the longitudinal direction, is extremely

Important for all tracks. Large variations in length could cause the track

to beconm "overpitched" or "underpitched" with respect to the sprocket and

could also affect static track tension. The total length change the track

could be expected to undergo was, therefor*, calculated using the specified

5-2

i y

minifmfm and maxiimum operating temperatures of -65 to *12"1 dv-ree5 Fahrenheit.

lhe calculations on page A-- show that the change In length would be only

0.1t4 percent or .3o07R Inches for an envelope length of 22.5 feet. It was

assumed that the fiber glass cord, being the ,"r1in tension member, would

govern the length change of the track; the effects of tMe rubber and tabric

were negler ted.

5.4 Road Pad inf lation Pressure

The development of a pneumatic pad and the selection of en ai- valve requires

some knowledge of the inflation pressures which will be required. In calcu-

lating the static Inflation pressure (page A-91, it was assunmd that the

pressure Inside the pad would have to be equal to the "footprint" pressure

on the grouser due to static roadheel load. Therefore, It could be said

that, when a roadwhiel Is directly above a road pad, only that particular

pad supports the Wheel and no vertical load is transmitted Into any other

pads. This was consdered to be a safe assumption since, In practice, a

certain amount of load will be carried by adjacent pads because of deflec-

tions. In addition, it was assumed that the walls of the pad do not contribute

to the support of the grouser area. The calculations showed that the required

inflation pressure would be 11.4 psi and that the average "footprint" pressue

for all grousers would be 3.91 psi.

5.5 Grouser Wear Rate

Another factor typically relating to ground pressure is the wear rate of e

rubber road pad. float road pods ore rigidly backed and cannot deftct to an

appreciale extent when experiencing concentrated ioad$. The pneumaTic pad

for the I Ightweight track, however, provides a flexible backing for the

rubber grouser. In attempting to estimate the wear rate and expected life

of the grouser, it is possible to draw certain conclusions based upon data

fron existing tracks.

A survey conducted by CUryster under another contract (3) inoicatec theat a

def ;ie rel" ;onship ePisted beweeen road pad wear rate and the gr,-und

pressure on a road pad calculated by dividing the pad area per pitch uf track

by the average static roadwneel load. In addition, a similar relationship was

shcwn to exist between wear rate and the average pressure on all pads in con-

tact with the ground. The curves on the following pages represent the results

of the survey. The curves were extrapolated for low preszsures because of a

lack of data in this area. Another factor which limits the ability to predict

wear rates for the Lightweight Track road pads is their flexibiIl;y. it would

be expected that a flexible road pad would have a lower wear rate than a

rigidly-backed pad because of its ability to deflect and distribute concen-

trated loads over an increased area. In addition, examination of conventional

road pads indicates that they may be subject to dwaage ny bruising, wherein a

concentrated load causes a breakdown of the rubber as it is pinched between a

smal! road irregularity and the rigid backing material. The pneumatic track

pad will greatly reduce this tendency.

Based upon maximum "footprint" pressure, the curve for band tracks indicates

a wear rate of approximately 4560 miles per inch of wear. Using an average

"footprint" pressure of 3.91 psi, the appropriate graph indicates a wear rate

In excess of 4600 miles per inch of wear. No attempt has been made to extra-

polate this curve beyond 4600 miles. Assuming a wear rate of 4500 miles per

inch, a life of approximately 2880 miles is indicated for the 5/8-Inch thick

5-4

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5.6 Maintenance Requirements

The Lightweight High Mobility Track has been designed to require a minimum of

maintenance. Once the track has been installed and the in.tial tension

adjustment made, no further tension adjustment will be necessary. The track

wiltl not take a "set" due to the nature of the fiber glass tension members.

It is expected that maintenance will consist only of replacing worn or damaged

road pads and an occasional restoration of inflation pressure during long

periods of inactlvity.

Depending upon the nature of road pad damage, It will be possible to make

repairs without removing the pad from the track -elt. For example, a sihrple

puncture may be repaired in the same manner a:e a tubeless tire; a plug is

Inserted Into the puncture and sealed with an adhesive. In order to Inflate

the pads, it will be necessary to lubricate the Inflater needle before itsert-

Ing It. To Inflate all of the pads In a minimum time, an air supply which has

been pre-set to the desired pressure would be adventageous. In the field

the pads could be inflated with a simple hand-<oerated pump, Little physical

effort would be required, owing to the tow pressure and the small volum to

be filled.

The replacement of a road pad raqulres only two wesnches. One would be used

to tighten or loosen the locking nut, while the other would be required to

hold the bolt. Locking nut torque will not be crlflcai, For normal opera-

tion, replacement of road pads will be required at intervals of approximately

2800 miles.

5-7

decause the < ;grtweg nt Track is continuous, its instal!ation wi Il require

a procedure wrth 5s qu te oiferent from trose used to install conventional

Din or .anC-type tracks. Mo.st traCks are laid fiat on the ground while the

ve<Cle ; s roiled onto them. Instal Iat on of the Lightwe[ght Track wil! re.-

qu re tha 3ne r bth s ; des o the ve!;ocle se read unftil the roadwheeis

are Approxirritei. sie inches aoove the ground. The track will then be posi-

tioned under thee roidwneeis and suspended over the idler and return rollers.

In order to ploce the track over these mermibers, the tension adjustment must be

in the relaed position, and the sprocket should be removea. The sprocket

would oe reinstaled wit; the track suspended on it, followed by the adjust-

nent of track tension.

5.7 Effects ot Damage

Because of the severe loads a track must withstand, one of the most frequent

causes of ve:ctie imr.ooi11ition is track failure. However, overdesign of

conventional pin and band-type tracks with respect to forseeabie operating

loads u-sualiy involves penalties in several areas, including weight and power

consumption. A pin-type track is subject to a disabling failure if only one

pin is overstressed. A similar condition exists with sectionalized band

tracks, especially where sections are joined together. The rigidity of con-

ventional tracks places severe demands upon the tension carrying members

because loads cannot De distributed iirough deformation. In this area, the

flexibility of the Lightweight Track and the fact that the load-carrying

members are distributed across the entire width of the belt present certain

advantages. First, 4he preuant:c road pads serve to distrinute concentrated

vertical loads caused by road surface [rregularities. Second, because the

Fl 5-8

track is designed to carry many times the expected maxin operating tension,

the failure of a significant percentage of the fiber glass tension members

will not cause total track failure.

Although the pneumatic road pads are essential to track buoyancy and serve

other Important functions, failure of several or all of the pads will not

affect the structural Integrity of the be.t. Similarly, although operation

could not be sustained with a number of damaged guide teeth adjacent to each

other, several isolated failures could be tolerated to provide a "get home"

capability. For the above reasons, a vehicle equipped with the Lightweight

Track could s-jstain considerable track damage before being irrmobilized.

.8 or-iaIon with Track used on XM571 VehIcIe

The XW571 is an articulated tracked vehicle consisting of two powered units

joined by a special universal Joint/propeller shaft. The gross wetght of

this vehicle Is approximately 8000 pounds, with the front unit slightly

heavier than the rear unit. Each unit, then, has a gross weight close to

4000 pounds. wich Is very similar to the hypothetical vehicie application

of the Lightweight Track (4). At present, the X#371 track Is the lightest

track made for any vehicle above a ,5000 pound gross weight. The objectives

of the Lightweight Track Included concepting a track which Is not only

lighter, but which will surpass other aspects of the XM.71 rrack such as

reiIability, durability, and buoyancy. :n view of this, a brief examinat ion

of the XM57 track was conducted, resulting in the comparison table shown

below. It must be pointed out, however, that the Lightwe:ght Track is at

present merely a concept and h4as not had the benefit of testing.

a-n

TABLE I COMPAR I SON OF L I GHWF i GHT TRACK AND XM571 TRACK

DATA UNITS LIGHTVEIGHT TRACK XM571 TRACK

Wi ch~s 12.00 18.^

Pitch I rches 6.00 4.75

We ight Pounds/Foot 9.83 14

Volum Cubic Feet/Foot 0.1748 .04i6

Buoyancy Percent 110.7 21.6

Grouser Height nches 2.38 (Pad) 1.59

5.9 Amphibious Ooeration

The most significant features of the track which favor amphibious operation

are its light weight and buoyancy. Unlike conventional tracks, this track

will help to support the vehicle in the water without a serious weight

penalty. It will, therefore, be possible to provide a given vehicle with

greater freeboard and/or amphibious load-carrying capacity.

Certain specialized vehicles, such as landing craft, have made use of tracks

specifically designed for maximum water propulsion. A number of these

tracks employ vane-shaped shoes or appendages and feature an "open" construc-

tion which all ms water to flow from the inslae of the track envelope to the

outside. Shrouds have been used to cover the returning portion of the track

to eliminate thrust in the direction opposite to that of the vehicle. The

Lightweight High Mobility Track, due to Its road pad appendages, will provide

some thrust in the water, but it is not expected to equal the efficiency of

tracks designed specif cally for water propulsion. It would be necessary to

cover the returning portions of the tracks with shrouds for the reason mentioned

previously. For certain vehicle applications, however, the buoyancy of the

track may make It possible to have the returning portion of the track above

or close to the surface of the water for maximum off iciency fran the stand-

points of thrust and power consumption. Any meaningful estimate of water

speed would require data defining the appropriate features of the vehicle

application. In view of the absence of these date, no) numerical estimate of

water spe4td has aeen made.

5.10 Cross-Country Sgeed Capability

The requirements listed in Section 2 include descriptions of terrain condi-

tions ranging from dry hard cross-country to wet margi'nal cross-country. The

Lightweight High Mob lity Track has no known features which would limit operating

speed on these various typ-. of terrain. On the other hand, experience has shown

that speed Iinvitc ions are mce often related to the ability of the vehicle

driver and crew tn .. Id severe vibration Inputs or the ability of the

vehicle power train to provide the necessary power and control. Other factors

which must be coildered are associated with the overall vehicle configuration,

Including ground clearance, dr iver field of vision, and lenoth/width ratio.

Even with in complete vehicle definitton available, bn estimate of cross-country

speed capability Is extremely difficult to make.

Given two Identical vehicles - one with ne Lightweight Track end the other

with a cofventional band track of the saen width and weight - It Is expected

that the v~hicle equipped with the Lightweight Track would be atle to attain

greeter cros.-couTtry speeds. The reasons for this Include low power con-

sunption and the inherent ability to absorb shocks.

5-!!

5.1 Overall Performance Summary

The overall performance of the Lightweight High Mobility Track is expected

to prov de cer tain advantages which have been heretofore unattainable with

existing track des:gns. The longitudinal flexibility and lack of a definite

"pitcn" wel provide extremely smooth operation with minimum power consumption.

The cushioning effect of the pneumatic road pads will serve to reduce vibration

caused by small surface irregularities and may ease suspension requlrewnts for

small vehicies. The fact that no mrtal-to-wtal contrct Is present anywhere in

tne track interfaces between roaiwheels, idlers, and sprockets will assure that

noise will be held to .a minimum. The low weight and high buoyancy of the trac:k

wilI allow better amphibious operation and en Increased cargo capacity In com-,

parlson to gross vehicle weight.

5-12

6.0 CONCLUSIONS AND RECONWIENDATIONS

6.1 Sumr

The outcome of this Investigation is a concept -f the Lightweight High

bIl ty Track nd Drive Sprocket. The track consists of a reinforced

rubber belt with guide teeth on Its iniNer surface and -ernovable pneumaltic

road pads on Its outer surface. The adoption of this concept was originally

prompted by requirements for positive buoyancy, I ght weight, smooth opera-

tlon, low power loss, long life, and ablity to absorb shocks. The analyses

performed to determine feasibility centered mainly upon weight, buoyancy,

tonale strength, and manufacturing. The resulting concept Is 12 inches

wide, has a pitch of 6 Inches, weighs 9.83 pounds per foot, an is 110.7

percent buoyanr.

6.2 2onclus on#

The analyses Indicate that the Lightweight High /obIlIty Track Concept is

feaible and that it will definitely meet or surpass most of the require-

ments. Due to tie unusual nature of this ,oncept. however, a meaningful

evaluation of some of Its characteristics such as belt life, power losses,

and road pad wear rate can best be performed by laboratory and on-vehicle

teesting.

A number of features of the Lightweight Track represent Improvements over

conventional pin or bond track*. The fact that the roadwhGel path is smoot:i

and continuous will eliminate the vibration caused by roadwheels traveling

over Individual shoes, The elimination of metal-to-ometal contact throughout

the track and its ,ntarfaces with suspension components will provide extremely

qviet cpera* tn. Thc ioqt 4nal r *Pioi Tyi the #rack and the teck of

rigid pitches willI serv'e to reduce vibration and power losses. The ability

of the pnieumatic road pads to cabsorb road shocks will attenuate low amplitude

SUSpenSion ~pt.The buoyancy of the track wHi allci% greater freeboard or

load-carry;nq capacity for amphibious vehicles.

Alf!!Ough the track concept developed Curing Inis study was Intended for a

vehicle with a gross weight of 3,000 pounds, it is expected that various

similar concepts would De applicable to cargo and reconnaissance vehicles

currently using -orv~fcindl band tracks. In general, the track seems~ best

suited for lightweight, high-speed vehicles. Variations of the basic concept

could probably be used on vehicles up to about 20,000 pounds gross weight,

with similar advantages.

6.3 ecomnenda t ionis

In viewi of the feasibility of the Lightweight High Mobility Track and the

inherent advantages of the -concept, it s recommewnded that additional pro-

gram~ be undertaken with the ultimate Seal of placing this track into service

on future or existing lightweir-ht vehicles. The following programis are pre-

sented as a plan involving the least cost and risk, preliminary to on-vehicle

testing.

6.3.1 Concept Definition and Test Plan Program

An essential phase of a future development program~ would be the produzt ion of

a fuui cev-.plemmnt of detail drawings for the track and the sprocket complete

with all necessary specificatiois regarding materials avid pfrformance. These

drawings and specificaliions wctld be based upon the concept presented In this

6-2

report and full use of the experience gained during the feasibitlty study

would be assured.

Chrysler is currently Involved in the design and fabrication of the Pitchless

Band Track Test Machine to be installed at ATAC (ContracI,- DAAEO.-67-C-4181 i.

It is further recomended that a plan be dev'sed for ta-sting the LIghtwelght

Track on this machine. In order to accomplish this, detail drawings for a

readwheel and other hardware for use on the mdichine wo jd have to be provided.

The test plan would be directed toward determining endurance, durability, and

power consumptlon factors as related to speed, vibration, tension, and applica-

tion of dynamic loads.

6.3.2 Material Procurement and Test

Upon complotion of the above program, Action would be initiated to procure all

material required for testing. Necessary modifications to the test machine

would be mad* and tlsting accomplished with technical azssisance provided by

Chrysler personnel.

7.0 REFERENCES

The following list presents references for data 'included In the report,

Each reference Is referred to by number in the report text.

(I) Modern Plastlcs Encyclopedia, Vol. 34 #IA, 1956, Now York,page 518.

t2) Handbook of M olded and Extruded Rubber, Second Edition,Goodyear Tire & Rubber Co., Akron, Ohio, 1959, page 9.

(3) Pitchless Band Track, Concept and Feasibility Study, ArmyTank Automotive Cormand, Contract DA-20.. 13-AMC-07701 (T),Crirysler Corporation, Defense Operations Division, DefenseEngineering, 11 February 1966, pages 3-3 to 3-6.

(4) Final Report of Engineering Test of Carrier, Utl t.Articulated. X*571, Aberdeen Proving Ground, Aberdeen,Maryland, USATECOM Project No. 1-3-5550-01-D, Report No.DPS-1462, October 1964, page 8.

(5) Burington, Richard S., Handlbook of Mathematical Tables andFormls, Handbook Publishers., Inc.., Sa.ndusky, Ohio, 1958,page 15.

16) rens Im Gs I 9, Inq w It h Re Inf Sree__P'43 1 1cs (P 6mphlle t I,Pittsburgn Plate Glass Co., October 1964.

7-1

8.0 DISTRIBUTION LIST

Ni and Address No. of Copies

Comaending General tArmy Tank A-itomotive Coinand

Attn: AMSTA-UTDetroit ArsenalWarren, Michigan 48090

DirectorDefense Contracts AdministratfonServices Region, Detroit1580 Ebst Grand BoulevardDetroit, Michigan 48211

Chrysler Corporation

Defense Engineering DivisionP. 0. Box 1316Detroit, Michigan 48231

A-!

APPENDI IX

CONTENTS

Page

Track Tension Requ':rements A-2

Belt Section Strength A-3

Weight and Buoyancy Anatysis A-4

Length Change due to Anb ent Temperature Change A-8

Road Pad Inflatlon Pressure A-9

A-I

t c 0.t ---- ---------- -

CH7YSLRDEFENSE ENGJNEER;NG

tIEDLGN UAL CULAT 10C-m'

V1 N

NIA - ~, W 2 .

LYQ KU~ N VAX) C. k-'T

A TFVC~h A - -

E A

F CiHRYSLER DEFENSE ENGINEERING/ OFL

OWG#4 CALCULATO#

(. IATO00 ULVJomm vur UTME4T1& To uMAX. OPCEfrru4 yemWM

V.11TM V wit I2..AO ... -, X-oi PM A17*CAI$.v u..* lot

OW. . erVAe1b4 L

2om c .ft T arrowic7ros

2 OKO~t B .L ~ DA.. T~h EvE DA_________

ACHRYSLER DEFENSE ENGINEERING SHF-ET_'

DEStGM CALCULATIONS

WEIGIHT ND e)0yA4JC A'JLYI

IN TCF=04 LQWINQ -THEt-~, 'A MA~It TRACIt< Am~D RO'MA PADiS

tARIL TWCATCO r4?M-rl-1LT. 0k-jA-ATINS AT,, FOR ONC plfCMH~~I~Q)

Toorm Scrom

TOoTH ~Wi So6,

vat-(.5 RA -1-0-.

1031uMr~ W MA I-SLW V

UiP Se~ow LjfM'f e~c*I

DISP~ VOL ml~l M 5AM AS ABoieE

MAT VO -1I-A[1 Z 5 4 42

A-4

I ~WoRKDOME Y____________ REVEWEOBy_______ -

DATE DATE

MEN

CHRYSLER DEFENSE ENG!NEERING J~0"G" CA#LCULAT#0WS

IULICTT

UP~ TO) LOCUJS OF~ RADIUS

OIS AL.% 22 L1( %)+ jsl2xfA2 Jr 11.57 IN3

bY PAPP4J5 T~nRWMJS): ____

13~.15 INS

AoWL OL uISM~ I(.o0)'v [11(.-S8~4LA) +* (A12 ~o(4~zi.*3

2 3.8a IN'

MOTM Air t cRul. -TO I.ocol 4W !!PO

0151' VOL - 1.25 ( a~ZGAO me

t ~. A4WORKAT DOEOATCRE EWDm

CHRYSLER DEFENSE ENGINEERING SHEET.

DESIMN CALCULATIONS

SU EJCT:

V TL. Sl- VOL : Z I.

= /.75, ;

-~kMARY

FOR CAE PITCH Dt SP.vck MAT.. VOL. MAYt. WT otr W .

sm-o' w Q 5 955 |.s 1.0(07PAO 9 zK 4. 1.827 S404

ZMCLIPM .430)TOTAL15 4,917- 5.445

WT/Fom, = 4,91 Z LBt Z ( = .BZ4 LS/FT

4.1Z

. .... ..... A -&=

WORK DONIE BY .OU _ REVIEWro ey

DAT£ DATE

CHRYSLER DEFENSE ENGINEERING I''~-- --

DESIGN CALCULATIOMS

SUBJECT-SPfRCXKET W44Et65ktA ESTIMATE

14) zlr (7.10-IS .8(Zel :408(5 ZT (a 37 .187 (VS) 14.4,0(4) ait (195s) 6ti~~ .71

12.75 wl

M.i c nxr s MA0

a 3sG~roe4/%Fft~tr * 1 0 ~

~TML VOL OF SPO~r 1111 1#4

A-7

WORKW DOWE BY OL U-7- REVEWED by________DA~rDATIE

CHRYSLER DEFENSE ENGINEERING ~

CDL8IGN CALCULATIONS

SUJ~~CALCULATE LENGTH CH^N45E OF BEL- DUE TO AMBIENT

TEMPER~TURE. CHANGE

AM15teNl EmVPERATURE RANCjE 4b'F Toa '125F

TEMPERATURE DtFEZENiTiAL -i)*

A3~5ume TOTAL L.ENcTH 0F TRPACK EN~eLOQPe ZZ5r

(41COEFICIENT OF THERMAI.. EXPANSION 01: FISSR 6LA55vwl0~ N

51-NCE THE F118ER c3LASS CC)RF is -r I= "AIN TENSILE

MEMSRTHNE EFFECT OF THE RUBIBEF I.3 N15CLECTED

UN 1 TA CH"JX4V - Cvx~Oi~rN it ZZ, FT a tZ IN it J'Or~ef

IN *F E?4VLf.op% FT

A- 9

WOM0RK DON my__________ el-7 fvIjEwD by-- ~DATE DT

CHRYSLER DEFENSE ENGINEERING -I9

09W6ft CALCULATIO040-

~~S~ O RGPDOW L~t~ ftuN

IDSPLATtO. P~RW - 04 P51

A'4WA4 MUM~J Om ALL 4M~U34*S 4 rTao& Am op o&~t .4 iou

Tforpii AAVA or com~cr'1JC l ' 7G8# AVI

AVW4UI PRSMUqe 0 as[ 3

A-1

woIw Dog my naV'*~1vtwff myDATE DATa

IED

DOCUUEWT CONTPOL DATA. R & .c-ftafiwi of119,14. bod of abs.fr and And.#Inj must b. antv'd hmr I* &. dciff."

C TIV I -r ( Caf.orwf* &. *Mj a. ft* a 1 aIjrv CI..ASIFAC&TI".

_rm- Tak-Autornotive Command I L,=ASSFIEDie, Suspension & Track Branch, AMSTA-RUT tr .

Warren, Michigan 480902. PUEPONT TTLI

LIGHTWEIGHT, HIGH MOBILITY TRACK

4. DESCftIPYIVS N0TES (7V~P**. X .Ieptaad tz

F_ inal Re'ort

David A. YoungDefense Operations DivisionS Chr- er C'rIorat-i'o)

9 Febrmary 1968 63 6Sd.COT'(TA OR9 gAANT MC- Ga. 0MGMiATOWS REPV" r JYVWENftS

DAAE07-67-C-3847b. PnoilmCN".

J-M-5-2.801-D-263

-AMCMS CODE 5521. 12. 26900

'Distribution of this document ib unlimited~I-2U P~gIENTA1tV NT~ , *o~sft". -u rAaV ACTIVITV

U. S. Army Tank-Automotive CommandTrack, Research & Engineering SectionWarren, Michigan 48090

This report presents 6 * .. xs, concept feasibility study of the LightweightHigh Mobility Tracko par- dme-&und-r Contract DAE07-6.7-?C-Ca7, effective

1O -M .- 7 %-. The subject track consists o a fiber gLass reinforced beltwith guide tooth projections on its inside surface and pneumatic pads on its

outside surface. This particular track was intended for use on a vehicle with

a gross weight of 3000 pounds. The resultant concept is 12 inches wide, weighs

9. 83 pounds per foot, and is 110. 7 percent buoyant. In addition, the inherentadvantages of the design include a smooth roadwheel path, the ability to absorbroad shocks, quiet operation, and expected long life.

The concept was analyzed from a number of standpoints including weight,

buoyancy, tensile strength, and feasibility of manufacture. It was concluded

that the concept is feasible and that it would be applicable to lightweight cargo

and reconnaissance vehicles. Recommendations for future activity on this pro-

ject are also 1: resented.

DD ,?..t1473

14 1' N A LNMH U

*my WORDS -

' ° ° ! I.-I

T

Fmilital pnimS'tm-rc~

L., ta.ig, 7 gT. ,nt. AU-R,bber Track I IPneumrnatic Road l-Pads

Fiber glass Cable Cords

I

I

UNCL.ASSIFIBD

-*, ..... .... ' ,., ,! h. ~, of.4 i,,t lrg.. s,,, Sn,, '..: *v,'c,,,flev.,n ,.r b.,Ftr d _.,wn .L_ ow.,I n o .. , __-,. p, , .. .

S~..A&rnor Think-Automotive Comnmand UMIA.SS I.FI EDPrarexi. Susension & Trac!- Branch. AMSTA-RUT iie L,.

F; ILC -ar run, Michigan 48090

LuCHTWBI'GHT, HIGH MOBILITY TRACK

4: -David A. YoungDefense OqPerations Div'ision

Chrysler CorporationV. Februar 0196O P3 & 6l. no. 01 REP$

9February 1968OC Ont R A CT O4R GRAN T 140. *A. OR*4Gtft&tOWS REPORT HVW*fRt5jrDi A F07 -6 7 - C - 3 84- F.o,.,t*,*-o-....

I -M-5-21801 -D-263-AMCMS CODE 551. 12.26900 , c. RCPCRT NO ,l ,A-,,a--ur n.d

Distribution of this document is unlimited

U.S. Army Tank-Automotive Command:1 Track, Research & Engineering Section____Warren, Michigan 48090

This report presents Chrysler's concept feasibility study of the LighbneightHigh Mobility Track, performed under Contract DAAE07-67-C-3847, effective10 May 1967. The subject track consists of a fiber glass reinforced beltwith guide tooth projections on its inside surface and pnaeumatic pads onl itsoutside surface. This particular track was intended for use on a vehicle witha gross weight of 3000 pounds. The resultant concept is 12 inches wide, weighs9.83 pounds per foot, and is 110.7 percent buo-ant. In addition, the inherent

Hadvantages of the design include a smooth roadv'heel path, the ability to absorbroad shocks, quiet operation, and expected long life.

The concept was analyzed fromn a number of standpoints including %%eight,auoyancy, tensile strength, and feasibility of manufacture. It was concludedthat the concept is feasible and that it would be applicable to lightweight cargoand reconnaissance vehicles. Recommendations for future activity on this pro-Sect are also presented.

PC ' ?A 4 aELCIs 0-0 POtan tA is J 44. WHICHr IS U CAS ll-f417 " iN C fA .S 4!Fil'f-

Se urnty cIassificatoc

ACV, **no$s r$ ________________ ~tI~2 U! OLI W,

IIi~hwt-i~h Buv~ t .All-Rt~er T rack d

I 'r,,u:nai* ic oad Pads

'iber glass Cabl'i Cords

I1

4 1

ii 2UNCLASSIFIED

- ecuvtty CnuselficsUon