minigun research program

70AP1119APRIL 1970

~ MINIGUN RESEARCH

AND

DEVELOPMENT PROGRAM

FINAL REPORT

AIRCRFT EUIPMET DIISIO

BURINGON VEMN

Apr' 11 19 70

SUKIRJMC, FINAL WI~ORT, R&D :oNrthACI' IAAF') I-68-C-060

Tim documonrt . ii n A In ro1port for Scopo Itomns I throtigh 5

of *iuh.joct cantract, with ono oxcoption. Whon tho L'in~il report

t to tixtoiI for OIw Doqign Studiosw, Sope Itemi 6, it will contain

A ooction doserthing the work performed to incorporate timing

CotAturteN In tho miniguin Oltith (Scope Item 2).

IP

AD

APRIL 1970

70AP819

MINIGLJN RESE-ARCH AND DEVFLOPMENT PROGRAM

FINAL REPORT

By

,ugene I. " r ymond

David R. Skinner

ll%-nry R. White

(erard J. lesany

(lharle I). Roumer

Prepared For: U. S. Army Wapons CommandRock island, Illinois 61201

Prepared by: General Electric CompanyAircraft Equipment DivisionBurlington, Vemont 05401

CONTRACT DAAF 01-68C-0060

AMCMS Code Number 5142"12"11209"14

The findings in this report are not to be construedas an offi rial Department of the Army position unless so

eisagnated by other authorized Joeunent&.

Fhe dhlribution of this dooiment ik unlimited.

AD

APRIL 1970

70APB19

MINIGUN RESEARCH AND DEVELOPMENT PROGRAM

FINAL REPORT

Bly

Eugene B. Raymond

David R. Skinner

Henry R. White

Gerard J. Desany

Charles D. Roaser

Prepared for: U. S. Army Weapons Command

Rock Island, Illinois 61201

Prepared by: General Electric Company

Aircracft Equipment Division

Burlington, Vermont 05401

CONTRACT DAAF 01-68-C-00

PRECEDING PAGE BLANKThe distribution of this document is unlimited.

2.

ABSTRACT

This report describes the design, development, and testing of a new

mnnigun bolt, clutch, side stripping feeder, guide bar (including tolerance

studies), and armament pod for the XM-18.

The new bolt functions independently of any external cam, other than themain housing cam, and is completely interchangeable in all existing systems.

Other advantages include reduced cost, longer life, and greater reliability.

The new solenoid operated clutch is located in the aft end of the gun

and, therefore, does not interfere with the feed systems of the numerous* Dminigun applications. The clutch stops the feed system at the end of a burst,

but allows the gun to rotate and clear. A large savings is realized because

no live ammunition is dumped during clearing.

The new delinking feeder sidestrips, rathe- than endstrips. It has

fewer parts and is more durable, thereby reduci,,g the cost and increasing the

life of the feeder.

Tolerance studies of the guide bar interfacing with gun and feeder, high-

speed films of round handoff from feeder to gun, and evaluations of various

guide bar concepts were performed in an attempt to design a new guide bar

which would decrease the gun's dependency on feeder timing and increase its

tolerance to damaged ammunition. Conclusions and recommendations based on

the studies, films, and evaluations are also included.

The new feed and storage system for the minigim pod incorporates a

storage drum similar to the MXU 470 Minigun Module with a new feeder design

that has fewer parts and is more durable. The combination of these new

features more than doubles the reliability of the pod.

PRECEDING PAGE BLANK

iii ii

L .... _ _ _ -

TABLE OF CONTENTS

Section Title Page

I MINIGUN BOLTS, SCOPE ITEM 1 ................... .. 1

A. INTRODUCTION ........... ............. ....... 1B. DESCRIPTION OF TANGLESS BOLTS.... ..................C. DEVELOPMENT .......... ...................... 2

1. Testing ............ ....................... 32. Stoppages. ............... ..................... 4

D. MAINTENANCE ............ ..... ...................... 5

SAPPENDIX I-A. Drawings ........... ......... ......... 6APPENDIX I-B. Photos and Illustrations ..... ......... 17APPENDIX I-C. Test Results ...................... 29

SAPPENDIX I-D. Weight and Center ofGaity .. .. . .. 33APPENDIX I-E. Tolerance Study .......... .............. 38

II MINIGUN CLUTCH, SCOPE ITEM 2 .............. ........ S0

A A. INTRODUCTION ........... ..... ..................... 50B. METHOD OF OPERATION .......... .................. So

1. Basic Operation ............ ................ 502. Detailed Operation ....... ............... .... 51

a. Firing Mode ........ .................. . . 51b. Clearing Cycle ......... .................. 52c. Power Loading ........ ... ................. 53

C. TESTING...... ........... ................... . ....1. Clutch Unit 1.......... ... ................... 55

D 2. Clutch Unit 2 ............. ................... 56SD. INSTALLATION PROCEDURE . .. .. .. .. .. .. . .. 58|

APPENDIX II-A. Drawings . . . . .............. 9APPENDIX II-B. Photos and Illustrations ..... ......... 77APPENDIX II-C. Test Results ....... ................. 82APPENDIX II-D. Weight and Center of Gravity .. ....... .. 99APPENDIX II-E. Final Report Minigun DeclutUiing SystemI Analysis ......... ................. ... 101

A. ABSTRACT . . ... ...... ... .... . . . 102B. INTRODUCTION ..... ................... 102C. APPROACH ..... .................... . 102D. TEST PROGRAM . . . . . . . . 0E. PEAK LOADS IN THE SEVERAL MINIGUN SYSTEMS WITH*

SEVERAL STOPS ........... . . . . . .. . 107F. ANALYTICAL INVESTIGATION ..... ............... 108

PRECEDING PAGE BLANKV

TABLE OF CONTENTS "cont)

Section Title Page

G. SUMMARY OF RESULTS OF THE ANALYTICALINVESTIGATION .............. ................... 108

H. DISCUSSION ........... ....... ............. ..._. 109I. MATHEMATICAL FORMULATION (FOR DIGITAL COMPUTER) 110J. DIGITAL COMPUTER PROGRAM . . ......... . .......... 111K. MATHEMATICAL FORMULATION (FOR ANALOG COMPUTER) " 114L. DISCUSSION OF ANALOG COMPUTER RESULTS ......... .. 117M. STRESS ANALYSIS OF THE DECLUTCHING MECHANISM . . 117N. RhLoi,4MENDATION ..... .................. .... 1180. CLUTCH HOUSING RESTRAINING LUG TORQUE

CAPABILITY.......... ... . . . . 119P. CLUTCH LUG SOCKET LOAD CAPABILITY IN CLUTCH 1

HOUSING ............ .................. 119Q. CLUTTCH LOAD CAPABILITY IN INTERNAL LUGS OF

ACTUATOR GEAR............ . ... .. .. .. . 120R. ANALYSIS OF STRESS IN REAR GEAR ON ROTOR (REGION

BELOW TEETH ROOTS) ............. ... ........ ... 121S. POSSIBLE MODIFICATION OF ACTUATOR GEAR DESIGN . . . 122

APPENDIX II-F .......... ... ...................... ... 123

A. DECLUTCHING MECHANISM ANALYSIS, MOMENT OF INERTIAOF THE MODULE FEED SYSTEM.... . ... . . . . . ... 124

B. CALCULATION OF MOMENT OF INERTIA OF THE MODULEFEED SYSTEM (ASSUMED LUMPED IN THE DRUM) .. .... .. 127

C. SPRING CONSTANT OF THE MODULE FEED SYSTEM ........ 128D. SPRING CONSTANT OF THE NEW POD FEED SYSTEM ... 131

III SIDE STRIPPING FEEDER, SCOPE ITEM 3 ..... ............ ... 156

A. INTRODUCTION ............. ..................... ... 156B. DESIGN OBJECTIVES .......... .................. ... 157C. HIFTORY OF DEVELOPMENT ......... ... ................ 157D. METHOD OF OPERATION ........ .................. ... 160

APPENDIX III-A. Drawing .......... ... ........... .... 161APPENDIX III-B. Photos and Illustrations ... ......... ... 163APPENDIX III-C. Test Results .. ........... . 173APPENDIX III-D. Weight and Center of Gravity . . . . ... 176

IV MINIGUN GUIDE BAR, SCOPE ITEM 4 ..... .............. ... 178

A. INTRODUCTION.._....... .._ .. .................. 178B. CONCLUSIONS AND RECOMMENDATIONS . . . . . . . ... . 178C. TOLERANCE STUDIES ..... ............. . . . . . . . 179D. HIGH-SPEED FILMS ............. . ........... 179

vi

- - - * - -,-

¢,L

TABLE OF CONTENTS (cont)

Section Title Page

E. EVALUATION OF VARIOUS GUIDE BAR DESIGNS ......... . 1801. Replaceable Guide Bar Fingers ...... ........... 1812. Modified Round Path ........ ................ ... 1813. New Rim Guide.................... 1814. Mechanisms to Increase the Gun's Tolerance to

Late Feeding ............... ................... 181a. Movable Rim Guides ....... .............. ... 182b. Accelerators ............. .............. .. 182

Cl) Angle-Multirpying MechanIsm .......... ... 182(2) Spring Lever Mechanism . . . . . . . . . . 183(3) Solenoid Kicker ........ .... 183

APPENDIX IV-A. Illustrations ...... ............... . 184APPENDIX IV-B. Tolerance Study...... . . . . . . . . . 195

V ARMAMENT POD, XM-18, SCOPE ITEM 5 ................. 248

A. INTRODUCTION. .. .......... ................. . . . . 248B. SU1iARYD. ............................ . . . . . . 248C. DESIGN DEVELOPMENT......... .................. 249D. END ITEM CONFIGURATION ......... ................ ... 253E. TESTING ..... ............ . . ......... . . 253

APPENDIX V-A. Drawings.... . ..... ....... . . . . . 255APPENDIX V-B. Photos and Illustrations . . . . . . . . . 264APPENDIX V-C. Test Results ...... ...... . . 276APPENDIX V-D. Weight and Center of Gravity .......... . 282

A-

Ii

Im

[:!. ..

rI

LIST OF ILLUSTRATIONS

Figure No. Title Page

1 Bolt Head Subassembly .......... ............... 72 Bolt Body Subassembly .......... ............... 83 Head Bolt .................. ................... 94 Body Bolt ........... ................... ..... 105 Firing Pin ........... .................. .I.I.. 116 Spring Stop Pin ......... .................. ... 127 Helical Compression Spring ...... ............ ... 138 Cam Roller ............. .................... .. 149 Thrust Washer ................ .................. 1s

10 Headed Pin ............. ................... ... 1611 Bolt Assembly ........... ................... ... 1812 Bolt Asscmbly ........... ................... ... 1913 Exploded Bolt Assembly ........... .............. 2014 Timing Diagram ........... .................. ... 2115 Modified Bolt Assembly ........... .............. 2216 Cracked Bolt Head ......... ................. ... 2317 Detent ............. ..................... .... 2318 Cook-off ................. ..................... 2419 Sheared Roller Stub ..... .............. ..... 2520 (Sheet 1 of 2) Computer Program for Self-

Actuating Bolts ......... ................. ... 2620 (Sheet 2 of 2) Computer Program for Self-

Actuating Bolts ......... .................. ... 2721 Computer Output for Self-Actuating Bolts ... ..... 2822 Center of Gravity of Bolt ....... ........... ... 3423 Tolerance Study Layout of Tangless Bolt ... ...... 4P24 Action Time Study for Self-Actuating Bolt Assembly. 4925 Power Loading ............ .................. ... 5426 Solenoid ............... .................... ... 6027 Bearing Housing ........... ................. ... 6128 Actuator Yoke ............ ................. ... 6229 Clutch Housing ........... ................. ... 6330 Actuator Arm ............. ................... 6431 Gear Actuator .................... ......... ..... 6532 Rotating Knife Ring ............ ....... ..... 6633 Liner .................... ............ ..... 6734 Rotor Spur Gear .............. ......... ..... 6835 Mounting Bracket .... ........................ 6936 Aft Gun Support ...................... ..... 7037 Rotor Housing .......... .................. 7138 Aft Gun Support ... ...... ................ 7239 Link .......... .......... ................ . 7340 Pivot Arm ..... ........ ................ 74

viii

4,

LIST OF ILLUSTRATIONS (cont)

Figure No. Title Page

41 Clutch Assembly ........ .................. ... 7542 Ball Bearing ............... ................... 7643 Clutch Assembly on Minigun (Rear View) .. ...... .. 7844 Clutch Assembly (Rear View) ... ........... ..... 7845 Clutch Assembly (Front View) ....... ........... 7946 Clutch Assembly Mounted on Gun Rotor (Side View).. 7947 Clutch Assembly Mounted on Gun Rotor (Rear View).. 8048 Clearance Between Decision and Non-Decision

Knives ...................................... . 8049 Exploded Clutch Assembly ..... ........... .... 8150 Clutch Assembly ........ .................. ... 10051 Peak Torque on Minigun Pod Feeder Shaft vs Rate 10352 Peak Torque on Minigun A-37 Feed System withSSudden Stops of Rear Gear of Rotor ........ 104

53 Peak Torque on Minigun Pintle Mount DelinkingFeeder Shaft with Sudden Stops of Rear Gear ofRotor .............. ....................... ... 105

Y 54 Peak Torque on Minigun Module Exit Shaft withSudden Stops of Rear Gear on Rotor ... ........ .. 106

55 Program for Feed Systems with Sudden Stops . ... 11256 Pod with Module-type Drum and New Feeder ..... 11357 Second Order Nonlinear Equation of Motion ...... 11558 Declutching Torque Estimated from Analog Computer

Results ............ ...................... ... 11659 Steady State Feeder Torque vs Rate at Several Drum

Loads for the Module System ..... ........... ... 12660 Module Feed System Spring Constant .. ...... .... 13061 New Pod Feed System Spring Constant . . . . . . ... 13262 Present Module ......... ................. .... 13363 Present Module ............... ................. 13464 New Pod ............ ..................... .... 13565 New Pod ............ .................... .... 13666 Module with 2000 Rounds ..... ............. .... 13867 Module with 2000 Rounds ................ ....... 13968 Module with 3000 Rounds ..... ............. .... 14069 Module with 3000 Rounds ...... ............ .... 14170 New Pod with 3000 Rounds ..... ............ ... 142I 71 New Pod with 3000 Rounds ..... ............. ... 14372 Module with 2000 Rounds ...... .............. ... 14473 Module with 2000 Rounds ...... .............. ... 14574 Module with 3000 Rounds ...... ............. ... 14675 Module with 3000 Rounds ...... .............. ... 14776 New Pod with 3000 Rounds ..... ............. ... 14877 New Pod with 3000 Rounds ..... ............. ... 14978 Module with 2000 Rounds .............. is79 Module with 3000 Rounds ...... ............. ... 151

ix

LIST 01, II,IAI0I'RATION.i (iont)

Figure No, T lIt Pt Io

80 Module witt% 3000 Htounds .. . . . 15I81 Modulo with .000 Hounds . . ... .. . .. , 15382 N,- Pod with 3000 Rounds. . 1.483 N, , Pod with 3000 Rounds , 15584 Sido Stripping Feeder ...... . . . . . 16185 Feeder . . . . . . . . .486 1embdyr and Geun .Mounted 10587 Sidu Stripping Mechanism , 166

Side Stripping Didram . . . . . . . 16789 Link Jam . . . . . . . . . . . . . . . . . . ... 16890 Disassoinblod lFeudar .. . .......... 16091 Entronoo Aron. . . . . . . . . . . . . . . . ... 17092 Food Si'le . . . . . . . . . . . . . . . . . . ... 17193 ,Assembly of Feeder Mounted to run . .%$011* 17294 Side Stripping Feeder . . ., ..... .. . 177

95 Cartridge Ilandoff - Feeder/Guide Bar/ Head Bolt , 18596 Modified Round Path . . .. .... . ..... 18097 New Rim Guide . . . . . . . .. . . .. . .. . . . 18798 Guide Bar, Adjustable Rim Guide . . . . . .. . 18899 Guido Bar Back Face Rim Guido, Foodor Side Self-

Adjusting for Excess Loading . . .... . . 189100 Spring Rim Guido ,... . . . . 190101 Spring-loaded Rim Guide . .. .. .. ....... 191

102 Angle-Multiplying Mechanism . ......... . . 192103 Spring Lever Mechanism to Control Round . . . . . . 193104 Solenoid Kicker ........... . . ....... 194105 Maximum-Minimum Positions of Feeder Components 233106 Maximum Allowable Delay to Feeder Sprocket from

Timed Position . . . .... ......... . . 236107 Clearing Guide Interference . ..... ..... ....... 243108 Barrel Plug .... ....... ........ ......... 247109 Aircraft Armament Pod...256

110 Exit Unit Assembly. .............. . . 257i11 Feeder Assembly......... ..... ..... . . . 258112 Loader Assembly , . ............... . . 259113 Gun Support Assembly ................ 260114 Drum Assembly ...... ................... . 261115 Aft Drum Assembly .,.... . .. .... .................. 62116 Battery and Control Assembly . . . ........ 263117 Feed and Storage System with Gun (Right

Side View) ....... ... ................... ... 265118 Feed and Storage System with Gun (Left

Side View) ....... ... .................. ... 266119 Loader and Exit Unit with Loader in Load

Position ..... ..................... 267120 Loader and Exit Unit with Loader in Stored

Position .. .. ......... ................. ... 268

x

I.0l 01t II0,10TRATIONSI (cont)

Figur. No, Title Page

.1 rPeodor nota&leid oi Prod ..... . . ... . 259.oodor Showing T'ime C~learing Mechanism . 270

123 Inner Dmrum ftxtrusion ............... 271124 Round P'ositloned in Inner l'Drum . ......... 27215I Pound I'ath Through Ioader and Bxit Unit,

Now Delsign . . . . . .. I I % % $ . . 273116 (.oht I of 2) Design Study of Inner Drum to bxit

Sprocket Handoff . . . . ............. 2741,1 (Shoot 2 of 2) Design Study of Ininer Drum to Exit

Sprockowt llandoff . 27S

ix

i,IST OF TABLEtS

Number Ti t Le Page

I R 4 1) Tlngles LUolts Firing Schedule . . . . . . . . . . 30, 31II Total Rotnds on H !I, 1) Bolt Assemblies by lholt Body . . .

Number . . . . . . . . . . . 6 . 4. .. . . . 32

III Live 'resting Clutch Unit I - Module System . . . . .. . 83-89IV Live 'resting Clutch Unit 1 - A-37 System . . * . . . . . 90-92V Continued Live Testing Unit 2, Prior Testing 246

Actuations, 21,500 Rounds Fired . . . . . . . . . . . . 93-98VI Peak Torquos for Sudden Stops from 6000 spin . . . . . 107

VIl Torque at Rear Gear of Rotor on Declutching of FeedSystem . . . ... ... ... . . . . . . . . . . . .. . . 122

Vill Spring Constant of the Module Feed System . . . . . .. 129IX Spring Constant of the New Pod Feed System . . . . . .. 131X Potentiometer Settings for Analog Computer . . . . . . 137

XI Side Stripping Feeder, Live Test Results, Design No. 2 . 174, 175Xil Summary of Results for High-Speed Films of 7.62-mm

Round Handoff . . . . . . . . . . . . . . . . . . 246XIII Par'ts Eliminated from'Feeder.;.. ...... ..... 252XIV Summary of Results on 1SO,000-Round Engineering

Reliability 'rest of Research and Development Foed andStorage System .. ...... 277-281

xv 7.62-mm Aircraft Machine Gun Armaent Pod, Weight DataReport ........... ......................... ... 283

xii

LL

SECTION I

MINIGUN BOLTS, SCOPE ITEM 1

A, INTRODUCTION

Scope Item I of this contract specified a new bolt design that will be

fully interchangeable with all existing guns and systems. The bolt will be

self-operating and independent of cams external to the bolt other than the

main gun housing cam. Other desirable features would be lower manufacturing

cost, longer life, and greater reliability than the present design. A design

requiring a minimum of maintenance with less dependence on lubrication when

resetting the firing pin was also desired. The design criteria attained in

the final configuration exceed all initial development expectations.

B. DESCRIPTION OF TANGLESS BOLTS

The bolt design finally accepted is commonly referred to as a two-pin,

self-actuating bolt. This design surpasses all original estimates of life

expectancy and operational characteristics. There are only seven parts in

this design, making greater reliability and greater ease in assembly

possible. Figures 11, 12, and 13 show the bolt assembly.

As the name "self-actuating" implies, both triggering and resetting are

performed as the bolt head locks and unlocks. Only the linear action of the

gun housing cam is required to actuate the firing pin. Triggering is con-

trolled by the "L" slot located in the bolt head. Resetting is performed by

a triangular camming surface in the aft portion of the bolt body.

The operating cycle is initiated as the rotor turns, feeding the bolt

assembly forward in reaction to the housing cam. The bolt head turns into

lock and makes contact with the barrel face. The aft pin located in the

bolt body prevents the firing pin from rotating with the bolt head. The"L" slot rotates relative to the forward cross pin located in the firing pin.

Bolt head rotation continues until the forward cross pin rounds the "UL slot

corner. The firing pin is then aligned to move forward in the longitudinal

slot and is accelerated by the firing pin spring to indent the primer of the ifully chambered round.

~II1_ _ _ _ 1

After dwell, the gun housing cam interacts with the rotor rotation to

pull the bolt body aft to rotate the bolt head out of lock. This action

rotates the firing pin and retracts it from the primer. Firing pin reset

occurs when the forward cross pin reacts with the cross slot in the bolt head.

During the last unlocking action of the bolt head, the aft cross pin inter-

acting with the bolt body cams the firing pin in a clockwise rotation to its

reset position. The two cross pins then transmit the extract loads. This

cycle is represented in Figure 14.

This bolt design eliminated the need for the firing pin camming surface

to be cut into the gun rotor and maintained at depot level. The new design

also has a longer bolt body, providing more control of the bolt assembly as

it moves forward in the rotor trackways. Primer indents are more nearly

central due to increased support in the trackways. Wear of the removable

tracks is reduced, increasing their life. Since the bolt head is firmly

affixed to the assembly by the forward cross pin, it is impossible for a

bolt head separation from the bolt body to occur, thereby a possible source

of gun stoppage is eliminated. Spring stress is reduced in this design by

increasing the coil diameter of the spring. Life expectancy of the spring

is 250,000 rounds. The life expectancy of the bolt assembly is not known as

five of the six original test bolts have been tested for over 300,000 rounds

and remain operational. Only the forward cross pin a:.d springs have been

replaced. The new bolts functioned well at all rates from 750 to 6500 spm

during tests.

All testing analyses and tolerance studies show this bolt to be a

superior product. This design is expected to far exceed the present standard

of reliability and part longevity at a significantly reduced cost.

C. DEVELOPMENT

Several designs were studied in the initial development state of a bolt

mechanism which would function independent of the gun rotor. After an

extensive evaluation of operating characteristics, reliability, producibility,

and cost, the two-pin design was decided upon as the best approach. Work was

then initiated on a set of prototypes. Concurrent work was done on tolerance

and timing studies.

2

Particular effort was given to the firing pin spring to decrease the

working stress necessary for the spring to deliver enough energy to insure

primer firing, while keeping spring stresses as low as possible. A computer

program was written to determine the parameters for an optimal spring. This

program made is possible to analyze many different spring combinations and

pick the best one for the new bolt. The program was also used to determine

theoretical values for firing pin velocity, acceleration, and fall time -

thereby, greatly increasing new design comprehension. The computer program

and a print out of the present spring are included in Figures 20 and 21. The

values of energy in this program are higher than actual values because they

are theoretical values - the effects of friction were neglected. However,

frictional losses will be a constant; therefore, the optimal theoretical

spring will also be the optimal actual spring.

1. Testing

When the calculations and tolerance studies were complete, certain

changes were made on the prototypes. They were then assembled and test

fired. The testing revealed misfire occurance at both high and low rates.

An investigation showed that under certain conditions firing pin protrusion

was insufficient to fire the round. Corrective action involved making new

pins with an additional 0.070 inch on the forward end.

Further testing indicated the misfire percentage had been reduced,

but a very low (1 in 2000 rounds) percentage of misfires still existed.

Further investigation of these persistent misfires indicated the aft pin

might be rotating out of its proper firing position. To eliminate this

possibility, a set of bolts was modified with a special cantilever spring

arrangement (see Figure 15). This spring, located on the underside of the

bolt, applied a force to the aft pin which returned it to its proper

position. Resumed testing showed this configuration reduced misfire occur-

ance, but did not eliminate it, A more detailed test was evolved to

eliminate certain variables and determine the ba. ic problem.

Velocity screens were employed in an effort to determine which

bolt(s) misfired in a burst. With m•sfires occurring so infrequently, this

test arrangement was needed to determine if one bolt was misfiring consist-

ently or if all the bolts were misfiring in a random manner. The test

Sshowed all the bolts were misfiring at random.

3!

The timing study was re-evaluated; it was fourvd that under extreme

conditions 0.030-inch of coast was possible in the firing pin. The fall off

point was advanced three degrees and 0.030 inch was added to the fall off side

of the "L" slot to correct this situation. During the surface welding of the

"L" slot to accommodate the three-degree change, a small crack was initiated

in each of the six bolts being welded (see Figure 16). The cracks have in no

way affected the operation of these bolts. The aft helix was also moved

three degrees to further reduce extract torque. These changes made a signifi-

cant improvement in bolt operation. No misfires were observed at any rate

above 1500 shots per minute (spmi).

Further testing indicated a zone between 1000 and 1500 spm where

misfires still occurred. It was observed, under certain conditions, the aft

pin could work its way out of its required firing position. A small detent

(see Figure 17' was added to the aft helix to hold the aft pin in its proper

position.

Wear on the forward pin was the only problem remaining. In some

cases, this wear amounted to 0.007 inch after 50,000 rounds. The pins were

given a greater surface hardness to eliminate this wear. Using the same

base material, a new process known as "Tufftriding" gave a surface hardness

in the Rc 70's. A set of these specially treated pins presently has been

used for over 150,000 rounds with only negligible wear.

Testing after the detent was added and the surface hardness of the

forward pin was increased revealed no misfires. In one test, over 10,000

rounds were fired at the previously troublesome rate of 1300 spm without a

single misfire.

2. Stoppages

Several stoppages occurred during the testing period. Two did

appreciable damage to the assemblies. One bolt head was split along one side

in a cook-off situation (see Figure 18). Another bolt was damaged when a

defective pit pin allowed the safing sector to open during firing. This

resulted in the shearing of a body bolt roller (see Figure 19). The

undamaged parts of these two bolts were combined to make one good assembly.

This left five of the original six bolts operational. This set of bolts has

been tested well over 300,000 rounds. Testing will continue on the set until

a complete mechanical failure occurs.

4

D. MAINTENANCE

Lubrication is of prime importance in bolt assembly maintenance. It has

a direct affect on part life and reliability and should always be performed

thoroughly and as often as use dictates. Mil-L-46000 is compatible with this

assembly. If Mil-L-46000 with teflon is used, the operational life of the

assembly will increase. The key lubrication areas are listed below.

1. Aft helix (top and bottom)

2. Head, body interface

3. Firing pin4. Forward pin*

Both pins must be removed to completely assemble or disassemble these

bolts. However, the bolt head, body, and spring can be separated by removing

only the aft pin.

The forward pin is held in place by a medium drive press fit. This pin

can be assembled from only one direction. When changing this pin make

certain the firing pin holes line up with the clearance hole in the bolt head.

Do not remove this pin unless it is absolutely necessary. Unnecessary

removal will wear both the forward pin and its mating hole, causing the pin

to fit loosely and reduce the bolt's efficiency.

The aft pin is held in place by the firing pin spring. Care must be

taken in replacing this pin to make sure the flat is correctly aligned. If

it is not correctly aligned, the pin may become loose and cause a malfunction.

*When the forward pin is lubricated, excessive grease may b.,ild up in the

"LU' slot, causing a malfunction.

is

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Photos and Illustrations

I.

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180

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00 0

w LL.

caa

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H 19

a

Figure 13. Exploded Bolt Assembly

20

FEED ASECTION A-A

LOCKED -B SECTION B-B

Cj

POINT OF FIRING SECTION C-C

D

S

04SECTION D-D

EIii iiRESET

SE CTION E-E

"•FF

--.EXTRACT "F SECTION F-FFigure 14. Timing Diagram

21

If

() (Side View)

Figure 1S, Modified Bolt Assembly

22

,,/.,CRACK AREA

BOLT tiEAD

-4,a .015 In. DETENT

BOLT BOOY

Figure 17. Detent

23

V ~ I

i IcRAC'K

('a) Bolt Assembly

(b) Bolt Assembly (End View)Figure 18. Cook-off

24

*1 ... .

Figure 19. Sheared Roller Stub

25

001 PRINT "THIS IS A SPRING PROGRAM THAT WILL AID IN"002 PRINT "DEVELOPING NEW SPRINGS. BEFORE USING THIS"003 PRINT "PROGRAi,4 CHECK ALL VARIABLES ."

004 PRINT "WHAT IS THE WIRE DIA."00S INPUT DI006 PRINT "WHAT IS THE O.D."007 INPUT D2008 PRINT "WHAT IS THE FREE HEIGHT"009 INPUT F3010 PRINT 2WHAT IS THE COMPRESED HEIGHT"011 INPUT F2012 PRINT "WHAT IS THE MAX. WORKIND HEIGHT"013 INPUT Fl014 PRINT "WHAT IS THE NUMBER OF TURNS"015 INPUT N030 LET G=11.SE06040 LET F=F3-F2060 LET P=(F*G*D1A4)/(N*8*(D2-D1)A3)065 LET PI=P070 LET R=P/(F3-F2)080 LET C=(D2-D1)/D1090 LET H=(D2*(N+2))/(C+1)100 LET SI=(8*P*(D2-D1))/(3.1416*D1A3)110 LET K=((4*C-1)/(4*C-4))+(.615/C)120 LET S2=S1*K130 LET P2=R*(F3-F1)140 LET EI=((F1-F2)*P2)+(.S*(P1-P2)*(F1-F2))141 PRINT142 PRINT "THE MAX. FORCE IS";P144 PRINT "THE SOLID HEIGHT IS ";H146 PRINT "THE SPRING RATE IS ";R148 PRINT "THE SPRING STRESS IS ";S2150 PRINT "THE SPRING ENERGY IS ";El155 PRINT160 PRINT "DO YOU WANT PIN ENERGY(YES=O,NO=1)";170 INPUT Z180 IF Z=1 THEN 310190 PRINT "WHAT IS THE WEIGHT OF YOUR PIN IN POUNDS"

Figure 20. (Sheet 1 of 2) Computer Program for Self-Actuating Bolts

26

200 INPUT W21) LET Ml=W/386220 LET S=S2240 LET I=(3.1416*S*DlA3)/(16*((D2-D1)/2)*K)250 LET J=(G*DI^4)/(64*N*((D2-DI)/2)^3)26U LET M2=((D2-D1)*3.1416*(N+2)*3.1416*(D1/2)A2*.282)/386270 LET M3=Ml+(M2/3)280 LET V2=(((2*I)/M3*(F1-F2))-((J/M3)*(F1-F2)A2)290 LET E2=.S*M3*V2300 PRINT "THE VALUE OF E2 IS";E2305 PRINT310 PRINT "DO YOU WANT PIN VELOCITIES(YES=O,NO=1";320 INPUT Q330 IF Q=1 THEN 410340 PRINT "THIS PART OF THE PROGRAM GIVES A THEO VALUE OF"342 PRINT"PIN VELOCITY , 4CCELERATION , AND TIME FOR EVERY"344 PRINT ".01 INCHES OF TRAVEL STARTING FROM REST ."

350 PRINT "DISTANCE VEL ACC TIME"355 LET K=O360 LET F4=F2365 LET F4=F4+.01370 LET V2=(((2*I)/M3)*(F4-F2))-((J/M3)*(F4-F2)A2)380 LET V=SQR(V2)382 LET A=(I-J*(F4-F2))/M3384 LET T=(1.0/V)*(F4-F2)390 IF F4>F1 THEN 410400 PRINT F4,VAT402 IF K=l THEN 413405 GO TO 365410 LET F4=Fl411 LET K=1412 GO TO 370413 PRINT "EO YOU WANT TO TRY AGAIN(YES=0, NO=l)";420 INPUT X430 IF X=l THEN 450440 GO TO 04450 END

Figure 20. (Sheet 2 of 2) Computer Program for Self-Actuating Bolts

27

THIS IS A SPRING PROGRAM THAT WILL AID INDEVELOPING NEW SPRINGS. BEFORE USING THISPROGRAM CHECK ALL VARIABLESWHAT IS THE WIRE DIA.? .060WHAT IS THE O.D.? .270WHAT IS THE FREE HEIGHT? 2.20WHAT IS THE COMPRESED HEIGHT? 1.62WHAT IS THE MAX. WORKIND HEIGHT? 1.78

WHAT IS THE NUMBER OF TURNS? 22.0

THE MAX. FORCE IS 53.0347THE SOLID HEIGHT IS 1.44THE SPRING RATE IS 91.4392THE SPRING STRESS IS 193761.THE SPRING ENERGY IS 7.31513

DO YOU WANT PIN ENERGY(YES=0,NO=I)? 0WHAT IS THE WEIGHT OF YOUR PIN IN POUNDS? .0514THE VALUE OF E2 IS 7.31513

DO YOU WANT PIN VELOCITIES(YES=0,NO=1)? 0THIS PART OF THE PROGRAM GIVES A THEO VALUE OFPIN VELOCITY , ACCELERATION , AND TIME FOR EVERY.01 INCHES OF TRAVEL STARTING FROM REST .DISTANCE VEL ACC TIME

1.63 85.4356 361789. 1.17047E-041.64 120.298 355442. 1.66254E-041.65 146.686 349094. 2.04518E-041.66 168.628 342747. 2.37209E-041.67 187.688 336400. 2.66399E-041.68 204.674 33(1053. 2.93149E-041.69 220.066 323706. 3.18087E-041.7 234.178 317359. 3.41620E-041.71 247.231 311011. 3.64032E-041.72 259.384 304664. 3.85529E-041.73 270.758 298317 4.06267E-041.74 281.448 291970. 4.26367E-041.75 291.528 2G3623. 4.45926E-041.76 301.061 2"')276. 4.65022E-041.77 310.096 272928 4.83721E-041.78 318.677 266581 5.02076E-041.78 318.677 266581. 5.02076E-04

DO YOU WANT TO TRY AGAIN(YES=O,NO=I)? 1

Figure 21. Computer Output for Self-Actuating Bolts

28

A P P E N D I X I-C

Test Results

29 A

Table I. R & D Tangless Bolts Firing Schedule

Bolt Arrangement

Bolt Set Bolt Body No. Bolt Set Bolt Body No.T- 2, 3, 4, 8, 9, 12 lb 3, 7, 8, 9, 12, Prod. bolt2 5, 6, 7, 10, 13, 14 Ic 3, 7, 8, 9, Prod. bolt, Prod. boltla 2, 3, 7, 8, 9, 12 ld 2+, 3, 7, 8, 9, Prod. Bolt2a 5, 6, 4, 10, 13, 14 A 7, 8, 9, 10, 13, 14

B 10, 13, 14, 4*, 5*, 6*

Firing RoundsBolt Set Date Fired System Remarks

1 3771/769 22,000 'R&D feederprod. pod

2 3/24 49,600 XN 21 standw/clutch

2 5/6 1500 A-37blast tube

1 5/9 9000 R&D feedseprod pod

2 5/12 1500

1 5/12 4500

2 5/12 7500

1 5/12 7500

1 5/13 13,500

la 6/3 5200 XCM 21 Bolt assemblies 4 and 7stand exchanged between sets

2a 6/3 100

la 6/4 6000

la 6/9 4400 A-37 w/clutch

A 6/17 20,000 XM 21 Amount of lubrication variedstand

B 6/18 8000 XM 21 Cantilever spring on 3 assys.

la 6/18 8000 XM 21 Safing sector moved tostand different spacings

la 6/19 12,000 Rates varied

B 6/19 8000 1

30

Table I. R & D Tangless Bolts Firing Schedule (cont.)

Firing RoundsBolt Set Date Fired System Remarks

la 7/9 12,000

la 7/10 8000

la 7/31 11,000 XM 21 standw/clutch

la 8/1 10,500

la 8/4 9000

la 8/5 6000

la 8/7 11,700

la 8/8 11,000 XM 21 clutch Cook-off split bolt headbolt assy. (body 2) replacedby prod. bolt assy.

lb 8/13 4500 XM 21 New bolt set (std. instead ofbolt assy. 2)

lb 8/14 9000

lb 8/29 10,000 Detent added to aft helix inrear of bolt body

lb 9/3 12,000 R&D podw/R&D feeder

lb 9/8 9000 Stoppage - safing sector pin cameloose - bolt assy. (body 12)sheared bolt roller

lc 9/8 36,000

lc 9/9 3000

ld 9/9 45,000 Note: + in Bolt Arrangement

Id 9/10 3000 XM 21 stand

ld 9/30 1500

Total 400,500

+ Bolt body 2 (from cook-off on 8/8/69, which cracked the bolt assemblyhead) combined with bolt head 15 (from sheared roller stud on 9/8/69.which lost the bolt body 12)

* Special bolt assemblies with a cantilever spring added to the rear pin(reset pin in bolt body).

31

Table II. Total Rounds on R&D Bolt Assemblies

by Bolt Body Number

RoundsBody No. Fired Sets Appearing in

2 36,800 1, la, la

3 47,217 1, la, .b, ic, Id

4 12,000 1, 2a, B

5 12,700 2, 2a, B

6 12,700 2, 2a, B

7 51,067 2, la, lb, A, 1c, ld

8 50,550 1, la, lb, A, Ic, ld

9 50,550 1, la, lb, A, Ic, ld

10 16,022 2, 2a, A, B.

12 40,717 1, la, Ib, id

13 16,022 2, 2a, A, B

14 16,022 2, 2a, A, B

Body 2 + Head 15 8250 ld

32

A P P E N D I X I-D

Weight and Center of Gravity

33

Pi

We )I , rov I t v

I'ho p rodmi t Ion tild At I f- ' a t %rII t Iin 'm It A $I' r all I) I Ifl x m tq I tfi, it

weight, with the s•l' f-acittIunt1 livb i1ng %I Ilht IY hri•Pvt (i, lFor Ior 0 s Io1 %i

the center of gravity ý,,vv oltclosd *Iktch.

1, SO I f - act uA t Iu+ tip27n~

I Produlct

Weight in1' as4 per bolt 0,01590 pound

.005 in.

.0 0 5 In. .0 13 in. - 1 .4 9 In.-

NOT TO SCALE

Figure 22. Center of Gravity of Bolt

34

11CHNIKAt ANAMAS~ P#AM

IV PAOI

0AT IU~ IVi (u

CL) KuP~t~ UEAM19

Cj)sv6% lck

cl) u6 12S.14 d

CY) KA~o bU's 14 -JPof 4

TICHNICAI ANAM14g FORM-By- PA04

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TICHNICAL ANAMYSI KAM

NY$,INIA,@IIUCT#IC ILOICK 4 j ~ t V ___ ___ __

- -AT W 1 -6 Nov

mil Lital1-1

' 6 ~',37

A P P E N I) I X I-

Tolerance Study

38

TECHNICA ANAL'VSI FORM

CK. IIA MODli mc t "I L140ADATE d)*~Crdo.15 aIy, ArmyOTtA"L95% %.tý, Ta~logec lI3u (g'3&

D 3t .0 46~

t,3E~'S ~ Cdr, I4am', 4o*Lr

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- ~ ~ ~ TL ori, ~.0

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fe-SO39

TUCH t4"C AKAIYSI KORM

CK. MODEL U0C t

Z.It- Alm~6y%

1495&X 061-1I

14:!,.

O iee CALC.L)1. i95 ±.vcO% areocr wei

. 54.0 to. OCtO 8 Lac Of COA~ 90

.3564%.006 ..O~

1! 2*= mtooi~ L!, T 0i

024609 toSo 40

TECHNICAL ANALYSIS FORN

BY GININALSILICTRIC PAGE s OppCK. MODEL 'I o7DATE 0) 0 06'r- 6 REV. REPORT

*Alt'r ?F.& C.AwooNr*c:r

00k 4. -X. 0- 1"Is LalS t-QQT &2L.ahh&

-*IS'3Z ±t61ZL

1014836 tN'z COL

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o 40 ±o i o 61- uL

did~A -. ~2 -T-.@ ov em4.O~8O.oo38~-rA.4.3Z2~ ±oi5

______ CO.A 1

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TECHNICAL. ANALYSIS FORM

BY GIIA LCRC PAGE 4o~CK. OE

DATE 4J &LT. 114. REV. REPORT

. %Zdb 0 .0 040 FL.AX 0 C ArPT Pý V

6. 1A4

S LZ T. 1 o 14-h k s&1%Kr

-. (d (4 0 C1. ol" 45tA

A 2~10 -' ±S . 0045 ~ e~~

ZIL. oft-, Q&.e. Wvro "BAMBEL:

.0040:. o i oo

024-6" to-so, 42

TECHNICAL ANALYSIS FORM

By GENftIERAL ELECTRIC PAGE OrCK. I MODELDATE '4 OCT Mal REV. I REPORT

ASICKSL~Et 44hotvSr T cM

14 -t, .9) 0 .M *OU6

Asic,4o ± 00

a0086±~k. aowI 6 * ~ E

Pi ou m~ P,4 FT. aoc rb 'T'nm, Kv

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cad-su eggS43


'By 0-4IuPAGE 4O'CK. IMODEL 1. CeZ t4h*DATE '% OCT ft REV. REPORT

T~eCI qir "ad~tC %wbyf

7=031 0146fA'C

ovzoW 'r. Ole I

a. :t, . aoo2i Gavid

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ay 0-albot GIE AelITC PAGECK. W LCRC jMODEL t4~ p4DATE S06CI'iREV. I REPORT

((*-k) /~- GUaZ.'q Or?

13. CotC SE+ ~4

47.0t~~~~~~~ (a4 sic4vA ~.wftTA'

@8.o 03 45.~sL~jSd

TICHW~AL ANALYIS FORM

l' *ININAt @IIICTRtC PAOI

CK MODIL (01 M M~

DAFýo l Rv REPORT

~ Te~AtA~ac~ Aftv

8cam l Qa I oo25

4.1 rb t,~ a~ OIL

z.~ 00aft 0.4*! OA-bt ±2.a A

~~-i 0W1 % ;A~or.n op I 4L mjw

-'114I 1.aOI I~i

084-94 030I 46

T[CHNICAC ANAIYSIS PORN

rF MO "I. WQcsMka

41. 304 t. ZS 46X

- 00 15r

0546. 06 437W

iii

if 0

! I /

[I .t !. 4

444

4. a.. 646 1 -.1i -oJul'~

ettv

roof

sil

44

Mi,?0ý CA - -

"°in'. Im. : .iI,."I' : g

0Sl~in1.• .4

nus , .. -•Ft • .vm*O a

"+ Is

* T.i++ . .. &.... ... .Ii MM ' S*.I I, I•,* I *+'1 1

I 0..*Js. P * ,I4 ~ lus

\\ pr•~ .a s...j ,SHISW+•-v+. . . ... - " W . " '

Figure 24. Action Time Study for Self-Actuating Bolt Assembly

49

.&('11ON 11

MIlN I OIN C AIT.lCH, SCOPE ITE- 2

A, INTROIIHIT ION

Ihit I'V ISiIn f0' tl ng .1 C lI, kLitch a, i means of" ensuring a safe gun are not

new to applicationsi involving a mult ibarrelled, Gattling-type gun. lEconomic

cunlsideration. of operating the gun with other forms of clearing, incrrea.ed

ei fective payload, and improved safety are all well establis!,,d needs

mwtvit: Ji ig the use of a clutch.

A major difference between thi c;ultch devNeleped utnter thi ; contract and

pteviously devwloped clutches is that the new clutch is designed to be

MOUTIted within the aft end of the present 7.b2-mm GAU 2B/A minigun rather

than as an integral part of a feeder. Several major de igni problems were

bt'oikght about by this placement of the clutch, but one inaior advantage was

gained. BiY locating the clutch within the gun, it could be used with the

several different types of feeders for all applications instead of requiring

a unique, s ,rafely desigred clutch for each application.

Anothei basic design criteria for this clutch was to design it in a

configu-,*tiun that could be supplied as a modification kit and installed on

any gun in th• field with no modification required to the gun housirg or

rotor.

B. METHOD OF OPERATION

1. Basic 2Reration

The underlying principle in the operation of the clutch as an

instrument for clearing is that the feed system is disconnected from thegun and brought to a controlled stop. The gun continues to rotate and fires

all of the ammunition remaining in the gun, thus ensuring a safe gun. To

fire, the gun and feeder are automatically re-engaged in a timed position.

The actuation of the clutch is governed by a solenoid in such a way that the

gun will fire when the solenoid is electrically energized. Figures 43

through 49 show the minigun clutch.

50

2. Deta.iled Operation

Figure 49 sh(ows -in .- ploded ".oc: •f the clutch assembly. During

firing of the gun, the torque used to drive the feed system is transmitted

from the gun rotor, which is driven by the main motor, to the rotor housing

(11839384). The interior coutour of the rotor housing matches the contour of

the, aft end of the present gun rotor and transmits both gun feeder timing andtorque from the rotor to two slots, which in turn drive the two interior lugs

(driven lugs) on the gear actuator (11839378). These two driven lugs cause

the entire gear actuator to rotate and transfer torque to the aft rotor spur

gear (11839381) by means of the four large tongs which maintain a mesh with

the four longitudinal slots on the inside diuamotur of the gear. This gear

in turn drives the feed system. The new gear is no longer pinned to the gunrotor as it is in the present gun, but is now capable of rotating indepen-

dently of the gun rotor. The axial location of the gear on the rotor is

ijcntical with the present gun. The timing between the feeder and gun is

controlled by the above train of components. The importance of the timing

oeLwecn the gun and feeder in the round handoff area necessiLa4ls relatively

close tolerances on the pertinent dimensions of these parts.

a. Firing Mode

In the firing mode the solenoid is energized (plunger retracted)

which, through the yoke assembly, forces the two actuator arms (11839377) to

the extreme forward portion of their travel. On the inside of each actuatorarm is a camming knife which cams the rotating knife ring (11839379) forward

or aft, depending on the location of the solenoid plunger. With the actuator

arms in the forward fire position and the gun rotating, the actuator camming

knives force the rotating knife ring toward the rear. This action causes the

driven lugs on the gear actuator to mesh with the driving slots on the rotor

housing. (There are two actuating knives in this clutch instead of the one

found in most other clutch designs.) Due to severe space limitations, it was

impossible to obtain a sufficient base on the rotating knife ring to allow an

asymmetrical force to cam it fore and aft without causing Lhe part to cock

and bind. This introduced another problem in that with two k.,ives it is

possible, due to tolerances and cocking, for the knives to try to cam the

rotating knife ring in both directions at the same time. This occurrence

would cause a stoppage. To eliminate this possibility, one of the knives on

51

the rotating knife ring was cut to a steeper angle, thus causing one knife to

make the initial decision as to which way to cam while the other knife pro-

vided a symnetrical camming force once the decision was made. The rotating

knife ring slides fore and aft in four longitudinal slots in the rotor

housing. Contact is maintained between the rotor housing and the rotating

knife ring; consequently, whenever the gun is rotating, the knife ring is

also rotating.

The rotating knife ring is connected to the gear actuator byfour lugs and the four 11839403 pins. This method of connection allows the

rotating knife ring to rotate independent of the gear actuator; however, the

two components translate fore and aft along the axis of the gun together.

The gear actuator, like the rotating knife ring, slides axially in the aft

rotor gear maintaining contact with it. Thus, these two parts always rotate

or stop together.

b. Clearing Cycle

The solenoid is first de-energized when going into a clearing

cytie. the return spcing in the tilaioid forces the plunger to the rear,which, through the yoke assembly, causes the two actuator arms to go to the

rear also. The rotation of the rotating knife ring and the interference

between it and the two actuator knives cams the rotating knife ring and,

consequently, the gear actuator forward. The driven lugs on the gear

actuator move forward, out of contact with the driving slots, and the four

stopping lugs on the outside diameter of the gear actuator mesh with the

four strpping slnts in th- ciutch ,wuuin• (11839376). The clutch hnusing is

rigidly keyed to the gun housing through the bearing housing (11839374) and

the finger on the solenoid mounting bracket (11839382). The meshing of the

stopping lugs with the stopping slots brings the gear actuator and, conse-

quently, the aft spur gear to an abrupt stop. (The gear actuator and the

entire feed system are now completely independent of any gun rotor motion.)

The feed system is stopped, and the rotor continues to rotate under power

until clear of all remaining ammunition.

The angular location of the gear and the amount of time requiredfor the feeder to come to a complete stop are extremely important. Once the

gear actuator driven lugs lose contact with the rotor housing, no timing

exists between the gun and feeder. Contact between two parts must be

52

r ;i

maintained until the bolt head has complete control of the last round to be

fed (i.e., the last round fed is completely free of the feeder sprocket).

Also, the feeder must be stopped before the feed system begins to feed the

next round to the bolt head (i.e., the next round to be fed is completely

clear of the bolt head). The time when the transition between the driving

slots and stopping slots begins is dependent on the camming angle and total

throw of the knives.

To fire the gun, the solenoid is energized, which moves the

actuator arm to the forward position. At the same time, power is supplied

to the motor, causing the rotor to turn. Since the rotating knife ring is

still in the forward position (from the previous clearing cycle) and the

actuator knives have moved to the forward position, an interference exists

which causes the rotating knife r.ng to cam aft under the power of the gun

motor. This action takes the stopping lugs of the gear actuator out of

contact with the stopping slots and meshes the driven lugs with the driving

slots on the rotor housing. Timing is also important in this transition,

since it is imperative that the two driven lugs be in a location which

enables them to mesh with the driving slots.

There are four stopping lugs, but only two driven lugs. This is

due to the generally higher loads encountered in stopping the entire feed

system. 7he fact that there are four stopping lugs implies that the gear

can be stopped in one of four positions, each 90 degrees out of phase.

However, a 90-degree phase shift would prod, e a•-uirebponding shift of 90

.- grees when the clutch was reactivated to fire, and no driving slots would

be available to mesh with the driven lugs. Also, during firing and normal

flight, recoil and "1g" forces could cause the gear actuator to translate

fore and aft. For these reasons, the knives on the rotating knife ring have

been lengthened to include approximately 90 degrees of arc. This allows the

gear actuator to move fore or aft only when the soleiioid is energized or

de-energized.

c. Power Loading

Although no present Army systems require the ability to power

load, several Air Force systems do have this requirement. Since it is

conceivable that such an ability will eventually be re4uired by the Army,

53

it has been included on the clutch.

In order to power load, the clutch must first be _ngaged. This

can be accomplished by manually engaging the solenoid and rotating the gun in

the firing direction until the feeder begins to rotate (approximately one-half

revolution of the gun). With the solenoid still manually depressed, the

power load will now operate. Depressing the solenoid and rotating the gun

cams the gear actuator into engager7ent with the rotor housing (see Figure 25).

The gun is then rotated in the direction opposite to the firing direction, and

the driven lugs on the gear actuator are driven by the power loading driving

surface of the rotor housing.

GEAR ACTUATOR DRIVEN LUG

POWER LOADING ROTOR HOUSING/DRIVING SURFACE -

FIRING DIRECTION ll

OF ROTATION

Figure 25. Power Loading

It was experimentally determined that the minimum height ("Y")

required for the pywer loading driving surface was 0.095 inch. The angular

cut intersecting the 0.095-inch surface is a clearance cut which allows the

driven lugs to enter the driving slot on the camming angle of the knives.

The dimension "X"7 shown on the sketch is the clearance resulting from the

addition of the power loading step. This increased clearance allows an

additional movement of the gear actuator, and consequently of the entire

feed system, equivalent to one tooth of rotation in the aft rotor gear.

This clearance was incorporated in such a way to avoid a latv feed. The

possibility of an early feed could occur only if the feed system rotated

faster than the gun (e.g., if the gun would receive a high momentary torque

which slowed it down slightly). If the feed were too early, the feed system

would pause slightly (since it would not be driven at that time) until

54

timing was again correct. No problems were encountered during any testing

due to this possible cause.

C. TESTING

1. Clutch Unit 1

Dry firing on a MXU-470 Module System was started on April 13, 1969;

356 actuations were completed. This dry firing included cycling with up to

1500 rounds in the module drum at rates of 2000 and 4000 spm. Live fire

testing was conducted at the Underhill Firing Range from July 7 to July 11,

1969. A total of 50,000 rounds were fired using the clutch; approxinmately

26,000 rounds were fired using the Module System; 22,500 rounds were fired

using a delinking feeder; and 1500 rounds were fired using a Pod System.

The equivalent rounds fired was 85,000 based on the 100 rounds per burst or

883 actuations.

One problem encountered early in this portion of the testing resulted

in a failure to start. When the feed system stopped at the end of a burst

with the stopping lugs on the gear actuator in the extreme rear position in

the stopping lug slots in the clutch housing, the driven lugs missed meshing

with the driven lug slots upon start-up, causing the system to jam. 'To

eliminate this problem, approximately 0.120 inch of material was added to the

rear portion of the stopping lug slot in two of the four positions. After

the addition of this material, it was impossible to duplicate this type of

stoppage..

Another major problem that became apparent during live testing was:

insuffi, ient clearance had been allowed between the two sets of caiming

knives to eliminate the possibility of the two knives being caught halfway

through an o--.. tion with one knife attempting to cam in the fire direction

while the other Knife attempted to cam in the clearing direction. To

eliminate this problem, the camming angle on the non-decision knife was

i.ceased to allow for additional clearance. Now when the decision knife

of the rotating knife ring is lined up edge-to-edge with the actuating knife

there is 0.07U to 0.081-incb clearance between the edges of the two knives

(see Figure 48). After the clearance was increased, there were no further

55

-. . . .

stoppages attributed to this cause during this portion of the test. Detailed

live firing data sheets are included in Appendix II-C.

After testing and modification had been completed on the first clutch,

the major unresolved problem was the inability of the clutch to perform a

power load operation satisfactorily.

In order to power load, first the loading sector must be installed;

then the clutch solenoid must be mechanically locked in the energized

position; and finally the gun must be hand rotated approximately one-half

revolution in the firing direction to engage the gun to the feeder. The

system is now ready to be power loaded.

The ability to drive the feeder in reverse was initially dependent on

a 0.040-inch step in the lead end of the driving lug slot in the rotor

housing (11839384). During power loading, the rotor housing transfers power

through this step to the gear actuator, which in turn drives the feed system

in reverse. Test results and a tolerance study of the area involved con-

firmed the fact that under extreme conditions and severe vibration it was

possible for the driving lugs to slip beyond the step and cam forward on the

relief cut -- causing a stoppage. To eliminate this problem, material was

removed from the power load drive side of the rotor housing. This shortened

the lead-in and increased the power load driving surface to 0.095 inch.

There were no further stoppages in testing with the revised configuration.

Over 10v cycles have been run without ammunition and 6000 rounds have been

loaded on an A37 system with no malfunctions.

2. Clutch Unit 2

Live fire testing was conducted at the Underhill Firing Range and the

G.E.Springfield Range. A total of 100,100 rounds, representing 884 actuations,

were fired on clutch unit 2. During this test, over 40,000 rounds were fired

using the side-stripping feeder. No interface problems between the clutch

and feeder were encountc,-d. The remaining rounds were fired using a

delinking feeder.

During testing, a stoppage which appeared to be the result of a burr

on the rotor housing occurred. One of the four arms of the rotating knife

ring appeared to hang up during transition from the forward to the aft (fire)

56

position. This caused the part to cock severely and resulted in a failure tofire. To eliminate any future stoppages of this nature, these four arms willbe lengthened by approximately 0.060 inch, on the third and fourth units,until they are flush with the rear portion of the rotating knife ring. Thischange yields better control of the rotating knife ring and greatly simplifiesthe configuration of the part. The slots on the rotor housing that receivethese arms will likewise be modified.

To help ensure maximum engagement of the driven lugs during firingand power loading, 0.030 inch of material was added to the forward end of theactuator arms. This change forces the rotating knife ring, and consequentlythe driven lugs, to seat approximately 0.030 inch deeper in the rotor hous-ing. Testing of the revised configuration revealed a greatly improved"operation, especially during power loading.

The pins which connect the solenoid mounting bracket to the bearinghousing are another potential problem. During a severe stoppage it is

possible for the solenoid mounting bracket to tip. This tipping allows the 'Ifinger on the bracket which attaches to the gun housing cover lugs to jumpposition and rotate. This type of stoppage requires the clutch to be reassem- -bled and the connecting pins replaced. The upgrading of these pins from thepresent roll to a spiral pin should eliminate any possibility of the solenoid

bracket's tipping as the result of a stoppage.

During handling, the pivot arm which connects to the solenoid plungerwas bent slightly due to a hammer blow's making it asymmetrical. When thearm was assembled one way, this bend made it possible for the solenoid plung-er to stick and cause a stoppage. By reversing the pivot arm, no moredifficulties of this nature were encountered.

Three stoppages were experienced in which the two actuator knivesattempted to cam the rotating knife ring in opposite directions. The firstof these stoppages occurred due to a failure of one of the yoke supportspring pins. The pin had been damaged during a previous stoppage and fellout during this burst. The stoppage occurred when the yoke could no longercontrol the axial movement of the actuator arms. The other two stoppages

were caused by a combination of two factors. During the first stoppage, theclearance between the decision knife and the following knife was reduced to

57

0.048 inch. Also, the four arms on the rotating knife were prone to cocking

slightly due to the small minimum engagement when in the forward position.

(This has been corrected on all new parts.) After the knives were resharpened

and the clearance increased from 0.048 to 0.078 inch, no further stoppages

of this nature were encountered.

Several stoppages were experienced during continued testing of the

second unit due to a failure of the mechanical joint between the solenoid

mounting bracket and the bearing housing. A detailed investigation revealed

the connector holes on the solenoid bracket had been damaged and were over-

size. The stoppages were minimized by using a screw and nut instead of a

pin to hold the parts together. There was some difficulty in keeping the

screws tight. In production quantities these parts will be made as onepiece, thus eliminating this potential problem.

D. INSTALLATION PROCEDURE

The clutch can be provided as a modification kit to be installed in thefield on an existing gun. The procedure for installation of the clutch is as

follows:

1. Remove the gun bolt assemblies and guide bar.

2. Remove the three bolts in the aft support.3. Remove the rotor from the gun housing.

4. Drive the pins from the aft rotor gear and remove the

aft gear and aft bearing.

58

A P P E N D I X II-A

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A P P E N D I X II-B


77

III

La

Figure 43. Clutch Assembly on Minigun (Rear View)

Figure 44. Clutch Assembly (Rear View)

78

L _

Figure 45. Clutch Assembly (Front View)

Figure 46. Clutch Assembly Mounted on Gun Rotor (Side View)

79

ii

Figure 47. Clutch Assembly Mounted oni Gun Rotor (Rear Viow)

Figure 48. Clearance Between Decision and Non-Decision Knives

80

MOUNTING ADBRACKET

AFT GUNSUPPORT 1

BALk SOLENOIDBEARING

PIVOT ARM-z f.. .N HOUSING

ACTUATORYOK'E

-, )/ "N.A

ACTUATOR- -. GUN ROTOR

ARM .I- LINER

ROTOR SPUR GEAR

CLUTCH HOUSING

GEAR ACTUATOR

ROTATING KNIFE RING

ROTOR HOUSING

Figure 49. Exploded Clutch Assembly

81

A P P E N D I X I1-C

Test Results

82

Table III. Live Testing Clutch Unit 1 - Module System 4/7/69

Burst No. Fired Gun Status Remarks

Loaded 500 rounds

1 34 Clear Erratic fire - aft support screws not tight

2 81 Clear OK

3 93 Clear OK

4 105 Clear OK

5 88 Hot Failure to cam by both knives - timing fingeron solenoid bracket jumped time and rotated1/2 rev. - replaced pins in bracket, in-spected parts, no damage

6 0 No go Feed system retarded too much at stop

7 91 Clear OK

8 91 Clear OK


Parts reworked

1. Filed steeper angle on non-decision knife so 0.050 in. clearancebetween non-decision knife and stationary knife when decisionknife lines up edge-to-edge with stationary knife

2. Added 0.030 in. to rear side of stopping lug cavity in twoplaces

TESTING RESUMED 4/8/69

10 90 Clear OK

11 96 Clear OK

12 11 Clear OK

13 19 OK fire out

Loaded 1000 rounds

14 104 Clear OK

83

Table III. Live Testing Clutch Unit 1 - Module System (cont.)


15 78 Clear OK

16 100 Clear OK

17 97 Clear OK

18 111 Clear OK

19 92 Clear OK

20 112 Clear OK

21 .0 No go Feed system retarded too much at stop -

parts inspected - no damage - must add morematerial to back end of stopping lug cavity

22 92 Clear OK

23 111 Clear OK

24 103 Fire out OK

Loaded 1500 rounds

25-35 Clear OK - 11 bursts fired all cleared

36 0 No go No damage, no jam - suspect wiring short

37-40 1500 Clear OK - four bursts fired out on burst 40

Loaded 1500 rounds


42-50 Clear OK

51 0 No go No damage, no jam - suspect wiring short

52 95 Hot High extract - gun cleared by hand - veryhigh extract on one barrel

53-56 Clear OK

57 1500 Fire out OK

Loaded 2000 rounds

58 Clear j OK

84




60 9 Hot Feed system mistimed - retimed

61-68 Clear OK


70-79 Clear OK

80 2000 Fire out OK

81-83 Clear OK


85 0 No go Feed system retarded too much at stcop

86 Clear OK

87 0 No go Feed system retarded too much at stop -

added approx. 0.060 in. to end of stoplug cavity

88-93 Clear OK

94 2000 Fire out OK

Rework

1. Added 0.030 in. to end of actuator arms

Loaded 2000 rounds

95-97 Clear OK

98 Hot Stoppage during firing - no apparentdamage - no jams

99 Hot Round (pierced in module exit shaft) feedinto gun left projectile in barrel -

stoppage when next round fed into pluggedbarrel - primer was blown on first roundbut propellent not fired

100-116 Clear OK

117 2000 Fire out OK

85



Loaded 2000 rounds

118-141 Clear OK


Loaded 200 rounds143-144 Clear OK

145 Clear Intermittent solenoid failure - replacedsolenoid and connector

146-149 Clear OK - battery very low - replaced battery -

this probably caused failure on burst 145

150-164 Clear OK


Loaded 1800 rounds

166-179 Clear OK


Loaded 2000 rounds

181-196 Clear OK


Loaded 2000 rounds

198-206 Clear OK


Loaded 2000 rounds

208-224 Clear OK


Loaded 2000 rounds

226-239 Clear OK


86

Table III. Live Testing Clutch Unit I - Module System (cont.)


Loaded 2000 rounds

241-260 Clear OK


262-265 Clear OK

266 Jam in drum hando.f - Module System shut-down as per original test plan - convertedto Pod System (this system has damagedrounds on scoop disc in prior testing)

Loaded 1500 rounds

267-274 Clear OK

275 Hot Bent round in conveyor wheel

276-282 Clear OK

283 Hot Bent round in conveyor wheel

284 1500 Fire out OK - changed to delinking feeder due todefective scoop disc on Pod System

Loaded 2000 rounds

285-292 Clear OK

293 Hot Mislinked round jammed in feeder

294-306 Clear OK


Loaded 2500 rounds

308 Clear Belt broke (ammunition can too full)

309 Hot Feeder jam

310-331 Clear OK


Loaded 2000 rounds

344-370 Clear OK

87




Loaded 1500 rounds

372-384 Clear OK

385 0 No go Pin in yoke assembly fell out (improperlyinstalled)

386 Hot System mistimed - retimed

387-396 Clear OK

397 1SO0 Fire out OK

Loaded 1500 rounds

398-415 Clear OK


Loaded 1500 rounds

417-420 Clear OK

421 Hot Feeder jam

422-440 Clear OK

441 150( Fire out OK

Loaded 1500 rounds

44I 4 Clear OK

464 1SO0 Fire out OK

Loaded 2000 rounds

465-405 Clear OK


Loaded 2300 rounds

487-51i Clear OK


Loaded 1200 rounds

88



513-526 Clear OK


50,000 rounds - total rounds fired

89

89

Table IV. Live Testing Clutch Unit 2 - A-37 System 6/9/69


Power loaded 1500 rounds

1-16 Clear OK

17 1500 Fire out OK


18-31 Clear OK

32 1500 Fire out OK

Power Loaded 1500 rounds

33-36 Clear OK

37 Hot Stoppage near beginning of burst - roundout of control ahead of bolt head -debulleted attempting to enter chamber -

no damage to gun

38-39 Clear OK

40 Hot Same stoppage as 37

41-42 Clear OK

43 Hbt Same stoppage as 37

44 1500 Fire out OK


45-58 Clear OK

59 Hot Same stoppage as 37

(Note: Further investigation revealed a damaged guide barin the gun.)

Testing changed to delinking feederI

Loaded 2000 rounds

60-75 Clear OK

90

Table IV. Live Testing Clutch Unit 2 - A-37 System (cont.)


76 0 No go Burr on one of four slots on rotor housingcaused cocking of rotating knife ring andsubsequent stoppage - finger on solenoidbracket jumped time and rotated 1/2 rev. -

burr removed, slight damage to knives

77-83 Clear OK

84 2000 Fire out OK

Loaded 2000 rounds

85-91 Clear OK

92 Hot Sol. bracket finger jumped time and rotated1/2 rev. - pins on sol. bracket loose

93-96 Clear OK

97 Hot Same stoppage as 92 - replaced pins

98-107 Clear OK


Loaded 2000 rounds

109-134 Clear OK


Loaded 2000 rounds

136-157 Clear OK


Loaded 2000 rounds

159-183 Clear OK


Loaded 2000 rounds

185-206 Clear OK


91

Tablo IV. Livo Tvitiii Clutch Unit 2 - A-37 SyNmtom (Cuont )

Burst No. Fi red Gn jSta .

Loadv, 2000 1nuund&

208-?28 Cle•ar OK

229 2000 Firo out A

Loadod 200u 1oundm

230-24 Cloear Ok

Clutch Test shut down duo to iiisuffict¢| lol timo

92

A~ble %, •10 l u•M li ve Tl•'lling "i f1 .1

h iml• I.u•"I W 11,iloo 0 >0 NI!1% I-IItm

:1 I,4

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I , *

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I o~.ad il o ')I i'tintda

,.1 --5 ,o I,'00 l"d & i il

I l 1hi t'd plungIer stuick

811 :'1u0 C I v ai r ilk

hi ildiigL I viin.&nnl r it'ol) I C' Isel dLoiadketk ditd hiiding wts trou ndmsnltd

1I9 - 8I3t :000 tk 1" i C I ntIdlk

L.o aded,1500 K'rounds

93

Soleoid lungr stck lnkag wa

rable V. Continued Live Testing Unit 2

Prior Testing 246 Actuations - 21,500 Rounds Fired (cont.)

Burst No. Firod Gun Status Remarks

107 -Hot Right yoke pivot pin fell out causingloss of knife control - set 1/16bearing pins - filed down resultingburrs on knife blades

108- 1a1 1500 Clear OK

LoaJed IS00 rolod's

122,138 1500 1 Clear OK

Loaded 1500 rounds

139-154 ISO0 Clear OK

Loaded 1500 rounds

155-164 1500 Clear OK

Loaded 1 00 rounds

Io5-172 1500 Clear OK

Loaded 1SO0 rounds

173-183 1500 Clear OK

Clutch disassembled, inspected, andrelubricated

Loaded 1500 rounds

187-201 1500 Clear OK

Loaded 1500 rounds

202-217 1500 Clear OK

Loaded 1500 rounds

218-237 1500 Clear OK

Loaded 1500 rounds

238-246 1500 1 Clear OK

Loaded 1500 roundsI

94

i •

Table V. Continued Live Testing Unit 2



247-256 1500 Clear OK

Loaded 1500 rounds

257-266 1500 Clear OK

Loaded 1500 rounds

267-276 1500 Clear OK

Loaded 1500 rounds

277-291 1500 Clear OK

Loaded 400 rounds

292-295 400 Clear OK

Clutch disassembled, inspected, andlubricated

Loaded 1500 rounds

"290-308 1500 Clear OK

Loaded 1500 rounds

309-325 1500 Clear OK

Loaded 1500 rounds

326-341 1500 Clear OK

Loaded 1500 rounds

342-347 - Clear OK

348 Hot Clutch jam - knife blades cammed bothdirections - solenoid bracket screwsbent slightly (replaced) no otherdamage

349-356 1500 Clear OK

Loaded 1500 rounds

357-372 1500 j Clear OK

95




Loaded 1500 rounds

373-389 1500 Clear OK

Loaded 1500 rounds

390-404 1500 Clear Clutch jam at fire out - knife bladesclearance 0.048 in. increased to0.078 in. per design change

Loaded 1500 rounds

405-419 1500 Clear OK

Loaded 1500 rounds

420-432 - Clear OK

433 1500 Clear Clutch jam - solenoid bracket screwsworked loose permitting finger tojump time

Loaded 1500 rounds

434-446 1500 Clear OK

Loaded 1500 rounds

447-452 1500 Clear OK

Loaded 1000 rounds

453-463 1000 Clear OK

Loaded 1500 rounds

464-476 1500 Clear OK

Loaded 1500 rounds

477-491 1500 Clear OK

Loaded 1500 rounds

492-506 1500 Clear OK

96

L.


Prior Testing 246 Actuations 21,500 Rounds Fired (cont.)


Loaded 1500 rounds

507-520 1500 Clear OK

Loaded 1500 rounds

521-531 1500 Clear OK

Loaded 2000 rounds

532-544 2000 Clear OK

Loaded 2000 rounds

545-557 2000 Clear OK

Loaded 2000 rounds

558-567 2000 1 Clear OK

Loaded 1000 rounds

568-572 1000 Clear OK

Loaded 1000 rounds

573-577 1000 Clear OK

Loaded 1000 rotnds

578-583 1000 Clear OK

Loaded 1000 rounds

584-588 1000 Clear OK

Loaded 1500 rounds

589-596 1500 Clear OK

Loaded 1500 rounds

597-608 1500 Clear OK

Loaded 1.500 rounds

609-623 1500 Clear OK

97




Loaded 1500 rounds

624-638+ 1SO0 Clear OK

+ 246 prio r actuationsI ITotal Rounds Fired a 100,000

Total Actuations = 884

98

A P P E N D I X II-D


99

Clutch Unit

Total Weight =3.4805 pounds

Center of Gravity = .S429 inch aft of the

forward edge of the bearing liner (see figure S0).

SOLENOID -III1X134 CENTER OFGRAVITY OF

t~1T5ZO4-3CLUTCH1 1I.5429

Z- P104- M30066-i1g

14OUS114@ - f.S 9774 (REP) -N *66

FigureOXMAW 50. Clthasseml

100

A P P E N D I X II-E

Final Report Minigun Declutching System Analysis

101

A. ABSTRACT

The declutching mechanism has been designed and is being tested at the

present time. Early test results showed some minor adjustments were needed;

recent tests on the Module System have been conducted with excellent results.

The dynamic characteristics of present minigun systems and the dynamic

characteristics of two forecast systems are included in this report. A stress

analysis of some critical system parts has been performed and is also included.

B. INTRODUCTION

The desired declutching mechanism for the minigun is one that would be

contained within the gun itself and hence be available to all of the several

feed systems.

The mechanism generally considered would disconnect the rear drive gear

from the rotor and stop the feed system at particular locations of the feeder

sprocket so there would be no interference due to the round's being between

the feeder and the gun during the handoff operation of the feeder. The

advantages of this mechanism are in the saving of ammunition and in stopping

the gun, normally with no ammunition in the gun, in the safe stopped condi-

tion. The two main difficulties in incorporating this mechanism in the gun

are - the space limitations within the gun and the probably high inertial

loads on the several parts of the feed systems after a sudden stoppage.

C. APPROACH

A two-part program was undertaken to gain knowledge of the dynamics and

loads of the present systems and to forecast the dynamics and loads of future

systems. The first was an experimental test program conducted to show the

torque-time-acceleration characteristics of the systems. The second part was

an analytical solution using the digital and analog computers to find

solutions that correlate with present systems and solutions for systems with

new design requirements.

102

D. TEST PROGRAM

A test device was designed to disconnect the rear gear from the gun

rotor at a particular location, where the rounds are fully contained in

either the feed system or the gun, and to stop the feed system almost

immediately after the disconnect. The stop device was instrumented to

give a trace of torque versus time during the very short time during

which the inertial loads build up. Several curves of peak torque versus

rate, presented on the following pages, iow the maximum torque which may

be expected for the several systems.

~t

ilALI

4 ! . . ,. 4, 1

Figure 51. Peak Torque on Minigun Pod Feeder Shaft vs Rate

103

I-*ý4 -4

4

I -' II

17,,

12,14

-7

.ZT .... ......

~~~~. . .....~.

.... --

- -IT~ "If

-_-

Figure 52. Peak Torque on Miniguni A-317 Fecd S~ystem

with Sudden Stops of Rear Gear of Rotor

104

40 ... ...

2 G

* .. .. '. *

4T- ýR IF

0' I I i

10

, •) .' a€ ; ... . ......................... ....... 17 [V. .........

iI............................................... ........... .*,•.J .... .

I F

wihSde tpso erGa f Roo

105

IS 1 1. - 4''4

I U7- l7-

V K~r ~A v~¶.~IflJ5DI~~h~q 5'ID

>10

E. PEAK LOADS IN THE SEVERAL MINIGUN SYSTEMS WITH SUDDEN STOPS

The peak torques on the several minigun systems are presented in thepreceding graphs and are tabulated below for sudden stops from 6000 spm with

full drums (where applicable). The most highly stressed part is indicated,

and the peak load is compared to the allowable load.

The peak loads expected on the most highly stressed parts are less thanthe allowable loads except for the new 3000-round Pod System with a new feederand a module-type drum. This system develops a 4900-pound load on a pin thathas a maximum allowable strength of 3000 pounds. This particular pin is aC-type pin; a roll pin could be substituted to increase the allowable load to4400 pounds. However, if this system were siowed to 3000 spm before a suddenstop the peak load of 2740 pounds is less than the allowable load of 3000

pounds.

Table VI. Peak Torques for Sudden Stops from 6000 spm

ALLOWABLEPEAK TORQUE LOCATION PIN SHAFT DIA. PEAK LOAD LOAD

SYSTEM (INCH-POUNDS) OF PIN MS NO. (INCHES) (POUNDS) POUNDS

Present Pod 280 Fdr. Drive 16562-231 0.375 1490 3000Gear

AT-37 760 Fdr. Drive 39086-250 0.500 3040 4400Gear

Module 900 Exit Shaft 39086-250 0.500 3600 4400Drive Gear

Delinking 950 Feeder 39086-251 0.624 3050 4400Feeder Sprocket(MAU-58)

3000-Rd. Pod & 1224 Fdr. Drive 16562-232 0.500 4900 3000New Fdr. & Mod.- GearType Drum

3000-Rd. Pod & 685 Fdr. Drive 16562-232 0.500 2740 3000New Fdr. & Mod.- GearType Drum at3000 spm

107

F, ANALYTICAL INVESTIGATION

Fundamental information regarding the dynamics involved with engagement

of the several miniguo systems is des.ired. When engagement occinrs at the

Lun, the feed sy~..t.em's ineirtia will develop loads depending upon the inertia,

spring constants, and friction involved. The most simplp" differential

oquation that might give teasonable answers to the above is the classic

sprin g-mass system equation with friction force porportional to velocity. A

second differentitk) equation that is more realistic for cases where ammui-

tion is rotated and sliides ir .3 dr'umL, as in the Module System, is the

differential equation for a spring-mass system, but with a friction force

which varies as the second power ut' the velocity. Both systems are investi-

gated here, and they agree to a large exltvt since friction does not occur

over a sufficiently long time to cause large differences.

G. SUNMARY OF RESULTS OF TIE ANALYTICAL INVESTIGATION

The present Module System, with' 2000 rounds in the drum ,nd a rate of

6000 spm develops 500 foot-pounds of torque at the drum clutch engagement.

Tile same type of system with 3000 rounds in the drum will develop 600 foot-

pounds of' torque at the drum.

A new Pod System w.t, 3000 rounds in a module-type drum will develop

680 foot-pounds of torque at the drum at 6000 spinl; if actuated at 3000 spin,

it will develop 380 foot-pounds of torque. The above results were obtained

with a measured spring constant of 3380 foot- pounds per radian at the drum

for the present Module System and with a spring constant of 4430 foot-pounds

per radian at the drwii for the new Pod System. *rhe new pod spring constant

was measured with the new ieavier feeder shaft.

108

The d g it al Compute r w an programmed fur t he equation:

B ko .)t *

tit d t

It' the first ternis arO thl,,ughlt of as total torque, tl'c second terms as

frictionl torque, und the third terins as spring torque -- and deceleration

begins from the same initial conditions - -it is obvious that during the

stop thle friction torquet fur the second equetion (analog) will decrease

more rapidly with time than the friction torque for the first equation

(digital). Consequently the peak spring torques for the unalog model will

ht: geiierail v higher than those of the digital model, but thle differences

are' not large (less than five percent) and thle two methods tend to verify

VZaCh other. One interest ing observation was that nei tho'r mode 1 damped as

kqui~ki>' as the experimental. The high-speed movies gave a possible

oxplanat ion for this. The camera angle was such to observe that during

th:,, stop, while the motion of the inner drum generally follows a dainped

s inie curve pattern, higher frequency oscillations occurred - thle Inner drum

t'i s very likely oscillated thle rounds from one fin to the next and back

many times during the stop. This would dissipate the stored kinctiLc energy

imi,ýh faster than either of the two mathematical models and would account

for the rapid experimiental1 damping obstrved.

Thle several, present minigun systems should be capable of withstanding

the suddta ztopping lu&ids owing to the declutching mtchanism. The AT..37

system will need ark additional bearing to insure continuous contact of the

drum ring gear and its mating pinion, but this modification is a minor one.

1-09

1. MATHEMATICAL 'ORMULA;,'ION (FOR DIGITAL COMPUTER)

The simple spring mass system with friction force, which varie- linearly

with velocity, may be written in terms of rotational inertia as follows:

42b + - 0dti Lit I

wiiere- b t

* - CC sin (at + a)

Ct "cos (.t + a) - Cbe-btsin (at + a)

b2 2 .*bt. 2b-bt-"d2 C (b 2 - a") e sin (at + a) 2Cabe coq (at + a)

dit

It will be found upon substitution of the last three equations intothe first that a necessary requirement is that a- = 2 + b2 .

The above four equations form the basis for writing the computer

program included herein for the digital computer and produce the results

indicated in the abstract. briefly, the moment of inertia of the empty

Module System was determined from acceleration tests with strain gauges which

found torque at the exit shaft and acceleration read from recording galvano-

meter tapes. The moment of inertia of a round in the drum is calculated

here, and the total moment of inertia is thereby available. The spring

constants of the Module System and the Pod System were found by torque-

deflection tests as specified herein.

In order to find the torque buildup of the feed system alone, a

solenoid actuated device was built which would disconnect the rear rotor

gear from the rotor while running, and then stop the feed system by

inserting a solid obstruction at the rear gear. This was dune with the

several feed systems, and exit shaft torque, speed, and high-speed motion

110

pictures were taken as the systems were stopped. This latter data along

with the steady state friction torque allowed a correlation of the system

behavier with the mathematical model. In effect, various values of the

damping constant b were inserted into the computer program until a good

match of initial friction torque and peak spring torque was obtained using

the Module System as the experimental system.

In order to predict the behavior of a new Pod System which would use

a module-type drum, the damping constant b was assumed to vary direLtly as

the drum load.

J. DIGITAL COMPUTER PROGRAM

In the following Fortran four digital computer program, the rate, spring

constant, rounds in drum, and frictional constant b are read. The inertia is

calculated as shown in Appendix II-F. Since a = 2T/TP where TP is the2 b2

period, the equation K/i = a + b gives TP. The initial speed of the drum

in radians/sec -j d = is calculated from spm and the gear ratio. The constant

C is obtained from C =dt t=O)(TP)/21T. 0 = FE is found from the second

equation of the formulation and converted to degrees FEDGR. do/dt = DFEDT2 2

is found likewise, from equation 3. And d 2/dt = DTODT is from equation 4.

The term total torque TOTQ in inch-pounds is from I) (dt (12). The program

listing gives time, degrees of deflection of the drum, ve,'ocity, total torque,

friction torque, spring torque, DELTQ a difference between the total torque,

and the sum of spring and friction torque and acceleratioi,. Also listed is a,

spm, spring constant, rounds in drum, period, inertia, the constant C, the

friction constant Beta, and a check oi. the inertia COPIA.

111

//JOR T//FOR

*ONE WORD INTEGERS*FXTFNDFD PRECISION*IOCSICARD,1132 PRINTER)*LIST ALLC ME-2439PROBLEM1 4-28

500 READ(2,1C,00)SPMSPCONRONDSBETA1000 FORMAT(4F10*4)1030 FORMAT(1N1,48X9.TANIK SLOWDOWN PROBLEMl//,4X,'TIME,97X.IDEGREES',

16XIVELOCITY',7X,'TOTOR0UE',5X,'F'RITOUE't5X,'SPRITOUE',6X(,'DELTUO,26X93'ACCL,9//. 4X.'SEC'.10X.'0 e1OX.'RAD/SEC *8X. ' NXLBS ,7X.' INXLBS.o46X., INXLSS' ,7X, INXLBS .3X. 'RAD/SECXSEC' *//)

1040 FORMAT(SE1305)1050 FORMAT(1H1,5X,'ALPHA¼99X.*SPM0',8X,'SPCON',18X,'RONDS'I,5

1X,6PERI0D1,7X,'ERTIA,99X,'CO,99X,'8ETA',8X~,COPIA',2X)1060 FORMAT(10F12@5)

WRITE(3#1030)TwO0*P1.3. 14159EPI=2. 71828

ERTIAs( 166*4RONDS*e8714) /4640.TPu2.*PI/U(SPCON/ERTIA)-RETA**2e)**95

DFEDO=SPM/3 83.SEE.DFEDO*TP/(2.'*PI)ALPH.An2o*PI /TP

20 DO 50 101940FEUSEE*SIN(ALPHA*T) /EPl**(9ETA*T)FFDGRmFE*57, 3DFEDTS((SEE*2.*PI/TP)/EP1**(BETA*T))*COSC2.*PI*T/TP)-(SEE*BETA/l(EPI**(BETA*T))H*SIN(Z.*PI*T/TP)DTODTu(SEE*(BETA**2.-ALPHA**2.)*SIN(ALPHA*T))/EP1**(BETA*T)-l(2.*SEE*ALPH.A*BETA*COS(ALPHA*T) )/EPI**(8ETA*T)TOT~nERT IA*DTODT*12*FR ITQu2.*B8ETA*DFEDT#ERT I A*12.

!ýPTQ=SPC0N*FE* 12.DEI.TQoTOTO+FR ITOWRITE(3,1040)TFEDGR.DFEDTTOTOFRITOSPT0,DELTODTODT

50 TxT+*002COP IAUSPCON/(ALPHA**2.+BETA**2.)WRITE( 391050)WRITE(391060)ALPHASPNISPCONRONDSTPERTIASEERETACOPIAGO TO 500

150 CALL EXITEND

Figure 55. Program for Feed Systems with Sudden Stops

112

I 1i

i.Ljj0 - ij4

113*

K. MATHEMATICAL FORMULATION (FOR ANALOG COMPUTER)

The spring mass system with friction force, which varies as the second

power of velocity, may be written in terms of rotational inertia as follows:

do+ 2B ( *J)2 + KV 0dt2 dt Y

or

2d,

d2 2BI ( 2 K = 0dt 2 dt

In the second equation the first term may be thought of as the inertia

torque, the second term as the friction torque. and the third term as the

spring torque or the torque which results in torsional deflection of the

system. This equation is thought to be more representative of the Module

Feed System, since the ends of the rounds slide on the stationary outer drum

and, if the friction coefficient is assumed to remain constant, the frictional

force and consequently the frictional torque may be considered to be a

function of the normal force between the rounds and the outer drum. Since

the normal force is a function of orientation of the drum to the gravita-

tional field and also of centrifugal force, the first effect is considered

constant; and the friction torque term includes a velocity squared term which

accounts for the second effect.

A diagram of the analog computer components is included oz the next

page, and the curves of spring torque at the drum versus the friction

constant B are presented as a summary of the data curves found in

Appendix II-F.

114

- I-

MQ T

'Uj

0 9 0

ItI

VA LLI

Nd

cc) -f z .

L4.

0,7

cr -o

~~ tin

4 t4 -4

I 41

I It

aa . 4a . a t

t, 4-1

~ 44

it -

Figure S8. Declutching Torque Estimated from Analog Computer Results

116

I., LISCLJOISION 01. ,NAIOt COMPTllilM REISLlLTS

Th, t', sviati of t h te liad tl %'ompute r prograni arv 41t' I vv en ol tthe prccedin

A,11Ph 111 +igaurt, SH) 44., 5;l'tlig toique tit thie drum for variouis valtue, of II antd

6o1l' tihe Modu11t, or Pod SV s te m with t.000 or 3000 rounds in t he t'ruaall. A range

ot' It Vallote was used to bht~aili a btst fit of init ial conditions of' frict ion

1c'que just prior to cltitch aictuat ion; tile best fit information agreed well

with tilte w ,•psI' tI ntal e, I tll t1.Ar orque fo t'ie ' 000-round moduloe tit C()OO spa.

T6, r't'skltt.i s 11 It 0. .1 t h,-lt C't th ,se, inl tiial condlt oos and are used to

p hctaae thlt ,.vsu lts stat cd prt'vioutsl . Tho ltitniti Iat the 3000- round load

i , tit sumond to be I .5 tme,,s that of tihe 2000 round load,

NI, STRESS ANALYSIS 01" III[: IiIllT'CIIiNL4 MIECHANISM

In ordlr to obtain dynamic informotit'n quickly , the test apparatus

descl'ibed in the i rst t'ow pages of this report wau. used tit ail early stage

of this investigation to stop the sveral food systems suddenly. High-

Spted movies 'Ind stroin g augo inst runac'ntat ion recorded the dynamic informa.-

tion presented there. It was expected that this exi'orimentz,.tion would cause

,iome deformation of the spring pins or roll pins, and theste were exanined

at sovvral stages, but no tsuch deformation (sot pins) actually occurred.

The feVer gear spring pin on the Pod System was monitored very closely

alnd a conwclusion was drawn that set pins that had been reported previously

with this system must have boon due to a stoppage of the feed system which

allowed peak drive motor toroue plus inertia to be applied in order to set

the pins. The several systems - Pod, Module, A-37, Pintle Mount with delink-

ing feeder - were actuated approximately 100 times from a 6000 spm rate with

no dvformation ,f parts. The allowable load summary for the pins is given

in the early pages of this appendix for the above systems and also for new

design requirements.

The present feed systems appear to be capable of withstanding the loads

inposed by the declutching action. However, the ne.vly designed clutch

which fits into the present minigun housing is ne,:essarily small, and a

stress analysis of some of the critical aruas of chis design follows.

117

The March 1, 1969 prcimin titary mini gun declutching mechani-sm design ws

studied for possible high stress areas. Regions examined in detail were as

fol lows:

I . The clutch housing restraining lugs were st ress analyzed for shear

tf-t lure.

2. 'he clutchc h•tuvig lug ',ket was examined toi n possible conlcal

shear fracture at the 4:11d Ut thibyS,,.ket.

3. Th'e internal lugs ot til, act uator gear, whi0h engage to start tilt,

food "iystam, were 101a4verd

4, 'rho roear rotor pgtvkr was ¢na led In the i rea between the root of the

teeth and the section of tile goaz" Cut Out to accept the actuator gear tilg.

The most highly stressio oea-s -ire at thle internal lug% of the actuator

gv'ar, which engage to 'tarit the lued v.tem. Tile maximum allowable torque at

the actuator gtAr is calcul atvd to but: .;1'0 inch-pounds, Recent tests and

calculations show the ma.ximun torque expected on a disengagement to be 1080

inch-pounds at this location. However, a greater applied torque probably

will o%,:ur on engagement to start the feod system, especially if engagement

occurs when the gun is turning rapidly with the fted system stopped and the

sy)tem motor on.

N. RF.COMflENDATION

It is recommended that part 11839384, rotur housing, be altered by

removing the note to chamfer 10 places 0.05+0.01. It is also recommended

that part 11839378, actuator gear, be altered by slightly undercutting the

ends of the inner engagement lugs as described herein to allow proper mating

of the two parts. The change will increase the allowable torque at the

internal lugs of the actuator gear by 87 percent. It will also decrease the

shell thickness of the actuator gear from 0.100 inch to 0.091 inch in the

local area of the cut, which is a less seriously stressed area.

118

-.

o C LUTi0 HOUIsNG RUsTRA INING MA. TOR()JJI: C:APABII I, TY

3,,149.hinch 01) 11)90-inch I 0 ,19% lnch or about .,050 thick seoction

( m i i li mum (, rgagement )

hug hoi~ght 0. lo Inich .

, 0O.16 ,In1

0.050 i,.- 0 1" i

SHEAR AREA

Shea Aroa - (0.050) (0, we) 0.0113 square inches

e S allowable . L0.6)(" ult tonsilo) - (0,b))(275,00() . lbS 000 psi

F-i - asA - (lb5,000)(0.011.1) - 1860 pounds per lug1860 = 26401Ibs.= F

FS

Mnoment capability + (F)(Dia) - (26,40) (2.950+0.050) 7b000 inch-pounds

P. CLUTCH LUG SOCKET LOAD CAPABILITY IN CLUTCH HOUSING

0.D. Actuator Gear - 2.720

ID. Clutch Housing = 2.4500.270 overlap on diameters

or 0.135 overlap on radius

0.123 In. DEPTH OF LUG SOCKET

119

I4

Assume a 90 degree conical shear fracture occurring on a 45 degree angle with

the surface.

900

45-

Cleavage surface area n 1/4 (cont, area)

- 1/4 (2n r mean)(slant height)

M - 0.0185 inches2

2 (0.7"7)

Load capacity in cleavage direction a (0.0185)(165,000) - 3030 pounds3030Allowable load in the tangential direction • * 4290

Allowable torque - (Dia)(Allowable tangential load)

- (2.50)(4290) u 10,700 inch-pounds

Q. CLUTCH LUG LOAD CAPABILITY IN INTERNAL LUGS OF ACTUATOR GEAR

The rotor nousing is chainfered back on the starting lug face 0.050 inch,

which leaves only 0.057-inch face width as follows: 2.181-inch - 1.966-inch2

- 0.050 inch0.215 0.107 , 0.057-inch wide lug face

2

The section is 0.136 inch high.

120

I

If the face shears on the muting gear actuator, the area sheared is

(0.057)(0.136) . 0.010960.7070

or an allowable tangential force of (0.01096)(165,000) 25600.707

Allowable torque - (2560) 2.181 + 1.966

- 5310 inch-pounds

This is the smallest allowable torque calculated thus far, and it indicates

a possible trouble spot. The allowable torque is based upon load carried

by buth lugs simultaneously.

R. ANALYSIS OF STRESS IN REAR GEAR ON ROTOR (REGION BELOW TEETH ROOTS)

2.576 Root diameter of gear teeth

2.400 - Dia. of slot inside gear ring

0.176 - Thickness below root of teeth

Width of gear = 0.61 inch

Tensile area = (0.61) (0.176)

Assume tensile strength of 4140 steel = 150 KSI

Tensile load - (0.61) (0.176)(120,000) = 12,900 pounds

Allowable torque based =

on tensile strength -- (12,900) = 16,150 inch-pounds torque

Allowable load based = (0.61)(0.176) (75,000) = 16,100 poundson shear stress (0.707)z

Allowable torque based= (16,100)(1.25) = 20,150 inch-pounds

on shear strength

J121

S. POSSIBLE MODIFiCATION OF ACTUATOR GEAR DESIGN

Part 11839378

Undercut the two interior lugs so that the O.0S0-inch chamfer on the

housing rotor mating recess is not necessary.

Drill 1/16-inch diameter holes on either end of the lug as per sketch

R = 0.03125

-•O.0125 - 0.0221 = 0.009(0.707 )( 0.03125 ) = 0.0221

If done in this manner, there is a 0.009-inch undercut. Since the shell

thickness is 0.100-inch, the 0.009-inch undercut does not appear to be tog

great.

Table VII. Torque at Rear Gear of Rotor on Declutching of Feed System

System Torque at Rear Gear of Rotor

(inch-pounds)

"Present Pod 336

AT-37 912

Module 1080

Delinking Feeder 728

New Side Strip Feeder

at 6000 spm 1470

at 3000 spm 820

122

A P P E N D I X II-F

123

A. DECLUTCHIN(J MECHANISM ANALYSIS, MOMENT OF INERTIA OF THE MODULE FEED

SYSTEM

The design of a test mechanism to obtain torque versus time during

sudden stoppage of the ammunition feed system was described previously. ThemomentF of inertia of the several systems will be most important in thatinvestigation, since in cases where the feed system is stopped rapidly, theinertial effects will generate forces which may require the redesign of

certain parts. The purpose of the following analysis is to describe the

method by which the mcment of inertia of the Module Feed System is obtained.This information will be used to predict peak torque at other inertias,

frictions, and spring constants.

The Module System was run in the Development Laboratory with no

ammunition using an Air Force drive at several speeds. The feeder wasinstrumented with strain gauges on either side of the drive gear so that

the torques for both the sprocket and for the drum drive were obtained. A

speed transducer was used on the system in addition to the rounds indicator

so as to have instantaneous speed recorded on the trace. The fundamental

basis for the determination of the moment of inertia of the Module Feed

System is the equation Tq = Ia or torque = moment of inertia of mass timesthe angular acceleration of the system. The velocity and torque data are

taken during the start-up acceleration period, and the moment of inertia of

the drum is calculated from these data as follows:

TI'e data are from test 20 for a module with no rounds in the drum. The

controller is set for Army low rate.

spm at 20 milliseconds = 810

spin at 10 milliseconds = 225

spin = 585

a 585 x 2 H z 1020 rrdians/sec' acceleration of the gun(0.01) (60) (6)2rotor. Since there is a 6;-- to I ratio between the drum and the rotor

1020drum 1020 = 153 radians/sec

124

The torque at the feeder gear is the sum of the sprocket torque plus

the drive gear torque and at the 15 millisecond time instant tq F 8.90

inch-pounds.

From the plot of steady state torque versus spm at 517 spin tqFSS = 0.70

inch-pounds.

So the torque at the feeder required for acceleration is

tqFa = qF - qFSS

tqFa = 8.90 - 0.70

= 8.20 inch-pounds

The Module System has a five-tooth feeder sprocket so the 6 gun = W

feeder and since (tq W) feeder ý (tq w)gun,

also

tq drun "drum - tqgun wgun

6 40tq (8.2) ( (v-) 6 6S.5

dru 6563221 Tq/a

.6S. 5 1F- : -- ) (144) (32.2) ( -)

166. in lbm

Data from three other tests verified the I = 166 for the moment of

inertia of the Module Feed System (drum to feeder) when considered lumped

Ai the drum (when empty).

125

77 Ji ;; IT

*1. 094 40 0,¶ ~

0 4

4

4 1 44 4 0 1 4 1

I o I t I

', I4 f I' . 4 4

*4~4 4.44 444 .6 4.

4.44~.:

::;::f:~T

.4 44

I L -

'4 ''~ ~ 1-

.

'-44+ - t99I

.4'.

4W44 4.3H

V' 4 fI 126

1, •A'A,CI'I ' l. ON ION ( )N N I 0 I fI I A QI I' )!40 r lU .(.1.f'q4

OASI IFI) ItMITI' I N tI: 1111i1m)

A at atiovl'd M 1011 il '. 0.' mm i voh r w0iov ha wo gratW. Oviilo Io Ilk NP

I llh%, l I g o

I1hw malhiont ar till I 1.11 4hokl Al I 1,01%oriU v 4 ) A 4I N i Ik0 0 froma C t'i Ihi

t)(1% oa f ~ t 110 ra'ssnt mlli hie ciii Ic tU CAt ' 4al (oill low,%

Ithea ds'ne I t ii hiet wi'i' Ii Il' 11,1mva and t lie I .- I 11'A h di mi'n I oil And I lip %loll It I

hoI wo 11 t hei, I Iý .1'1 h d 11,1 11 M011.4I oll h lip 4 I'i' 11AIlh Ve'iic 0 o di'l1r'd to 1'0 1 (d'f r1-

oil I Iki tillIfI I'mon, I-oi 1 h i b a ct p iolns i ),h

Oleh moiloH i t'I of illl'tt 4 o hi'11 rrotind aboUt itta v nt or of j•Ir*v ity tIran1i-

verhe~i 4X~x a t inciv. Inh 'v om the bAA.') uMay be' Calculated 45 follows,

I) / it, * C1,22 l,SDI

I f 0.0.5s93dr J r f 0,0 15 Iar

0 0

1 0 O,036l3 i'llbs

The distance from the1 transverse axis of the round to the center of thea 392 )

module drum is 3,8S5 inches so My* ) (3.855)) - 0.83S or

I per round - 0,8713 pound inch' per round.

Since the modulus of ine_-ia of the Module Feed System when empty was2found to be lbb inch poundsthe iner'ia of the feed system at any

particular load is then as follows:

1b6.0 + (ROUNDS) (0.8713) 2a 732. ft slugs

12K 127

C, SPING' CONSTANI'1 111 lii; 11g t +111) 1 S ITEM

Tho I nlmor drtul W44M~ It hito Ir1d IINv I liptt i trg a p1ov of'' rodt b0t woo'i t lip

Ila 1It i t I kill ith .o 'el Vl 000111P. killp t o theii out or d rum atid Ikolt t ho h ino'r dri'm

fromi rot 141 Ini pl0 o [',t C bt IIdr (I o, t i %m ofto t lho part it .on wh Ich the' rod had

beta ring 11poti It'l at 'Cokl lit lutn e t i mo a rn I move'me'tit it lik imor :' rum, .i i ;%,41 -

wolrd. 111%1 ati Or WAR illt At It %I d o#twoctr the' tnnor And tit Or drtuma . and tho

MA11114eUt'od ri't at i kil o t ho I Mik llWr 1l'kimlon IV oiVOrto ed to rotlit i on bett weon t ho

I)r re' I 'A mind Itou n Ili 111d Wil tib I I a%: to %I from t lip moan it ouro 'sa ro I - to - hous I ng

rot i t ioln The' ilivn emikitain it'' C he Cooed syvitm fr'om t he ujppcr ond of

tho dirtu to the' bairrolx iA 3,1180!i foot punridal [lot, radickn at the' drum.

128

Table VIII . Spring (Ontrant of the Module Feed System

SC81o (in. Last Word Allous.ing Inner AllousingI-oad 'Torquo on Ilous.ig A1/32 lnd. In, Reading Drum 0 -Inner

(l0.j) (jp..:.v, J 112 Inch 0.001 (deci Lmj) Converted Drum 9

0 0 1.2 0 0 0 0 0

1 11 2.0 0.8 0.75 0.0250 0.0040 0.0210

2 22 3.0 1.8 1.0 0.0562 0.0050 0.0512

3 33 4.0 ,.8 1.1 0.0875 0.0055 0.0820

4 44 5.0 3.8 2.0 0.1190 0.0100 0.1090

5 55 b.5 4.7 2.9 0.1470 0.0140 0.1330

6 66 7.8 6.0 3,7 0.1870 0.0180 0.1690

7 77 8.8 7.0 4.! 0.o190 0.0200 0.1990

8 88 10.1 8.3 6.0 0.2600 0.0300 0.2300

9 99 11.3 9.5 7.6 0.2970 0.0380 0.2590

lU 110 14.0 12.0 17.0 0.3820 0.0840 0.2980

00 @ Q0 0 0 0The moment arm is 11.0 inches.

Inner Drum O.D. = 6.800 in.

-Radii on Ends of Fins = -0.12 in.6.68 in. * Diameter to Last Word Indicator

Diameter of Gun Housing = 4.95 in.

To Convert Last Word Indicator Reading to Gun Housing

.495SInner Drum Converted = (Indicator) (-g-- 8-) Gear Ratio

Column 7 = (Indicator) (--.) (6.67) = Indicator (4.95)

Spring Constant = K = (A inch-pounds) (6.67)2

(12) (A Housing,( 2 f)..95 a j 2 1

= (110.5)(44.5)(4.95) = 3380. ft.-lbs./radian(24) (0.300) at drum

129

I T It

~~~~ -I .

-t --- '

I r'

-41 .1-tJ~

.-4LZ

444 -

I Tf

D. THE SPRING CONSTANT OF THE NEW POD FEED SYS'rT•

The new feeder and exit unit assembly with the new heavier parts was

mounted on a pod drum assembly, and the exit gear of the exit unit assembly

was blocked by inserting a screwdriver (which fitted the tooth space closely)

into the exit gear teeth and fastening the screwdriver firmly to the drumSassembly. A llt-inch arm was inserted transversely between the barrels, and

weights were suspended from this arm. The rotational deflection between the

rotor and housing was measured on the ).D. of the housing. The spring

constant of this new pod feeder system was found to be K = 4330. foot-pounds/

radian at the drum if it is assumed that there is a 40 to 6 ratio between

the rotor and the inner drum.

Table IX. Spring Constant of the New Pod Feed System

Deflectionat Gun

HousingLoad Load (32nds

(pounds) (pounds of inches) Radius Arm = 11- inches

4.2 0 25.5

5.2 1 26.3

6.2 2 27.0

7.8 3 27.8

8.2 4 28.6

9.2 S 29.5

10.2 6 30.4

11.2 7 31.0

12.2 8 32.0

13.2 9 32.4

14.2 10 33.0

15.2 11 33.2

K u 10 x 11.625 x (6.67)2 4330 ft-lbs/radian(12)(33.4-25.S) 211

S 4.9--- at the drum

131

7~ 7

4A ~

IT4WIt 7 T.- iI r.I

4 L'41,;- 41-t40- -- -

TVTt 7:2B:7 V~> z

-- 2 t ----- 4.. 4-t

-4

MM M4"M '4 4 44 434 4 4 Mn eri)N~im"I Mcq4 414 4 4~N C ). 4 4MNMmfU 0000 el ("I C? 0 it C 0 ) n(J Utlt) (3C U C% 0) 00 0 C)RtC) C) 00" UCC R0C) C )o: 0 ) 0,

U W W ta iwJ W W W LUUJ W LLcit)LI LaLIJWWWW WWWW WUJ i UiJLJiWiUiWiWW iUi WWiWiW

-A U I, ' .01C) *l - n M 41" N. IC'' 4 - ýO 7I nNI ýI0ý44ýC n0i j--

U vi 0 . . -...- 4-4-. 0 0 0'6 0 N 40 0-'4 - a - 0 " cCn.0 4

0 C, O.0 n l0 n0 a a0C 0 C)00 OO c c)C) C)O-)0 C, 4OOQ o, wo

4t 4 4

Wi Wi Wi L W US LAJ W Li Wi L Wi 6A Li LJ W Li Lf Ui Wi Ui Ui Ui Li LiJ Li UJ i WW Ui Wi Wi Wi Wi Wi Wi Ui US

0 0 J -N-( 0e' MIA~NC eC)4-4 '0 'c (.1 ne f'C0 - 5- ft) k 0.0RMf" 0NG OIU) . i iI- cc N -o RN in In RN 0N- a 00(-4 4('RnRA MNN 0 0,f-4 t-0 o 'N 0 m ,m 0 ti 0A j IN oNL -we-InN "Mi 1-0i 4C N~ cJp"C 0 'I-* 404 10 0 1r ýM(IW 0c

Li

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a a a a136

Table X. Potentiometer Settings for Analog Computer

*/20 K/10000I I Xxl 2B/20Pot. Po 1 Qo Po 2 Po 3 Qo 3 Qo 4

3930.0 0.8000 0.4120 0.0825 3380.0 0.0400

3930.0 0.5460 0.6180 1,2360 3380.0 0.0400

7860.0 0.5460 0.6180 1.2360 3380.0 0.0400

7860.0 0.7000 0.6180 1.2360 4330.0 0.0400

3930.0 0,7000 0.6180 1.2360 4330.0 0.0400

3930.0 0.7000 0.6180 1.2360 4330.0 0.0500

7860.0 0.7000 0.6180 1.2360 4330.0 0.0500

7860.0 0.5460 0.6180 1.2360 3380.0 0.0500

3930.0 0.5460 0.6180 1.2360 3380.0 0.0500

3930.0 0.8000 0.4120 0.0825 3380.0 0.0500 47860.0 0.8000 0.4120 0.0825 3380.0 0.0500

7860.0 0.8000 0.4120 0.0825 3380.0 0.0500

7860.0 0.8000 0.4120 0.0825 3380.0 0.0300

3930.0 0.8000 0.4120 0.0825 3380.0 0.0300

3930.0 0.5460 0.6180 0.0236 3380.0 0.0300

7860.0 0.5460 0.6180 0.0236 3380.0 0.0300

7860.0 0.7000 0.6180 1.2360 4430.0 0.0300

1 137I '

A.1 .4 .4AA A A h4 A .& ýk A4 A Ak .1 A 'k & ýA A .4 . A k . A

-- T

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S:4: .xhif- TT.:}.a j - ->

4 138.

L- j J

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16'

tra I Ili A

Figure 67. Module with 2000 Rounds

139

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140

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14-

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I V,


141

N Q!VJ. r6llgT$: 1& 51

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L• , I

Figure 7. Ne Po wit 300 Rounds

142-

-Jr--l - - ' !! !' - t+ = -- t •PL4444 --- ii iI1I I J 1 -I. I- - 1 .J

' I +: .. . .. . -4 4r] r" .., •. . ;pp

;~ ~ ~ ~ Fgr 70'.J _]-- .... '--w Po wit 300 IRounIds.

I ... LA '- • . .... _ .. . • • • t r•142k_

S . . . . . . . . .

.. . .. . .. .-

Fi. . . .7. N .wi h 3143.....

f . . 4.... . . . .

S. .. . . . .~.. . .. . . . . . . .

. ,, . .V..

,: Figure 71. New Pod with 3000 Rounds

'| 143

+ +14- 4- - i7

J, i I J • fI

+4 I t f

litt if t

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1 4 -4- -1 -

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f I t 1 -I /-

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4. 0

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144

NST OMF INT S OIVISIC'j. I ~ I II (,N'4 jq IIINII1)IN 1N'

~~ K-

lvf I'I---

-4- -44 4 - 4- - 4- --- 4- +

- + + -T 4 4f-4-i ----

Figu-re- 73 Moul wit 200Rud

tjt~j iiiI4S

-1 1 . I 1 1 1 17t 11 11 1 1I I

-1 ! 1 I -- "Z " I I 1 iJ---, I 1II L.4 4 -• I V-l-t-i. I I1 I I

1 4.

-A F. ,

.... .--- --- -- -


146

I J-- ~~~~lee~ z z--------------

=OZT:f1gur 75 Moul with 300 Rond

-4-4147

I I f I I I II. I

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-- -4 4

I FTI

Figure 76. New Pod with 3000 Rounds

148

t11 tA111

F! 7-

- ~- 4- - 4---4- -4--t--- - 4-+ -~ - - -ý--- -- +

j Figure 77. New Pod with 3000 Rounds

149

-. A A

= I $ I I II 1 A

-. *i -:j.

-+- I-4--+----4-- 4- --- 4-4 4- 4 4 4


ISO

-i I.- I-t me 4

4-. ~ .4- , 4 4 4 4 6 4 4 *9 4-S-

ism, ~- 414 94 -- ~-

-74.

Figure 79. Module with 3000 Rounids

151

A .. I A1A A A A AAA A A A A A A A A A A A

iýp A

. ........Ill7. ... .. - -... . ....

iT

.4- * -. - -- - - ---- - -

I X.

1) V7 . _---- ...- - - - ..... f.:IjV•-- 4~ * .. .. 4 7 .4 ...... 4-4-+~-1 -- 4-4 - 4- - * ............. 4' • .4..... . ..

.4 ...... ,_ N . S... 4 $ . .. 4 .. .4- .. ..... ~ . .. .. . ..~4 ....~ .. ~ .. .... ........

i i . . .. .. . . ..|l,

T W


152

~~'[

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-4Ii I FO

Figure 81. Modtile with 2000 Rounds

153

! ! -I

I--,-. ~ CIýE\ITj SeCCf!4 lo4 ,ASJUgN *ujI~ NqT5UjEITJ D4VleIN CdF~L ND. OHIO,, IOlq

- -I

1544

aA Aa a a ~ 9 A9 9 a99 a9 At A f 1

I~

-- Is

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- + ~ i-*~-+ -- 44 + +-

Figure 83. New Pod with 3000 Rounds

155

SECTION III

SIDE STRIPPING FEEDER, SCOPE ITEM 3

A. INTRODUCTION

The object of this program was to design a feeder that will side strip

7.62-mm linked ammunition belts. These links are designed specifically for

end stripping by the inherent reciprocating motion found in most gas-operated

rapid-fire machine guns. However, for feeding the minigun the rotary action

of the side stripping device is ideal.

The side stripping feeder is designed to replace the end stripping

feeder and has many advantages. The new design eliminates many close

toleranced, high cost parts. This feeder will cost less and will be easier

to maintain. The feeder operation will be less complex; timed clearing will

eliminate potential jams. The engineering design objectives were to make the

side stripping feeder as simple as possible with reliability equal to or

better than the delinking feeder. The side stripping feeder chuting attach-

ment was to be designed with minimal system modification. The XM-28 system

was given design priority. While these requirements were closely complied

with, four basic external differences from the delinking feeder evolved.

1. The chute attachment is one round length further forward.

2. The links are ejected in the same axial plane and general direction

as the spent cartridges.

3. The ammunition enters the feeder with the double loop of link

first.

4. The chute attachment location makes it easier to attach chuting in

the XM-29 than the present feeder; it is also completely compatible with the

XM-21 TAT 102 applications.

The XM-27 system will require modifications due to items 1, 2, and 4

above. The chute path from the ammunition box to the feeder needs to be

rerouted. A provision in the cover fairing for the new link ejection

location will also be necessary.

156

I ___

In the initial studies three feeder design concepts were generated, two

of two shaft design and one of single main shaft design. The chosen design

was a two shaft feeder which will be elaborated upon in the history of

development portion of this section.

The side stripping feeder hardware which evolved from this design

program is shown in Figure 85. Figure 86 shows the feeder mounted to the

7.62-mm minigun.

B. DESIGN OBJECTIVES

The following objectives were established, and the feeder w, s designed

with them as a guide line.

1. Performance - this new stripping concept had to be developed into

a working gun feeder and perform as well as conventional end stripping

feeders.

2. East of Maintenance - the simplicity of this new design should

produce a more easily maintained assembly.

3. Reliability must be a primary consideration.

4. Minimum Size and Weight - design a feeder of minimum size without

excess material.

5. Low Cost - the inherent simplicity of the new feeder should

result in drastic cost reduction.

C. HISTORY OF DEVELOPMENT

The initial design studies produced a side stripping mechanism that

delinks the round and pulls the belt with one sprocket (see Figure 87).

The studies also produced three feeder design concepts. Two concepts

incorporated a two shaft system. Both two shaft designs are alike in

having one shaft support a stripping device and the second support a

feeding sprocket. The third concept utilize a single main shaft which

supports one sprocket that both strips and feeds the rounds to the gun.

The first two shaft test feeder fabricated was basically a side

stripping mechanism attached to a module feeder (66D10013). The basic

differences between it and the present end stripping MAU-56 feeder are as

follows:

157

1. The ammunition entrance is relocated 20 degrees counterclockwise,

looking forward, and one round length further forward longitudinally along

the gun.

2. The ammunition belt feeds a double loop of the link first; in the

end stripping feeder the single loop is fed first.

3. The nunher of parts and the overall length of the feeder have

been reduced.

Initial fire testing of design 1 showed that the timing between thestripping and feeding sprocket needed adjustment. Four M-13 NATO links

were broken during stripping. This was corrected and testing continued.

After the feeder accumulated 12,000 rounds, the following effects were

noted.

1. The stripping action of the links severely marked the rounds

producing small brass chips. However, the marked cartridges and brass chips

did not adversely affect gun operation.

2. Slightly higher torque peaks than the end stripping feeder were

experienced during stripping, although the average stripping torque was

about the same. The higher torque peaks did not effect gun operation.

3. Rates of 420C spm were attained without mishap. Above 4500 spm,

some ,inks were broken at the base of the double loops while being

strinped.

At this point the feeder sprocket handoff to the gun worked finel

the round control was good, but some links were broken in feeder 1.

Design 2 was built and both feeders were further tested to determine

which was the more desirable approach. Design 2 is a two shaft feeder.

One sprocket both strips links and feeds the gun bolt. The feed to the

gun is excellent. The good feeding action is attributed to the location

and shape of a six-tooth feeding-stripping sprocket. This sprocket is timed

so that it fully seats the round in the bolt extractor lip, then follows

the bolt to hold it there until the nose of the round has entered the breech

of the barrel. The round handoff is not critical to the slight mistiming

between the gun and feeder. The belt pull capability is excellent and

greater than the strength of the belt itself.

158

Both feeders were tested and compared. Design 2 was chosen over the

first design tested for the following reasons: (1) the design is muchsimpler; (2) is lighter and less expensive; (3) performs better; (4) ismore reliable; (5) has greater belt pull capacity; and (6) is easier to

maintain.

At this point problems still existed with peak torque and link breakage.Modifications to the stripper sprocket and a new support shaft were made toallow more link clearance while stripping the round. The modificationschanged the pivot point of the link single loop while the double loop isstripped (see Figures 88 for stripping action diagram). The first modifica-tion tried was the support shaft. A broken link jam occurred immediately.In observing this jam it was noticed links were hung up in the link ejectionarea. It was possible for the links to pivot upon entering the link chute,allowing the single loop to catch on the edge of the round guide. Thiscaused jamming of the links in the link chute,breaking the captured singleloop. The possibility of this recurring again was eliminated by removingthe round guide protrusion adjacent to the link ejection chute. Rotational

control of the link was gained by adding an extension to the link ejectionchute (see Figure 89).

A clear jam on complement 4, burst 8, caused another stoppage (seeAppendix III-C, Test Results). A round rammed the clearing finger, shearingthe clearing stop pin. The feeder was repaired by replacing the spring

pins, and testing continued successfully for 20 complements to complement 24when a broken link caused a jam. Visual inspection of the parts revealed nodamage and the cause of the stoppage was not readily apparent. Testing wascontinued in an attempt to determine the cause of the link breakage which

recurred infrequently (see Appendix III-C). After complement 31, burst 4,the feeder was removed and disassembled for a dimensional check of allparts. At this time 42,100 rounds had been fired with the feeder. Theinvestigation revealed the inner round guide was bent and consequentlymoved the round out of position, causing it to be bound up between the aftsupport sprocket, inner round guide, and stripper sprocket. The inner roundguide was straightened and the feeder was tested further.

During the next complement, number 32, repeated clearing jams occurred

159

I

due to a bent clearing finger. This was repaired and no further stoppages

have occurred. The feeder will continue to be tested for durability and

wear.

In addition to the 44,100 rounds fired at the range, 1800 dummy rounds

were stripped and fed to the gun. This brings the total accumulated rounds

on the feeder to 45,900. As previously agreed, 500 steel cased dummy

rounds from Frankford Arsenal were cycled to see what effect the steel

cases would have on the feeder. The results were good. The side stripping

action of the M-13 link showed no damaging marks on the steel cases and the

feeder performed perfectly. Aluminum cases are still not available for

test, but no difficulty is expected in the stripping or feeding of these

cases.

D. METHOD OF OPERATION

The basic operation of this feeder is the very reliable rolling action

of two sprockets. As can be seen by the disassembled feeder (see Figure 90),

there are not many parts. Figure 91 shows the ammunition entering the feeder,

double loop first. The stripping action starts when the stripper sprocket

engages the ammunition belt between the single and double loops of the link.

Stripping occurs in sequence with the trailing single loop first and the

double loop second. The belt pulling sprockets carry the linked ammunition

belt into the sprocket. It supports the round whilE the single loop is

stripped. The single loop uses the belt pulling sprocket shaft as a pivot

point while the double loop is stripped from the round (see Figure 88).

The stripper sprocket is aiso the feed sprocket and carries the round with

the aid of a guide to the gun bolt. Figure 92 shows this area of the feeder.

Clearing gates are controlled, as in the MXU-470 module, by timing the

finger's movement through the round path, thus eliminating clearing jams.

This feeder is mounted to the gun in the same way as the delinking feeder.

The timing device is an improved wide spring, more easily used than the pin

used in the delinking feeder. Figure 93 shows the feede- mounted to the gun.

160

A P P E N D I X III-A

Drawing

1

161

i

i i '

, .x "" -

N~ /

A V ik I N 11 1 I*t

I'lton al I I ~stro ol

00

1 64

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00

165

• TR!PPING A:JD FEEDING

SPROCKET

INCOMING

BELT

S•)• BELT PULLING AND

STRIPPING SUPPORT

OUTER GUIDE \ SPROCKET

PT ,APIVOT POINT FORSTRIPPING SINGLE LOOP

PT.BC "-• f"" ' PIVOT POINT FOR

V STRIPPING DOUBLE LOOP

DELINKED ROU

•._.J ,

Figure 88. Side Stripping Diagram

167

NOTE: ADDED EXTENSION AND REMOVAL OFMATERIAL PREVENTS LINK FROM PIVOTINGAND HANGING UP ON INTERIOR OF OUTER GUIDE

AMMO

STRIPPED ROUND" ENTRANCE

OUTER GUIDEADDED EXTENSION

REMOVED MATERIALLINK EJECTION

Figur 8,.. Link Jan

1,58

Cu

'2U4

169I

w

Q

zc

zI

170

LUI

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A P P E N D I X III-C

Te-t Results

173

k'_ ___ __ ti __l__ -|} r/ ,Llilllll) IIIig

} ~ ~ 0'~ll 0dl '00il 1

*',lil ,'lIil ~I~lit) o'ill! Id Iitl',l- , I lk

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t' I re out

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16 1So0o 54001- 500 6tili i am l Inll I Illcd cIL, i 11,vdlong tr-.t tO I I IT Wit 300 rds

17 1 S L) 1 S500t I otK

18 150(1 2700 - 2 8 00 OK

19 1500 1500 OK

20 1 500 700 -- 110 0 Long burst to fti re out 400 rds

21 1500 700-800 2(10-rd Burst OK

22 1500 1300-1400 OK

23 1500 1400 OK

174

Iui Am mv,41 4 bt't k.il il

A ~IaII

I I)VI 100) ~1tI AI Ilk

I o ft hl I I I thivk I' food l, O

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gi ti v found - a t I I I Is 101) diced

Nua It vt~ .ei t: I' i ~ r gh 1. enl

rtp. cd c I Vi a~ v~ I i acend -,~ cc ij I,

1800 fL ilumiv rilunt.1%Ok ______

175

iW e A I I 1 % I r I . IYII -

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UUCLI)

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177~

lCI':l'ON IV

MINIG;IUN (3~ 1110 BIAR, SCOPIF l'IliM ,4

A. I NTODUCTI' ION

The rescitIrch and dete lopilnnt work on tile guide bar h as been completed.

The work has shown nfit) 6irthew improvement s can be made without Changing the

highly dvsirable charactrist ics of the present one-plece bar. The present

devsigi is best for thc existing gun and feeders.

The purpose of this work was to design a new guide bar that would

increase tle gun's degree of tolerance to feeder timing and damaged

Umiun ttion. The approach taken was that of determining the status of the

present guide bar's interfacing with the gun and feeder through the use of

tolerance studies and high-speed film,,. With this known, a ba-sis could be

est ablished for futrther imflrovement

1B. CONCLUSIONS AND REICOMMIINDA'rIONS

1. The tolerance studies and high-speed films show that the present

system is the most desirable design for the existing gun and feeder systems.

2. The .. ent to which the guide bar can compensate for late feed is

limi ted. To further decrease the dependency of round control on feeder

timi ng during handoff, some other mechanism(s) must be added to the guide

bar or feeder.

3. 'The amount of damage to guide bars due to late feeding and damaged

ammunition is small and does not justify any further engineering effort on

this part; therefore the research and development work on the guide bar has

been terminated.

4. Interference exists between the round and the guide bar rim guide

during the transition of the round from the feeder to the guide bar. The

tolerance limit on the dimension that controls the feeder rim guide location

should be tightened for both the pod and delinking feeders to correct this

condition.

178

C, TIOLLRANCL1 SniL) I: S~

1'ho to lerianet St Lid I s wvre lildvrt akeil to dietermiilie the 11 .hi lilty o1.

llinilg at lilte teed sit klat i til and damlaged amniui it i of) wi thI th, present ties Ign

01 eralev onl the go ide bar, gun , and feeders. A l arge share of the val ues

use~d inl those studie!s was kub! ai ned fromn a 1(0 to I I ay out. . heactual

ana v is, including all of' the faCturS considered in determining results,

is found i n Append i x I V IL. Tthe follow ing is it summary of' these re SUItS.

Ill ii ve Y feeding Svtethe dtsi red amount of Crush- up exists

bet ween the bolIt head , rouLnd, Mnd guide ba r ( see Appendi I iV -B, pages 198 and

lt)) , Evory system feedis the round into the gunl early. it is iipossil

to ha1Ve a late feeding situoat ion due to the aCCUMUl ati on of toleranIces.

-. Marginal i nt erterence exi st s between the oudandthgudbari

guide foix tho pod and del inking feeders during the transition from feeder toguide bar (see Appendix lV-il, pages 2214 through 227).

3. Clearance alway's exists between the bolt head keyway and the guide

bar, key, and between the bolt and the guide bar (see Appendix IV-13, page 202).

4. The rim guide always controls the roun1d SO that it is always free to

enter the bolt head extractor lip (see Appendix IV-13, page 2103).

S. Lither clearance or a I inc-to-line condition was foutnd to exist at

all times between the rim guiJe flat and the feeder housings (see

Appendix IV-Il, page 240)

D. IIIGlI-SPIIED FUIS

In ordcr to thoroughly understand the actual dynamic conditions of round

handoff to the bolt for all feeding systems, high-speed films were taken of

the round cycling at high rate. The sumimar-/ of results for, the films is in

A ppendjix IV-B, Table Xi1, page 246

The filming was accomplished by removing the barrels from the rotor,

inserting plexiglas plugs (see Figure 108) into the rotor's barrel holes,

and cycling dummy rounds through the gun while simultaneously taking high-

speed films through the plexiglas plugs.

179

These H I ills show thai a I I sYS t c ,, fe'Od the round i in to the gun ar I y

The module, pod, and A-37 feedeir sprockets push the round against the guide

bar mt all t ines. The effect of this is seen in the dcflcction of the guide

bar t'i ngers. on tile other hand, thit, deli nk i ng feeder p resses the round

aglinl1.sthe inne ,eder guides aind then cIuse.,s tile round to bounce several

times against the fingers before it is fully seated in til head bolt. 'File

filns have shown that tilt, feeders move tile round into tile gun very

et'ficiently.

1'. J'VAI.UA'rION OF VARRIOUS tU IDE- BAR DESIGNS

The areas of the guide bar that are susceptible to damagc are the

fingers and the rim guides. The fingers may be damaged when a bolt assembly

has a sheared roller stud. A broken rim guide occurs when a round is pushed

against it by the bolt head - as in a late feed.

The average hangfire and late ',ed occurrences were 1 in 1,000,000 and

I in 100,000, respectively, based on General Electric's SEA malfunction

reports from ,January 1968 to March 19b9. Approximately 25 percent of the

hangfires cause bent fingers, and a very small percentage of the late feeds

cause broken rim guides.

Even though these statistics indicate a very high reliability for the

present guide bar, ideas for decreasing the cost and/or increasing the

already high reliability of the present guide bar were accumulated and

evaluated. The following ideas for possible guide bar and round control

improvement are discussed below.

1. Replaceable guide bar fingers

2. Modified round path

3. New rim guide

4. Mechanisms to increase the gun's tolerance for late feeding

a. Movable rim guides

b. Accelerators

180

I. Replaceable Guide Bar Fingers

It was thought that replaceable guide bar fingers would help to save

the guide bar when a bolt body roller stud shears because of a hangfire. The

entire guide bar would not have to be disposed of if bent fingers could be

replaced.

This idea has been found impractical because of the infrequency of

damage to guide bar fingers, the additional machining required for new

finger:, the added cost of casting fingers, and the uncertainty in the

capability of designing new fingers with the same strength as the present

guide bar fingers.

2. Modified Round Path

During the initial guide bar studies, it was felt that removing

material from the guide bar fingers, as shown in Figure 96, would increase

the degree of tolerance to late feed. Such a modification would allow the

feeder sprocket to be set ahead, consequently increasing the zone in which

the sprocket can be retarded.

This approach cannot be used because the sprocket is already

advanced as far as it can be - the feeder sprockets press the round against

the rotor's stationary tracks in the present design.

3. New Rim Guide

Changing the present guide bar rim guide to the other side of the

guide bar (see Figure 97) would reduce manufac'uring costs. However,

investigation has shown this idea is infeasible. It was found that the

minigun's removable track ways would prevent the proposed rim guide from

extending far enough to the bolt head extractor lip to ensure full control

of the round as it passes from the rim guide to the lip. The guide bar

would lose control of the round before it was fully seated inside the

extractor lip and, consequently, a double feed situation could occur.

4. Mechanisms to Increase the Gun's Tolerance to Late Feeding

The extent to which the guide bar can compensate for late feeding

is limited. Some other type of mechanism must be added to the guide bar or

the feeder to lurther increase the gun's tolerance to feeder timing. Two

181

possible approaches involve having the guide bar rim guide and the feeder

inner guides move out of the round's way and having a mechanism push the

round ahead of the sprocket. Ideas employing these approaches are as follows

a. Movable rim guides

(1) Rotational displacement rim guides

(2) Translational displacement rim guides

b. Accelerators

(1) Angle-multiplying mechanism

(2) Spring lever mechanism

(3) Feedback system with actuated solenoid (solenoid kicker)

Since only a very small number of guide bars are damaged because

of late feeding, it would be impractical to pursue any design employing the

above ideas. The increased gun reliability resulting from such a mechanism

is not worth the engineering effort or additional cost required to develop

and produce one. However, the ideas will still be discussed.

a. Movable Rim Guides

The whole theory behind a movable •im guide is that the excessive

force exerted on the rim guide during a late feeding situation would create

sufficient clearance for the round to pass over the top of the rim guide.

This would prevent broken rim guides and gun stoppages cause by the late

feeds.

Figures 98 through 101 illustrate various ways of producing a

movable rim guide.

b. Accelerr.,or-

(1) Angle-Multiplying Mechanism

This mechanism would accelerate the round into the bolt

body at all times. It is based on the same principle used for a shaper. The

pin on the feeder sprocket would traverse a certain predetermined arc length

while the accelerator would travel a greater arc length during the same time

period. A kicker would be mounted on the irKde surface of the feeder

182

forward inner guide as shown in Figure 102. One of the pins on the feeder

sprocket would engage the track of the kicker and push the kicker 180 degrees,

where another pin would engage the track. The pins would engage and disengage

the kicker every 72 degrees of feeder sprocket rotation.

The difficulty in employing such a device lies in the interference

that exists between the kicker and the feeder shaft. Reduction of the shaft's

size would overcome this problem, but would jeopardize the required strength

of the shaft.

(2) Spring Lever Mechanism

The spring lever mechanism shown in Figure 103 ensures

that the rounds are in the head bolt extractor lip at all times during

handoff. The mechanism consists of a lever and a spring. The top surface

of the head bolt travels along the cam of the lever (kicker) and activates

it, causing the lever arm to push the round into the head bolt. The head

bolt directly controls the position of the lever, independent of the feeder

sprocket.

(3) Solenoid Kicker

This mechanism is different from the others previously

discussed. The other mechanisms would work at all times, regardless of

early or late feed. The solenoid kicker mechanism (see Figure 104) would

operate only when a late feed situation existed. The head bolt would push

the round against the rim guide and cause a microswitch to actuate a

miniature solenoid. The solenoid kicker would accelerate the round into

the head bolt, at which time the microswitch would be turned off and the

kicker would return to its original position.

Some of the problems with this type of device are the

feasibility of producing such a small solenoid with the required characteris-

tics and the reliability and time delays involved with the use of such an

electrical system.

183

A P P E N D I X IV-A

illustrations

184

FACE OF BOLTCLEARS GUIDE BAR

RIM OF CARTRIDGEj* .ALWAYS FREE TO

ENTER EXTRACTOR L)

CARTRIDGE ALWAYS CLEARS \ MARGINAL CARTRIDGE

FORWARD LIP INTERFERENCE ON PODDELINKING FEEDERS

TY'PICAL FEEDER

Figure 95. Cartridge Handoff - Feeder/Guide Bar/ Head Bolt

185

MODIFILD ROUND PATH( INCREASE IN TIMING(TOLERANCE. ) --- \

/ h

Figure 96. Modified Round Path

186

NEW RIM GUIDE

'ELIMINATED RIM GUIDE

0LE

Figure 97. New Rim Guide

187

TEFLONWA S HER(S)

ALTERNATE DESIGNCOIL SPRING (ELtM.LEAF SPRING)

COVR /RLEAF SPRING

VIEW SHOWN, COVER REMOVED

Figure 98. Guide Bar, Adjustable Rim Guide

188

SPRING ,

FASTENER(HEADS NOT SHOWNFOR CLARITY)

BACK rACERIM GUIDE IDEA I

S[ BACK FACE

---- •IDEA 11

BUNA-N O-RIJC (2)FASTENER ()

Figure 99. Guide Bar Back Face Rim Guide,Feeder Side Self-Adjusting for Excess Loading

189

RIM GUIDE--

S R ACE - - -- -

Figure 100. Spring Rim Guide

190

COIL OR

LEAF SPRING

Figure 101. Spring-loaded Rim Guide

191

ii,

INTERFERENCE EXISTS BETWEEN TIP OFKICKER AND FEEDER SHAFT ( DUE TOLENGTH REQUIRED FOR KICKER)

KIC KEER--- •

ONE OF FIVE PINS 0ON SPROCKET

Figure 102. Angle-Multiplying Mechanism

192

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193

KICK PUSHES ROUND INTOHEAD BOLT

MICROSWITCH

//

- MINIATURE SOLENOID KICKER

Figure 104. Solenoid Kicker

194

A P P E N D I X IV-B

Tolerance Study

195I.I-

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A• CARTRIDGE SEATED, STARTS TO TRANSLATE FORWARD OUTOF DWELL.

4, CARTRIDGE MAKES FINAL CONTACT WITH GUIDES.DEGREE OF INCREASE REQUIRED TO ELIMINATEEARLY FEED.

198

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227

ThIM1CAL ANALYS FORM

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228

TIcCMN ANALWIS FORM

dC. MODEL

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MNW.M ANALYS PO

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IAT It/31 ~~u.uu i to*ALL

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232

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235

MAXIMUM DELAYED POSITION

FEED SYSTEM a

MODULE 50

A-37 50

POD 50

DELINKING 3 1/20

Figure 106. Maximum Allowable Delay to Feeder Sprocket from Timed Position

236

, A

By VT "shz-SINhSALO I*ILICTRIC pA(CK. MMOWDAM %-~-I o9C REV. fomQ4 Vw11

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TECHICA ANALYSI FORM

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241

TECHNICAL ANALYMI FOEM

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CA1qTRID6E CLEAIZAI4C-G W/ 1RIM GU VVe

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242

GUIDE BAR

.015 MAX. INTERFERENCE-. 03 - .06 R.

S~GUIDE, CLEARING, AFT

65C 10732

RESULT: RECOMMEND .05 .02 R. TO CLEAR

Figure 107. Clearing Guide Interference

243

110MN AKMMO POWM

DATE 3 /ý/, MEV, IM IMI l

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I247

SECTION V

ARMAMUINT PO1), XM-18, SCOPE ITUM S

A. INTROQ)UCT ION

Wh'on the doigl gn ad development of the new feed aind storage system for

the minigun pod was initiated, objectives were Ostablishod to make the l1nL.

less •,:tom mort' reliable, eaon-er to operate and maintain, and more economical

to produce. Th'li approach taken to improve the existing system was to decrease

the oumbor of mc\,'ng and fixed parts while simplifying the fabrication of the

pod's components. The objectives tstablished to improve the pod system were

as follows:

1. Use steel Investment castings to replace the aluminum castings on

the feeder and cit unit, to eliminate the necessity for separate guides and

wear plates and reduce the machining requirements.

2. Eliminate the shoet metal conveyor guide and crossover guide on the

feeder to increase reliability, durability, and ease of installation.

3. Include a timed clear mechanism in the feeder to eliminate

clearing jams.

4. Eliminate the drum ring gear, geared retainer partition, and scoop

disc assembly by using a single lead sheet metal helix similar in design and

function to the MXU-470/A Minigun Module,

S. Incorporate a power load feature to decrease load time and increase

ease of operation.

B. SUMMARY

The efforts of this Research and Development program have resulted in a

new design that meets and surpasses the target levels of reliability and cost

savings established at the beginning of the program. The proven reliability

of the minigun module drum has been combined with a new feeder that fired

over 200,000 rounds without being responsible for a single stoppage. This

combination makes possible a pod system that will easily exceed 100,000 mean

248

rounds between failures. Thv new feeder, which is interchangeable with the

fteeder used on all product ion ml nigun pods, weighs approxinately 1 3/4 pounds

more than the uni t it rep 1) 1,ac. '-The weight difference iý due to the use of

steel castings where aluminun was employed. However, tihe added weight is a

small price for the tremendous increase in performance. The now system has

many fewer parts and is, therefore, much easier to assemble and maintain

which is extremely important when related to down time in a combat area.

C2. DLESIN DVLVLLOPMIhN'I'

Pursuing those objectives established to improve the pod, the design

phase moved through layouts to Class I drawings. The ammunition storage area,

see Figure 114, incorporates a design similar to the MXU-470/A Minigun Module,

which has a rotating finned inner drum and a stationary outer drum helix.

The new design elininates the expensive honeycomb outer structure and

replaces it with the forged support, part number 11839419. Loads are trans-

mitted from the suspension lugs through the support and into the drum cover

and aft bearing support at each end of the storage drum. This design also

i'limin!ttes the scoop disc assembly, drum ring gear, and geared retainer. The

nwumber of moving parts is reduced from 17 - for the scoop disc assembly,

geared retainer, and inner drum of the old pod - to one for the inner drum of

the new pod. With fewer moving parts, costs and wear are reduced and

reliability is increased.

The inner drium design deviates from the module configuration in that the

round space is not radial to the centerline of the drum (see Figures 123 and

124). The round spaLCe is canted so that when the drum is rotating in the

firing direction the round is held radial to the drum and the base is not

permitted to lag. Holding the round radial reduces the fricL.on force on the

base of the round and reduces the driving torque required for the drum.

The new exit unit utilizes a precision steel investment casting for its

housing, wnich eliminates the need for four separately attached guides and

year plates. The configuration of the exit unit has been changed from the

old design to allow relocation of the loader. The new loader feeds the

stripped rounds into the exit sprocket (see Figure 1251 rather than into the

gear sprocket as in the old design. An intermittent Geneva-type drive was

required between the old loader and exit unit for the rounds to be picked up

249

by the exit gear. By moving the pickup point to the exit sprocket, the

intermittent drive is no longer needed, which causes a smoother operating

assemb ly.

When dry cycling of the pad system was initially attempted, rounds

jaumed in the handoff from the inner drum to the exit sprocket. To determine

the cause of the poor handoff, a detailed layout similar to Figures 126 and

127 was drawn. Two problems were apparent when the round path was established.

First, the timing of the sprocket was such that in the firing direction the

sprocket could cram the round, under some tolerance conditions, into the inne,

drum fin ahead of the round before the round was far enough up the 11839363

guide to be clear of the drum. This condition was experienced with the

prototype. Secondly, as the round moved from the drum into the sprocket,

round control was minimal. The sprocket did not pick up the round before the

centerline of the nose had passed the end of the drt.'. As the round continued

out, the effective working diameter on the nose became smaller. Therefore

the drum allowed the base of the round to lag, making pick up by the sprocket

impossible.

Two modifications were made to correct the handoff problem. First, the

inner drum fins were moved 0.060 inch closer to the sprocket, which gave the

drum control of the round for a greater distance up the 11839363 guide. The

second modification involved enlarging the retarding the nose round space of

the exit sprocket to accommodate the difference in velocity of the nose and

base of the round as it moves into the sprocket. With these changes incor-

porated, dry cycling was successful using rates of 2000 and 4000 spm.

W'hile loading for the first fire tests of the new feed and storage

system, approximnately one out of every 100 rounds hung up between the loader

and exit unit. A design study of this area revealed a possible interference

between the loading guide, the round, and the inner round guide (see Figure

125). The guide surface of the inner round guide was lengthened 0.260 inch

and moved 0.023 inch away from the round to provide a smoother transition

from the loader to the exit unit and prevent any possible interference. The

loader and exit unit functioned as desired when the modified parts were

installed.

2S0

Thc new loader and exit unit have been designed so the loader is always

attached to the exit unit (see Figures 119 and 120). In storage, the loader

is held in place against the front of the drum cover by a quick release pin.

To load the pod, the quick release pin is removed and the loader is swung into

position and secured by the same pin. Having the loader attached to the exit

unit in this manner cuts the time required for loading the system.

The primary engineering goals for the redesign of the feeder assembly

were that it be interchangeable with the MAU-S7A/A production design which is

used on all minipods and that the troublesome features that exist in the old

feeder be eliminated. These goals have been achieved in the new design (see

Figures Il and 121). The sheet metal conveyor guide, the crossover guide,

the 63DI0900 and 63C10904 guides, as well as all wear plates, have been

eliminated by the use of steel investment castings. See Table XIII for a

list of those parts eliminated.

The functions of conveyor guide and crossover guides are now being

performed by features incorporated in the feeder housing and sliding wheel

support castings. After it leaves the exit unit, the round is controlled

by the sliding wheel support base and nose guides for about 70 degrees

rotation of the conveyor wheel. The nose guide is an integral part of the

sliding wheel support casting. At approximately 12 o'clock, •ose control is

transferred to the feeder housing. The nose guide then rotates the base of

the round down under the base guide of the feeder housing. 'his action

eliminates the function of the scoop guide. The outer guide and clearing

jams have been eliminated by a timed clearing mechanism which is similar in

principle to those used on other minigun feed svytems. This design has

produced a unit that has fewer parts, is extremely reliable, easier to main-

tain, longer lived, and less costly to manufacture.

The rounds counter drive assembly, part number 11839429 (see Figure 109),

has been relocated to provide more direct routing for the flexible drive

shaft. The assembly is now mounted on the drum cover nearly in line with

the counter. This will greatly increase the life of the flexible shaft.

The new pod is provided with redesigned slides to support the battery

and control assembly. The stationary portions of the slides are machines

from an extrusion and riveted to the aft drum structure (see Figure 115).

251

The male pirtions of the slides are mounted to the support assembly frame of

the control package. For ease of operation, the mating surfaces of the male

and female slides are treated with a dry film lubricant. A latch similar to

that used on the old pod is used to secure the control assembly in the pod.

The material used for the strika or hook has been changed from aluminum to

steel to prevent yielding under high "g" loadings.

A power load capability has been developed for the new pod design. A

small motor and gearbox is used to drive the drum, exit unit, and loader when

the feeder is disconnected for loading. This motor would be mounted on the

aft bearing support in the aft drum, which would require lengthening the aft

drum fcir inches if the present control pack configuration were maintained.

Engineering feels the added weight, length, and expense are not justified for

the 1500-round pod. However, a new control pack configuration could be

developed to reduce the length increase and provide power load capability for

a larger capacity pod. A pod capacity of up to 3000 rounds could be developed.

The design of the new pod assembly is tailored to adapt to an increased

storage capacity by replacing the outer drum and helix assembly, the rotating

inner drum, and a power cable adapter.

Table XIII. Parts Eliminated from Feeder

Part No. Part

1. 63EI0829 Conveyor Guide

2. 63D10843 Crossover Guide

3. 63D10900 Scoop Guide

4. 63C00903 Rim Guide

5. 63CI0904 Outer Guide

6. 63C10907 Nose Guide

7. 63D10916 Solenoid Bracket

8. 63D10917 Chute

9. 63CI0920 Guide Plate

10. 32 Pieces Miscellaneous Hardware

252

D. END ITEM CONFIGURATION

To save large tooling expenses, the prototype pod deviates from the

drawing in several areas. All components that form a part of the new design

and are delineated as castings, forgings, or extrusions were fabricated from

hogouts and/or weldments. One exception is the inner drum extrusion for which

a die was built.

While the prototype pod was being built and tested,several changes were

made in the drawings which would have required welding to bring the parts to

the new configuration. These changes were not critical tu the function of

the assembly; therefore, to avoid possible warpage of the parts by welding,

the following items are not to the latest drawing revision:

1. The holes for two MS3S207-264 screws (see Figure 110) which secure

the inner guide, part number 11839304, to the exit unit housing were located

so that under some tolerance conditions the nuts could interfere with the

exit gear sprocket, part number 11839319. The drawing was changed, but

because there was no interference on the prototype unit the parts, were not

changed.

2. The timing pin, part number 11839397, Figure 114, was mislocated on

the design layout. If the pin in the exit unit and the pin in the drum cover

are depressed as the exit unit is placed on the drum cover, timing will be

correct. However, after the exit unit is secured with hardware, both pins

cannot be engaged simultaneously. A simple check by running a round through

the exit unit and into the drum will insure proper timing has been obtained.

3. Figure 121 shows a guide at the left of the solenoid that is mounted

to the feeder housing by one screw. On the drawings this guide is not a

separately attached part, but is cast as an integral part of the housing.

E. TESTING

The feeder was the first assembly of the new pod to be completed.

Because it is interchangeable with the old pod design, it was mounted on an

XM-18EI pod and successfully fire tested. High-speed films were taken to

study the movement of the rounds through the feeder. The transition of the

round from the sliding wheel support to the feeder was very smooth, and round

control was maintained at all times. Final design configuration was

253

established after the first two complements. In final form, 52,000 rounds

were fired with the feeder on an XM-18E1 pod. During this testing only three

stoppages occurred, and these were caused by bent rounds which were caused by

a faulty scoop disc assembly. There were no feeder stoppages or malfunctions.

Additional testing of the feeder began when the prototype storage drum

and exit unit were completed; 150,000 rounds were fired with the feeder on

the new pod. The feeder performed flawlessly throughout this test with no

stoppages or malfunctions.

The 150,000-round engineering test was conducted on the prototype feed

and storage system to prove the design and establish the system's reliability,

See Appendix V-C for summary test results. Rates fired were from 2000 to

6000 spm, utilizing both Air Force and Army gun drives. Burst lengths were

varied from 50 to 300 shots.

After firing the first two complements, design changes were made in the

loader and exit unit as explained in Section IV, Part C,"Design Development."

Following these changes, the feed and storage system, which was in its final

design configuration, successfully fired the remaining 147,000 rounds. Six

stoppages occurred, four resulted from hangfires, one was caused by a safing

sector pin's coming loose, and the last was caused by a personnel error when

loading the system. Thus the new feed and storage system handled 147,090

rounds without being responsible for a single stoppage. It also proved to

have a high level of durability as ..one of the system's primary components

was damaged by these stoppages. The only repairs required for the feed and

storage system were the replacement of the feeder drive gear pin and the exit

gear pin on three of the six stoppages.

The 150,000-round test established that the new pod design has both high

reliability and high durability, which combine to save many dollars in repair

parts and labor and to keep the system operational for many more missions.

254

A P P E N D I X V-A

Drawings

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Figure 124. Round Positioned in Inner Drum

( ~2721

S~EXIT

SPROCKET

, •'• SCOOP , ,

IGUIDE

• ~LOADING /| GUIDE EXIT GEAR

•_ SPROCKET

GUIDELOADER SPROCKET

/I

Figure 125. Round Path Through Loader and Exit Unit, New Design

273

GUIDE -11839363

SPROCKET -11839307

GUIDE -11839309

BASE OF HELIX

Figure 126. (Sheot 1 of 2) Design Study of Inner Drumto Exit Sprocket Handoff I

274j

--.- EXIT UNIT

.--- GUIDE - 11839363

SPROCKET - 11839307

NOSE SHOW

UDGUIDE - 11839309

t I ~j~.DRUM COVER

INNER DRUM

Figure 126. (Sheet 2 of 2) Design Study of Inner Drum

to Exit Sprocket Handoff

27S

A P P E N D I X V-C

Test Results

276

Table XIV. Summary Results on 150,000-Round Engineering Reliability Test

of Research and Development Feed and Storage System

No. of RateComp. No? Bursts (spm) Status

1 15 2000-4000 No go burst 7 - round damaged during

loading jammed at exit sprocket

2 11 3000-6000 Stoppage burst 4 - same as above

Installed modified loading guide and round guide toeliminate loading damage

3 8 2000 OK

4 S 4000 OK

s S 4000 OK

6 5 3000 OK

7 8 60no OK

8 8 6000 OK

9 S 6000 OK

10 8 6000 Stoppage burst 5 - bent round jammedin feeder - personnel error damagedrounds during loading

11 8 6000 OK

12 8 6000 Hangfire burst 6 - gun stoppageresulted

13 8 6000 OK

14 8 6000 OK - installed Research and Develop-ment bolts in gun

is 8 6000 OK

16 8 6000 OK

17 8 3000 OK

16 8 3000 OK

19 5 3000 OK

277

Table XIV. Sumnary Results on 150,00O,.Round Nnpineering Reliability Teot

of Research and Development Poed and Storqe System (Cont.)

No, c RateComp. Not Burstr. ( 8O*t

20 5 3000 OK

21 5 3000 OK

22 5 3000 OK

23 5 3000 OK

24 7 3000 OK

25 S 3000 OK

26 5 4000 OK

27 8 4000 OK

28 5 4000 OK

29 5 4000 OK

30 S 4000 OK

31 8 4000 OK

32 5 4000 OK

33 8 4000 OK

34 5 4000 Ox

3S 8 4000 OK

36 5 4000 OK

37 8 4000 OK

38 8 2000 OK

39 8 2000 OK

40 8 2000 OK

41 5 2000 OK

42 8 2000 OK

278

L. -.. . . . ........... ........-

Table XIV, Summary Results on l 0,00O-Rouwd RngIneering Reliability Testot Research and Development Peed and Storage System (cont.)

No, of Rate

.UK I I I a lll

43 5 2000 OK

44 5 2000 Stoppage safing sector pin cameo016e fTrO gun - damaged (1) Research

and Development bolt, guide bar, androll pins

45 8 4000 OK

46 a 4000 OK

45 8 4000 OK

49 1 4000 OK

so a 4000 OK51 a 200 OK

52 S 2000 OK

537 a 2000 OK

54 a 4000 OK x

560 4000 OKso 8 4000 OK

62 5 4000 OK

63 6 4000 OK

279

Table XIV, Sumary Results on SO,000-Round Ingineering Reliability Testof Research and Development Feed and Storage System (cont.)

No. of RateAOIt NL . (soml Stlatus

64 S 4000 OK

6S A 4000 Hanlfir* stoppage - no damage togun or pod

66 a 4000 OK

67 S 4000 OK

66 5 4000 OK

69 a 4000 OK

70 8 4000 OK - Removed Research and Developmentbolts

71 S 4000 OK - Reinstalled Research andDevelopment bolts

72 6 2000 Hangfire stoppage - no damage

73 8 2000 OK

74 8 4000 OK

75 S 4000 OK

76 S 2000 OK

77 5 2000 OK

78 5 4000 OK

79 6 4000 OK

80 S 4000 OK

81 S 4000 OK

82 5 4000 OK

83 £ 4000 OK

64 5 4000 OK

280

iij~.- -. -- ---. -~ 4

Table XIV. Summary Results on 150,000-Round Engineering Reliability Test

of Research and Development Feed and Storage System (cont.)

No. of RateComp. Not Bursts Csp In Status

85 S 4000 OK

96 5 4000 OK

87 6 4000 Hangfire stoppage - no damage

88 5 4000 OK

89 5 4000 OK

90 5 4000 OK

91 5 4000 OK

92 5 4000 OK

93 5 4000 OK

94 5 4000 OK

95 5 4000 OK

96 5 4000 OK

97 5 4000 OK

98 s 4000 OK

99 5 4000 OK

100 S 4000 OK

*Each complement is 1500 rounds.

I2

281 '

A P P E N D I X V-D


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283b.

UNCLASSIFIE! _

DOCUMINT CONTROL DATA. R & D(Seetwofty 01Uleaeion of title, 66 o fem .. a" nImdISMd annaetio mammal be twend .W## me Oerall not Is cessined)

I. ORIGINATING ACTIVITY (Cespwle-emikeu) 111 REPORT SECURITY CLASSFICATIONGENERAL ELECTRIC COMPANY UNCLASSIFIEDAIRCRAFT EQUIPMENT DIVISION 86. GeouPBURLINGTON, VERMONT Not Applicable

I. "%PORIT TITLE

Minigun Research and Development ProgramContract Scope Items 1, 2, 3, 4, and S

4. OES~ftVPTIV3 NOTES (•p .1vel me d Uahmv. ate)

Finagi ReoortS. AU TmsIlu) (JMf nae, aS1ide* Mihd~hlosat rne)

Scope Item 1 - Eugene B. Raymond, Scope Item 2 - David R. Skinner,Scope Item 3 - Henry R. White, Scope Item 4 - Gerard J. Desany,Scope Item S - Charles D. Rossier

4- REPORT DATE 70. TOTAL NO. OF PAGES |b. NO. OF REPSMarch 1970 292 None

C& CONTRACT OR GRANT NO. S. ORIGINATON*$ REPORT NUMrERII|

DAAF 01-68-C-00606. PROJECT NO. 70APB19

Not Applicable6. 8 TE. 0T1CR REPORT NO(S) (AIm ltw A inbff. Admmy be "a.I d

Not Applicable W"s'q'

'LNot Applicable AMCMS Code Number 5142"12'11209'14IS. OITINUTION STATEMENT

Distribution of this document is unlimited.

IN. SUPPLEMENTARY NOTE* to. SPONSORING MILITARY ACTIVITY

Not Applicable U. S. Army Weapons CommandRock Island, Illinois

uS. AETRAT This report describes the design, development, and testing of a new minigun

bolt, clutch, sidestripping feeder, guide bar, and armament pod for the XM-18.The new bolt functions independently of any external cam other than the main

housing cam, and is completely interchangeable in all existing systems. Other ad-4s vantages include reduced cost, longer life, and greater reliability.

The new solenoid operated clutch is in the aft end of the gun and does not interfere with the feed systems of the many minigun applications. The clutch stops thefeed system at the end of a burst, but allows the gun to rotate and clear. A largesavings is realized because no live ammunition is dumped.

The new delinking feeder sidestrips, rather than endstrips. It has fewer parts,is more durable, and thereby reduces cost and increases feeder life.

Tolerance studies of the guide interfacing with gun and feeder, high-speed filmsof round handoff, and evaluations of various guide bar concepts were performed to tryto design a guide bar which would decrease dependency on feeder timing and increasetolerance to damaged ammunition.

The new feed and storage system for the minigun pod incorporates a storage drumsimilar to the MXU 470 Minigun Module with a new feeder design that has fewer partsand is more durable. The combination of these two features more than doubles thereliability of the pod.

11"doww"1473 UNCLASSIFIED

-

UNCLASSIFIED"Ott

dLINK A LINK S LINK C00166 WT ROS6 WY ROL- W-

1. Self-Actuating Bolt2. Tuftrided Pins3. Spring Energy4.- MinigunS. Clutch6. Clearing7. Sidestripping8. Feed9. Link Ejection

10. Stripper Sprocket11. Minigun Guide Bar12. Guide Bar13. Round Accelerators14. Feeders15. Ammunition Feeder16. Storage Drum17. Minigun Pod

K

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IL b~nINWW OcbkslM=

minigun research program

Documents

new feeder designthat

stripping feeder

feeder timing

new guide barwhich

new bolt functions

new solenoid operated

feed systems

guide bar interfacing