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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-
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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
I.
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Photos and Illustrations
I.
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180
L-4
00 0
w LL.
caa
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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 $I' r all I) I Ifl x m tq I tfi, it
weight, with the s•l' f-acittIunt1 livb i1ng %I Ilht IY hri•Pvt (i, lFor Ior 0 s Io1 %i
the center of gravity ý,,vv oltclosd *Iktch.
1, SO I f - act uA t Iu+ tip27n~
I Produlct
Weight in1' as4 per bolt 0,01590 pound
.005 in.
.0 0 5 In. .0 13 in. - 1 .4 9 In.-
NOT TO SCALE
Figure 22. Center of Gravity of Bolt
34
11CHNIKAt ANAMAS~ P#AM
IV PAOI
0AT IU~ IVi (u
CL) KuP~t~ UEAM19
Cj)sv6% lck
cl) u6 12S.14 d
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TICHNICAI ANAM14g FORM-By- PA04
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oy36
TICHNICAL ANAMYSI KAM
NY$,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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fe-SO39
TUCH t4"C AKAIYSI KORM
CK. MODEL U0C t
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14:!,.
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. 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&
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o 40 ±o i o 61- uL
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______ CO.A 1
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TECHNICAL. ANALYSIS FORM
BY GIIA LCRC PAGE 4o~CK. OE
DATE 4J <. 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
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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
TECHNICAL ANALYSIS FORM
'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
-Z.3OIZ.o A aS21 Tw wr
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_____________ f
2..0(oa t.ocP 1 r
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TECHNICAL ANALYSIS FORM
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
Drawings
59
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A P P E N D I X II-B
Photos and Illustrations
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
9 0 No go Feed system retarded too much at stop
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.)
Burst No. Fired Gun Status Remarks
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
41 0 No go Feed system retarded too much at stop
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
Table III. Live Testing Clutch Unit 1 - Module System (cont.)
Burst No. Fired Gun Status Remarks
59 0 No go Feed system retarded too much at stop
60 9 Hot Feed system mistimed - retimed
61-68 Clear OK
69 0 No go Feed system retarded too much at stop
70-79 Clear OK
80 2000 Fire out OK
81-83 Clear OK
84 0 No go Feed system retarded too much at stop
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
Table III. Live Testing Clutch Unit 1 - Module System (cont.)
Burst No. Fired Gun Status Remarks
Loaded 2000 rounds
118-141 Clear OK
142 2000 Fire out 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
165 2000 Fire out OK
Loaded 1800 rounds
166-179 Clear OK
180 1800 Fire out OK
Loaded 2000 rounds
181-196 Clear OK
197 2000 Fire out OK
Loaded 2000 rounds
198-206 Clear OK
207 2000 Fire out OK
Loaded 2000 rounds
208-224 Clear OK
225 2000 Fire out OK
Loaded 2000 rounds
226-239 Clear OK
240 2000 Fire out OK
86
Table III. Live Testing Clutch Unit I - Module System (cont.)
Burst No. Fired Gun Status Remarks
Loaded 2000 rounds
241-260 Clear OK
261 2000 Fire out 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
307 2000 Fire out OK
Loaded 2500 rounds
308 Clear Belt broke (ammunition can too full)
309 Hot Feeder jam
310-331 Clear OK
332 2500 Fire out OK
Loaded 2000 rounds
344-370 Clear OK
87
Table III. Live Testing Clutch Unit 1 - Module System (cont.)
Burst No. Fired Gun Status Remarks
371 1500 Fire out OK
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
416 1500 Fire out 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
486 2000 Fire out OK
Loaded 2300 rounds
487-51i Clear OK
512 2300 Fire out OK
Loaded 1200 rounds
88
Table III. Live Testing Clutch Unit 1 - Module System (cont.)
Burst No. Fired Gun Status Remarks
513-526 Clear OK
527 1200 Fire out OK
50,000 rounds - total rounds fired
89
89
Table IV. Live Testing Clutch Unit 2 - A-37 System 6/9/69
Burst No. Fired Gun Status Remarks
Power loaded 1500 rounds
1-16 Clear OK
17 1500 Fire out OK
Power loaded 1500 rounds
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
Power loaded 1500 rounds
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.)
Burst No. Fired Gun Status Remarks
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
108 2000 Fire out OK
Loaded 2000 rounds
109-134 Clear OK
135 2000 Fire out OK
Loaded 2000 rounds
136-157 Clear OK
158 2000 Fire out OK
Loaded 2000 rounds
159-183 Clear OK
184 2000 Fire out OK
Loaded 2000 rounds
185-206 Clear OK
207 2000 Fire out 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
I.a dl ta. I i.'0 0 I ai0 lLI
I , *
YI 21)11 I ' I a, .Ilk
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
Prior Testing 246 Actuations - 21,500 Rounds Fired (cont.)
Burst No. Fired Gun Status Remarks
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
Table V. Continued Live Testing Unit 2
Prior Testing 246 Actuations - 21,500 Rounds Fired (cont.)
Burst No. Fired Gun Status Remarks
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.
Table V. Continued Live Testing Unit 2
Prior Testing 246 Actuations 21,500 Rounds Fired (cont.)
Burst No. Fired Gun Status Remarks
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
Table V. Continued Live Testing Unit 2
Prior Testing 246 Actuations - 21,500 Rounds Fired (cont.)
Burst No. Fired Gun Status Remarks
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
Weight and Center of Gravity
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
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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
-- -- -- -- -- -- -- - -T I
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S:4: .xhif- TT.:}.a j - ->
4 138.
L- j J
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4 ,4 4. 4 * 4 + 4 1 f k4 - *4 4. 1 1+- 4 - - - 4 - 4 4
16'
tra I Ili A
Figure 67. Module with 2000 Rounds
139
' t ,...- . ,.r. .
| . LKII! kj I NJ .I2
1J. I
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4- - - +- -4
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---..- s- - - -,.,
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Figure 68. Module with 3000 Rounds
140
S. . -..-
- . . ..--
. . . . .
14-
N - -- - m -AE&V3211
I V,
Figure 69. Module with 3000 Rounds
141
N Q!VJ. r6llgT$: 1& 51
L I ' I 1 1 j 1 ::_. :t - - - - - - - - - - - - - --1-- z
--41--A ! . .. L- - - .... - I - / - -- --- 4_ -4 I- 4 I - + +1 I- 1 +-1 -4-
- ill I - i .- ' --. J 1--17 I1 1 1 1 11 -I1I I I - EE
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- r. I I "1_ ' L_ - "1 1 I I L '
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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
S4 4 ,4 -, - 4 4
1 4 -4- -1 -
~ -.... ..........14-t-___
~~41~ T i7
_- -, ;+ N ! tC -t -f • . .' • • - ......--
*--t -t '. •-+ -- t-- - + t 4.. +- t t ' +- ,+- + + -+ 4 4 +-+_ + •--- -'-- - -. ' 1 -;- 1-
f I t 1 -I /-
-It A I
....t7 4-]L3 F ? -,,, 4
•, • t -t t- t - I •-• -- -I:-.
4. 0
_____________...... 1....I.....~....... , i ;-'i i iii
' * --4----!- -- 'i
______________ _ _ I T• o 1 y, -i T
Figure 72. Module with 2000 Rounds
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. ,
.... .--- --- -- -
Figure 74. Module with 3000 Rounds
146
I J-- ~~~~lee~ z z--------------
=OZT:f1gur 75 Moul with 300 Rond
-4-4147
I I f I I I II. I
X8; • I vq Z .. •i i ,
-- -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
Figure 78. Module with 2000 Rounds
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
Figure 80. Module with 3000 Rounds
152
~~'[
I f I
-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
K - ---fil---'--
- + ~ 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
Cd
'-44)
00
165
r 166
• 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
171
LUI
C-
0 3_o 000C9~
0A LzL
0
An - 00~
172-
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
""() .1 *,'i1'4)1d p in, li t I
"00 , 0 ,il 0t ) ( ýt'tt
'' . l : ,;i0l wI t)Il! C clu Itcl In it I I l Id al t t lt il I1i1
h t , I .I ght I \ 111 it
7 :000 !8-00 I'dL tit tI rs t -t.1 .'tltl!! , . i- O Otr 'liiot)I- t ilk
I!itt Ilk) mtSil'mll, tiO
t' I re out
14150l-5 ' 'l10 O2 I- t 0K
! , 0 l2 00- Sl400 200'- rd lkiirs t AK
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
I1 0 1: 0IS 4t I'd lki I I, litidd r tidtu
I SOO I I0 20 IIAI. lbrkt)Il I iIl
A~IIS I I 10 Ift hkO Jm t'ti s A and 4 - rkis l0 - tuitjv,J' ro"ItillVd for'
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 -
176
UUCLI)
- r-4
IFI
7--
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
0
0= 0< $4
ILJJ 0> 0
W ý- 0
LL
<0> U ix
W LL J< z
j0 LU2
V) < 0
< <1
LLJ J(
0
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-
T3CNr-UA AHALYII FORM
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.197
AINY FED CARTRIDGE IN1TIW10 PASit A/ /-1ACTUAI. NOMI IA CONDI1 IONSI
FOR MAU-6A FEEDER
Y INI1NtRfIE•X 0 1 Nit Am AM x
CARTRIDGEISPIOCKET'4OLT CIEW!LINE
SX MINmA YMIN/MAX 0-2.5 .000
.0 .0001.012 .75+2.5 .014/.023 1.005.0 .0301.039 2.257.5 .0351.048 2.510. 0 .0361.050 2.5
12.5 .08i/. 042 O2.5
15.0 .0391. 046 2.0017.5 .0101.015 1.2520.0 ,, .015/.022 .5022.5 .0151.025 2.5 INTERFERENCE25.0 .015/.028 EXISTS WITH SPROCKET27.5 .0241.035 THRU FEED CYCLE30.0 .022/.03132.5 .0151.02535.0 .009. 01637.5 .000
A• CARTRIDGE SEATED, STARTS TO TRANSLATE FORWARD OUTOF DWELL.
4, CARTRIDGE MAKES FINAL CONTACT WITH GUIDES.DEGREE OF INCREASE REQUIRED TO ELIMINATEEARLY FEED.
198
AVFRACf.E CARTRýDGLF INTERPERE NCE
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202
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1IOCHHA AN"YSE FORM
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215
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BY AvrAVAM 71- IUINAL@ ICTAIC PAEOV44CK.MODCDbLAk/K/Ai4
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TI~CHM AHMYU FORM
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ucMMKAL ANALYIN FORM
BY itT ASSE I~ 'IIAOIITI PACCK. moonLIICIC
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ThO*4CM ANMLYS FOMABy X ýAltrr."T_ ININAL0IEIECTRBC PAG ZsOU.DATE %lI jk/. REV.A, I EPWORMINIW
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TICHN ANALUS FOM
CK. ADAR T!5 REV. N I P=R "MN
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227
ThIM1CAL ANALYS FORM
BYV EB 7SNIAOLCI-I PAGEN /.5YK 5v. I MEIA@UCIC AOM VEL114KIN&MR .IS,/G.,b REV. A newR'MN1
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228
TIcCMN ANALWIS FORM
dC. MODEL
DATE IZ/JC1'Li REV. A REipmR ..MINI"LoCArt~bg Wl G~UIDE rSAP-)"Th¶PFv"CoNVDIT)0N
J&.. 00$l X
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229
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DATE O&A-6/.. REV. RPOT'V44 4var a Re, V*:='
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CK. ..uI/ .. iiv"#e7..(AW 4MOL A LL..DATE itjib m~y. A AfP) Jrf1'f54(Afli~w) K9Wof MMI'I
MYNGO G Avr s'it %ruv-Je, stv/ As. ov ,'Doh' sj'0t
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231
MNW.M ANALYS PO
ly WT J *haaatuma PAOI 34A/ 46
IAT It/31 ~~u.uu i to*ALL
7W4400 41wo AWf 4Vy# dw"~vf 00'PbfP4 E~~ 4k, .0oso O. 4f1 .
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232
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W R 14vtFRT hNRAItwlhICuAI PAGI -16144CILPODELIW
,C~vUI"-UlP VALUSS
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IW/ A ___ MO S/ - MAU S-15/
mA~lolLm m MA11MU16A + mINIMUtA~ + 1AA110iUM.000f 6OB.00 SACMAL %
04-0 .4010, 0l;
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"I S .00ce/ .010 o oo los -Cis'10.0 0(/ .0601 O~bbG .060 doOL
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Z%0 L%t4E* L ME .~ ~ j ors t-N IE
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l-Is LINE TD LINE - 0 Z.1 wm*Aýk wprAJy- CWThC3~0CAIT.T LEAVE%~ CoJTACT 6
WIT1U SPROCK~rI
31.CART LMEI cPecbmiwr
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234
byRK. WE~ GIUIIALOILICTIIC PANI 3~4/41.Cv. MmOS
MAU -S'C Amum. tibuM4 MAXJMUW4ý
-S.0 ~.000 ab02.%.000 .005
02 .060./.Oos. t
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2LIS .005 .010 -7T-545.0 CAWTL LE)4iEV. cw~TwhL1%
c CAWT. LZFNJE"S colpcT
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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to R5% vI4 1z I
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237
-4
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238
.-. ___ N,•
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TECHICA ANALYSI FORM
BY AT W S F- GININALItICdTSI PAGE A I/#4CK. MODILDATE Z/1V5/acS*y REV poRMI a)ROUM MJOVEMENTr W~ EYTAC07 L-iýA -G-L
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241
TECHNICAL ANALYMI FOEM
"PY 'KT REbFMrT PAGE 4Z14CK. SINERALO lucli LCTI MODELDATE AS RV. IREPORT% MIN VI'
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
A -. e- 37P rciA sr t,.e p e% ic
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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
255
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A P P E N D I X V-B
Photos and Illustrations
264
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271
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
Weight and Center of Gravity
2I
282}
4 J-
m0 Go CV) C4N N I. -e o~ m 0A*4 t!~ 00 cm -t G 00 00 'D00 vI m
0) 4.1 M~ 00 vlo C;0 I,:'0 . t. ~r4J cz U) N V tn m ) m n 1- 0000 v v 4 Itn In
0 v- 0 I I ' n 0 0:0 ~ .0 r~- In N Rt v m N w0 t- 0 In
1- -4 0 4 Ol 0 M tL' n -1 " n
Cu 4
4J U
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4-40
o cm .4. 14 400, m n C4 a LGo ~ ~ ~ ~ ~ 0 In 00V4% ( m CA i h C
Cu9 0I 0 4.% c o00 c-1-1 0 O 0cNoZ 0 4 %0 r-- 4 In 4 014 t4 In4 r-4 In-
cc 00 ~L0 '0 0 0 0 0 0
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000
C4 v o o4w c f4
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
Ii - - -
IL b~nINWW OcbkslM=