TDR-64-33 0 4J /,/0 p ;;. cJ MAU-i2A / A BOMB EJECTOR RACK STRESS ANALYSIS Fi nal Rep or t P re par ed by D. E. O'B an no n WL TDR 64-33 TECHNICAL DOCUMENTARY REPORT NO . WL TDR-64-33 J une 1964 Re se ar ch and Techno logy Division 1\IR FORCE WEAPONS LAB O RA TOR Air Force Systems Command Ki rtland Air Force Base New Mexi co Project ESP 012 36 • r l L• " r -" l - L; I t<A ,.--.._ II I I I d I
107
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~WL /,/0 p · slave piston is actuated which contacts a striker block attached to the main ... this piston force j roduces sufficient moment to overcome the existing closing moment
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~WL TDR-64-33
~ ~
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MAU-i2A/ A BOMB EJECTOR RACK
STRESS ANALYSIS
Final Report
P repared by
D . E. O'Bannon
WL TDR
64-33
TECHNICAL DOCUMENTARY REPORT NO . WL TDR-64-33
J une 1964
Re searc h and Technology Division 1\IR FORCE WEAPONS LABO RA TOR
Air Force Systems Command Ki rtland Air Force Base
New Mexi co
Project ESP 012 36
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Reiearch and Technology Division Air Force Systems Command
AIR FORCE WEAPONS LABORATORY Kirtland Air Force Base
New Mexico
When Government drawings, specifications, or other data are used for any purpose other than in connection with a definitely related Government procurement operation, the United States Government thereby incurs no responsibility nor any obligation whatsoever; and the fact that the Government may have formulated, furnished, or in any way supplied the said drawings, specifications, or other de.ta, is not to be regarded by implication or other- wise as in any manner licensing the holder or any other person or corporation, or conveying any rights or permission to msnufacture, use, oi* sell any patented invention that may in any way be related thereto.
This report is made available for study upon the understanding that the Government's proprietary interests in and relating thereto shall not be im- paired. In case of apparent conflict between the Government's proprietary interests and those of others, notify the Staff Judge Advocate, Air Force Systems Command, Andrews AF Base, Washington 25, DC.
This report is published for the exchange and stimulation of ideas; it does not necessarily express the intent or policy of any higher headquarters.
Qualified requesters may obtain copies of this report from DDC. Orders will be expedited if placed through the librarian or other staff member designated to request and receive documents from DDC.
A13STRAC 1
This report contains detail loads and stress analyses showing that the
MAU-12A/A Bomb Ejector Rack is adequate for external carriage of stores
on US Air Force aircraft. It was determined that carrying a 20-inch-
diameter store on the 30-inch shackles produces the largest stress in the
components of the rack. Therefore, these conditions were used exclusively
in the analysis.
The load conditions for the 14-inch shackles were investigated to ensure
that no critical local stress problems are produced. Determination of the
allowable ultimate vertical load for these shackles is included.
Stress analyses are presented for critical conditions of each component.
PUBLICATION REVIEW
[AYMOND J. SWAIM 'Major USAF Project Officer
QcD^rwut. LUTHER C. COX R. A. HOUSE Lt Colonel USAF Colonel USAF Chief, Components Development Branch Chief, Development Division
CONTENTS
Lists of Figures and Tables
List of Reference Drawings
Summary of Minimum Margins of Safety
Introduction
Structural Description
Load Analysis
Applied Loads and Store Reactions
Aircraft Attachment Reactions
Linkage Mechanism Reactions
Structural Stress Analysis
Body Analysis
Linkage Mechanism and Drag-fitting Analysis
Ballistic Gas System Analysis
References
Distribution
Page No.
iv
v
vi
1
1
I
I
5
11
27
28
46
87
98
99
iii
LIST OF FIGURES
1 Sign convention and geometry - aircraft attachment reactions 6
Z Linkage mechanism geometry \Z
3 Static balance of rack for load condition No. Z 28
4 Body loads for load condition No. Z Z9
5 Shear and moment diagrams (vertical plane) load condition No. Z 30
6 Shear and moment diagrams (horizontal plane) load condition No. 2 31
7 Static balance of rack for load condition No. 6 32
8 Body loads for load condition No. 6 33
9 Shear and moment diagrams (vertical plane) load condition No. 6 34
10 Shear and moment diagrams (horizontal plane) load condition No. 6 35
11 Linkage mechanism system 47
12 Ballistic gas system 88
LIST OF TABLES
1 Applied loads and st >re reactions 3
2 Calculation of aircrift attachment reactions 7
3 Calculation of linkage mechanism reactions 25
iv
-«->—■ »—I—
LIST OF REFERENCE DRAWINGS
AIR FORCE DRAWINGS - MAU-12A/A BOMB EJECTOR RACK
o2BI3022
bOC4bS30
bÜC46S™
60C4b540
60C46S41
63C14370
63C14371
63C14383
t)4CI3032
OÜD46528
63014368
b4Dl3ü82
63D14374
b3D14375
63D14378
b3DI4379
bOH4b522
bOH46534
bOH4b535
63H14361
63H14366
63Hl437b
63J143b2
63J14363
Bolt, Mounting, Breech
Link, Connecting, Shackle
Clevis, Guide, Over-Center Spring
Trunnion, Clevis
Bellcrank, Inflight, Safety Lock
Rod, Shackle Actuating, Forward
Rod, Shackle Actuating, Aft
Pin, Linkage
Piston, Slave
Shackle, 3ö-inch Spacing
Body, Retainer Cartridge
Plug, Slave Piston, Retaining
Tube, Gas, Assembly of
Tube, Gas
Retainer, Cartridge
Retainer, Cartridge, Assembly of
Block, Cylinder, Ejection Piston
Sideplate, Left Hand
Sideplate, Right Hand
Breech, Bomb Ejector, Rack
Block, Orifice Housing
Tee, Connecting, Gas Tube
Bellcrank, Actuating, Rod
Shackle, 14-inch Spacing
Fitting, Drag, Vertical, Assembly of
SUMMARY OF MINIMUM MARGINS OF SAFETY
Part Refer to page
Critical section
Type stress or loadipg M.S.
Side plate 39 Section A-A Bending and tension + 0,05
Swaybrace 41 Section D-D Bending + 0.09
Swaybrace 42 Section E-E Bending t 0.02(Yield)
Swaybrace 43 Section F-F Bending + 0.09(Yield)
Swaybrace (Cylinder block)
44 Section G-G Bending and compression
+ 0.07
Swaybrace (Cylinder block)
45 Aircraft attachment
Shear Bearing
+ 0.02 + 0.22
Forward 30" shackle
49 Section A-A Bending f 0.13
Forward 30" shackle
53 Section D-b Bending, tension and shear
+ 0.11
Aft 30" shackle 54 Section A-A Bending 0.28
Aft 30" shackle 55 Section B-B Bending + 0.24
Aft 30" shackle 57 Section D-D Bending, tension and shear
+ 0.10
Forward link 59 Section A-A Bearing + 1.89 connector
Aft 14" shackle 66 Section C-C Bending and compression
+ 0.46
Forward actuating rod
68 Section A-A Compression + 0.67
Forward actuating rod
69 Section B-B (Connecting pin)
Bending + 0.11
Center bellcr-nk 71 Section A-A Bending and shear + 0.23
Center helle rank 72 Lug analysis Shear + 0.10
Safety lock belle rank
76 Section B-B Bending + 0.13
Clevis trunnion 80 Section A-A Bending and shear + 0.85
Aft actuating rod 82 Section B-B Compression and + 0.43 bending
vi
SUMMARY OF MINIMUM MARGINS OF SAFETY (cont'd)
Part Refer to page
Critical section
Type stress or loading M.S.
Vertical drag fitting
85 Side plate fastener
Shear * 0.01
Vertical drag fitting
86 Side plate attachment
Shear-out + 0.10
breech 89 Section A-A Tension + 0.01*
Slave piston 90 Compression + 0. 32*
Slave piston plug 90 Thread area Shear + 1.84*
Cartridge body retainer
91 Section B-B Tension + 0.32*
Cartridge body retainer
91 "O" ring groove
Compression 4 0. 15*
Cartridge retainer 92 Thread area Shear + 0.52* cap
Cartridge retainer 93 Section B-B Shear + 0.32* cap
Tee gas tube 94 Section A-A Tension + 0.42*
Tee gas tube 95 Section C-C Tension + 0.06*
Gas tube 95 Tension + 0. 14*
Tee gas tube 96 Side plate attachment
Shear + 0.06*
* 1 he ultimate factor of safety Is 2. 5 times the gas pressure limit load for all Ballistic System components. Ultimate factor of safety of 1. 5 times limit loads is used for all other components.
Vll
WL TDR-64-33
1. INTRODUCTION
This report presents the load and stress analysis of the MAU-12A/A Bomb
Ejector Rack in accordance with the requirements listed in paragraph 3. 7 of
MIL-A-8B68. Stress analyses are presented for critical conditions of each
component.
The design for the bomb ejector rack was determined by loading conditions
No. Z and No. 6, shown in table 3, which produce the most critical local loads
in the structural parts of the bomb rack.
Unless specifically noted, all loads, load factors, and allowables shown
are ultimate values.* Included in the report is a Sum-nary of Minimum Margins
of Safety above ultimate values.
Since forces and moments presented refer to left- hand, wing-mounted
store installations, all loads and strets analyses in this report also pertain
to left-hand assemblies with right-hand values opposite, unless otherwise
specifically noted.
2. STRUCTURAL DESCRIPTION
The MAU-12A/A Bomb Ejector Rack has been designed to function as a
structural support and release mechanism for external carriage of stores on
US Air Force aircraft. The rack is basically a ballistic-gas actuated
mechanism which is enclosed by a structural body composed of side plates
and close-out channels. The major gas system components (i.e. , breech and
piston blocks) also serve as primary structural members.
Within the housing, two sets of shackles are provided; one set on 3Ü-inch
spacing and the other on 14-inch spacing. The 30-inch and 14-inch shackles
are designed so the drag load (longitudinal) applied to the store will be reacteo
by the end drag fitting or the provided section of the cylinder block respectively.
The 30-inch shackles and 14-inch shackles are connected by compression links.
From the shackles, load is transmitted through the compressing links to a
central bellcrank. The link loads on the bellcrank are overcenter, producing
an unbalanced moment on the bellcrank. This unbalanced moment is reacted
♦The ultimate factor of safety is 1. 5 times the limit load for all components except ihose in the gas system. The ultimate factor of safety for those com ponents is Z. 5.
1
WL TDR-64-33
by a tension link. Under normal conditions, a down load on the shackles tends
to keep the hr' age closed.
A breech block is provided which holds two ARD 446-1 cartridges. These
cartridges fire, when subjected to a dc potential of 24 volts, furnishing a
high-pressure gas source. Each cartridge is provided with a separate firing
circuit. Should one cartridge fail to receive firing current, the other cart-
ridge is capable of igniting it sympathetically.
From the breech, the high-pressure gas is used in two ways: (a) a small
slave piston is actuated which contacts a striker block attached to the main
bellcrank; this piston force j roduces sufficient moment to overcome the
existing closing moment due to the link loads, thus opening the linkage; (b)
The main portion of the gas is piped through a tee-shaped tube to the forward
and aft cylinder block where the gas is then utilized to drive *he ejection
pistons down on the store. After the pistons have extended through their full
stroke, trapped, high-pressure gas is used to return the pistons to their
normal positions.
The rack is capable of varying thrust output to the ejection pistons by
orificing the gas flow. Orificing is accomplished by the proper positioning
of a slide containing two through-drilled holes. Two slides are located in the
gas system, one each between th^ ends of the tee tube and the cylinder blocks.
Through the use of these orifices, the peak thrust may t varied.
The rack design also includes an in-flight lock system which is composed
primarily of a solenoid, locking pawl (bellcrank), and three rotary switches.
The («awl is spring.loaded to the normally closed position and is actuated by
an electrical impulse delivered to the solenoid.
3 LOAD ANALYSIS
a. Applied loads and store reactions
The loads and moments in table 1 which are used in this analysis are
derived from data presented in MIL-A-8591. The moments and forces are
reacted at the 30-inch spacing shackles and the 20-inch spacing swaybraces
of the bomb rack. The reactions of the shackles and swaybraces aro based
upon the method of load distribution shown in MIL-A-8591 except for the
WL TDR-64-33
reactions caused by the yawing moment distribution. In this analysis, 60 per-
cent of the yawing moment applied at the C. G. of the store is assumed to be
reacted by a couple at the 30-inch shackles, and 40 percent of the yawing
moment is reacted by the swaybraces. This assumption is based upon
empirical data obtained from static load tests conducted at the Sandia Corpora-
tion, Albuquerque, New Mexico. Thirty-three tests conducted on the MAU-1ZA/A
Bomb Rack verifys the percentage of the yawing moment reacted by the sway-
braces.
b. Aircraft attachment reactions
The calculated loads at the forward and aft shackles and swaybraces
of the bomb rack (table 1) are reacted at the forward and aft aircraft attachment
points. Calculations for the aircraft attachment reactions are based upon the
following assumptions:
(1) Vertical and lateral reactions
The bomb rack is assumed equivalent to a simply supported beam.
( Z) Longitudinal reactions
The longitudinal load applied in the aft direction is assumed to he
reacted entirely at the aft aircraft attachment point, and when applied in the
forward direction is assumed to be reacted entirely at the forward aircraft
attachment point.
( 3) Rolling moment reaction
The reacting rolling moments are due to the side loads applied
to the shackles and loads applied to the swaybraces. Since the swaybrace is
an integral of the part attached to the aircraft, the forward reacting rolling
moment is assumed to be due to the loads applied to the forward shackle and
swaybrace. The same assumption is used lor the aft reacting rolling moment.
Sign convention, geometry, and general equations for calculation of
aircraft attachment reactions are shown in figure 1 and on pages 9 and 10.
Table 2 contains actual calculations of aircraft attachment reactions.
R^ = 0. 2195 Rw - 0. 212 P„, - 0. 272 P vEz K H' H
.f PH, = 0.4195 P (Reference page 19)
PH = 0.406 P* (Reference page 21)
Rw ■ 0.036 P{ ♦ 0.0336 Pa (Reference page 23) 7. I, K
0.2195 10.036 Pf ♦ 0.0336 Pa
L z z z [o. 036 P^ + 0.0336 Pa] - 0. l\Z [(0.4195 PM
[0.406 P'] - 0.272 0.406 P
= 0.0079 Pf + 0.00738 Pa - 0. 1105 P* - 0.0889 P z z z z
= -0.081 Pf - 0. 103 P* z z
REx + PH' COS 12- 24 ' PH C08 15, 78 + RK c
REx = -0. 976 PHt + 0. 9625 PH - 0. 975 RK
os 12.68 = 0
= -0.976 0.4195 P
0.975
[o.4195pM + 0.9625 [o. 406 Pa]
[0.036 P^ ♦ 0.0336 Pal
= -0.410 Pf ♦ 0. 3904 Pa - 0.0351 Pf - 0.0328 Pa
z z z z
= -0.4451 Pf ♦ 0.3576 Pa
z z
24
WL TDR 64-33
4. bTRUCTURAL STRESS ANALYSIS
Tht" stress analysis for the MAÜ-12A/A Bomb Ejector Rack is presented
in three sections: (a) body analysis (side plates and swaybraces); ( b) linkage
mechanism and drag fitting analysis; and (c) ballistic gas system analysis.
The body analysis is based upon the loads and moments produced by load
condition No. 6 (reference tables 2 and 3) shown in figure 7. The components
of these loads, in a vertical and horizontal plane, are shown in figure 8 with
the shear and moment diagrams presented in figures 9 and 10.
Loads and moments produced by load condition No. 2 (reference tables 2
and 3) presented in figures 3, 4t 5, and 6 are for comparative purposes only.
The analysis of each component or assembly of the bomb rack was made
using conservative methods as much as possible. However, the plastic
bending methods were used in computing the ultimate bending allowability of
the side plates and swaybraces. Static load tests to ultimate conditions 2, 4,
5, and 6 have verified the accuracy of these methods.
27
WL TDR-64-33
a. Body analvai«
APPLIED LOADS AND AIRCRAFi REACTIONS
4.063.
Z(UP)
. P ■ 33,600 Ibt. 1 / ML '
Figure 3. Static balance of rack for load condition No. Z
(Reference table 2)
(1) All loads and reactions are shown in proper direction
(2) Left-hand rule coordinates
28
WL TDR-64-33
7191 Ibt. 90361b« INBOARD
A
A 27,761 Ibt.
FWO z 60H46535
144,663 in-lbl. -/ "~ < V
250,073 in-lb«.
V e
60H46534
290 lbs
fi3 3 2901^
t 90361b«.
PLAN VIEW 14^13 Ibr
A 6520 lbs_
FWD
UP
t j
"8069 let
\
4- ^ 4-°
"^-sOte
4- -f0^- +-$-"*"
t 24,651 lb«
15,402 Ibr
4- 4- Ü
O^T 30,442 lb«
SIDE VIEW
t 35,782 lb«
Figure 4. Body loads for load condition No. Z
Z9
WL TDR-64-33
40-r-
30--
?g 20 + M
5 10 --
-10--
-20--
-30 J-
SHEAR DIAGRAM
10
-2729 Ibr
-24.651 lb«
15 4-
■»•35,782 lb»
20
POSITIVE SIGN CONVENTION
Figure 5. Shear and moment diagrams (vertical plane)
Load condition No. Z
30
WL TDR-64-33
10-p
8-" 'O S
3 2 2 o
-4--
-50-1-
♦9036 l^t
10
SHEAR DIAGRAM
IS 20 25 30
-4518 Ibt,
.•••45,180 in Ibt
POSITIVE SIGN CONVENTION
- 45,180 In lb«
Figure 6. Shear and moment diagrams (horizontal plane)
Load condition No. Z
31
WL TDR-64-33
P^ «5340 lb«.
19.54
Pj «30,833 lb«.
/ Pf «34,200 lb«.
Figure 7. Static balance of rack for load condition No. 6
(Reference table 2)
(1) All loads and reactions are shown in proper direction
(2) Left-hand rule coordinates
32
WL TDR-64-33
▲ 20,468 Ibt
A 1
A6457lfci.
INBOARD
FWO L 60H46S35
®' 209,021 in Ibt. -V
195,474 in Ibt.
V 9340 Ibt
60H465S4
A e 000 'A
12,478 Ibt
w ] 3000 lbs
PLAN VIEW 9340 ibt
14/67 Ibt.
A UP
FWO
B
49,744 Iftt 26,7271^1
4432 I^L
-§- -f-®^) -(f)- T
SD ± -VH-.A ]
3000 Ibt (RED
SIDE VIEW 30,989 Ibt
Figures . Body loads for load condition No. 6
33
WL TDR-64-33
440--
430--
?0 420--
*4-l0--
5 o--
5 .20-- z ■ .30--
-40--
-50-"
SHEAR DIAGRAM 430,833 1^1
4-4280 lb*.
I 20 29
-45,7441fc|. c t J 1 "FWD
UP
POSITIVE SIGN CONVENTION
)
>r
-240-,- -228,720 Inj^
30
Figure 9. Shear and moment diagrams (vertical plane)
Load condition No. 6
•NOTE: The unbalanced moment (considering vertical loads) is balanced by the 3» 000 lbs drag force (applied to the aft drag fitting) acting aft on a 3.688 in. moment arm.
34
WL TDR-64-33
♦4T SHEAR DIAGRAM
♦26,700 in\b%.
POSITIVE SIGN CONVENTION
Figure 10. Shear and moment diagrams (horizontal plane)
Load condition No. 6
35
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11
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6
W L TDR-64- 33
SIDE PLATE REACTION CALCULATION
(Reference Drawings 60H46 534 and 60H46 535 for dimensions )
Right- hand Side I-' late .(+\ rMA = 0: (-9789+430-595+6598)(0 . 938)-(9356)(4.25) +(1 700)(3 .7 5)