~ FFieIAL USE ONLY
Fie 52.55 / 8
AIR SERVICE INFORMATION CIRCULAR
CH EAVIER-THAN-AIR)
PUBLISHED BY THE CHIEF OF AIR SERVICE, WASHINGTON, D. C.
Vol. II October 30, 1920 No. 121
REPORT OF TESTS ON SHOCK ABSORBER CORD
SUBMITTED BY VARIOUS FLYING FIELDS
AND GENERAL SUPPLY DEPOTS
( MATERIAL SECTION REPORT)
Prepareci by Engineering Division, Air Service
McCook Field, July 3, 1920 n Otaughon
Ra\~" 6~~:R~R'l
WASHINGTON
GOVERNMENT PRINTING OFFICE
1920
t:,.?R u 3 7.0f\
oeposi\or'4 .
I\Uburn Un\vets\\'l
REPORT OF TESTS ON SHOCK ABSORBER CORD SUBMITTED
BY FL YING FIELDS AND SUPPLY DEPOTS.
PURPOSE.
The purpose of this investigation was to t est and determine
the value for service of all rubber shock absorber
cord in storage at va:·i ous flying fields and general supply
depots. Where possibl e, the direct effect of storage conditions
upon the cord was studied.
CONCLUSIONS.
Thi rteen points submitted samples for test. Of these
only five flying fields and three aviatio11 general supply
depots submitted cord of more recent manufactme. The
remainder submitted cord which was very old and in some
cases almost ready to decay. Four flying fields submitted
some of the older cord as well as the new.
It was found that considerable of the old cord with black
outer covering was still in storage . This was manufactured
to meet old speci fications which have been obsolete for
over two years. It is recommended that all black shock
absorber cord, except that ordered for the Handley-Page,
be rejected for further use.
In a period of 18 months (so far as is known) tha cord
has su ffered a loss of approximately 50 per cent in strength,
and it is seen from Tables I and II that storage condition5
have a great influence over the life of rubber cord . Where
the storage has been improper, such as too much light,
heat, or moisture, the cord gaYe poor results.
The Handley-Page cord with oversize rubber thread has
had good storage and shows good preservation through
little less than 18 months. This cord is still serviceable.
The merits of oversize rubber thread are being studied .
The French cord submitted by aviation general supply
depot, Richmond, Va., and shown in Table I under mark
of SC-7 A, was only about eight months old, and was in
very good condition. The rubber strands were under
greater initial tension than was given to the American
cord. It was not_possible to analyze the rubber.
MATERIAL.
Under instructions from the Director of Air Service
dated September 25, 1919, 3-foot samples of all ! inch cord
in storage at the station was sent by all flying fields and
supply depots to McCook Field for test.
In a few cases second samples had to be requested, due
to confusion as to what lot the sample represented.
METHOD OF PROCEDURE.
Inspection .- A section from each sample submitted was
cut open and thf thread and rubber strand count carefully
taken. Condition of the rubber and of the fabric adjacent
to the rubber was noted, and the rubber cross section was
obtained with an Eimer & Amend thickness gauge measuring
in thousandths of an inch . The initial tension of the
rubber 'was noted by removing the fabric casing from a
4-inch length of cord and observing the final length of the
rubber strand.
Physical tests.-Each piece of cord was tested in tension
in a Henry L. Scott fabric testing machine with 300 pounds
capacity. Special knurled jaws were provided which
would continue to grip the cord satisfactorily with the
decreasing cross section. In this test, loads were read at
15 and 100 per cent extension, which is the real test of the
cord.
In addition, destruction tests were made upon a few
samples in order that types of failure, togethe~ with ultimate
loads of elongations, might be studied upon good and
bad cord. For this test, it was necessary to fasten one end
to the floor and apply the load by means of a chain hoist_
fastened to the ceiling. This was fastened to loops in the -
ends of the cord. -
DISCUSSION OF RESULTS.
'rabies I and II show all information obtained froni the
tests. -j
The curves on Plate I show :relative performance of
various cords submitted.
The curves on Plate II ar.e typical for repeated tests on
- rubber, showing effect of repeated loads and the relative
hysteresis loss.
Incomplete information as to storage forbids a proper
calc ul ation of the life of the cord.
14320-20 (~)
4
-,
---
----~- Lo,qo .sre,q1N CURVE'S
H/lLF INCH Rt/8BER C0.21)
34.:,
1,
3~-
PL!lTE I
......... 1,
I .e
- IJ
z"" I
I
2,-- ' I/
ii
I
Za. I " >--
>-- - ~ ,
zoe,':.. ~ >-- I- ~ I /
/8G: ~ ,/
I/
- ~ · I , 16 rJ I- -...;
I- ' /60 ~ II
~ I/
"' V - J
'
·,
/40
/ n '
,I V
' .
IZO .,. V
l ,,
/ ... I .,.
V v
/00 V I
/ ,~
V
,' ~ - - L., 80 ., V ' ~
V
6u - ~
. ,., - ..... ,_ - 1.. .. - . ,_
40
,_ ,,..
,_
I,
V
.to I
PcRcENT ELoNo;:;noN I
!
I
I I I I I I l I I I I I I ! ) ". /0 zo 30 40 so 60 70 80 .90 /00 //0 120 /30 /40
FIG. 1.
5
I I I I I I I II I I I f. J I i I I 11 I II
' I ,~ .I, ..I I I I T :
rno::rnu~-w.4 w~-++·'° '-!, ~ C L. , 1 / ~ t?,:;, U/~ c::>.. .}1 ..--1;. l-""..)..J.i.+-~· 4-H-HY"t't-H
· : I I ,j I I I I I I i I Tl I
,., I I I I I \- ,W~~,+-f
.. ,.
-·~
' ,~
I '"
l~ LI
~~ ~v, .. ... "
~ .0 ..... - L,
L. ' ._
L.
ff) a I.
._ ...... (( 1111;,
~ (
,~,.
- ,_ 7,]
0:::0:::W::W"'"~-_ j~~+l+++++f+ t+titt:t±t:tttt!1 ,t,te t , .z. "-· .. _.I. _ ,,..
I~ ,• _ Lei. ..
I I
, 1
I I I I
I
FIG. 2.
Mark. Received
from- Size.
TABLE !.-Test data black shock-absorber cord.
SUBMITTED BY VARIOUS FLYING FIELDS AND SUPPLY DEPO'l' S.
Rubber strands.
Number. D~!;.n-
Extension
to
rupture.
Original
tension.
Cord load.
15 per
cent extension.
100 per
cent extension.
Cord failure, stress, and strain.
Outer. Inner. Maximum.
Rubber
condition.
-----1------1---- -------- _____,_ ____ ------- -
Inch. Per rent . Pounds. Pounds.
SC-lA . .... {Sarnr eAxn. tonio, } t 120 0.044 671 4"- 2t 25 48 . .. ..... ... .. . ............. . ··········· ··· . ........ . ... .
SC-4 .... ... {Ba rr o n} ' 190 .033 720
{No rupture: } ............. {237 per cent, F r esh-no
Field, 'l'ex. ···- · ······· 24 58 s1l lop poe c f.. s 400pounds. talc.
SC-5 ....... {Houston, } ~ 190 . 031 785 4"-2fi 19 41 Not tested .. {'l'alc-g o o d
'l'ex:. ····· ···· ·· ··· ···· ···· ·· · · · · life.
SC-6A .•... Dallas, 'l'ex . ~ 192 . 031 750 4"-2!! 38 .... . do .... ... ... . .. .. ... .. . ....... . ...... {Btaal cd. -n 0
SC-8 .... .. . r et roit,} 2 120 .046 710 28.5 58-70 {150percent, }155 per cent. {155 per cent, } .............
Mich. · · · · · · ···- ·· 220 pounds. 240 pouncls.
A.G. S. 0., }
SC-9a .... .. Litt I e ' 120 . 04<1 790 4" ? ' 27 58 Not tested .. Good ... .. ...
Rock,Ark.
- -n --·-········· · .. ............
SC>9b ...... ... .. do .. .... . ~ 120 . 044 750 ··· · ·· ·· - ·· · 28 68 ··· · ····· · ···· .............. Looks good . .
SC-9c . ... .. . .... do ....... ii 120 . 043 720 . . ... . .. .. . . . 28 64 Not tested .... ............ :::: : :: : : : :: :: 1F air ... .. .. ..
SC-9d .... .. ..... do ....... ! 200 . 028 725 ····· ·· · · · · · 17 34 . . ... .. .. . .. .. ·· ·· ··· ··· · ·· · ...... .. . . .... Stale ... .....
SC-9e .... .. ..... do ....... 198 . 028 775 ····· ···· ··· 17 37 ·········· ·- · · .... . .. . ...... ·· ·· ··· - · ····· · · ·······-··· ·
SC-9f.. ..... ..... do ...... . ! 200 .028 715 ............ 21 50 ···· ··· ·· ····· --·-···· ······ ············ · · Good .... ....
SC-9al.. . .. .. .. . clo ....... ' 200 .028 800 ············ 17 34 ·· ····· · · · ···· ··--· --· ·· · ··· . ..... . . .. .... {Stuck- not
bad.
SC-9bl.. ... . .... do ....... ' 165 . 032 750 4"-2k 22 42 Loops 3llpped ... ... . . . . . ... {225per ce.nt,
335pounds. }'.l'alc-falr .. .
SC-9cl. .. .. ..... do ...... . ........ 200 . 027 700-300 ············ 18 37 . . . . .... . ....... . . ... .... .. . ..... . .. ... . .. Bad .... .....
SC-9dl. .. .. ..... do ....... 200 . 028 I 720 14
{Inlt lal ten- } ............. {1~1a';~~.u . No ta lc-
······ ·· ·· · ········ · 28 lso1w0n. very bad.
SC-9el. .... ..... do ...... . . .... ... 200 . 028 800 19 40 ... ......... ·· ·· ········ ·· ·· ·· ···· · · ···· ro2o8 0p pero cuenndts, . }'ralcbacl .. ..
SC-911 •.... ..... do .. ..... ! 200 . 028 780 16 34
... ...... . .. 187 per cent, }. . . .......... -···· ·· · ·· ··· · ·· · · · ···-··· · · 240 pounds. Jw i I bur
f
Wright {162 per cen t No talc-
SC-HA •.•. l Fl e Id, 176 .034 800 4"- l ii 25 58 Day ton,
······ · · · · ···· . ..... .. ...... 330pounds. bad.
Ohio.
SC-12B ... . {Bri ghton, } t 80 .047 x.085 690 36 146 {144percont, }370 pounds .. 550 pounds .. {Good-some
Mass. ··· ·· · ······ 300pounds. talc.
SC-12C ..... .. .. . do . .... .. ! 80 . 084 X. 049 770 4"- 11' 40 148 ...... . ..... . . ·· ····· ······ · ·· ············ ······· · ······
SC-12D .• •. .. . .. do ..... .. ~ 120 .045 790
{Loops 156 Outer175per}
............ 28 67 percent,215 cent, il20 370 pounds .. Good ...... ..
pounds. pounds.
SC-13 ...... ............. . 124 .042 545 ·· · ·· ·· ··- -- 22 .5 64 mo frer cen~ · · ···· · ·· · · ·· · 187 per cent No life-poor
2 0 poun s 270 pounds., or rotten.
Thread
count and
strength.
e-48 4 .45
1-32 4 .24
e-32 4 .2
1- 48 4 .6
{0-72 4 .2
1-32 4 .5,
e-47 5
1- 32 .5 .4
e-48 5.5
l- 32 4 .4
e-48 5.25
t- 32 5
e-48 4 .5
1-32 4.35
e-48 5.2
1-32 4.9
e-48 4 .4
1-36 4 .8
e-48 4 .7
1-36 5.2
e-52 3 .2
1- 37 5 .43
e-48 4 .74
1-36 4.24
t48 4 .2
1-32 4 .7
e-48 3. 7
1- 36 4.8
e-48 3.9
1-36 4 .2
e-48 3 .7
1-36 4.6
e-48 4
1-36 4 .5
0-48 6 .6
1- 32 6 .6
t48 5.3
1-32 5 5.4
1-32 4 .2 t48 5.2
l-32 4 . 7
0- 48 4
1-32 3
( ('
Remarks.
}Lire and storage condltions unknown. l""ol'd "a't" l'e a's"t., m-o,re 'i"s "un "c"er't~ai·n . ,-,oo,
Shlpped ln from other fields. Ligh t,
clry, and moderately cool storage.
18 months old. Packed ln boxes. Con-dltlon
of storage unknown.
}very li ttle old cord in stock.
} Do .
} Do .
} Do . l Do .
Do.
Do.
t Do.
Do .
} Do.
} Do.
} Do.
}At least 1-year old. No further history
a vailable. ·warm storage.
r-yearold. MadeforHanclley-Page. In
boxes plied in unheated ground floor.
Bulldlng. No ex treme heat.
}18months old, but same storageas above.
TABLE II.-Test daw white shock-absorber cord.
SUBMITTED BY VARIOUS iFLYING FIELDS AND SUPPLY DEPOTS.
Color
Rubber strands. C0rdload. Cord /allure, stress and strain.
Received of Rubber Thread
Mark. from- Size. mark- Exten- l.\i i)er iooper condition. count and Remarks.
ing Number. Dimen- sion to Original eent ex- cent ex- Outer. Inner. Maximum. strength.
thread. sions. rupture. tension. tension. tension.
------------
Inch. Per cent. PJ)U11,dS- Pounds. I SC-1. ... . .. {San Antonio, } t 3 red . . 240 0.034 677 4''-1} -42 139 { 0-48 4 .8
'!'ex. ··· ·· ··- · ····· ........ ..... .. ...... ....... ···· -····· ···· 1-48 4
{Received from Curtiss Corpo-
SC-2 ... .... Waco, '!'ex . . Red ... 212 .0336 750 S8 93 Fresh . . .... . { 0-72 5 ration 8 months previous. -- .. -- ------ ·- ·-········· · ··· ·····-···· · ········ · · · ··· 1-45 4 "Stored according to instruc-tions."
SC-3 ....... {Middletown, } ! 1 red .. 215 .034 800 1 4"-H 38 149 {150 per cent, 200 per cent, }430 pounds .. Good ........ { 0-72 5 .8 {Wrapped in paper. Storage
• Pa. 285 pounds. 430 pounds 1- 48 4 .7 cool and dry and in boxes .
Good preservation.
3A .... . .... ..... do .. ... .. t 3 red .. 232 .034 820 24"-ltJ 43 125 Loop slipped {169 per cent, w;~J"el.re· { 0- 48 6 { Concrete floor. Light ancl alry
........ ...... 750 pounds. 1-48 6 at all times. Boxes unopen-ed.
SC- 6 ... .... Dallas, Tex .. t Red .. . 230 .033 790 42 121 { 0-48 5 {Don't know. Stored in light,
.... --- ------ ···· · ········· ·············- · · ·· · ········- ······· ··· ···· 1-48 5
cool and' dry. Just received
[rom other storage.
{Am er icus, } {Loops 167, } {197 per cent,
r 2 montl1s old. Stored in [airly
SC- 10 ...... ! 3 red .. 240 .034 810 24"-lli 40 150 }Fresh ....... { 0-47 7 light and wrapped ln water-
Ga. 340 pounds. · · · · · · · · · · · · · 470 pounds. 1-48 5 proof paper. Average 75°
temperature. {w i 1 bur SC-11 ...... Wright } J; . . do ... 240 .033 700 2 4"-1·! 47 •l05 N , , {200 percent, } ..... do ..... { 0-48 6 }No information. -1
Field, Day- 0 "anung. · · · ·· ·· ··· · ··· 700 potmds. 1-48 5
ton, 01110.
SC-!2A . ... {Bri ghton, } 1 .. do .. . 240 .034 790 39 104 {204 per cent, }······· ··· ··· 690 pounds .. {Diel not [ail, { 0- 48 5 } Ground floor o[ unheated build-
Mass. ··--------·· 680 pounds. good. 1-48 5 ing. Good preservation.
SC-13I. . . ..
{Da yton- } {Failed at }···· ········· ..............
{Rotten- no { 0-56 5
Wright,Mo· t 1 red .. 162 .039 300 '4"-2iir •Jl 140
aine, City.
loops. talc. 1- 35 3
SC- 13J . .... ..... do .. .... . t .. do ... 140 .044 465 39 110 {200percent, } d { 0-71 3
-- --··· -···- _ 450 pounds. 490 ponn s. · ··············· ········· ···· 1-32 2
SC-13K .... ... ... do ...... 1 ..do ... 160 .039 485 30 90 {No destruc- } J 0-58 5
--·-· --·--·· tions. · · · · · · · · · · · · · · ··-··-······· ······ ······· · \ 1- 36 3
SC-13L .• ... .. ... do . . .... t .. do ... IGO .042 463 · ·······- ··· 29 90 ········· ····· ....... . ...... {!75percent, } { 0-56 5
350 pounds. ·· · · ·· · · · ·· · · 1- 36 2 r· G.S.D., } {Rubber is {Well packed in boxes in dark
SC-7 ..... . . Richmond, } 3 red •. 120 .043 700 4'."-2! 38 97 · · · · · · · · · · · · · · fs°0
d1ut~f } 0-48 3.7 and dry storage. About 18
Va.
.... ... ....... ···· · ········· 1- 72 1.5 months old. Received from
cated. Curtlss.
SC- 7B •.... , .. . . do .. . .... t 275 .031 4"-2ls {Loops, 200 }· ............ {225 per cent, }············· { 0-32 4 {Built [or Handley-Pa~e at Old-
52 88 per cent. 675 pounds. 1-32 4 ham, England, and receil'ed
SC-7A . .. .. 1 . .... do ..... ..
from there Mar. 25, 1919.
t 3 red. ·I 268 .034 700 4'"-?-H 156 {175percent, }··· ·········· 725 pounds .. { 0- 72 4 {Received from A. S. P. C., No.
I I 725 pounds. Very good ... 1-80 1. 8 2. Romorantin, France, May
31, 1919.
1 Before physical test. 2 After physical test.
0
Air Service Information Circulars
