CENTRIFUGAL 10AD TESTS ON FIRESTONE TIRE A:W RUEi3ER ·:cvi"PANY
BULL:ST PROOF SELF SEALING GAS TANKS
fFunel oge and rtear Wing Tanks for P-40 l\.ir?l an0~
Introduc.~~~.a~d. Surrmary
Tests vre r o conducted a+, the Daniel Guggenheim Air 3hj ~ }~1::;ti:c.t1 t u on the
f 1H e l a ge and r ear wing t onks for the P-40 airplane . 1:1 the E"3 t .rnl 3, the t anks
v1'Jrc fille d with water a ild ..iubj ected to ce ntrifuga l a c ceh~:r-e.U G~!s sn as to
G.u:ili ca t e as closely as :PO s si ble a 12 g downwa r d load. De~.' ] c. :'.ticI.J.s of the
b1.r'·t om surfa ces of t he +;anks wer e measure.a. at certa i r ud.n ~;s ' :y .,:irn.1; J.e wire
po ~: nt cr s s c :;.·a t .)hi ng· on wax 3d paper.
For thu fu se l a ge t a:::k , t he maximum de fl ection T'lGa3UI' J cJ -ND. s 1.. 56': • occurring
c.. ::; the °'!:)a so c. f the surr,p f.'i t·Ci ng. For tho wing t ank! t i10 ftl[ xlmum d0£'le ntion
vvaR 1., 9111 , '.lcc1H"ring a t a point on the transve rse cent er 15.ne midwn.y between
tw1 0 11te:"' s- .~pp > r t~_ng st~ a.ps r
J t.3 v,hir lil:g ~ rm a t the Danie l Guggenheim Airs h ~ . p )~nsti ti..Jt0 ha~ ·o::-· en de s -
G!'7.b oo_ l n di.ff01·e-r1t +,c c.hnin a l j ourna lsl,2. In brie1'. t b3 Yrhi~l i :;i. g o.rm con-s
i '1t s of a lone; hJri z on~n. l tubula r a.rm bui 1 t onto a. ceni. r a ::... s·:: ru~.tu:.: a l fr o.mework
n t~a c '.'lGd to o. v e r ti c a ] ~l1 be of 1611 diame t er. This ve rtica l ·t-i..:i.b0 i s o.t the
cF:J::.1t 0r of rota t ion of the entire structure . The hori z Jnt l j. 1:nr. extending from
c..1e side of the centro l structure r ea.che s through o. no.!·ro N· slot in an inside
WJ.1.1 into an annular test channe l of approxima t ely 16' x 20 1 l'lro~ s s e ction and
2,JO ' mean circ11mfe r ence., The outer wall of this t est channe l is the outside
wa ~ . l of the building, The inner sheet metsl wo.11 scpo.ro.t es the te st channe l
from tho spa ce imme dia t 0ly surrounding t he centra l structm·0 uf the whirling
a :.rn, Mode l s to be t est ed a0rodyno.mica lly a r c curri ed on the end of the long
hJrizontal ar m. The centr a l structural framework and the horizontal arm a r e
so de s i gned that they c o.n be made to b a l ance freely a.round a horizonta l cross
snaft at tho inte r section of the axis of the horizonta l n.rm with the axis of
ro,Jo. tio n~ and pe rpendicula r to both. When a model i s su sp0ndod on tho end of
tho long horizontn.l arm, t he whole a ssembly is balanced by counter we i ghts
f a stened a t t ho opposite side of the centra l structure so tha.t t ho centrifuga l
forces ·..1,rhich a r e s e t up on opposite sides of the center shaft when the arm
rota. co s ba l ance out.
Power for driving the whirling arm is supplied by an 6-cylinder automotive
typo engine through a V-bolt drive to a cross shaft. A large be ve l gear
koyod to the lowe r 0nd of tho ve rtica l center shaft is driven by a small
pinion on t his cross shaft.
Ho Troller, The New Whirling Arm, Journa l of the Ae ronautica l Sciences,
Vol. 1, Page 195.
H. Troller, The Dani a l Guggenheim Airship Institute ~ Journa l of Applied
Physics, Vol. 9, Pago 24.
The Dani el Gt.g: v.0.ohGim Airship Institute
2 Akro11, Ohio
?or testin~ under centrifugal acceleration, the tanks were mounted on
the sl1ort inne:.4 enri of the whirling arm, and counterweights to balance were
secured at t:be :i.ong end of the arm where models would ordinar:i.ly be suspended ..
Figure l is a diagram showing the positions of the fu 3elage and rear wing
tanks on the whirling arm for the test runs. For convenience :in filling and
draining the tanks and to cut down the rotational speed the taLks were filled
with water instead of ga soline. The tests were then run so that the actual
resultant a cce leration wc.. s equal to the desired load factor multir:ilied by
t he r atio of the specific weight of gasoline to the spel'.'ific wei ght of water.
f i e;ure 2 is a photograph of the fuselage tank installat~_onc !'!o pho·cograph
of the r ear wi ng t ank installation is available. Figurb ~ is e O.Li gram showin;
the points at which deflections were measured 0:1. t he bottom of the fuselage
t a;.1k, while fi gure 4 is a similar diagram showing the-pai n.ts a t which deflect~
Jn s we r e r e corded on the r ear wing tank.
As sho':ni in figure 2 , t he fuselage tank was supported on two wood cradle
b:l_ r.cA:s a·'.1d he l d i ;:i po si t ion by the four sets of holri d'.)vm ~tr aps used in the
ac-.u8.::. t "mk i n0tal l atio:i.1 in the airplane . The wing t ank wa s mounted in a
w<?:..d e(~ .3·...;ee :;. box f r arn8 ht..:ilt up to the dimensions of t he wing cavity in the
a Ycu3.J. 9..l r ple.ne. Li gl:t angles were set spanwi se a long t he top to r e pre sent
the stringer s Ul1dAr the she et aluminmn wing cover. and strap s under the bottom
oi the t ank held it snugly up against these stringers. VFn ticaI members
beJcween the top and bottom frames located the t ank si dewise, and endwise.
The location of the supporting straps on both t anks and the points at which
t~~ s e supporting strap s were attached to the fixture s holding the t anks were
similar to the actua l insta llat ions. The fixture s holding the t anks were
mounted on the whirling arm so that the resultant force acted in t he proper
di r ection with r e f er ence to the thrust axis of the airplane . In both tests
t he t anks wer e vented to the atmosphere and no constraint wa s pla ced on the
fl apper va lve a ction.
Defl e ctions we r e mea sured at the chosen points on the bottom surfaces
of t he t anks by wire scratch pointers. These pointers were attached t o the
t ank by airplane model cement and stood perpendicular to the surfa ce • The
end of the pointer was rounded off and bent at right angle s so as to scratch
on a waxed pape r t ape mounted on a separate wood frame close to the t ank. In
thi s manne r the movement of a given point on the tank surface during the t est
run was r ecorded.
In making the t est runs, the empty t ank was first located properly in its
mount on the structural framework. The wire pointers were then cemented to
t he t ank a t the proper points, and strips of waxed paper were mounted opposite
to the wire pointers on a separate wooden framework. Zero marks were made
on t he t ape s while the tank wa s still empty. It was then fill ed and t he t est
run accomplished. Since from the force diagrams of figure l the downward
gr avitational acceleration was utilized in conjunction with a oentrifugal
acce l er ation, the deflections in all cases wer e measured from the original
zero marks made while the tank was standing empty on the whirling a rm~
The Daneil C-ugcanhe"t1 A:: rship Institute
Ak.r en ... . • 0 !rt o
·r:t.e f.:tr 3t ~ P SG o·J.1 thP rear wing tank was run on June 0 aDi' : e suJte d in
ia:L;.1.rru 01' 211c.. of' the f i tti n gs u s e cl to fasten the hold d nwn s·craps ti the
box fTarr10 , ;:r:-1:i :.o f ittine; was not a standard part for t he ti::.~:i.k ins t a::. l ation.)
8i nr-e t h.J. :-; t e s t r uu gave f; xagge rated deflection measureTllents d.1 .. ::;. t o ·che slackf'>
nir..g 0f 0ne hu ~ d c.own st ra:~; ~ a new fitting wa s made t.p and t :le · ~ c.:; ~-t re-run on
~i-w:1c 4 . Ho fa.iLure occurr0d on this second test.
The fuse l si.ge t ank wa s t E; sted on June 8.
1'5 ...;t ::1e sults
Measu r er.:.ents of the d8;Jections obtained in the fu c-e l P.ge ·~ a.::k te st are
g,i -.:•on i .a 'l'a"f:>::i.e l, l'he dE: f :..e c ~ i o ns measured from t he r e1:..r ·king tt-..nk: tests are
g,i -:r0:i.1 in 'IaYi .. 0 :LI In all :rnstu.:a ce s, the defloctio:"ls l i ste d i n t t e t ables
n. r ·~: a.:,rmcJ . ·c0 ~he tank sn r i'3.ce o.t t he pa rticula r po i nt ~ Defl e cti cns a re
c o1 ... ~ ·i..:.... e r t; cl. iJO s::.. -:-i VP, if t t e ~:: a nk wall moves outward, cir 8"'"..'i"J..Y from t ~1 e center
cf t'1t; ~ t'l r· 'c{, 1x rid nc gativE. ;__:·the t ank wall move s inwe.r<l or towarr.. the center
cf ~ t 8 fusela ge t ank
"' i gu r e 5 sho-Ns ·che contour a long the bottom c en t er li~ur_l e. r ·che 12 g
doy,nwc..rd loa ding. The def l e ctions are plotted to t he G81lla sca l 0 c..s the tank
is s:'.1.own. The maximum de flection occurs at the base o:i.' the suml-J fitting.
T';.:•.2 is undoubtedly due to the 11 1/2 •. inclination of 1.-he tank ·;ri th respect
t .J t:ie thrust axis, which results in a greater fluid h8c.J a t this bottom corner of
t ~ ; o ·sank.
Figure 6 is a similar diagram, showing the contour of the bottom of the
r :: ur wing t ank along a spanwi se cente r line. The maximum deflect ion occur a>
n ~. t u.t. -~he ce:..1t e r of the t ank , but be twe en two outer straps.
M. E. Long
July, 1943
Po :~nt =#=
l
(.
3
4
5
6
7
8
9
10
11
12
13
Table I
Daniel ~uggcnhe im Airship Institute
Akrcn .• Ohio
Fi r e stone P-40 Fuselage Tank
12 g down loa.d
Defl e ot ~_ on lj'ormal to Tn.nlc wall, inohe So
+0.52
0.12
'0,;97
1.28
o.78
0,79
1.56
o.40
0 . 87
0.82
0.47
0.11
1.04
Poir.t 'ff
1
2
3
4
5
6
7
8
9
ThG Daniel GuggenhGim Airship Institute
Akror: , Ohio
Table II
Fire stone P-40 Rear Wing Tank
12 g down load
DeflGction Normal to Tank Wall, inchGsQ
+l,18
1,56
i.02
1.19
1.30
0,96
1.44
1.91
1.06
F<J.SEL,t:/(7£ MNX
SPEC'D oF RorATION '/0·9RPM
Ce-,yr: Ac(. ~ w~R i
: r~:·9xzrr) 16·'/
-- .300 Fr. I .2. 1 .sec.
DANIEL GUGGENHEIM
AIRSHIP INSTITUTE
AKRON, OHIO
9.35 . CENT. Acc. r:
rr~~~;;~6S·/~·==J , , o..f~AV. 9·1.f Res. ~cc. Ace.
83·'1" / -= ,.35 J
~i----------1~ '-s"--------~
(...).. . "~
~
W1Nt; TANK
SPEED OF RoTATIQN L/0·6 RPM
lEN7. Acc. =- w:z.R
x
= {~0~6 x 21r} x 16·7
= 300•5 FT-/.SEC. Z.
:- 9·35 9
90°
~-----u,'- a~"
Fiq../ /1CC£LERATION D1~<:;RAMS FOR IZj DowN loAD
Nor£: 9-'11. ACClflERArtoN o,: TANK Fill.ED w1r11 WEITER
fSP. wr. 833 #/GAL.) IS EQt.JIVALENT ro IZ'j· ~cCELEl(ATt<JN
OF TANK Flt-1.ED WITH AVl,tJTJ(JN (jASOLINE fSP.WT- 6-s#/t;Pll)
Fig.2: Photograph showing fuselage tank installed on whirling arm
for 12 g down load test.
.. '
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·,..
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• ·.' .... ,,.,
·-4-· ~I ·.I
'
. ·-4·
•
·.~
t
'-r ~nheim Airship Institute
lcron, Ohio
Fig. 3. Diagram sholrl.ng points at whioh deflections were
. measured on bottom ot fue-el~,,e tank . .
.f
. ..
'.
•
f
15z•- "~
0
a Si----. .... ----
1 •
-()
-- • 5 1--.---s
-()
--:._.=b::: -.....= :....: __ L-~-
Fig. 4. Diagram showing points at which deflections were
measured on bottom of rear win~ tank.
•
~ I;' ") ...
;, ,,
..
,,
. I
~·
.,
·,
,, .,.- - ;'.~ . ' ... ..
>
~ .
I
t- : • l.
·'
•,1 .-
,.l
' ·
t( ... \
,1
··'
..... -- ... ..
c'
t.'.f ••
. ' ...
;.
';.',•.
,,
. ·'
, .
.. .
,,., ..
'.f'.
Fig..
"
·,.
,.
.......
-.
-·
,.
.•
- - "°-- - --o- - . _:...-~-
....._... --- I • -- -- __.o- -~~- --
·:. ' ·~ . '
Outllne~ diagram . showing defleO"tion along bott.om £,of tank
under 12g down load... tank and. defleotions a.r'3 to . same
..Scale .. ·'·
o.5 am. l"
Firestone Fuselage T&Xlk
' ' ........
......... --o- - -- -- - .......... ---- --- --o-- -- --- -
........ ---- --0-
Fig. 6. Outline diagram throur.h chordwise £ showing deflection of
~ otto~ tanv surface under 12g cown load. Tank an<l deflection
are , to same scale, 0.5 cm al"
Firesto~e Rear Winr, Tank
-
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