DEFENSE DOCUMENTATION CENTER DEFENSE SUPPLY AGENCY

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1 1p~0^3<B UNCLASSIFIED ADEQUATE HEAD ROOM IN TANKS Medcal Research Laboratory Fort Knox, Kentucky 27 November 1942 AD Processed for... DEFENSE DOCUMENTATION CENTER DEFENSE SUPPLY AGENCY y^h FOR FEDERAL SCIENTIFIC AND TECHNICAL INFORMATION U. S. DEPARTMENT OF COMMERCE / NATIONAL BUREAU OF STANDARDS / INSTITUTE FOR APPLIED TECHNOLOGY UNCLASSIFIED

2 . NOTICE TO DEFENSE DOCUMENTATION CENTER USERS Ths document s beng dstrbuted by the Clearnghouse for Federal Scentfc and Techncal Informaton, Department of Commerce, for the Defense Documentaton Center, Department of Defense. As a result of an agreement between the Departments of Defense and Commerce, the Clearnghouse dstrbutes to DDC users unclassfed unlmted AD documents that have been announced n the Clearnghouse journal, U.S. GOVERNMENT RESEARCH AND DEVELOPMENT REPORTS. The prce does not apply for regstered users of the DDC servces.

3 ? /«tfroject No. P5-1 ^le No,. 7a *0 so Q x - PROJF T: ARMORED FORCE MEDICAL RESEARCH LABORATORY Offce of the Commandng Offcer Fort Knox, Kentucky ADEQUATE HEAD ROOM IN TANKS Adequate Head Room n Tanks. November 27, 1942 a. Authorty - Letter, Commandng General, Headquarters Armored Force, Fort Knox, Kentucky, /6 GNOHD, dated September 24, r b. Purpose - To determne the sttng heghts of Armored Force personnel and to compare these wth exstng head clearances n tanks. Sttng posture s a sgnfcant factor n fatgue* 2. DISCUSSION: a. The sttng heghts of 541 men from the 1st Battalon, Armored Force Replacement Tranng Center were measured wth the men sttng erect on a flat table. Attached hstogram (nclusons I & II) gves the actual dstrbuton. Statstcal analyss shows ths group to be an adequate sample from whch to draw conclusons. b. The thckness of the crash helmet at the vertex was determned and found to vary, dependng upon the helmet desgn, from one-half ( ) to one and one-half (l ) nches,, c_. The maxmal dstance between the cushon of tank seats and the overhead closed hatch or armor plate has been called net head room. See attached ncluson III. d. The heght of each man s ncreased by the dstance from the,top of hs head to the top of hs helmet. There s a slght and varable compresson of the seat cushons. There s an ndetermnate stoop n each ndvdual whch wll tend to decrease the space needed for hm. However, he must st nearly erect to operate hs perscope effcently. The vertcal adjustablty of the perscope s small, the range of men's heghts relatvely larger; therefore, vertcal seat moblty should be such as to make t possble for all szes of men to adjust themselves comfortably to ther perscopes and stll not be t touchng the roof of the tank. > ;. n has been eppvov!,. av nod rate; «IJO" n I 'MH Reproduced by the CLEARINGHOUSE for Federal Scentfc & Techncal Informaton Sprngfeld Va D D C BfHlTJn.prrr ~< "tp?tf 1967!!! jj

4 3. CONCLUSIONS: a. The range of sttng heghts of 541 solders taken at random from the Armored Force Replacement Tranng Center, 1st Battalon, s from 32^ nches to 40-3/4 nches. b. The mean sttng heght s nches.. Approxmately one and one-half (l ) nches s added to ths heght n each nstance by the crash helmet. d. Incluson IV shows the avalable seat space n the drver's compartment of the M-5 lght tank. It has been determned that the tank can be drven satsfactorly f the maxmum requred head room s made avalable. A major change n seat desgn s necessary to effect ths change. Incluson IV also ndcates the poston and heght adjustablty requred n such a redesgned seat. e. Improper seat heghts result n cramped postons, ncreased fatgue and decrease the combat effcency of men. f. Incluson VII shows the per cent of men accommodated by varyng degrees of head clearance both wth and wthout crash helmets of 1%" thckness. Recent reports ndcate that the helmet s perhaps unnecessary. The Armored Force Board s testng a helmet of consderably less thckness.. An 8" adjustment s requred to cover the total range of subjects n ether the hgh or the low poston, wth or wthout helmet. h. Forward and backward adjustment should be retaned.. The feature of a two-poston change s good snce t requres a mnmum of tme n changng from the "open" to the "buttoned up" poston. Addtonal adjustment to ft the ndvdual s also requred. J_. Snce the hgh and low ranges overlap (see ncluson IV) t mght be ^possble to nstall an adjustng arrangement smlar to that n the turret seats of the new M-5 lght tanks whch moves thru the total range by small ncrements. A. RECOMMENDATIONSt a. These basc data be passed on to the Dvson of Tank Desgn, and Ordnance Department, wth the recommendaton that proper seat heghts be provded n all future models. b. That tank manufacturers be requested through proper channels to provde adequate clearance for men n the seats of new tanks now n producton.» - 2 -

5 c. That the degree of elevaton and lowerng of the seats be related to the known facts about the sttng heghts of men here ncluded. d. That tank seat desgn be facltated by excludng from all future tank crews the upper and lower 52> of men. The resultant acceptable range of sttng heghts then becomes 3k n to 38 ". The excluson of 10^ of men results n dmnshng the requrement for seat vertcal adjustablty at ether the hgh or low poston of 505&. e. Recommend that the Dvson of Tank Desgn, Ordnance Department, and the Armored Force Medcal Research Laboratory collaborate n the desgn of proper seats to replace those whch do not permt adequate headroom n exstng tanks. It s apparent that such an alteraton cannot readly be made n the feld and the practcablty of makng a substtute seat should be serously consdered. 7 Inclusons Reported by Captan W. F. Ashe Captan L. B. Roberts Major E. A. Blar APPROVED U/^^ ^d^ HILLARD MACHLE, Lt. Col., Medcal Corps Drector of Research - 3 -

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7 j "" '.!] j mjcmsdn u!)'! ^ Sttng Heght Data Inches Percentle Number of Men % of Total Dstrbuton ' * _ t

8 -.INCLUSION III < NET HEAD ROOM Poston M - 5 Lfht M-4 A-2 Medum M-4 A-3 Medum - M-4 A-4 Medum Drver - Lowered 35* 36 n\ 35-7/8 Ass't. Drver - Low 35* /8 36* Tank Comd'r. - Low /8 40-3/4 40* Gunner - Lowered 37-3/4 40* 37 Gunner - Rased 34* 40* 34 Leader 35* 34-7/8-38* 35* Leader - Lowered 33* Loader - Rased 25

9 Lj/7<5 Crf S/'j6t - /7<7^c/7 of&/7-2 > >or?a& r-/a?&&- & V tf<jh acfj'us'no reo/on < r ^ *; v. \ V_ Zl o^/ adjustncj rcf/on < Tank f/oof M-3 L/GHT TAMK: v. //JCLUSJOAJ JY

10 L//7& a/ /ouses "front obs-rtjetjo/7 -f7& cfr ope/7 fl 0= ">, /c7/?/c hor-. M-3 L/Q/-/T TAAJK: //UCLU^/OAJ ~%T

11 m UL ^^*" ^Lowest p*//7 above head «1 ' / ' ' ; j' T H4+t fc*- -/SI TanK /Ioar L M-5 L/GHT TAA/A? /,,*..,-,_

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