ARUORSD MEDICAL RESEARCH LABORATORY Fort Knooc, Kentucky

D D C

^ SEP 2 8 1967 |

Project No. 45 B SPUEA 724-i*l ■ 31 July 1945

1, PROJECTt No. 45, Operational and Phyoiological Characteristics of the ank 12653,(^26), Final Report, Subject: Study of the Proposed Relocation of • 1000 cfta Tank Ventilating Blower to the Turret Bulge.

Ä a. Authorityi Letter AGF, File 470.8, dated 1? July 1944, GKRQT-6/91272.

* . . b. Purpose! To determine the suitability of relocating the 1000 cfm QQwntilating fan in the turret bulge.

iO 2. DISCUSS ION I

vO Limitations hnve been Imposed on the Heavy Tank, 1126 by the adoption of

a the present location of the 1000 cfm tank ventilating blower in the bow. Among these arei ballistically weakened front plate, vision obstruction for the driver '

< and bog, vulnerability to mud, rain, snow, water splash from fording, excessive 'noise, and direct air blast on bow crew members. Investigation of other possible positions indicted that a blower of similar size and capacity could be installed at the rear of the turret bulge. The details of tests to determine the suitability of relocating the blower are contained in the Appendix.

3. CONCLUSIONSt

a. Relocation of the 1000 cfm axial flow tank ventilatLig blower to the turret bulge position will provides

(1) Adequate ^un fume removal from the fighting compartment.

(2) High but tolerable dust conditions within the fighting compart- ment provided fenders and sand shields remain on vehicle and provided vehicle does not follow closely behind another vehicle on a heavy dust-covered terrain.

(3) Reduced air blast on crew members,

b. Blower will not provide satisfactory air movement to remove moisture and heat from bow compartment when vehicle is buttoned up in hot, numid climates.

c. Blower noise level la excessive when tank is static .ry and engine is Idling or not operating. Blower noise level, when blower is covered by dis- charge duct system, is annoying but still below that of the tank noiee level wher the vehicle is in operation. With the discharge duct removed noise level is excessive.

d. A potential carbon monoxide hazard results fror the proximity of the turret bulge blower armored intake to the auxiliary generator engine exhaust

Outlet, I Thin aommotxi h,os boor £■> >.'C-vGd for ODV^

CLEARINGHOUSE

• • Power consumption is high, but no greater than the power oonsumption of the bow blower*

f. That, with regard to factors tested, the turret bulge location of the 1000 ofta blower is as satisfactory as the present bow location*

I», RECOllfflNDATIONSl

a* That if the 1000 cfm tank ventilating blower is relocated to the turret bulge position in future production U26 tanks I

(1) A recirculating fan be located in the bow for additional air movement«

(2) An improved armored intake be designed and produced to give reduced resistance to air flow, either by the addition of turn* ing vanes, improved air flow turns, or both*

(3) An improved discharge duct be designed to provide mlnlmia resistance to airflow*

(4) . Development be continued on a dust filter to reduce the dust concentration in the vehicle fighting compartment*

(5) Development be instigated to reduce the noise level of the axial flow blower«

(6) Adequate diversion of the auxiliary generator exhaust gases be accomplished to prevent entry into the fighting compartment,

NOTSi Concurred in by Armored Board and Hqs. Armored Center with following additional

recommendationsi

That the 1000 cfm blower be relocated to the turret bulge in the Heavy Tank, U26, at the earliest possible date*

If the 1000 cfm blower is to be retained in the Heavy Tanks, T29 and T30, recommend consideration be given to relocation of these blowers for the same reasons set forth in Paragraph 2 of the attached report*

Submitted byt Robert H* Walpole, Captain, FA Norton Nelson, Uajor, SnC Edward D, Palmes, 2nd Lt., SnC

APPROVED Ut/Uuf U/a^cA WILLARD UACHLE Colonel, iledical Corps Comaanding

3 Incls* |1 - Appendix w/table 2 #2 - Tables 1.3,4,5,6 #3 • Figures 1 • 4

APPENDIX

The following teats were conducted to determine the suitability of relocat- ing the 1000 cfm axial flow tank ventilating blower from present production location In the bow to a new, proposed position, mounted horizontally, at the rear of the turret bulge. The desirability of the relocation Is a result of limitations imposed by the location of present blower equipment; namely, vision obstruction for the driver and bog due to the elevation of the armored air Intake; ballistic weakening of the casting; vulnerability as to the pickup of mud, rain, enow, and water splash from fording; excessive noise at the ear level of bow orew members; and direct high velocity air blast on the driver and bog.

Tests have been conducted on the turret and bow blowers which permit comparison with regard to air flow quantities, dust, noise, power, and gun fume removal« Details are listed below.

The subject blower Is the axial flow type, manufactured by American Air Filter Company, Louisville, Kentucky, designed to produce 1000 cfm at a minimum voltage of 2U volts against 1.4 Inches static positive pressure plus the resistance of the bow armored air intake. The standard blower housing was reduced in length to 7-7/3", placed In a triangular frame and mounted In the turret bulge in a horizontal plane. See Figure 4. For test purposes a box was constructed to surround the blower, diverting thi air flow downward and through a duct built approximately one (1) inch above the easting floor, the full width of the bulge, channeling the air forward. On the bulge exterior there was a wooden mockup of an armored intake, directing the air vertically up to the blower«

The bow blower is of the same type, a pilot model for present production blowers, designed to supply the same volume flow as the turret blower under Iden- tical conditions.

JUOi /

AIR VOLUME, POWER, SPEED UEA3UREUENTS

PROCEDUREt

Air volume flow measurements wer« made on the turret bulge blower to determine its capacity under varying conditions and as a comparison with the bow blower.

To measurs the air volume of the turret blower the armored inlet was removed i] and replaced by an 18 foot length of ton (10) inch diameter straight pipe,, the center of which contained a six (6) inch diameter sharp edge orifice with proper '] pressure take-off nipples« A water U-gauge was attached to the nipples to measure the pressure drop »cross the orifice, which In turn was calibrated for air . | flow, using the equation! \ j

where Q s Air volume, cfm C ■ Orifice coefficient, • 0*61 R r Dj/Di D^-a Pipe diameter, ft* Dj ■ Orifice diamoter, ft, T z Mjr temperature, 0F, Abs h * Pressure drop, inches H2O b - Barometric pressure, mm. Hg.

The tank static pressure was measured with a U-gauge.

By controlling the intake area of the pipe, various air volumes were obtained« This was done for a variety of conditions; i.e., tank open^ tank closed breech open, tank dosed breech closed, etc« In this way air flow versus tank positive static pressure measurements were secured«

y&H

T!

Hi

These data were plotted on double logarithmic graph paper yielding a straight line curve« The inlet pipe and orifice were then replaced by the armored inlet and tl a tank static pressure measurement was made and plotted on the same curve« The corresponding approximate air flow was thus determined for this condition«

The air flow from the bow blower was determined in a similar manner» The conditions measured were tank open and closed, blower discharge duct installed and removed, breech open and closed« The data are illustrated in Table 1«

Power input was calculated from current and voltage measured at the supply line near the turret blower switch« A calibrated stroboscope was used for meaaur- ' ing the blower speed« Several conditions were measured which are elso listed on Table 1«

V; Pressure loss due to the resistance of the armored inlet and the discharge \

duct system were measured (see Fig. k) to illustrate the cost of reduced sir flow !|

1

^1

with the restricted discharge* These data are given in Table 2«

Using a themal-anemometer, air movement measurements were taken at the head-shoulder, waist, and ankle-leg location for each of the crew member positions under different tank conditions. The data are presented In Table 3.

RESULTS >'

Ueasurements of air volume flow conditions with the turret-bulge blower when the discharge duct is in place indicate a reduction in quantity below that of a free discharge« This is to be expected due to the air direction change and restriction with resulting pressure loss. The air flow under these conditions, however, can be increased by an improved duct system design.

i TABLS 2

PRESSURE LOSS l/EASUREMKNTS OP TURRET ARUORED INLET AND BLOWER DISCHARGE DUCT

1 POSITION MEASURED -STATIC PRESSURE INCHES H2O ,

i (See Figure U for location) | Tank Open Xank Buttoned Up 1

| P^ - Armored Inlet

j ?2 " Side of Blower ! ™ Boac Enclosure

P^ - Flat Exhaust | Duct Near Box

1 P. - Plat Exhaust Duct Near Opening |

' 0.55»•■

1.57»

0.67»

0.55»

0.30»

0.51»

0.2?» j

^1 ^ I'2""Blower Equipment i 2.12* Resistance |

1,64" i

In spite of the airflow reduction the tank positive pressure is adequate for gun fume removal*

Power requirements are high but are to be expected for this air flow quantity delivered with a small blower operating against these pressures. Reduction in power input can be secured only by an increase in the blower size; this is diffi- cult because of the space limitation.

Air movement in the bow, particularly when the turret is reversed for travel- ing, is too low. Some additional means of air movement are required for maintain- ing the efficiency of the crew members in the bow for operation in hot, humid climates. This may be accomplished by increasing the capacity of the present hot- water heater fan with directional vanes or by the addition of one or more efficient propeller-type fans. The conditions in the turret are satisfactory, and the location of the air discharge at knee level, rather than on the shoulders, as with the present bow fan, is particularly desirable for cold weather operation.

3c*U.H

:1

QUM FUME REMOVAL

PROCEDUREI

Gun fume trials were run on a T2521 tank (hull and turret conditions similar to U-26) blower of nominal 1000 ofm capacity! and with the proposed turret fan of nominal 1000 ofm capacity. Data were collected on three days (3, kt and 6 July 1945)«

CO concentrations were determined simultaneously by the N.D.R.C, Infra-red Gas Analyzer and the U.S.A. CO Indicator. Since virtually identical results were secured by the two methods only the N.D.R.C. Gas Analyzer results are reported. <

The turret was sampled at the loader's position, and the bow was sampled at the assistant driver's position. Sampling time was five minutes for each 5 rounds ,' of 90 nan ammunition or each 250 rounds (l belt) of .30 oal. machine gun aLjiunltion. !

Zero test time was the time of firing the first round in either case. When several bursts or belts were fired they were fired at 5 minute intervals. J

■ -I:

Sin a the Intake for the turret fan is very close to the main and auxiliary A engine exhiuat outlets, tests were run to determine CO pickup from these sources while no gun was fired. i!

H

To produce more severe conditions, the M-l muzzle plug was used in several of the tests on both the bow and the coaxial machine gun. The U-l muzzle plug gave i higher CO concentrations than the 0.718 muzzle plug in previous tests (Armored '; ,, liedlcal Research Laboratory, Final Report on Project No. UU - The Physiological and j Operational Characteristics of M-2i* Tank, dated 8 November 1944). Since the air 1 stream from the turret blower is directed toward the bow when the turret Is in j firing position, one test was run while the turret was in traveling position during t firing of the bow machine gun. On all other tests the turret was in firing position» i Static pressure in the turret was measured by means of an Alnor Velonster. Test | condition« and results are shown in Table 4« I

RESULTS! | , 'i

Wh m the turret blower was used while running the main or auxiliary engines, ; no carbon monoxide was detected (see Table 4). However, there was a strong exhaust fume odor in the turret while running the auxiliary generator and it is to be anticipated that, with poorly adjusted motor and/or adverse wind conditions, a GO j hazard will develop from this source.

As shown by the data in Table 4, the CO concentrations were satisfactorily low I (0.05Ü6 permissible for one-half hour) using the turret fan while firing the 90 mm * rifle, the coaxial .30 cal. machine gun, and the «30 cal. bow machine gun. No sig- nificant increase in CO concentration was noted in the bow while firing the bow machine gun with the turret in the traveling position, using the turret blower* \\

V\ The bow fan gave satisfactorily low results on all except one test in which V

the turret was sampled while firing the .30 cal. coaxial machine gun with the U-l muzzle plug. This confirms previous tests (Armored Uedlcal Research Laboratory, First Partial Report on Project No. 41 - Physiological Characteristics of the T25S1- T26E1 Tank. Subjects Control of Gun Fume Hazard, dated 19 July 19A4). N

-. ■..■.■. . . ,. -. _. . .-...,■ ...—, -i

.I1

Th« propoMd turret blow«r i" "a satiafaotory for the removal of gun fumec from the turret and bow of the l -n the bow blower, and according to the standards of this Laboratoigr* is accvrbable from the standpoint of gun funs reaoral«

JU^.-*/

OUST

PROCEDURSt

Dust concentrations ware measured under varying conditions «1th comparisons being made between the bow and turret bulge blower under approximately similar dust conditions. Dust was sampled with an U.S.A. Midget Implnger Apparatus at both a bow position (bog) and in the turret (loader) at the breathing level.

A driving course 0*90 miles long was laid out over an unvegltated clay terrain with reference to the prevailing wind to allow a maximum of driving up or down wind. The dust condition of the course would be considered severe in terms of normal tank operation.

Tests were broken into two groups, (a) test vehicle operating 10-20 yards behind a leading 1(26 Heavy tank and (b) test vehicle operating alone. Test speeds were 6-10 mph* In test (b) sand shields alone then, in addition to front fenders were removed to measure their benefit on dust reduction. Average wind velocity oeasuremsnts «ere made during the above tests.

Moving pictures and still photographs were taken of an U26 Heavy tank with and without fenders and sand shields to observe the dust pattern about the hull and turret.

RESULTSi

Oust concentrations in all positions measured in tests (a) were excessive, more so with the turret bulge blower than with the bow blower (see Table 5). In comparative tests, with the gun in rear or forward positions, the bow location.wass the more satiofactory of the two inlet positions. During these tests the wind velocity was 6-10 mph. In actual practice it is doubtful if vehicles could travel so closely behind one another for safety reasons and because of the danger of clog- ging the engine oil filter.

Tests JA and rB in group (b) were repeated on the second day of test operation " when a lower wind velocity prevailed. The first teat serves to Illustrate the con- dition arising with a strong wind blowing over an extremely dusty terrain. Tests 5A through 7B made on 12 July show entirely satisfactory conditions with the turret bulge blower equivalent to the bow blower. Removing the sand shield and .front fenders Increases the dust concentration in the vehicle from k to 10 times the value for the same positions with the shields and fenders installed. This is an excellent illustration for the requirement of sand shields and fenders, durable enough to remain intact through the hazards of normal tank employmsnt.

Figures 1 through 3 attempt to show the dust pattern about the moving vehicle for a variety of conditions. These Include movement In opposite directions, fenders and saod shields installed, sand shields only removed, front fenders and sand shields removed. Visual, observation, substantiated by notion pictures taken froa a 20 foot

JU^. #/

height looking angularly down, show the dust pattern of the moving vehicle to be heavier at the engine air intake than at the bow« Thia ia partially due to the negative pressure created at that point of air intake and partially because of air pattern of the ooving vehicle» In any event the turret bulge blower intake ie ■ore apt to be vulnerable to a dusty atmosphere than the bow blower intake.

With either blower operating there it a definite requirement for an adequate duet filter.

i

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5Ue^. #/

MOISS

PROCEDURE I - ■" ' — i

Noise level measurements were made at ear level of all crew positions, and at the face of a simulated radio in the test vehicle with the turret bulge blower ■: on and Off, under a series of conditions, moving and stationary. MeasuremenU were also made for comparison on the bow blower« i

A General Radio Company Sound Level Meter No. 759 with a microphone extension was used for obtaining the noise level values« The mean'value rfhown in Table U for the noise level represent» the average of several readings varying over a rang» of approximately 5 Db.

RESULTSt :

Noise level intensity of the blowers operating without baffling Is objectionably high (pee T&b. 6), particularly because of the high frequency sound range. With ear | phones the noise is tolerable althoußh extremely unpleasant. The influence of enclos- ing the turret bulge blower with the discharge duct system is to lower the intensity 1 10-15 Db. The noise level of the enclosed turret blower is exceeded only by the , ' noise of the vehicle operating on a concrete road at 10 mph. Even in tho»» »ituation» 1 wh»re the tank noise» are of great»r intensity than the blower, the higher frequency ; d^-the latter »till add» to the confusing din for the tank crew member». -j

A »eriou» »ffort »hould b» mad» to r»duc» the noi»» lev»l of tank Yentilating

blower» • . • ^v-.. -

8

TABLE 1

AIR VOLUME, TANK S.P,, POWER, SPEED UEASURaiENTS

8 S I

MO

X H o pi 1^^ a s

J3 (S

M o M MX

O

M

PL,

• o as

Pa

CO

^ h Turret

Turret

Bow

Turret

On

On

On

On

Closed

Closed

Closed

Open

Closed

Closed

Closed

Open

M o en

X o o o (0 Q

Orifice in Duct

Armored Inlet

Block

Orifice

C

L

0

s E

D

2.45

2.80

800

820

910

860

1.26

1.30

1.54

NOT

USASURSO

Turret

Turret

Bow

On

On

On

Closed

Closed

Closed

Closed

Closed

Closed

On

On

Orifice in Duct

Armored Inlet

Block

0

P

E

N

2.52 820

860

950

1.10

1.15

1.32

NOT

MEASURED

Turret

Turret

Turret

On

On

On

Closed

Closed

Dpen

Closed

Closed

Open

None

None

None

Orifice in Duct

Armored Inlet

Orifice In Duct

C

L

0 S E

2.99

3.85

880

1020

1000

1.65

2.09

41.0

20.5

40.5

27.5

28.5

28.0

1128

1155

1135

6125

6200

6200

Turret

Turret

Bow

On

On

On

Closed

Closed

Closed

Closed

Closed

Closed

None

None

Orifice in Duct

Armored Inlet

0

P

S

N

3.19 910

960

970

1.30

1.34

1.38

40.0 28.5 1140 6150

NOT MEASURED

Turret

Turret

Off

On

0

0

26.0

28.0

NOTSt All test! conducted with vehicle stationary, engine off.

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TABUS k i

oas Ptarn REMOVAL DATA

OFT TEST NO. g ä

B Ö a 8 « 1?

«

p

1^. I ft, o

a 0

§

9

NO FIRING

U 2A

0 0

0 0

Nona n

Off Cn

Cn Off

Turret Turret »

0.70 0.73

.000

.000

PIRIN0 90 MM RIFLE

5A U* 6A 7A 7B 5D

2 2 2 2 2 2

9 8

10 10 10 10

None Comm,

n n

None Coroni.

Off On Off cn

n n ■

Turret N

n Bow

Turret n n

Bow Turret

0.60 0.02 0.02 0.01 1.55 0.03

.031

.028

.032

.022

.023

.007

FIHINa .30 CAL. B0VT MACHINE GIH Loader i Comm None Comm.

8A 2B IB IC»

.718 M-l M-l M-l

2 2 2 2

500 500 500 500

Off n n H

Oa N

n n

Turret Bow n if

n

0.01

0.02

.009

.001

.014

.020

FIRING .30 CAL. COAXIAL MACHINE GON

5C UG 3C 7C

.718 2 500 Comm« Off On Turret Turret] M-l 1 250 None M H n n

M-l 2 500 Comm. n n N H

M-l 1 250 N N H Bow n

0.01 0.90 0.01 0.01

.010

.032

.020

.074

♦ Turret In travelling poeition on thla teat only.

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Dual Pattern for HN17 Tank, IC26 with Fandara and Sand Shlalda

ARMORED MEDICAL RESEARCH LABORATORY Tip,r. X. Proj.ct fe. 45 *">*• " • J<dj.

Duo t Pat tam fop Haavy Tank, *Cfc without Front Fandara and Sand Shialda

ARMORED MEDICAL RESEARCH LABORATORY P l g u r a 3 , P r o j e c t Ho. US K>«T KNOX, KY. July, 1945