Armored Medical Research Laboratory Fort Knox, Kentucky Final Report On PROJECT jJQ, 5 - Operational and Physiological Characteristics the Tank T26E3, (M26) SUBJECT: STUDY OF THE PROPOSED RELOCATION OF THE 1000 CFM TANK VENTILATING BLOWER TO THE TURRET BULGE Project No. 45 31 July 1945 AKLGR4D MdDICAL RESEARCH LABORATORY Fort Knox, Kentucky Project No, 45 SPESA 724-41 31 July 1945 1. I ROJLGT: No, 45 > Operational and Physiological Characteristics of the Tank T26£3, (l*26), Final Report. Subject: Study of the Proposed Relocation of the 1000 cfm Tank Ventilating Blower to the Turret Bulge, a. Authority: Letter AGF, File 470,8, dated 1? July 1944, GKRh.T-6/91272, b. Purpose: To determine the suitability of relocating the 10C0 cfm ventilating fan in the turret bulge, 2. DISCUSSION: Limitations have been imposed on the Heavy Tank, LI26 by the adoption of the present location of the 1000 cfm tank ventilating blower in the bow. Among these are: 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 indicated 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. CONCLUSIONS: a. Relocation of the 1000 cfm axial flow tank ventilating blower to the turret bulge ]osition will provide: (1) Adequate gun 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, humid climates, c. Blower noise level is excessive when tank is stationary 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 noise level when the vehicle is in operation, .»ith the discharge duct removed noise level is excessive. d. A potential carbon monoxide hazard results fron the proxii it;* of the turret bulge blower armored intake to the auxiliary generator engine exhaust outlet. e, Power consumption is high, but no greater than the power consumption of the bow blower. f. That, with regard to factors tested, the turret bulge location of th 1000 cfm blower is as satisfactory as the present bow location. 4. RECOMMENDATIONS: a. That if the 1000 cfm tank ventilating blower is relocated to the turret bulge position in future production 1126 tanks: (1) A recirculating fan be located in the bow for additional air movement• (2) An improved armored intake bo designed and produced to -ive 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 minimum resistance to airflow, (4) Development be continued on a dust filter to reduce the lust concentration in the vehicle fighting compartment. ($) 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, MOTE: Concurred in by Armored Board and Hqs. Armored Center with following aduitionil recommendations; That the 1000 cfm blower be relocated to the turret bulge in the Heavy Tank, M26, 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 by: Robert H, Walpole, Captain, FA Morton Nelson, Major, SnC Edward D, Palmes, 2nd Lt., SnC APPROVED^ WILLARD liACHLE Colonel, Medical Corps Commanding 3 Incls. #1 - Appendix w/table 2 rf2 - Tables 1,3 ,4,3,6 $3 - Figures 1-4 2 APPENDIX The following tests were conducted to determine the suitability of relocat- ing the 1CC0 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, snow, and water splash from fording; excessive noise at the ear level of bow crew 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 24 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 7-7/8”, 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 the air flow downward and through a duct built approximately one (l) inch above the casting 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. AIR V0LU13, POWiSR, LU^SURilliKTS FROG SPURS; Air volume flow measurements were made on the turret bulge blower to determine its capacity under varying conditions and as a comparison with the bow blower. To measure the air volume of the turret blower the armored inlet was removed and replaced by an 18 foot length of ten (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 across the orifice, which in turn was calibrated for air flow, using the equation: x V Th/b V i _ rA where Q = Air volume, cfm C s Orifice coefficient, m 0,61 R - D2/D1 s Pipe diameter, ft, I>2 « Orifice diameter, ft. T - Air temperature, °F, Abs h r Pressure drop, inches H2C b - Barometric pressure, ram. 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 closed breech closed, etc. In this way air flow versus tank positive static pressure measurements were secured. 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 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 measur- ing the blower speed. Several conditions were measured which are also listed on Table 1. Pressure loss due to the resistance of the armored inlet and the discharge duct system were measured (see Fig, U) to illustrate the cost of reduced air ilow with the restricted discharge. These data are given in Table 2. Using a thermal-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: Measurements 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. TABUS 2 PRESSURE LOSS MEASUREMENTS OF TURRET ARMORED INLET AND BLOWER DISCHARGE DUCT POSITION MEASURED STATIC PRESSURE INCHES H2O (See Figure 4 for location) Tank Open Tank Buttoned Up - Armored Inlet 0.55" 0.30" Pp - Side of Blower Box Enclosure 1*57” 1.34" - Flat Exhaust Duct Near Box 0.67" 0.51" P; - Flat Exhaust Duct Near Opening 0.55" 0.27" P-. -f Po " Blower Equipment Resistance 2.12" 1.64" 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 J or travel— ingj is too low. Some additional means of air movement are requires 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 in- water heater fan with directional vanes or by the addition of one or more efficient propelier-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 ior cola weaiat ' ■ - - • GUN FUME REMOVAL PROCEDURE: Gun fume trials were run on a T2531 tank (hull and turret conditions similar to M-26) blower of nominal 1000 cfm capacity, and with the proposed turret fan of nominal 1000 cfm capacity. Data were collected on three days (3, 4, and 6 July 1945). CO concentrations were determined simultaneously by the K.D.E.C, Infra-red Gas Analyzei and the M.S.A, CO Indicator, Since virtually identical results were secured by the two methods only the K.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 ram ammunition or each 250 rounds (l belt) of ,3.0 cal, machine gun ammunition. Zero test time was the time of firing the first round in either case. Alien several bursts or belts were fired they were fired at 5 minute intervals. Since the intake for the turret fan is very close to the main and auxiliary engine exhaust outlets, tests were run to determine CO pickup from these sources while no gun was fired. 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, Hie M-l muzzle plug gave higher CO concentrations than the 0,718 muzzle plug in previous tests (Armored Medical Research Laboratory, Final Report on Iroject No. 44 - The Physiological and Operational Characteristics of M-24 Tank, dated 8 November 1944). Since the air stream from the turret blower is directed toward the bow when the turret is in firing position, one test was run while the turret was in traveling position during firing of the bow machine gun. On all other tests the turret was in firing position. Static pressure in the turret was measured by means of an Alnor Velometer. Test conditions and results are shown in Table 4. RESULTS; When 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 CO hazard will develop from this source. As shown by the data in Table 4, the CO concentrations ’were satisfactorily low (0,05$ 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, Ho 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. The bow fan gave satisfactorily low results on all except one test in which the turret was sampled while firing the ,30 cal, coaxial machine gun with the U-l muzzle plug. This cpnfirms previous tests (Armored Medical Research Laboratory, First Partial Report on Iroject No, 41 - Physiological Characteristics of the T25S1- T26S1 Tank, Subject; Control of Gun Fume Hazard, dated 19 July 1944)« The proposed turret blower is as satisfactory for the removal of gun fumes from the turret and bow of the tank as is the bow blower, and according to the standards of this Laboratory, is acceptable from the standpoint of gun fume removal. DUST PROCEDURES Dust concentrations were measured under varying conditions with comparisons being made between the bow and turret bulge blower under approximately similar dust conditions. Dust was sampled with an L.S.A, Midget Impinger 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 unvegitated 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 M26 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 measurements were made during the above tests. Moving pictures and still photographs were taken of an M26 Heavy tank with and without fenders and sand shields to observe the dust pattern about the hull and turret. RESULTS: Dust 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 was the more satisfactory of the two iplet 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 and 5B in group (b) were repeated on the second day of test operation when a lower wind velocity prevailed. The first test serves to illustrate the con- dition arising with a strong wind blowing over an extremely dusty terrain. Tests 5A through ?B 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 4 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 employment. 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 samd shields installed, sand shields only removed, front fenders and sand shield removed. Visual observation, substantiated by motion pictures taken from a 20 foot height looking angularly down, show the dust pattern of the moving vehicle to be heavier at the engine air intake than at the bow. This is partially due to the negative pressure created at that point of air intake and partially because of air pattern of the moving vehicle. In any event the turret bulge blower intake is more apt to be vulnerable to a dusty atmosphere than the bow blower intake. With either blower operating there is a definite requirement for an adequate dust filter. NOISE PROCEDURE; Noise level measurements were made at ear level of all crew |ositions, 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. Measurements were also made for comparison on the bow blower, A General Radio Company Sound Level Meter No, 759 with a microphone extension was used for obtaining the noise level values. The mean value shown in Table 4 for the noise level represents the average of several readings varying, over a range of approximately 5 Db. RESULTS: Noise level intensity of the blowers operating without baffling is objectionably high (see Tab, 6), particularly because of the high frequency sound range. With ear phones the noise is tolerable although extremely unpleasant. The influence of enclos- ing the turret bulge blower with the discharge duct system is to lower the intensity 10-15 Db, The noise level of trie enclosed turret blower is exceeded only by the noise of the vehicle operating on a concrete road at 10 raph. Even in those situations where the tank noises are of greater intensity than the blower, the higher frequency the latter still adds to the confusing din for the tank crew members, A serious effort should be made to reduce the noise level of tank ventilating blowers. TABLE 1 AIR VOLUME, TANK S.P., POWER, SPEED MEASUREMENTS BLOWER AUXILIARY GENERATOR TURRET HATCHES — 2> 5 X BLOWER DISCHARGE RESTRICTION BLOWER INLET RESTRICTION X e s rsJ o s|^ E g vO Q AIR VOLUME CFM 9 X • o CO cv X • cn VOLTS WATTS INPUT BLOWER RPM Turret On Closed Closed w Orifice c 2.45 800 1.26 o in Duct X L Turret On Closed Closed &HI Armored - 820 1.30 N 0 T _ X X o Inlet 0 Q O CD s U E A S U R S D Bow On Closed Closed co Q Block - 910 1.54 M E Turret On Open Open Q Orifice V) 2.80 660 - in Duct J Turret On Closed Closed On Orifice 2.52 820 1.10 in Duct V P N 0 T Turret On Closed Closed On Armored - 860 1.15 Inlet E I E A S U E E D Bow On Closed Closed - Block N - 950 1.32 Turret On Closed Closed None Orifice C 2.99 880 1.65 41.0 27.5 1128 6125 in Duct L Turret On Closed Closed None Armored 0 _ 1020 2.09 20.5 28.5 1155 6200 Inlet S Turret On Open Open None Orifice E 3.85 1000 .. 40.5 28.0 1135 6200 In Duct P Turret On Closed Closed None Orifice o 3.19 910 1.30 in Duct p Turret On Closed Closed None Armored r 960 1.34 40.0 28.5 1140 6150 Inlet E Bow On Closed Closed - N - 970 1.38 NOT L E A S U I I E D Turret Off - - - - - 0 26.0 - 0 Turret On - - - - - - - - 0 28,0 - 0 NOTE: All tests conducted with vehicle stationary engine off. AIR MOVENT IN FBI AT VARIOUS CREW POSITIONS AIR MEASUREMENT POSITION e hB CO M W Q O I GUI IN FORWARD POSITION ALL HATCHES OPEN II am IN FCR’i&RD POSITION BOW HATCHES CLOSED CGM'DR HATCH OF®! m Gin IN FORWARD POSITION AL7 HATCHES CLOSED IV Gin IN REAR POSITION ALL HATCHES CLOSED V Gin IN REAR POSITION i ALL HATCHES OPES Legs mist —Shoulders s I o 155 - 160 160 - 180 98 - 120 215 - 240 240 - 265 180 - 195 145 - 160 82 - 90 60 - 70 60 - 67 90-98 98 - 105 145 - 155 160 - 170 195 - 205 Legs Waist Shoulders I 78 - 120 74 - 98 190 - 195 180 - 195 195 - 215 195 - 215 125 - 132 74-82 67-82 255 - 265 160 - 170 140 - 145 180 - 190 140 - 145 120 - 145 Legs waist Shoulders g o 132-145 ..90 - 98 140 - 155 180 - 195 265 - 290 215-240 no - 132 155 - 180 132 - 145 n5 - 120 n5 - 132 78-82 120 - 125 170 - 180 160 - 170 Legs Waist Shoulders 8 m 82-88 82 - no 240 - 265 45 - 50 98 - no 160 - 180 37 - 45 74-82 60 - 67 17 - 20 45 - 50 78-82 37-41 45 - 47 132 - 140 Legs Waist Shoulders 04 Q no - 132 160 - 180 195 - 215 145 - 160 240 - 265 240 - 265 74-86 190 - 205 180 - 195 37 - 47 50 - 60 37 - 47 31-41 70 - 74 90 - 95 TABLE 3 AIR M07SJSNT IN MEDIUM TANK, T25E1, WITH TEST BLOWER LOCATED IN TURRET BULGE POSITION TABLE 4 GUN FUL3S RE];’OVAL DATA GFT TEST NO. s a B hi CQ 5 s CO 6 m TOTAL ROUNDS FIRED OPEN HATCHES m 3 3 3 M a o % M 3 M 3 g < i 3 0 1 oa 3 a < to s M C-h M I i§9 CO ■< CO 3c f-f i~3 O M o csi o 3 X K IH E- • ■x ” q 3 w \s o <5 si <5 M ►4 O > O << o NO FIRING 1A - 0 0 None Off On Turret Turret 0.70 .000 2a - 0 0 n On Off it n 0.73 .000 FL RING 90 MM RIFLE 5A — 2 9 None Off On Turret Turret 0.60 .031 4B - 2 8 Com. »» Off n IT 0.02 .028 6A - 2 10 n n On n M 0.02 .032 ?A - 2 10 it ti H I! Bow 0.01 ,022 73 - 2 10 None if II Bow Turret 1.55 .023 5B — 2 10 Comm. u If ti it 0.03 .007 FIRING .30 CAL. BOW MACHINE GW 8A .718 2 5« Loader & Comm , Off On Turret Bow 0,01 .009 2B L-l 2 500 None it ii h » - .001 IB M-l 2 50i. Comm. ii it 1! n 0.02 .014 1C* M-l 2 500 if ii II ti — .020 FIRING .30 CAL. COAXIAL MACHINE GW $G .718 2 50C Comm. Off On Turret Turret 0.01 .010 4C M-l 1 250 None It •i it ii 0.90 .032 3C M-l 2 500 Comm. It it n n 0.01 .020 7C M-l 1 250 M II Bow it 0.01 .074 * Turret in travelling position on this test only. Tost Vehicle Operating 10-20 Yards Behind Tank - (a) DUST' HATCHES ELOiER LOCATION OfM FENDERS AND SAND SHIELDS CHEW TEST AVG. WIND DUST COEC. T NO. — Driver — Co&’dr POSITION POSITION SAMPLED DURATION VELOCITY MPH MILLION PART. PEE CU. FT. 1A Open Open Turret Rear On Louder 7*49" 7.8 153.5 IB Open Open Turret Rear On Bog 7* 29" 8.4 368.0 2A Open Open Bow Rear On Loader 7*29” 6,6 136.4 2B Open Open Bov* Rear On Bog 7*26» 9.6 185.9 3A Open Open Turret Forward On Loader 7*30" 7.8 274.0 3B Open Open Turret Forward On Bog 7*56" 7.2 199 oO Test VehicI .e Operating Alone -(b) 5A* C iosed Closed Turret Forward On Loader 7*05" 7oB 352.00 5B* Closed Closed Turret Forward On bog 7*20» 8.4 229.00 5A Closed Closed Turret F orward On Loader 7*25» 1.2 32.40 5B Closed Closed Turret- Forward Cn Bog 7*47" 2.4 38.80 6a Closed Closed Bow For'ward On Loader 6*25" Trace 22.20 6b Closed Closed Bow Forward On Bog 8? 25" 2.4 74.00 7A Closed Closed Turret Rear On Loader 7*15" 0.6 23.80 7B Closed Closed Turret Rear On Bog 8100" 5.4 30.95 9A Closed Closed Turret F orward Off Loader 6*2btt 1.8 187.00 9B Closed Closed Turret Forward Off Bog 7'30" 4.2 159.00 10A Closed Closed Bow Forward off Loader 8*34" 3.0 216.00 10B Closed Closed Bow Forward Off Bog 8*32° 4.2 343.50 11A Closed Closed Turret Rear Off Loader 8*09" 1.8 71.00 UB Closed Closed Turret Rear Off Bog 9*01” 1.2 36,60 * Tests conducted with Sroup 1A-3B on 10 July 1945 Others conducted on 12 July 1945 TABLE 5 COMPARATIVE TOOTS, Bu/« BLO.sSR VERSUS TURRET BLO.iSF TEST C 0 N D I T I CO se 0 TEST NULBEE S TAT ION AR1 K OV IN G Remarks Stationary teats conducted in open space. All tests conducted with gun in forward position. Noise level measurements made with General Radio Co. Bound Level Leter No. 759 with microphone extension. All noise level values are mean for a 5 decibel range. Tank buttoned up in all tests unless otherwise indicated. 1 2 3 4 5 6 7 8 9 10 11 12 i5 S !H Mi 0 w a* a 0 os 0 pfti s ft • m tsa « H '-J 33 05 ft ft M Sc H 0 3 G5 ft SC M S c5 cc t*2 O' 1"* • & CL ys c5 fig ft ft §9 e -c ft 0,24 O otJz ft>o> ft 05 ft E- afg g§si *TB” '6S0 ® Sos eucf 3gB H q ft BhCJ C5 JS-i 22 03 OttJHft ft Oh 05 ft CKO M i-4 M HW O H !>2h ft B oft 05 ft >:d w g 9‘Vk O • ft M • Oh > w ft .55 2S E ft ej a , 4 CO 6 0 ft E-c ft §S^5 ft ft 0 Oftftft ft CJ ft ft C3 Eft ft C5 “ H M ft OH > ft t-PoK 05 ft a CO ft ai§ 0 s i 0: Ts§ 6 E-* ft CO i=s |S§ BgSS ft (V ft fto 3 & S 0. 05 ft 24 CO a ag@ Hife ft i ft > • p lag Be- " «R-J 3“ g S O M ft ft as*? 6.c ''4 B 0 CftrH rH ft • - > i; h ft 03 O ft ft ft ft ft cO ft At Radio Face 83 64 99 81 72 83 88 93 94 83 SO 102 Commander Ear Level 82 64 99 81 61 81 91 93 93 84 79 102 o o 33 M Loader Ear Level 84 63 98 82 69 83 90 93 94 82 80 97 O M Gunner Ear Revel 86 63 96 83 70 84 87 93 93 84 81 97 SB Driver Ear Level 76 63 91 12 68 75 93 93 94 80 81 100 Bog Ear Level 76 63 91 73 68 73 93 93 94 80 81 97 TABLE, 6 LEAN NOISE LEVEL LEASURELENTS, Db., QF LEDIUM TANK T-25E1 WITH 1000 CFL TEST BLO/VER LOCATED IN TURRET BULGE Dual Pattern for Heavy Tank, K26 with Penders and Sand Shields ARMORED MEDICAL RESEARCH LABORATORY figure 1, Project Ho. 45 FO*T KNOX' XY- July, 1945 Dm! PitUm for Hwory TMt, 106 with fondoro without Sond Shlolda ARMORS) MEDICAL RESEARCH LABORATORY Flgurw 2, Projoot Bo. ki **T knox, icy. Juijt 194? Dual Pattern for Heavy Tank, 106 without front Pondara and Sand Shialda ARMORED MEDICAL RESEARCH LABORATORY V Prolaet No. k5 K»T KNOX, KY. Jul*» W45 JiCZL&M Th&U JUR.RET Shokjikjg J-ocatiotJ Or Bl/L'SE feLO