After seeing how the M5 Light Tanks did with British forces in the Western Desert the US Ordnance Department and Cadillac, in April 1943, begin work on a new light tank with a 75 mm gun.8,9,10
The M24 was named after US Army tank pioneer General Adna R. Chaffee.6
The armor was welded. The track was center guided and the tank used a torsion bar suspension. The engines were mounted on rail for easy maintenance. Each engine was identical and were interchangeable. The engines were the same engines as used in Cadillac automobiles.6 There was a bulkhead between the fighting compartment and the engine.6
There was a Cletrac controlled differential installed in the front of the hull for steering and braking.6 A synchronizer was incorporated in the transfer unit and the M24 was capable of 8 speeds forward and 4 reverse.5 In reverse the M24 could get up to 18 mph.5
The M24 used the same 75 mm gun that was originally designed for mounting in the B-25 Mitchell bomber for anti-ship use.4,8 It had a concentric recoil system which saved turret space.1 The firing trigger for the 75 mm was on the elevation hand wheel and for the machine gun on the power traverse control.9
There was recoil guard for the gunner and loader.9
For travel there was a lock that fastened to a bracket in the turret roof.9
The gun and a .30 cal machine gun were mounted in a Combination Gun Mount, M64.5,9 Ammo was stored in water protected containers in the floor.5,9
The hull machine gun had a bag that captured the expended casings.9 The gun was fed by a supply box on the left of the radio operator.9 There was a spring that helped counter balance the machine gun.9
The AA machine gun could be fire manually or electronically.6 The antiaircraft gun was mounted on a pintle at the rear of the turret.9
The 75 mm used a hydraulically operated stabilizer.6,9 It could fire a 14.4 lb shell at a muzzle velocity of 2,050'/sec.7,9
The 2" mortar was located on the right front side of the turret.9
In the front hull the driver sat on the left and the assistant driver / radio operator on the right with each having driving controls.6,9 In the turret the gunner and loader were on the right and the commander on the left.6,9 Originally it was intended to have only a four man crew with the assistant driver moving to the turret to load the gun.6,9 The M24 had no turret basket, as the seats for the crew were suspended from the base ring.5,6,9
The gunner used a combination telescope-periscope sight for sighting the main armament.9
The hatches for the driver and assistant driver could be opened regardless of the turret position.1,9 There was an escape hatch placed in the floor of the hull.5
Two pilot models (T24) were delivered in October 1943 by the Cadillac Motor Division.9
The Ordnance Department immediately ordered 1,000 before service tests had begun and then raised to 5,000 vehicles.1,8,9
Was Standardized in May 19448 / July 1944.1,5 First delivered in late 1944.
First delivered to Western Europe in November 1944.1 First saw action in Italy.
A small number was supplied to Britain in 1945 and were named Chaffee.1
Some M24s were used in crossing the Rhine in late 1944.9
The M24s such much service during the Korean War and were used by French forces in Indo-China.9,10
| T24 | M24 light tank, Chaffee | |
|---|---|---|
| Crew | 59 | Commander, gunner, loader, driver, co-driver/radio operator2,9 45,7, 4 or 51,6, 52,3,4,8,9,10 |
| Radio | SCR-5085,9 | |
| OR | SCR-5285,9 | |
| OR | SCR-5385 | |
| OR | British No. 195 | |
| Radio - command tank | SCR-5065 | |
| Physical Characteristics | ||
| Weight | 38,750 lb9 | 38,750 lb5, 40,414 lb10, 40,500 lb2,3,8,9 18,370 kg8,10, 18,371 kg1 18 tons1, 18.37 tons4, 20.3 tons7 |
| Weight - empty | 36,250 lb9 | |
| Length w/gun | 18'9 | 18'1,2,3,4,5,8,9,10 5.486 m8, 5.49 m1,4,10 |
| Length w/o gun | 16' 3"9 | 16' 3"5, 16' 4.5"2,4,8,9, 16.5'7 4.99 m4, 4.991 m8 |
| Height | 8' 1"9 | 8' 1"1,3,5, 8' 1.5"2,4,8,9,10, 9.1'7 2.46 m1, 2.4765 m8, 2.48 m4,10 |
| Width | 9' 4"9 | 9' 4"3,5, 9.5'7, 9' 8"1,2,4,8,9,10 2.946 m8, 2.95 m1,4,10 |
| Width over tracks | ||
| Ground clearance | 1' 5"9 | 1' 5"5, 1' 6"7 |
| Ground contact length | 9' 4"5, 10'7 | |
| Ground pressure | 10.7 psi9 | 10.5 psi7, 10.7 psi5, 11 psi9 |
| Turret ring diameter | 60"5 | |
| Armament | ||
| Main | 75 mm9 | 75 mm3,4,6,10 75 mm M61,2,5,8,9 75 mm M6, L/407 |
| Secondary | ||
| MG | 3: MG3 2: .30 cal MG8 2: 7.62 mm MG10 1: .50 cal MG8 |
|
| MG - coaxial | 1: .30 cal MG1,4,6 1: .30 cal Browning M1919A42,5,7,9 |
|
| MG - hull | 1: .30 cal MG1,4,6 1: .30 cal Browning M1919A42,5,7,9 |
|
| MG - antiaircraft | 1: .50 cal MG2,6 1: .50 cal Browning M2 HB5 1: .50 cal M2 MG7 1: .50 cal Browning M29 1: 12.7 mm (.50 cal) MG1,4 1: 12.7 mm MG10 |
|
| Side arms | 2" M3 Mortar, in turret5,9 1: 51 mm smoke mortar10 1: M2 .30 cal Tripod mount5 4: M3 .45 cal submachine guns5 1: M1 .30 cal Carbine with grenade launcher5 Grenades |
|
| Quantity | ||
| Main | 489 | 481,2,5,7,8,9 (AP, APC, HE, WP, Canister, Smoke) |
| Secondary | ||
| MG | .30: 3,7502,5,7, 4,1258,9 .50: 4208,9, 4405,7 |
|
| Side arms | Mortar: 145 .45: 720 Grenades: 8 (2: smoke, 6: fragmentation)5 |
|
| Armor Thickness (mm) | 92, 252,
12 - 384,10, 1" - 2.5"3 Front: 1"7,8 Front: 25.48 Hull: 2.5"6 |
|
| Hull Front, Upper | 1"5, 1"@60°9 | |
| Hull Front, Lower | 1"5, 1"@45°9 | |
| Hull Sides, Upper | 0.75"8, 0.75" - 1"5, 1"7, 1"@12°9 198 |
|
| Hull Sides, Lower | 0.75" - 1"5, 0.75"@12°9 | |
| Hull Rear | 0.75"8, 0.75" - 1.25"5, 0.75"@0°9 198 |
|
| Hull Top | 0.5"5,9 | |
| Hull Bottom | 0.375" - 0.5"5, 0.375"9 | |
| Turret Front | 1"5,7, 1.25"6, 1.5"8 388 Gunshield: 1.5"5,9 |
|
| Turret Sides | 1"5,7, 1"@25°9 | |
| Turret Rear | 1"5 | |
| Turret Top | 0.5"5,9 | |
| Engine (Make / Model) | 2 x Cadillac Twin 44T241,2,4,6,9,10, 2 x Cadillac Series 425, Twin Cadillac3, 2xCadillac7 | |
| Bore / stroke | ||
| Cooling | Liquid5, Water7,9 | |
| Cylinders | V-84,10, 2xV-85,7,9 | |
| Capacity | ||
| Net HP | 2: 1109 | 110 each3,4,10, 110@3,400 rpm9, 110@3,600 rpm7, 2208, 220@3,4005 |
| Power to weight ratio | 10.86 HP/ton9 | |
| Compression ratio | ||
| Transmission (Type) | Hydra-Matic, 8 forward, 4 reverse5 Planetary, 4 forward, no reverse and Cadillac helical transfer case with 2 forward, and 2 reverse7 General Motors Hydramatic 4F, 2 forward, 1 reverse9 |
|
| Gear ratio - 1st speed | 9.19:15 | |
| - 2nd speed | 5.96:15 | |
| - 3rd speed | 3.62:15 | |
| - 4th speed | 2.34:15 | |
| - 5th speed | 4.05:15 | |
| - 6th speed | 2.62:15 | |
| - 7th speed | 1.59:15 | |
| - 8th speed | 1.03:15 | |
| Reverse gear ratio - 1st speed | 9.57:15 | |
| - 2nd speed | 6.17:15 | |
| - 3rd speed | 3.78:15 | |
| - 4th speed | 2.44:15 | |
| Steering | Controlled differential7 | |
| Steering ratio | ||
| Starter | Electric7 | |
| Electrical system | 24 volt9 | 24-volts5,7 |
| Ignition | Distributor7 | |
| Fuel (Type) | Gasoline7,9,10 | |
| Octane | 805 | |
| Quantity | 110 gallons9 | 110 gallons5,7,9 |
| Road consumption | 0.9 mpg7 | |
| Cross country consumption | 7 - 8 mpg9 | |
| Performance | ||
| Traverse | 360°2,5, powered5 Hydraulic and manual7 |
|
| Speed - Road | 30 - 36 mph9 | 34 mph1,7, 35 mph2,3,4,5,8,10 55 kph1, 56 kph4,8,10 |
| Speed - Cross Country | 20-30 mph7, 25 mph2,3,8 40 kph8 |
|
| Range - Road | 100 miles9 | 100 miles2,4,7,8,9,10, 175 miles1,5 161 km4,8,10, 281 km1 |
| Range - Cross Country | 100 miles5 | |
| Turning radius | 23'9 | 40'5 |
| Elevation limits | -10° to +15°2,5 | |
| Fording depth | 3' 6"9 | 3' 4"2,4,5,7,10 1.02 m4,10 3' 4" unprepared9 6' 6" prepared9 |
| Trench crossing | 7' 4"9 | 6' 6"5, 8'2,4,9,10, 8.25'7 2.44 m4,10 |
| Vertical obstacle | 2' 8"9 | 3'2,4,5,7,9,10 0.91 m4,10 |
| Climbing ability | 31°9 | 31° (60%) slope7,9, 60%5 |
| Suspension (Type) | Torsion bar2,5,6,7,9 | |
| Wheels each side | 55,7,9 | |
| Wheel size | 25.5" x 4.5"5,9 | |
| Wheel size - idler | 22.5" x 4.5"5 | |
| Return rollers each side | 37 | |
| Tracks (Type) | Steel-rubber bushed, single pin5,7, T.729 | |
| Length | ||
| Width | 1' 4"9 | 1' 4"2,5,7,8,9 0.406 m8 |
| Diameter | ||
| Number of links | 759 | 755,7,9 |
| Pitch | 5.5"5,7,9 | |
| Tire tread | Rubber7,9 | |
| Track centers/tread | 8'2,5,7,8, 10'9 2.438 m8 |
Sources: