M5A1 LIGHT TANK "STUART"

INTRODUCTION

During the 1930's the United States Army did not consider tanks to be a relevant weapon on the battlefield. Consequently, little research and development was performed. German victories in Europe exploiting firepower and mobility of tank warfare rekindled interest in tanks among U.S. military leaders, resulting in development plans for a light tank. Several models of the light tank were developed, including the M1, M2 and M3 series. In 1942 production began on the M5 series light tank at the Cadillac Division of General Motors Corporation. There was no M4 light tank designation in order to avoid confusion with the M4 medium tank, then under production. In September of 1942 design improvements were made, culminating in the M5A1, the ultimate refinement of the 1930's vintage U.S. light tank technology. A total production of 6810 M5A1 tanks occurred from 1942 to 1944.

DESIGN CONCEPT AND DEVELOPMENT

Evaluation of the M5A1 design concept entails the basic principles of tank warfare; armor, firepower and mobility. The inherent nature of the light tank implies light armor which is an obvious deficiency for a combat vehicle. The frontal armor was rolled homogeneous steel approximately 1.125 inches (29 mm), sufficient for the Far East theater, but insufficient for German munitions especially toward the end of the war. The vehicle had a relatively high profile (height 101 inches), easing the job of enemy gunners to acquire a target. Light tank also implies light firepower which, in the form of a 37mm main gun, was inferior to other combat vehicles at the time in the European theater. However, the armament was quite effective against Japanese combat vehicles in the Far East theater. Mobility was impressive with a maximum speed of 36 MPH. Interviews with actual drivers indicated that speeds in excess of 45 MPH were readily achieved. The V8 engines were very quiet and the Hydramatic transmissions allowed easy gear shifting, resulting in a stealthy vehicle.

ENGINEERING CHARACTERISTICS

The M5A1 was equipped with a .30 caliber bow machine gun, .30 caliber coaxial machine gun, 37 mm main gun and .50 caliber anti-aircraft machine gun. The M5A1 was originally equipped with a .30 caliber anti-aircraft machine gun on the turret but most tankers acquired the .50caliber machine gun since it was more effective. Ground pressure is 12.3 psi. The suspension uses vertical volute springs. The controlled differential is on the right side of the driver. This is essentially a 2 speed automatic shift gear box coupled to 2 drive shafts from 2 automatic 4 speed transmissions. This gives the vehicle 8 speeds forward and 2 speeds in reverse, all automatic shift. The power plant is the 346 cu.in. flat head V8 engine, two of which are mounted in the rear of the vehicle, connected to 4 speed Hydramatic transmissions. Each engine generated 110 horsepower. A two barrel Carter carburetor provides fuel to the engine with thermal spring automatic chokes for cold starts. The tank commander/main gun loader sits on the right, while the gunner sits on the left. A gyroscope to the right of the turret is used to aid in aiming the main gun on irregular terrain. The M5A1 had a crew of 4: the driver, assistant driver/bow gunner, main gunner and tank commander/loader. The M6 periscope was used in 5 locations on the vehicle with 4 looking forward and one to the rear.

USAGE IN WORLD WAR II

The M5 made its debut in the invasion of Casablanca in French North Africa. By 1943, and at the time of the invasion of Sicily, the M5A1 was becoming the standard light tank of the American armored divisions. Because of limited firepower, the M5A1 eventually took on reconnaissance and escort duties in Italy and, after the invasion of Normandy, throughout Europe. In the Pacific theater, the M5A1 made its debut at Roi-Namur in February of 1944 and on Saipan, the same year. The M5A1 was quite effective against most Japanese armor, even the Japanese Type 97 Chi-Ha medium tank typically used in the Pacific theater. The 37 mm main gun, although obsolete in Europe, was found to be effective against Japanese targets. Consequently, many other vehicles carrying the 37 mm gun, such as the M8 armored car and M3 anti-tank gun were retained and used in the Pacific theater.

This tank was manufactured by Cadillac Motor Car Company in 1942. Cadillac was chosen to build the M5A1 because Cadillac engines and transmissions were readily available to replace the Continental radials of the earlier light tank models that were in short supply. The M5A1 is the most advanced version of the "Stuart" light tank series used by the U.S., England, Poland, France, Russia and China in World War II.

Figure 2

Figure 2 is a frontal view of Stuart 1243 with frontal armor stowage configuration typical of that found in Normandy, 1944. The Culin (named after Sgt. Culin, the inventor) hedge row cutter is shown, fabricated from steel obstructions deployed by the Germans along the French Coast. A length of extra track was usually secured to the frontal armor for stowage but also acted as added protection from shape charge anti-tank weapons. A single road wheel (bogie) is mounted in the center of the glacis plate. The anti-aircraft machine gun mounted on the sponson to the right of the turret was originally .30 caliber, but was typically replaced in the field with the .50 caliber Browning, which carried more punch.

Figure 3

The vehicle is equipped with a dry pin volute spring suspension with rubber track blocks and track pins with rubber bushings (Figure 3). This is the same suspension design for all the Stuart variants. The four road wheels gave a smooth cross-country ride on rubber block tracks. The rubber block tracks were light and fast but did not perform well in ice or snow and were prone to skidding. Grousers, which enhanced vehicle traction and reduced skidding, were stored on the turret and installed on the tracks during snowy conditions.

Figure 4

Figure 4 is a view of the driver's compartment at the left side of the vehicle. The twin Cadillac engines with automatic transmissions made for a smooth running machine, which is why the British often referred to the tank as a "Honey." The automatic transmission facilitated the training of drivers and the operation of the vehicle, and is great for reenacting as many present-day folks have difficulty operating a manual shift. To the right of the driver's seat is the controlled differential unit, which is essentially a 2 speed automatic gear box, giving the driver options of up to 8 gears in automatic. Steering levers are mounted above the driver when stowed and pulled down when the vehicle is being steered. The driver pulls on the right lever to go right and the left lever to go left. To stop, both levers are pulled. During turns, vehicle drag increases and power must be increased to keep the vehicle moving and help in skidding the turn, which is typical of fully tracked vehicles of that era.

Figure 5

Figure 5 is a view of the turret fighting compartment showing the breech end of the 37mm gun. The breech has been removed and a cannon simulator using propane and oxygen as fuels is placed in the barrel. An oil reservoir contains diesel fuel that is pumped into the gun periodically to add smoke and realism to the gun smoke signature. The tank commander and gunner sit on a turret basket in this area. A gyroscopic gun stabilization system was provided, an advanced feature at the time. During reenactments, the gunner and tank commander sit with open hatches as a safety precaution, watching out for other reenactors.

Figure 6

Figure 6 is a view of one of the two Cadillac 346 cubic inch flat head V8 engines as viewed from the rear of the engine compartment. The engine utilized the General Motors Hydramatic transmission making shifting easy, along with reduced training time for new drivers. The engine and transmission were nearly unaltered from the automotive application, which was usually found in the Cadillac LaSalle and other top of the line General Motors civilian vehicles. Since the Ordinance Department had failed to anticipate tank engine development requirements for future tank design, civilian automotive engines, especially those in large supply, were hurriedly adapted for tank usage. The Cadillac engines operated reliably but were underpowered. With one engine not functioning, the vehicle had difficulty operating without disconnecting one of the driveshafts, a time consuming task. The gasoline fueled V8's ran very quietly unlike the noisy radial aircraft engines in previous models.

Figure 7

Figure 7 shows Stuart number 1243 in action at the Lowell, Indiana reenactment in 2001 carrying troops as would typically be seen in the Normandy breakout of 1944. The Stuart is easily and economically transportable on tractor trailer units, since it is neither oversize or over weight. Stuart 1243 can be seen at many reenactments throughout the Midwest. Information on scheduled events can be found on this website.

ADDITIONAL TECHNICAL DATA
Weight................33500 lb.
Length.............15 ft.11 in.
Width...............7 ft. 6 in.
Height..............8 ft. 5 in.
Ground Clearance.......16.5 in.

Armament:

1 37 mm Gun, M6; ammunition
A.P.C., M51B1, M51B2; A.P.,
M74; H.E., M63
2 caliber .30 machine gun
1 caliber .50 machine gun
Maximum speed............36 mph
Turning radius...........21 ft.
Maximum grade..............60 %

Copyright 1995 Charles C. Roberts, Jr

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