The M4 High Speed Tractor was a tractor that was used by the US Army to tow artillery; it can also be called an artillery tractor. Today the M4 tractor is just a fond memory but is a popular item for modeler’s that were around in the 50s and kits are available for building a model of the tractor if one desires.
HISTORY OF THE M4
The real M4 Tractor was first put into production in March 1943 and by June 1945 there were 5,552 of them; up until that time ammunition was primarily transported by trucks, however trucks often had a difficult time in soft terrain and so were not the most reliable transporters. The answer to this problem was the 18 ton M4 High Speed Tractor which was developed by Allis-Chalmers, the commercial tractor manufacturing company in 1941; the vehicle had to be redesigned several times but in late 1942, final testing began and in 1945 the improved M4A1 came on the scene.
Towards the end of production of the M4 Tractor, it was decided that the M4 would be used in a supportive ammunition carrier role to the new M40 155 mm GMC and M43 8 inch HMC; as a result the gun crew was carried in the rear compartment and were called the M4Cs. Some variations of the M4 included a crane to move the heavier projectiles.
FUNCTIONS OF THE M4
The three main artillery pieces that the M4 was intended to transport were the 155 mm gun, the 203 mm howitzer and the 90 mm anti-aircraft gun; the M4 HST was designed to carry ammunition at the rear of the chassis. From the outside the ammunition box for the 155 mm gun and the 203 mm howitzer looked the same but there were slight differences inside to accommodate the size difference between the two; the box for the 90 mm anti-aircraft gun however had to be stored differently because of its size and so it had side-opening doors for accessing the ammo inside.
DESIGN OF THE M4 TRACTOR
The M4 was built based on the chassis and drive train of the M2 Light Tank; basing the design of a new vehicle on an older model was a common practice at the time because it simplified the design of the new vehicle, allowed for easier production and easier maintenance and repair in the field.
The M4 tractor weight a little over 14 tons, had no armor – probably because of the purpose it served – and its primary weapon was one 12.7 mm anti-aircraft machine gun. It used a Waukesha 145GZ six-cylinder inline petrol engine, a vertical volute spring suspension system and traveled at a maximum speed of 53 km/h (33 mph). The M4 was also equipped with air and electric brakes and could carry a total of 11 passengers including the driver; however the driver was usually the only crew member on board.
Throughout the time that the M4 Tractor was in service, there were several production changes made to it including the removal of ammunition box vents and the modification of the rear hull openings to accommodate the winch system.