M1 Combat Car, 1st armoured division Fort benning, Georgia, 1938. The M1 entered service in 1937. Notice the exercizes unit colors, painted on the turret. The two extra sponson machine-guns were rarely mounted.
M1 Combat Car at Fort Raily, Kansas, 1940. The M1 and its derivatives never left the American soil. They were kept for training and drilling exercizes.
M1A1 light tank of an unidentified training unit, 1941. This variant (17 built in 1937) received a new octogonal turret. The hull was 40cm longer (to 4.44m - 17ft7in) and the twe bogies more far apart. The next M1A1E1 (7 produced) received a new Guiberson diesel engine. They led to the development of the M2 light tank.
M1 Combat Car gallery:
Links on the M1 Combat CarThe M1 and M1A1 combat cars on Wikipedia
The M1 and M1A1 combat cars on wwii vehicles
The M1 combat car on globalsecurity.org
Other interesting facts and details about the M1
Background - US Tank development 1920-1930:The first U.S. tank (M1919) was mass-produced on the basis of the French Renault FT. A near-postwar design, the US-British Tank Mark VIII Liberty was the first heavy tank in US service. Over 100 were built. Then, following a 1920 specification for an US army tank, Ford and several other companies proposed prototypes, and in the twenties, without urgency, all these projects never reach the production line. The M1924 designed by Cunningham was not satisfactory either. One of these engineer, William Christie was proficient in designing a revolutionary cavalry tank, soon called "the Race tank". The M1928 was only produced in limited numbers for trials and never reach large-scale production. By 1933, Douglas MacArthur, then the army chief of staff of the Cavary, ordered the development of armored vehicles. The term "Combat car" was derived from a federal act of 1920 forbiding the cavalry to have "tanks". His specifications asked for a fast, manouverable machine with firepower to fulfill traditional cavalry missions (reconnaissance and raids behind enemy lines, rapide fire support for the infantry).
The T5 prototypes :Developed as a Cavalry Tank, by Rock island Arsenal, the T5 at first found the Vickers Armstrong 6 ton tank was as an inspiration. The need of new all-terrain, better protected vehicle led to the development of a well armed fast tank. As an interim measure, its main armament was a heavy machine-gun : A Cal.50 browning 12.7mm, deemed sufficient against armored cars. The British with the development of their MkVI light tank also followed the same path, with a Besa heavy Mg, as well as the germans, with the Panzer II and a 20mm autocannon, as many other light tank designs. Rock Island Arsenal however replaced the traditional leaf spring by a new vertical volute spring suspension. Instead of a raised idler it had a trailing idler wheel. The Vertical volute spring were easier for maintenance than other suspensions systems like Christie torsion bar or the traditional leaf springs. The wheeltrain comprised 2 double wheel bogie, and Steel, rubber pads, dry pin tracks. The two other prototypes, T1E1 and T1E2 all built and tested between 1934 and 1935.
Design of the M1 Combat Car :Other modifications including a fully traversing turret led to the T5E2, the blueprint for the standardized M1 Combat Car, over which 89 were built from 1937 to 1939, entering service with US Army in 1937. The M1 was a short, wide and tall tank, with a cylindrical cross-section turret with an extention for the weapons, equipped with the Browning cal.50 and a coaxial cal.30, and later a "D" shaped turret. The top was fitted with two large hatches. The hull was made from flat plates, mostly wielded with some elements bolted, and can accomodate at both forward corners, two other cal.30 in sponsons which could be dismounted easily. Another AA mount was fixed on a rotating device at the rear of the turret in the last batch. The M1A1 was produced as a longer variant (hull 4.44m - 17ft7in) in 1937 (17 units) with a new octogonal turret and more space between the two bogies. This led to the M1A1E1 (7 units) which had a Guiberson diesel engine, and then to the M2 (34 units), with a new Guiberson diesel and a trailing idler. The latter was again modified to create the M2A1 light tank. By july 1940, the distinction between cavarly and army vehicls was abolished, and the M1 were called officially "light tanks". Most of the M1 features served as a basis for all subsequent US tank development during the war.