T7 Combat Car

T7 Combat Car

Type	Light Tank
Place of origin	United States
Production history
Designed	1937–1938
Manufacturer	Rock Island Arsenal
Specifications
Weight	11 tons
Length	5.12 m (16 ft 10 in)
Width	2.63 m (8 ft 8 in)
Height	2.46 m (8 ft 1 in)
Crew	4

Armor	16 mm maximum
Main armament	0.5 in (12.7 mm) M2 Browning machine gun
Secondary armament	M1919 Browning .30 in (7.62 mm) medium machine gun
Engine	Continental R-670 Radial 250 hp
Suspension	Coil spring-based wheel and track.
Speed	56 km/h (35 mph) on tracks, 85 km/h (53 mph) on wheels

T7 Combat Car was a prototype United States light tank design of the interwar period. It could run on rubber-tired wheels on roads or mount tracks for cross-country use. Although adequate in some areas, it lacked armament compared to contemporary vehicles and the project was cancelled after only one was built.

Development

In November 1936, the US Army's cavalry branch decided to modernize and needed a fully armored vehicle, capable of keeping up with the cavalry and of fulfilling regular combat duties. Prohibited from developing tanks by the National Defense Act of 1920 which defined "tanks" as the responsibility of the infantry, the phrase "combat car" was used as a legal formality. The T5 Combat Car had been built on similar lines to the infantry's T2 Light Tank, leading to the M1 Combat Car.^[1] After the T4 Combat Car had been tested, the Ordnance Committee recommended working on a road-track convertible tank design. The T6 Combat Car design was cancelled but in November 1936 the Chief of Cavalry ordered that work continue on designing a convertible tank.^[2] Designed and built at the Rock Island Arsenal between 1937 and 1938, the T7 Combat Car was based on the M1 Combat Car but with an extended chassis and a convertible suspension – the ability to travel using wheels or tracks.^[3] Theoretically, it was more versatile than a conventional tank, having the ability to move with and without tracks on roads, much like the Christie designed tanks. The main gun of the project was traditional – one .50 cal (12.7 mm) M2 Browning heavy machine gun and three .30 caliber (7.62 mm) M1919 machine guns. However, this armament was useful only against infantry, and was inadequate for use against other tanks of the period.^[4]

Description

Since the vehicle was – like the cavalry – expected to drive as much or more on the roads as off, the design featured a wheel-track layout capable of both modes. Given the limitations of that era, it was expected the tires would have greater durability over roads than the tracks themselves. The US Army had already tested and dismissed Christie’s all-steel road-wheel design. In order to avoid that failure, the Combat Car was designed using three big road-wheels with rubber tires that also served as rollers. All six wheels were 38x7 inch pneumatic tires with bullet resistant tubes and were fitted with metal disc supports to help reduce the chance of bullets or shrapnel piercing the tires, potentially disabling the tank.^[5]

The vehicle was powered by a 7-cylinder radial engine Continental R-670, producing 250 horsepower. The four rear wheels were powered and were equipped with brakes. The two front wheels were steerable when driving without tracks.^[5] Since the vehicle weighted only 11 tons, it could go as fast as 56 km/h on its tracks and 85 km/h on its wheels. Another advantage was that the external suspension components saved a lot of space inside this small vehicle. The crew consisted of the tank commander, driver, and gunner. The rear wheels were attached to bogies and the construction was generally similar to commercial 3-axle trucks of the period. As a tank, it was not ideal. However, its simple and more promising design was much better received than Christie’s designs.^[4]

Test

The only prototype T7 Combat Car (No. W40223) was shipped to Aberdeen Proving Grounds in August 1938 for testing. While it showed good speed and performance, cavalry branch representatives were not significantly impressed. Tests were delayed until 1939, but they were reasonably successful. The vehicle even participated in the First Army maneuvers at Plattsburg, New York in 1939, where the cavalrymen liked it. However, in October 1939, the cavalry branch formed new requirements for their combat vehicles which specified regular tracked (not combined) suspension. The reason for that decision was that the tracks were already available in reasonable quantity and quality and thus there was no need for the complexity and higher cost associated with convertible vehicles.^[5] Furthermore, the heavy machine gun was determined insufficient for the role. The ongoing war in Europe at the time proved that, in order for a vehicle to be successful, it needed a proper cannon. In October 1939, despite its potential, the Mechanized Cavalry Board recommended further development and test of the T7 Combat Car program, and all other such convertible vehicles, be canceled. Thus ended the last wheel-tracked combat vehicle development for the U.S. Army.^[4]

Notes

↑ Chamberlain & Ellis British and American Tanks of World War II (1969) p84
↑ Hunnicutt p88
↑ Chamberlain & Ellis (2002), p. 203.
1 2 3 Ogorkiewicz (2015), pp. 84–85.
1 2 3 Hunnicutt (1992), p. 88.

References

Chamberlain, Peter; Ellis, Chris (2002). Tanks of the World, 1915–1945. London: Cassell & Co. ISBN 9780304361410.
Hunnicutt, R.P. (1992). Stuart, A History of the American Light Tank. Volume 1. Novato, CA: Presidio Press. ISBN 978-0-8914-1462-9.
Ogorkiewicz, Richard (2015). Tanks: 100 Years of Evolution. Oxford, UK: Osprey Publishing. ISBN 9781472806703.

External links

Tank T7 Combat Car, USA (in Russian)
T7 Combat Car Lightweight wheel-track tank

Interwar tanks

List Category

Tankettes	L3/33 L3/35 Carden Loyd Morris-Martel T-27 TKS Type 92 tankette Type 94 tankette Type 97 Te-Ke Tančík vz. 33 AH-IV

Light	H35 R35 Fiat 3000 Leichttraktor Light Tanks Mk I–V Light Tank Mk VI Light Tank Mk VII M1 Combat Car M2 Light Tank Panzer I Panzer II LT vz. 34 LT vz. 35 LT vz. 38 T1 Light Tank T7 Combat Car T-18 T-13 T-15 T-19 T-26 T-37 T-38 7TP Type 95 Ha-Go Vickers 6-Ton Vickers-Carden-Loyd Light Amphibious Tank

Medium	Char D1 Char D2 Grosstraktor Medium Mk I Medium Mk II Medium Mk III Panzer III T-24 T-28 Type 97 Chi-Ha Type 97 Chi-Ni Type 98 Chi-Ho

Cavalry, Cruiser or Fast	AMC 34 AMC 35 AMR 33 AMR 35 BT tank Cruiser Mk I Cruiser Mk II Cruiser Mk III SOMUA S35

Infantry	FCM 36 Infantry Mk I, Matilda Renault R35 T-26 Type 89 I-Go

Heavy	Char B1 Neubaufahrzeug SMK T-35 T-100 Type 95 Heavy Tank Vickers A1E1 Independent

Super-heavy	FCM F1 Char 2C T-42

Armoured Carriers	UE Chenillette Bren Gun Carrier

History WWI Interwar WWII Cold War Tank

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