Christie suspension
The Christie suspension is a suspension
Suspension (vehicle)
Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Suspension systems serve a dual purpose — contributing to the car's roadholding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants...

 system developed by American engineer Walter Christie for his tank
A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility, tactical offensive, and defensive capabilities...

 designs. It allowed considerably longer movement than conventional leaf spring
Leaf spring
Originally called laminated or carriage spring, a leaf spring is a simple form of spring, commonly used for the suspension in wheeled vehicles...

 systems then in common use, which allowed his tanks to have considerably greater cross-country speed and a lower profile. The system was first introduced on his M1928 design, and used on all of his designs until his death in 1944.


Christie advocated the use of lightweight tanks with long range and high speed, designed to penetrate enemy lines and attack their infrastructure
Infrastructure is basic physical and organizational structures needed for the operation of a society or enterprise, or the services and facilities necessary for an economy to function...

 and logistics
Logistics is the management of the flow of goods between the point of origin and the point of destination in order to meet the requirements of customers or corporations. Logistics involves the integration of information, transportation, inventory, warehousing, material handling, and packaging, and...

 capabilities. His earlier designs in the 1920s were hampered by poor cross-country performance due to limited suspension capability. In the late 1920s he devised a better solution. The major problem he faced was the limited vertical space for springs to move in: for a 25 cm movement it might need 50 or 75 cm of vertical space for the spring and strut, and his small designs did not offer such space.

The solution was the addition of a bell crank
Bell crank
A bell crank is a type of crank that changes motion through an angle. The angle can be any angle from 0 to 360 degrees, although 90 degrees and 180 degrees are common....

, which changed the direction of motion from vertical to horizontal. The road wheels were individually mounted on a pipe that could move vertically only, at the top of which the bell crank rotated the direction of motion to the rear. Springs were mounted on the end of the crank, and could be as long as needed, lying along the inside of the hull. The result was a substantial increase in range of motion, from only some 10 cm in his original designs, to 25 cm on the M1928, 35 cm on the M1930, and 60 cm on the M1932. The most famous Christie-based tanks, the Soviet
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 BT tank series and the T-34
The T-34 was a Soviet medium tank produced from 1940 to 1958. Although its armour and armament were surpassed by later tanks of the era, it has been often credited as the most effective, efficient and influential design of World War II...

, used coil springs mounted vertically (on the BT) or at a slight angle from vertical (the T-34).

Another feature of Christie's designs was the "convertible" drive: the ability to remove the tracks for road travel, allowing for higher speeds and better range, and reducing wear on the fragile caterpillar track systems of the 1930s. In one public test 1931 in Linden, NJ, Army officials clocked a Christie tank going 104 mph, making it the fastest tank in the world: A record many believe it still holds. To allow this, Christie used large rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...

-rimmed road wheels, with no return rollers for the tracks. As with many track designs with center guide teeth, dual wheels were used, allowing the guide teeth to run between them. By 1939, the Soviets found that the BT tank's convertible drive was an unnecessary complication which occupied valuable space in the tank, and the feature was dropped in the T-34.

Rubber-rimmed road wheels became a common feature of almost all tanks, because they dramatically increased track life. Some Soviet tanks were produced with less rubber due to wartime shortages. The steel-rimmed wheels with only small internal rubber disc springs were unpopular with tank crews as contact with the metal track at high speeds set up harmonic vibrations that were noisy and unpleasant for crews, and could damage the T-34 by loosening parts. As rubber became available again, rubber-rimmed wheels were used in the most-loaded first and fifth positions. With increased rubber supplies in 1943, the steel-rimmed wheel was phased out from production, yet it remained in service until VE Day.

Because large road wheels and "slack track" are characteristic of the Christie suspension, other designs with these features are sometimes misidentified as such. The real Christie suspension was used only on a few designs, notably the Soviet BT tanks and T-34
The T-34 was a Soviet medium tank produced from 1940 to 1958. Although its armour and armament were surpassed by later tanks of the era, it has been often credited as the most effective, efficient and influential design of World War II...

, the British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 Cruiser tank
Cruiser tank
The cruiser tank was a British tank concept of the inter-war period. This concept was the driving force behind several tank designs which saw action during the Second World War....

s, including the A13's: Cruiser Mk III
Cruiser Mk III
The Tank, Cruiser, Mk III was a British cruiser tank of the Second World War. It was the first British cruiser tank to use the Christie suspension system which gave higher speeds and better cross-country performance, previous models of cruiser tanks having used triple wheeled bogie...

, Cruiser Mk IV
Cruiser Mk IV
The Tank, Cruiser, Mk IV was a British cruiser tank of the Second World War. It followed directly on from the Tank, Cruiser, Mk III . The first Mk IVs were Mk IIIs with extra armour fitted to the turret...

, Covenanter
Covenanter tank
The Tank, Cruiser, Mk V, Covenanter was a British Cruiser tank of the Second World War. It was named for the Covenanters, a Scottish religious faction in the British Isles at the time of the Wars of the Three Kingdoms...

, Crusader
Crusader tank
The Tank, Cruiser, Mk VI or A15 Crusader was one of the primary British cruiser tanks of the early part Second World War and perhaps the most important British tank of the North African Campaign...

, Cromwell
Cromwell tank
Tank, Cruiser, Mk VIII, Cromwell ,The designation as the eighth Cruiser tank design, its name given for ease of reference and its General Staff specification number respectively and the related Centaur tank, were one of the most successful series of cruiser tanks fielded by Britain in the Second...

 and finally the Comet
Comet tank
The Tank, Cruiser, Comet I was a British cruiser tank that first saw use near the end of World War II. It was designed to provide greater anti-tank capability to Cromwell tank squadrons. It was armed with a 77mm HV, a derivative of the 17 pounder, with the result it was one of the few British...

, as well as some experimental Italian
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...


See also

  • Horstmann suspension
    Horstmann suspension
    Horstmann suspension is a type of tracked suspension devised by the British engineer Sidney Horstmann in 1922.The system uses coil springs and has the advantages of a relatively long travel and, consisting of a self-contained bogie that is bolted to the hull, causing little or no encroachment on...

  • History of the tank
    History of the tank
    The history of the tank began in World War I, when armoured all-terrain fighting vehicles were first deployed as a response to the problems of trench warfare, ushering in a new era of mechanized warfare. Though initially crude and unreliable, tanks eventually became a mainstay of ground armies...

  • G-numbers
  • Tank classification
    Tank classification
    Tank classification is a taxonomy of identifying either the intended role or weight class of tanks. The classification by role was used primarily during the developmental stage of the national armoured forces, and referred to the doctrinal and force structure utility of the tanks based on design...

External links

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