Horstmann suspension

[2] Fletcher claims that in 1934, John Carden of Vickers-Armstrongs had a "bright idea" for a new type of tank suspension and partnered with Horstmann's Slow Motion to turn it into a working design.

Among their many problems, the Vickers-supplied "box" suspension proved to be very springy and led to the tank rocking for some time after firing the main gun.

In fact, the earliest attestation of the term "Horstmann suspension" itself dates back to January 1934, when Christopher Ainsworth Davis presented his joint paper with Horstmann on "Slow Motion" automotive suspensions and mentioned that "a special type of high-speed cross-country tracked tractor" (presumably the Dragon) performed very well in tests.

E3 had also been fitted with a more powerful 500 hp Thornycroft RY/12 marine engine in an effort to improve performance, but in testing, this showed no benefit and ultimately only three examples of the Medium Mark III were produced.

[8] Carden was killed in an air crash in December 1935,[3] but by this time he had designed a lighter tank platform that had been taken up as the A10, although later known as the Cruiser Mk I.

[11] In 1943, a single Ram tank, a Canadian-built version of the M4 Sherman, was modified to trial Horstmann type suspension.

This used two full bell cranks like the earliest designs, but moved the shock absorbers to the lower side of the wheels.

Although this was highly successful, running over 2,000 miles (3,200 km) in testing, the Ram was cancelled in favour of purchasing US-built M4s and turning Canadian production to other designs.

By this time the US Army was testing a huge variety of new suspension concepts, eventually choosing one of these for the late-war M4E8 models.

This was essentially identical to the original two-bell system, but had three coil springs, one inside the other, to give it the required weight performance.

[14] When the Centurion finally began to be made obsolete with the introduction of the newer Soviet types, little development of new systems had taken place.

[16] An advantage to the Horstmann design is that the suspended weight is not placed entirely on the rising wheel: its paired partner will also increase its downward force due to the shared spring, spreading the load.

From a maintenance standpoint, the fact that the spring connects at a single non-moving point and is otherwise self-contained makes it easy to remove and replace in the field.

The name "Horstmann suspension" was sometimes applied to any transmission system that has two opposed swing arms, no matter the type of springing between them.

The Light Tank Mk Ia (A4E8 prototype) became the first tank in the world to use the Horstmann design. In this case the spring is outside the track area, leaving room for track return rollers to lie directly over the suspension in a particularly compact layout.
The Light Tank Mk III introduced a slightly modified version with only one bell crank per bogie, causing the spring to lie somewhat angled as a result. This system was used on the Universal Carrier .
The horizontal volute spring suspension used on late-model Sherman tanks is similar to the Horstmann design. The two wheels per bogie, two crank arms, springs between the cranks and single mounting point are all evident. This model also includes a shock absorber for further improvements in ride quality.