Preselector gearbox
A
preselector gearbox is a type of gearbox used on a variety of vehicles, more commonly until around the 1950s. It was originally invented and patented in 1928 by Colonel Walter Gordon Wilson (1874-1957) and was first used in
World War I tanks. Various manufacturers produced preselector transmissions under licence to the Wilson patents.
As its name suggests, gear changes were made by selecting a gear ratio in advance of it being needed. The chosen gear was then brought into operation by pressing and releasing the 'gear change pedal', which was normally the left pedal, installed in place of the usual
clutch pedal. It is not to be confused with
automatic transmission, in that gear changing is initiated by the driver. Unlike the "crash" gearboxes of the first half of the 20th century, the gearwheels in a preselector box are permanently in mesh in an
epicyclic layout.
They were common on
Daimler Alvis and
Armstrong-Siddeley cars as well as on many
London buses. They have also been used in racing cars, such as the 1935
ERA R4D [
1], and tanks, such as the German
Tiger I and II in
World War II.
On some cars, starting off from rest involved using the gear change pedal like a clutch. On others, first gear could be selected but while the engine was still idling the car would not move even after the gear change pedal had been pressed and released. When the accelerator was pressed a centrifugal clutch would engage and the car would begin to move.
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Technical data on the gearbox and transmission of the Tiger I tank*
http://www.geocities.com/registen/regis04.html
