The Evolution of a Tank Transmission

Abstract

This paper describes, substantially in chronological order, the stages of an investigation into the theory and design of steering mechanisms for armoured fighting vehicles.

The first step was an inquiry, partly by simple experiment and partly by analysis, into the mechanics of a skidding track; the application of the conclusions to a complete vehicle led to unexpected results in regard to the forces and powers involved, and explained the unsatisfactory behaviour of earlier transmissions designed on a purely empirical basis. This was followed by review and analysis (although not necessarily in the classified order given in the paper) of existing or known types of mechanisms applicable to tank steering. An experimental mechanism of the coupled-differential type was then constructed in order to verify the conclusions drawn. Before it could be completed, the necessity arose for a rapid increase in the production of tanks beyond the limit of size and weight at which existing steering mechanisms could be expected to be satisfactory, at a time when limited production resources put a premium upon economical design.

There were grounds for believing that the triple-differential mechanism, devised at that time, would combine the desired technical performance with comparative economy in production; this expectation was confirmed, although only after a period (outside that covered by the paper) of development of detail reliability. The problem of testing tank transmissions was also studied and the plant finally devised and constructed for this purpose has a number of interesting technical features. The technical elaboration of the internal mechanics of tank transmissions, accumulated in the course of the study, has been omitted from the paper as lacking in general interest. It reached its maximum of complexity in the case of the test plant and is left as an exercise for the student. The problem of the effect of centrifugal force still awaits a complete solution.