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explanation of transmission
The trolleys were designated 2w-2 PMR under the [[Whyte notation]], denoting that they were 4-wheeled, petrol-engined, mechanically driven and reversible. They were lightweight, cheap to operate and very flexible, so they were popular with operators of railways of all kinds. The SVR includes one Pre-War example; post-War more than 600 were built for BR before the Wickham factory closed in 1991.
The Wickham trolleys feature an unusual stepless variable speed and reversible transmission.<br>
Power is transmitted via a steel flywheel attached to the engine to a wheel with a friction lining on its surface which is able to slide along a splined shaft set at 90° to the crankshaft. Sliding the driven wheel towards the outer edge of the flywheel increases the gearing. Sliding it across to the opposite side of the flywheel reverses the drive.
<gallery>
File:Wickham 1.jpg | Detail of the Wickham transmission
File:Wickham 2.jpg | Detail of the Wickham transmission
</gallery>
==See also==