Photos of full size mechanical signal and point operating equipment.
Standard 90 degree crank.
Prototype 90 degree crank with equal length arms. This photo was taken at The Swanage Railway of a spare crank laid on a stack of old sleepers. The hole at the pivot point is larger than those at the outer ends of the arms, this is to allow a large diameter bearing pin to be used providing a very strong fixing point capable of withstanding relatively high loads. A signal arm or points and rodding covered in snow or partially frozen can require an incredible amount of force to free the mechanism, start and complete the movement. Modellers! For those of You modelling in larger scales bearings can also be fitted reducing the amount of friction acting on the pivot point, minimising the effort required to move the rodding run and reducing stresses throughout the length of rodding thus extending the operational life of the crank pivot in service. Take note of the rounded arm ends and "web" effect between the arms caused by the large pivot tube not being central to the flat metal "L". Also note that the pivot point is not a hole in a flat metal "L" shape, it is normally cast as an integral part of the crank but in model form could be easily and effectively emulated with a short length of pipe attached at 90 degrees to the flat crank plate.
