Installing the top shaft into the gearbox of the Baldwin Tractor. Although rated at 50hp, the Baldwin gearbox is vastly over-engineered. It’s a slightly curious design. The engine drives an input shaft, which runs parallel to the long axis of the loco, and has a bevel gear on the end. This bevel gear drive the two large gears visible on the middle of the shaft – one clockwise, one counter-clockwise. These gears are free to rotate on the shaft, and turn the drive through 90 degrees – the shaft being fitted sits transverse. A dog clutch slides on the shaft and transmits drive from the rotating gears to the shaft itself. In this manner, the dog clutch determines if the loco is going forward or backwards, depending on which gear is transmitting drive. Spur gears then transmit drive to a lower shaft, which selects high or low speed – note that the spur gears at each of the shaft are different sizes.
The input shaft has had new bearings and a general fettle; the top shaft was fully dismantled and shims fitted to combat excess wear (manifest as alarming wobble) in the bearings within the large bevel gears where the shaft rotates within them.
This is one of those odd moments when one reflects on the fact that you’re doing something which only a handful of people on the planet have ever done before!
