Matt's Desk

Mamod Steam Engine Gears

Having acquired an old Mamod steam engine in a charity shop, it became apparent that the toy had a significant drawback: the simple oscillating cylinder must run very fast to be able to drive the engine’s movement or any auxiliary items powered by it.

The gearbox was designed to slow the output speed of the engine, with the additional benefit of increasing torque. The housing was constructed from two steel plates with holes drilled for simple brass bushings to be oiled prior to use.

The gears were cut on the shaper machine, using Lego gears as reference for diameter and tooth profile. The brass blanks were first cut to diameter, then held in a 90 degree indexing head on the shaper to cut each individual tooth.

Cuts were taken in 0.10mm intervals to a total depth of 1.2mm per tooth. For a 24 tooth gear, this worked out as 12 cranks of the handle per tooth and a total of 576 cranks to produce a gear. A good album in the background was an essential requirement for this work!