A series of models to demonstrate different gearing systems. With transparent slideplates, the gears may easily be seen and where necessary there is an index on the primary and secondary shafts to show the change in the direction of rotation and the relative speed of rotation. A simple three-speed and reverse-gear system using spur gears. Reverse gear is obtained by interposing a small lay-shaft mounted pinion between the two main shafts. Gear selection is by means of a short ball-ended lever.