The 2.8:1 ZG38 reduction gear unit is available in two versions, side mounted and inline. The side mounted system has the drive shaft running alongside the carburettor and is ideally suited to radial cowls, such as our Sopwith Pup. The inline version has the drive shaft running over the top of crankcase making it suitable for in-line engines aircraft such as the Tiger Moth.

The distance between the drive and crankshaft is 70 mm centre to centre. The length of the motor fitted with the reduction gear is the same as the standard motor when fitted with the standard motor mount. Fitted with reduction gear the complete ZG36 and gearbox assembly weighs 2700 grams. The reduction gearing uses two miniature Polyflex ‘V' belts produced by Gates in the USA. These Polyflex belts are more flexible, smaller and thinner than any other belts around and in spite of this can transfer more power as well as requiring a lot less space.

The life of these Polyflex belts is unusually long, with units being run regularly over a 6 month period before belts require changing. Because two belts are fitted, it is highly unlikely that the belts fail simultaneously. When a belt fails, you can carry on flying without noticing anything until the next start. With only one belt it is nigh impossible due to slippage to start the engine, but a pair of new belts are easy and quick to refit.