Hello forum,

I want to build a gear reduction for an engine using timing pulleys and timing belts.

The engine is a 2-stroke gasoline engine capable of producing 12-15hp at a maximum RPM of 7500. It is for a RC airplane so it drives a propeller.

I need some advice on selecting the pulley and belt type.

Pulley material is easy, it must be light weight, so aluminium or maybe injection molded, glass reinforced nylon, would that work for an engine power transmission application?

Gear ratio is also easy to calculate. And I have found some advice saying that a minimum of 6 teeth of the smaller pulley must be engaged to transfer the torque.

But there are so many options of pulley teeth profiles. My local supplier has a wide range, but these seems to be the ones made from aluminium:

Type: HTD - GT
Teeth profiles:
14M
3M
3MR
5M
5MR
8M


Type: T/AT
Teeth profiles:
AT5
AT10
T2.5
T5
T10

The driving pulley should be around 30-50mm in diameter to be able to fit the engine. The driven pulley would be larger to accommodate a gear reduction ratio of 1.5:1. The two pulleys would be placed very close to each other.

So which pulley type and teeth profile would fit such an application?

Thanks.