Steel pinion vs. plastic

[AshleyJean]

This is a fallow up question from the students that are building the high mileage car. In a coast and burn situation where the engine is on for 3 second and off for 45 seconds while reaching 6000 RPM, is a steel pinion nessessary? Because of the short amount of run time, low temperatures, and relatively low forces do you think plastic will be okay? The entire car only weighs 200 lbs. and only reaches speeds of 25 mph. The main reason that we like the plastic, is we have a small CNC machine and can mill our own parts. Not in steel. The Master CAM program that we have, will calculate simple spur gear profiles. What do you think? Please any sugestions are welcome. Thanks for your help!

 

[MattRR]

Plastic gears usually are ok to 1 hp.

 

[umreng]

There are many engineered plastics on the market that can be (and are) used in successful gear and pinion applications. The important thing is to look at the maximum expected actual beam load on the gear teeth at operating temperatures. The lubrication is also very important from an operating temperature standpoint. Some plastics (such as Nylatron GS) have built-in lubricating properties which may be helpful. Be sure to look at the effect of thermal expansion in your design.