How to Calculate the Correct Gear Modulus for a Motorcycle Project?

[Kleinelars1]

Hey Guys,

Sorry for my poor englisch, I'am Lars from the Netherlands and currently working on a project. For my motorcycle racer I'm making a "paddock starter" by a 12V car starter from a VW T5 transporter 2.5tdi.

No I am having difficulties finding the right gear to match the current starter motor Gear/pinion. Obviously I tried finding the Modulus, but encountered the problem of receiving a 2.3 as a result, but this sould be 2 or 2.5

So, is there anyone who can help me find the matching gear, or explain how to calculate it properly?
Specs of starter motor gear;
Outer theeth top diameter 27.7mm=1.0905 inch
Pitch diameter 23.7mm=0.9330 inch
Diameter of axle at bottom of the teeth 19.7mm=0.7755inch
height of teeth from foot to top 4mm=0.1574
Teeth is 4mm=0.1574 wide at bottom

Hope anyone can help me.

Lars

 

[jrmichler]

How many teeth on your gear? How did you measure the pitch diameter?

Small gears (small number of teeth) are sometimes designed with profile offset to make the teeth stronger. If that is the case, the pitch diameter will not be what it looks like. Can you measure the flywheel gear from the VW? Any profile offset will have only a small effect on your measurements.