Starter Motor Tooth Profile 1

[jgrayfpr]

Hi

I am designing a flywheel and starter motor package. I know the stub tooth profile detail for the flywheel but not for the starter motor gear. what tooth profile does the starter motor gear use? It looks like an involute tooth form that is quite different to the straight cut fly wheel gear.

Any help is greatly appreciated

Regards

Jason

 

[tbuelna]

The geometry of a starter pinion and flywheel/flexplate ring gear mesh is highly modified. This is due to the extremely high gear ratio, and the very low number of teeth used for the pinion (typically around 9T to 12T). I believe both the pinion and ring typically use involute geometry, but I imagine there are lots of tweaks to the basic involute geometry (profile shift, tip relief, etc).

Getting this type of extreme gear mesh to provide acceptable performance is not easy, and requires someone with lots of relevant gear design experience. There are companies that specialize in high-performance aftermarket starters/flywheels/flexplates such as Tilton. You might try contacting them to see if they would be willing to provide some guidance.

Good luck with your project.
Terry

 

[gearcutter]

As tbuelna has mentioned; the pinion is going to be modified so as to remove the undercut which is created below the active portion of the tooth profile when generating teeth numbers of 18 or less (for 20deg PA). The modification will be a shift in addendum which will result in a stronger tooth.
If you're going to be using an existing ring gear; the most important aspects to determine first up are the centre or mounting distance and the number of teeth that you intend on using for the pinion.
Another important thing to remember is that both gear and pinion will have a tooth modification known as a 'lead-in chamfer'. The chamfer is generally applied to the drive flanks only but I have seen older designs where it is applied to both flanks.
The geometry of the chamfer can be somewhat tricky to reverse engineer and to also manufacture.
You're probably best off to take tbuelna's advice and try to get in touch with someone like Tilton.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181