Sprocket Teeth

[shazim]

Hi everyone!

I was hoping some can help me with a modeling issue; I'm trying to replicate a bicycle sprocket but i can't get the teeth right. I've attached a few photos. The teeth on my model keep coming out too sharp unlike the smooth curve of the sprocket.

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[JimTVancouverCa]

Are you using standard engineering gear fundamentals to drive your choices in geometry creation?  It looks like you have the right curve, but the tip diameter to pitch or something along those lines isn't working out for you.

It's been a while since my mechanical eng undergrad, but perhaps this reference can help? http://www.molenberg.nl/downloads/Chain%20rexnord%20Auslegung%20Kettentrieb%20(En).pdf

- Jim

[TomD.inPDX]

Bicycle chain rings are a strange animal when it comes to design.  They have very little logic to the shape of the cut.  And often, they are not even the same.  Much of these deviations are accounted for in the quest for quick and smooth shifting.

In general, you simply need an 8mm pocket on a 1/2" cord length along the chain-line diameter.  You can treat the ends any way you like as long as they miss the incoming and exiting chain roller.

Try putting your picture on a plane and just overlaying a model to get a feel for the true geometry.