There have been some discussions recently about drive train sprockets being too small for certain wheel sizes. I have been looking for references to guide sprocket and chain selection for various wheel sizes but have not found anything. Are there general recommendations (for non-engineers) on what size sprocket is too small for a certain wheel size? And does the type of wheel matter?
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Why can certain sprockets be too small for large wheel sizes?
Torque = force * distance. Larger wheels result in larger torque for the same surface force. Smaller sprockets result in larger force (on the chain/teeth) for the same torque. It’s possible to have force high enough to cause failure of either the chain or the sprocket teeth.
I’ve never heard for chain, but we used 12t #35 sprockets this year on 8" wheels and never had an issue with throwing chain or breaking sprockets.
The rule of thumb I’ve heard people use here for sizing pulleys on drivetrains is 7*(diameter of wheel). So on a 6 inch wheel, the smallest pulley you should use is 42t HTD 5mm.
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