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sprockets

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Philip Burley04/10/2020 19:43:52
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198 forum posts
1 photos

If I wanted to make a sprocket for a 1/2 pitch chain , would the calculation for the pitch circle be the same as for a gear with 1/2 pitch teeth ?

regards

Clive Foster04/10/2020 20:01:49
3104 forum posts
107 photos

According to this link sprocket and gear PCD aren't the same. **LINK** . The bit of maths in there looks as if it should be simple enough to follow.

Clive

Oily Rag04/10/2020 20:16:51
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540 forum posts
184 photos

Philip,

A lot depends on the number of teeth you need on the sprocket. Small numbers between 16 and 20 require a different calculation to higher numbers, from about 35 and up there is a small difference from gear tooth calculation. The system is orthagonal, in that the drive is not a constant speed due to the straight line links from one roller to the next. This induces a torsional oscillation in the drive which is why motorcycle drives incorporate a 'cush drive' system.

I have some sprocket cutters which are for 0.25" roller x 3/8" pitch, and one which is for a 0.335" roller x either short 1/2" or long 1" pitch! I see Clive has posted a link for a calculator which has saved me digging out my calculations for the sprockets I cut - generally they were 18/19 tooth gearbox and 43 - 53 for the rear wheel on my BSA racer (see avatar!!)

img_3388.jpg

Oily Rag04/10/2020 20:29:57
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540 forum posts
184 photos

Philip

Just looked at the equation in Clive's link posted above and the ANSI method is the one to go for, my calculation was based on the ANSI standard from Machinery Handbook.

Regards

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