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Unread 28-10-2012, 16:37
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FRC #2175 (The Fighting Calculators)
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Re: Center to Center Distance in Power Transmission

Quote:
Originally Posted by boarder3512 View Post
I am designing a drivetrain and I am trying to design the center distances from the center wheel to each outside wheel so that no chain tensioners will need to be used. I think I am doing this right but can you check it?

Both wheels will have 22 tooth AM sprockets with #35 chain. The pitch diameter of the sprockets is 2.638" and the pitch of the chain is 3/8"

Now distance= ((#chainlinks*chainpitch)-sprocketdiametral pitch)/2

Since I want my distance to be approximately 16", I solve for # of chain links and get 92. Then I put 92 in for #chainlinks and find my center distance to be 15.931"

Is this the right way to do it? Will this make the chain at a perfect tension when it is put on?
Using my approach that you quoted:

You are taking the sprocket's [b]circumference[\b] (an integer number of teeth) into account when calculating center to center distance. If you have two equally sized sprockets with N teeth each, each will take up N/2 links of chain. Then the length in the middle has to total an even number of links, unless you're fine with using a half link, so the separation between the sprockets should be an integer multiple of the pitch.

So in your case, 16" is not a multiple of 0.375" (#35 pitch), so the chain will not be tight. You would want to go with 15.75" or 16.125". If you want exactly 92 links in your chain for whatever reason, it would be (92-22)/2 times the pitch for the c-c, which is only 13.125".