Center to Center Distance in Power Transmission

[Andrew Zeller]

Originally Posted by compwiztobe

The next simplest is chain and (timing) belt stages with two pulleys or sprockets of equal size. If the number of teeth is even, it's apparent that each sprocket uses half of its teeth in belt at any given time, and its pretty simple how that can be extended to sprockets with odd numbers of teeth (for large enough sprockets). This basic approach leads to a CD of the belt or chain length minus teeth on one of the sprockets, all divided by two (CD = (length - pulley size)/2 (in teeth) ) appropriately converted via the pitch. This means that the CD should be an even multiple of the pitch. But what tolerance matters in this case? Would experts typically undershoot by that tolerance or some percentage to ensure it is not over tight? Are there other considerations that should be taken into account?

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?