# pic: 3 CIM PTO With Break

Any reason as to why you have such a huge gap around the CIM motor’s raised face?

If its the spot I think you’re talking about, I would bet its so the gear on the CIM (which appears to be a bit larger than most) can be taken off with the motor… but that’s just a guess.

Yup. That’s right.

If you use the 12t pinion instead the 14t it fits in the profile of the .75" boss, so this is guaranteed. And a smaller pinion gets you the needed reduction in fewer and smaller stages. But 14t may be appropriate in this case, I wasn’t around for your decision-making process.

I was thinking about doing something like this, but I couldn’t figure out how to do the gear spacing. Because I didn’t know the spacing for different gear-sets, I couldn’t choose the right ones. How did you avoid that issue?

In FRC a lot of people use the following formula to calculate gear center to center dimensions:

C to C = ((N1 + N2) / (2 * DP)) + .003

N1 and N2 are the number of teeth in the two gears you’re meshing, and DP is the diametrical pitch of the gears (which in your case is 20).