Gear Spacing Help

[AdamHeard]

I'm updating a transmission design without much experience and I can't find the right spacing to match the 50 tooth gear from the old KOP gearbox (5-11 in this manual (http://www.ifirobotics.com/docs/2006-first-transmission-manual-rev-d.pdf)) with the 28 tooth gear (http://www.andymark.biz/am-0108.html) from AndyMark meant for the Large CIM motors.

I've heard "sum of the diameters divided by 2", but I can't find any dimensions for the gears. And which diameter? the teeth, or the bottom of the teeth?

[Raul]

You the "pitch diameter". Like you said, A rough rule is to use the sum of the two PD's and divide by 2. In some cases you need a few thousands of an inch more, but as long as you lube it properly, it willwork just fine with your formula.

Raul

I forgot to mention that you can find PD if you now the "Diametral Pitch" of your gears - DP's come in standard sizes such as 32, 20 or 16. This represents the number of teeth / inch of diameter. So, you can find the PD like this:
PD = Nt / DP (where Nt = number of teeth on a gear).

[CraigHickman]

If this is 20dp, or 24dp, I have the catologue of all Martin gears (a common supplier), and would be willing to look up all the sizes you need. Either shoot me a PM or AIM me.