Black FP Transmission Gears

Hey Cd,

I was looking for the specs on the gears that inside the “2009 Black FP KOP Transmission”. I don’t have access to the shop till next week, but a local team needed some plates machined out because their banebot planetaries finally kicked the bucket. All the gears were grinded and worn out, very kewl to see. I just needed the teeth count and the DP/module of each gear.



If you can wait until Tuesday evening and want to PM me an email address, I can send you a picture of the gears and you can count teeth. I’ll also measure the OD of each gear and you can work backwards to the rest. Unfortunately, that’s about the best I can do for you.


I would love that.

Thank you,



Here are the ODs of the gears and the tooth counts. As far as I acn tell, all of the gears in the FPs are the same regardless of color. The motor pinion may change. In the 2009 KoP I think the motor pinion had 16 teeth. The other option is 19 teeth. I don’t have a 16 to measure, but the 19 tooth one measures .673" OD.

            Large OD            Count	                Small OD      Count

Gear #1 2.283” 72 teeth .870” 25 teeth
Gear #2 2.510” 79 teeth .919” 19 teeth
Gear #3 2.634” 62 teeth 1.300” 12 teeth
Gear #4 3.501” 38 teeth

Hope this helps,


I’m pretty sure the FP gears are .8 Mod. (Based on my recollection that stock FP pinions are 31.75 DP, aka ~32 DP. Knowing DP = 25.4/Mod you can solve and get .8 Mod)

Pitch Diameter (mm) is Mod x Toothcount.

So, for the 72T gear.

PD (mm) = 72 * .8 = 57.6 mm

PD (in) = 57.6 mm x (1 in / 25.4 mm) = 2.268 in (although I imagine it’d be more accurate to just enter the metric units into SW)

I know you already know how to get C-C distances, so that should cover it for you.

Thank you Ivan and Adam, big help there. Now I can get to CAD’ing that gearbox.


Adam is probably right about the .8 mod but that would only be correct for the pinion and the first 2 plastic gears. Second to third is a larger tooth and third to fourth is larger yet.

Here are some approximate CC distances measured from the one in my basement:

Motor to #1 1.375” approximately
#1 to #2 1.630” measured across the idler shafts and subtracted .375”
#2 to #3 1.707” also measured across the shafts.
#3 to #4 2.247” approximately because there isn’t much to measure to on the last gear.




Ivan is totally right, I’m an idiot. Of course the Mod would increase as the reductions do.

I guess set up some formulas to get an approximate mod based on those C-C, then round the Mod to the nearest actual (it should be pretty darn close), then calc a precise C-C from that.