FP motor gear DP & PA, source ?

Does anyone know the specs of the stock metal gear that is on the FP (not cim) motor ?

What Diametral Pitch ?
What Pressure Angle ?
What shaft diameter ?

Anyone know of suppliers that sell gears that can mate to it ?

I am presuming the thin plastic gear in the black transmission won’t survive long in a First environment ?

Anyone know if noisy planetary gear-case could be less efficient than a standard 2 gear transmission ?

I can answer some questions but not others.

Historically, FP uses gears on their motors that are 32DP, 20 Deg. Pressure Angle. They do not usually enlarge the pinion. It is essentially a standard gear made to the slightly modifed standards for plastic gears – for anything we do in FIRST, you can pretend it is a standard gear.

The upshot of this is that you can verify the DP data by just measuring the OD of the gear and dividing (Nteeth +2) by the OD.

For example if the OD is .563 and the gear has 16 teeth, you would get a DP of 18/.563 = 31.97 or 32DP.

As to the planetary gear effeciency vs. straight spur gears, spur gears will almost always be more effecient. I typically estimate spur gears to be 95% effecient per stage and planetary gears (with ratios less than 5.5 to 1) to be 85% effecient per stage.

If you get two stages the planatary gears would give you 72% eff. while spur gears would give you 90%.

As to the shaft diameter, it is the same as the Mabuchi motor. From the Mabuchi print the shaft diameter is 3.17mm +.007/-.005 = (.125"+.0000"/-.0005").

As to surviving a FIRST application with the plastic gears, this is done by many teams. It depends on the application. Big arms or main drive motors would make me nervous. Pitching machine wheels and auxilary ball collector belts wouldn’t give me heartburn at all.

A word of caution about Nteeth. There has been variation from kit to kit in the past over the number of gear teeth on the pinions with some getting N and others getting N+1 or N-1 or N+2 or N-2. If you count the number of teeth and share them with us here, please provide the part number of the motor as well so we can sort things out.


Joe J.

Our F-P is a 9012, and it has a 32 pitch, 19 tooth pinion on it.