Fisher Price Breaker Size

We are using 40 amp breakers on our FP motors because there are times when we want that extra power kick. The FP motor can handle 40 amps but only for short periods of time at high RPM. We know we could conceivably burn up a few if something goes wrong (gearbox jam, stall, etc).

More important than breaker sizing is watching your loads. FP motors have a very distinct smell when they burn up (the insulation on the motor windings burns off). The first time you blow one up, you won’t forget it.

Watch your loads! Don’t rely on the breaker to save the motor.


John’s advise is sound (as always). The FP suffers at “high loads” because it requires active cooling. Look at those vents at the rear and you will see fan impellers integrated into the motor assembly. This is why the body is so small in size compared to the power of the motor.

An FP at stall will almost immediately destroy itself regardless of the circuit breaker used (it might survive with a 20A, but I doubt it).

Bottom line, never stall a Fisher Price motor…



If you don’t see the fan blades it is because you may have already melted them off. In which case this is another warning sign that you’ve overloaded the motor.

I wish I was joking.


Okay I have a question about how many Fisher Price Motors we are allowed. I was under the assumption that we were allowed an unlimited amount, but now I’m not so sure.

According to this:

COTS – A “Commercial, Off-The-Shelf” COMPONENT or MECHANISM, in it’s unaltered, unmodified state. A COTS item must be a standard (i.e. not custom order) part commonly available from the VENDOR, available from a non-team source, and available to all teams for purchase.

<R51> Motors specifically permitted on 2009 FRC ROBOTS include:

A. All motors, actuators, and servos provided in the 2009 Kit Of Parts,

B. An unlimited number of COTS servos with a maximum output torque of 55 oz-in andm aximum rotational speed of 100 rpm at 6 Vdc (e.g. HITEC model HS-322HD or HS-325HB servos, as provided in the Kit Of Parts),

C. An unlimited number of FIRST Tech Challenge (FTC) servos (HITEC HS-475HB servos),

D. One or two additional 2-1/2” CIM motors (part #FR801-001 and/or M4-R0062-12) in addition to those provided in the Kit Of Parts. This means that up to four, and no more, 2-1/2” CIM motors can be used on the ROBOT.

E. COTS motors used as one-to-one replacements (i.e. identical vendor and
part number) for motors, actuators and servos provided in the 2009 Kit Of
Parts that may have failed or become inoperable.

According to R51 E. it appears that we are allowed two fisher price motors.

Am I reading this wrong? I always thought that each team could have as many fisher price motors as they wanted?

Thank you for any help you can give in clearing this up for me, and thank you for all the previous posts they helped a lot.


You are allowed only two FP motors on your robot.

Madison is correct. If you read rule <R52>, it bans any motors except what is specifically allowed in <R51>. One-to-one replacement means that if you are got 2 motors in the KOP, and you can’t put more on by some other portion of <R51>, you can only use 2 that are identical to the KOP ones.

Note: My advice on how to determine if a motor is allowed is to read <R52> first, then read <R51> to see if the motor is one of the exceptions to <R52>.

If you are using the 2009 KOP FP’s that came attached to those big black transmissions, they have changed since last year. The new motors have a stall current of 109.410 amps. Yes, this is absurdly high for such a small motor, but that is just how amazing these things are. So, I’d say you should start with a 30, because based on your explanation of your application that seems like it will work. If you blow those, go to the 40. The motor will be just fine. The important thing is, as others have said, don’t stall the FP… Even though they have a stall current near that of a CIM, if you do stall these, their internal cooling fans will not be spinning, causing the motor to overheat.

Can you show the data for this rating? FP motors have never been rated over 100 amps.