[Andy A.]

The fisher-price motor has been with FIRST for years, in various models and makes. They all are around a 100 watt motor in a 550 can. They have, far and away, the highest power to weight/volume ratio of any motor in the kit.

The downside of that power in a small package is heat. These motors will very quickly overheat and fry if allowed to stall or even under load at low speed. They work fantasticly, right up to that critical temperature where the insulation melts. Reach that and the motor dies in seconds. There are ways to avoid that point, however.

1. Don't worry much about using heat sinks and fans etc. These motors, like all motors, overheat in the windings. Cooling the can doesn't do you any good over the course of a two minute match and the duty cycle these motors encounter. By the time the heat makes it through the end bearings to the can it's already done it's damage. If the rounds lasted longer and the motors ran a consistent speed the whole way through heat sinks and fans would make more sense.

2. Do not stall or overload the motor. I've heard 2/3 free speed kicked around as a good number to gear for. That means that you should gear such that, loaded, the motor should not drop below 2/3's of it's free speed.

3. Do not block the cooling vents. These motors have plastic fins attached to the back end of the armature shaft. These provide the only real means of 'active' cooling. If you don't block the vents and keep the motor spinning fast they are perfectly adequate at keeping the motor from frying. Let it get too hot and the fins melt off. After that happens it's about 3 seconds before all the magic smoke comes out. As always, the faster these motors are spinning the happier they are.

4. If at all possible, keep the vents on the front of the motor clear. If you can stand off the motor just a little bit to keep the front vents open then a good deal of air from the fan will pass over the armature and right out the front. I can't offer any hard data on how much this improves cooling, but it can only help.

5. In between back to back matches you can hose the motor down with cool-in-a-can or compressed air cans turned upside down. It's not good for the motor but it's probably better then running into a match preheated.

Always keep in mind that these motors have to make it through two minute matches at a time. You can get away with just about anything short of a stall or low speed under load. If you get through a day of matches on one set of FP motors, I consider it a win. Balance the longevity and health of the motor against the design of your robot. Maybe beating the snot out of the motors is the only way to get something to work right on the robot. If so, then balance that against your budget and ability to find replacements.

-Andy A.