Drill Motors....OVERHEATING, DRIVETRAINS!

[Gope]

A quick blast of "Cold Spray" should keep your breakers from tripping.

[LoganB]

Originally posted by Guyute
the drill motors on our robot have overheated sooo bad that the plastic case they sit in is melting.

You really might want to fix that with the little muffin fans and or using the large muffin fan to keep the fans cold.

[Al Skierkiewicz]

The rules still state only one large fan, unlimited small fans. Actually, this is the rule we are quoting...

C7
You must use 16 AWG or larger diameter wire to connect the window motors to the
Speed Controllers. You must also use 16 AWG or larger diameter wire from the
Circuit Breaker Panels to the Robot, large muffin fan, and any other connections to
and from the Relay Modules. The only exceptions are that 24 AWG wire may be
used to connect the small muffin fans and any LEDs to the outputs of a Relay
Module.

Since this rule uses the singular for the large "fan" and the plural for the small "fans" in reference the interpretation is one large fan only.
I always caution teams to use freeze spray sparingly, as shock cooling can cause some parts to crack and the spray can wash lubricant out of the bearings. Cold parts in a humid environment will also condense water on the surface, be sure to allow it to dry first.

[Andrew]

We're using a 4:1 planetary on our drill motor and feeding that into a 29:1 spur gear box. We have six inch wheels. This gives us a GR of 116:1 from the drill motor output to the wheel axle.

This gives us about a 4.1 feet per second top speed and about 1000 lbs of pushing power (barring slip of course). We have four motors in the drive system, so don't go trying to figure out how to get these numbers with just the two drill motors.

Since our second year (2001), we have used a big, achin' aluminum tube heat sink surrounding the motor with small muffin fans constantly forcing air through and across the motor.

We have not (knock on wood) experienced any over-heating with our system and we have pushed it pretty hard.

We had two years (2000, 2002) where we used a much higher gear ratio. I don't have the numbers in front of me, so I cannot give them to you, but figure at least 2x the above GR. In those years, we popped circuit breakers when we really ran our robot roughly.

There are issues of gear box efficiency that factor into this mix. If your GR is comparable to the one I quoted, but you still have these problems, you might discover that you are losing a lot of energy in your gearbox and therefore increasing the current your motor draws in order to run at the above torque/speed point.

There may also be issues with how your drive system is laid out. If you are using differential rear wheels and casters, you will have some difficulties with maneuvering on the hill. You have to use a lot of torque when you correct to go straight on the hill, because your system will not naturally resist turning.

I don't know what you can do at this point. If you have sprockets driving your output, you might be able to put a big sprocket on your wheels and keep motoring.

[camtunkpa]

THERE IS AN EASY AND LOGICAL SOLUTION!!!

The motors are getting too hot and popping breakers simply because your gear ratio is not low enough. This is also causing the dead band when you move the stick. To correct the problem first try switching the gearboxes to low range, if they are already in low range then decrease the size of the gear on the motor and/or increase the size of the gear on the output shaft. I highly doubt it is a problem with the brushes because he had our assembly pop, but they were still working fine. I suggest this is not a problem with the motors or electronics, but a problem with the gearing. Since you tripped the breakers repeatedly (I am guessing) I would also suggest replacing them after solving your gear ratio problem. Good luck and if you ever need any advice, call on 222.




P.S. another tip is instead of using the plastic mounts provided, make your own aluminum ones, not only will they be stronger, but they will dissipate heat.