Hot Motors

[Lisa Huang]

How can we prevent motors from overheating?

[sanddrag]

heat sinks and/or fans. If the problem is really bad, you are geared to high and need a larger reduction.

[Phil_Lutz]

Muffin Fans mounted over the motors.

Use the 4 inch muffin fan over the pair of Drill motors works great.

Phil

[JP_1163]

Our team also uses the muffin fans and that seems to help a tremendous amount. I'd like to discuss the idea of a heat sink with any team that uses them. Team 1163 is using the CIM motors and they are quite large. We're not sure how a heat sink could be built and how it could reduce heat while promoting designability and amterials usage.

[Joe Ross]

Originally Posted by Lisa Huang

How can we prevent motors from overheating?

Make sure that your motors are geared low enough that they don't come close to stalling.

[KenWittlief]

one thing we have noticed about the drill motors and the supports FIRST supplied for them - the black plastic supports block a lot of air coming from the blower inside the motor.

We experimented with the parts from last year, cutting an angle into the flat sections of plastic, and the increase in airflow from the motors is VERY noticable.

We intend to mod the ones on this years robot if/when we have the motors out of the bot again.

[Greg]

If the motors are REALLY overheating, nothing can save them Electrical motors don't like spinning slowly. We just melted a drill motor yesterday. Some advice - never allow a motor to sit there with some power applied to it This happened to us when the default robot code was uploaded into the RC and an uncalibrated joystick was left connected to the OI for aout 2 minutes. So, either recalibrate speed controllers or create a large "deadzone" in your code.

[bigqueue]

We have plenty of tem problems with Drill motors....and we simply blow the muffin fan over them and they are totally tamed!

Our CIM motors seem to have a much larger themal mass, and seem to overheat much slower. I suppose if we kept them running for extended periods, they would also turn into red-hot pokers eventually......but our batteries seem to die in about 10 minutes.....

-Quentin

[Srkasner]

For our drill motors, we made an intricate prototype cooling system (Though we're not using it because of weight issues):

We measure the motors to be 1 3/4 inches in diameter. When in the mount, 1 1/4 inches of motor was accessible. If you buy a copper pipe 1 3/4 in diameter, cut it in half so u get 2 semi-circle pieces of pipe. Then cut those pieces to be 1 1/4 inches long. Polish the inside and put some thermal compound on the inside. Then get a pipe 1 inch in diameter and solder the two end pieces you just made. Drill 2 1/2 inch holes 1 inch from the end of the pipe. Then drill a 1 inch hole in the middle and put a small muffin fan on the top so it’s sucking air out. This device becomes very cold and is a great way to cool off motors easily.

~Steve
Team 1124

[pryoplasm]

Originally Posted by Srkasner

For our drill motors, we made an intricate prototype cooling system (Though we're not using it because of weight issues):

We measure the motors to be 1 3/4 inches in diameter. When in the mount, 1 1/4 inches of motor was accessible. If you buy a copper pipe 1 3/4 in diameter, cut it in half so u get 2 semi-circle pieces of pipe. Then cut those pieces to be 1 1/4 inches long. Polish the inside and put some thermal compound on the inside. Then get a pipe 1 inch in diameter and solder the two end pieces you just made. Drill 2 1/2 inch holes 1 inch from the end of the pipe. Then drill a 1 inch hole in the middle and put a small muffin fan on the top so it’s sucking air out. This device becomes very cold and is a great way to cool off motors easily.

~Steve
Team 1124

luckily enough, when disnging brackets for our CIMs and drills that are used on the drive train, we included a heat sink, however, some overheating occurs no matter what.

in the past we used a anti static circut coolant that goes about -60degrees F and -51degrees C. be careful, it is intended for industrial use only,and is the kind of stuff that gives you instant frostbite if applied to skin. as someone who has had cold hands on the team, trust me and keep this safe if you get it.

its called freez-it, and is made by chemtronics

hopefully this helps

[henryBsick]

Kast year all we did was make our own completely aluminum mounts for the drills. They were connected directly to the frame. They acted as a huge heatsinc on each motor and it was all we needed. Never over heated once. This year we us ethe CIM's and we also have them mounted in an aliuminum gearbox/mount. The aluminum only touchs the black part of the CIM's though. It does some good, but because it is not on the endplate where the wires come out, and all the heat goes, it can't absorb that much. We are going to go with it though. Through our practices we have only had two cool down a couple of times, after ten min. of continuos running. Good luck with the heat problem.

[psyco_klown]

last year our team had that problem we just put springs around the motors and it worked so we did it just in case

[Jay H 237]

If you do attach a heat sink to the motors it is also a good idea to put some heat sink compound between the motor and where it touches the heat sink. This will aid in transfering the heat from the motor to the heat sink. A small tube of heat sink compound is available at Radio Shack for under $5.
It's also possible that over time the cooling fans/fins in the motors will get dust and debris stuck to them decreasing air flow. This is also possible if you were doing any work on the robot (filing, grinding, ect.) near the motors that could cause debris to enter them. In this case you would want to blow the motors out with compressed air or one of those aerosol cans used for dusting electronics.

[Al Skierkiewicz]

Originally Posted by Lisa Huang

How can we prevent motors from overheating?

Lisa,
You have a lot of good ideas here. The absolute best one is to make sure that the mechanical design is such that the motor is running in an efficient area of the motor curves. By designing your drive train to optimize power and speed you lower the electrical current and hence the heat caused by the excess electrical current. When the motors are run at these design speeds, the internal fan also is efficient enough to remove some of the excess heat. Adding external fans is the next best, but the tradeoffs are more weight and current demand. Heatsinks are also useful but only to the extent that they can effectively remove heat generated within the motor through conduction. In the case of the drill motor, the majority of heat is generated in the armature which is only connected to the case at the bearings and brushes. Fans can move air around the armature but heatsinks cannot.
I am not a big fan of the coolant spray idea used by some teams. The spray does produce a thermal shock on the metal parts of the motor and if you use enough, the metals change size (thermal contraction) and affect clearances inside the motor. The compounds used in the spray also tend to wash the lubricant out of the bearings. Finally, that nice white frost that occurs when you spray the motor is moisture from the air being frozen by the spray. As the frost melts that moisture may end up in your motor or other electronics where it can cause some real damage.

[petek]

This topic has been flogged pretty thoroughly before in these fora (do a search for "motor overheat"), but seconding Joe and Al's recommendation - choose gear ratios that will let your motors run at efficient speeds. Remember that motors convert electrical energy into mechanical energy and heat.

To see how the drill motor speed is related to its efficiency, download the Skill Bosch with Gearbox Performance PDF from FIRST.

There are a number of excellent white papers (in the technical section) on motor and gear ratio selection.