smoking drill motors?

We are well into power distribution and onboard systems but when we hooked up our drill motors for a brief test, we got a small puff of smoke after they began to run (only 2-3 seconds had elapsed). A melted plastic smell was also apparent. Is this normal burnoff due to being new motors and being run for the first time or have we done something truly wrong?

Any advice is greatly appreciated…


It didn’t happen to us, so I assume it isn’t normal. :frowning:

When Team 25 ran our drill motors last year for extended periods of time or under strenuous conditions, they would heat up and the plastic ‘spiders’ would begin to melt in the couplings. Not certain if this is related at all.

I’m sorry, this is a nonsmoking forum please extinguish your motors before entering. (just kidding!!! :smiley: )

Seriously, with out seeing the motors it’s tough to tell if something is truly wrong. It is possible the “smoke” you saw could have been dust that blew out of the motor when it was first turned on but since you mentioned a burnt smell I’ll lean away from the dust idea. It is also possible that during assembly at the factory grease could have gotten somewhere it shouldn’t have, say near the brushes or electrical contacts, and that is what you saw plus it could also give a burning smell. The final possibility is that something is wrong with the motor or the way you hooked them up. You did mention “motors” which I take as more than one and the possibility of two defective motors in the same kit is unlikely although still possible. Did you do any modifications or disassembly to the motors before running them? Can you see anything burnt or discolored in the motor? You may have to use a flashlight near the motor vents and if there was anything it would most likely be at or near the brushes. My last question would be did you run them anymore and the smoke was only at the initial start up? We haven’t had any smoke from our Bosch motors.

We did do a little engineering on the motors, but nothing that would smoke or cause melting. We have not tested the motors again since we saw the smoke. We will be dissasembling the motors tomorrow for another looksee. I will let everyone know if we find the problem and a solution.

Thanks for your responses…

I have seen these motors:

  1. Smoke

  2. De-solder themselves (no joke)

  3. Cut off their own fins because the black plastic melted and hit other components inside

  4. Break off their black connectors after falling a mere 3"

And so much more…

Just make sure you always have a fuse in there when you’re testing and/or messing around with them, and be careful–you don’t want your hand anywhere near the pinion when they are just firing up or stopping.

This is not normal. With everything else being normal, this condition would indicate the the brush assembly had become loose and either the brushes were overheating or they were contacting the fan and melted it from the friction generated. Had you soldered new wires on the drill motors or were you using the original supplied wire? Soldering to these motors takes a real expert and I would recommend that you remove the brush assembly to solder new wires on. Last year’s rules required you to keep the supplied wire intact but I have not seen anything about it this year.

From FIRST QA board.


Section: Status: Answered Date Answered: 1/26/2004
Q: Can we replace the small blue wires that provide power to the drill motors with 10 gauge wire?

A: You may not replace the blue wires, however, you may shorten them such that there is a minimum of 1.5 inches still attached to the motor and solder heavier gauge wire to their cut ends. Do not attempt to unsolder the blue wires from the brush housings. The plastic brush support housing will distort if exposed to soldering temperatures and the alignment of the brushes will be affected, which can permanently degrade motor performance.

when you ran the motors did you use Victors and the 40 amp breakers, or did you connect them right to the battery to test them?

also, were you doing any machining, fileing, drilling on the bot or drivetrain with the motors present?

its possible you got metal chips into the motors

also, were the motors loaded down or spinning freely? if your drivetrain is binding up, and you didnt put breakers in the circuit, then yes, you can smoke them in a few seconds connected straight to the battery if they are stalled, or can just barely turn.

I have seen motors throw their commutators and have the brushes jam (defective motor)

the fact that you said ‘motorS’ is disturbing - I doubt you would get two defective motors - if more than one smoked its most likely something you did to them.

OK, one stupid question: you do know these motors are 12DC, right? you didnt hook them up to two batteries in series, or plug the motors into a wall outlet, did you?

DID YOU? :c)

Could be a lot of things:

  1. Did you dismount the motors and gears? Check your assembly (happened to us last week, overheating and all)

  2. De-solder: have you ever seen some begginer student soldering something? That big ball of metal, huge and ugly? :ahh: Try that, because this motors actually drain a lot of power.

Are you sure Al? I know we desoldered the 16 gauge wires and replaced them with 10 gauge ones. I know a lot of other teams did as well. I find it hard to believe that inspectors would have overlooked this, as it is quite obvious.


Initially, there was no rule against it, then there was an update that STRONGLY suggested not doing it. This year, as Al linked, they specifically tell you not to do it.

Last year in a match at nationals one of our wires desoldered itself from the drill motor. It didn’t break off, you could actually see the hole where it used to be soldered. They were the original blue wires too. We never used a soldering iron on them at all. This was after several elimination matches in a row, so they got very hot even though we did our best to cool them down between matches.

They desoldered themselves again in the summer while we were demonstrating the robot to some people.

Cory et al.,
As others have already posted, FIRST has come out with a rule against replacing the wires on drill motors. Now don’t get too excited about this rule, it is the same as last year. The wires, although smaller guage are very short, so the resistance is negligible and the wire has 200 C insulation, so there is no worry about melting or fire. There were significant quality control issues last year with the way the wires were soldered at the factory. You need to check that the solder job is done correctly. If you need to make repairs, I suggest you remove the brush assy. by gently lifting the retaing tang and slipping the brush assy. out of the motor. A magnifier might help here as the tang is very tiny. An additional suggestion if you must make a repair is to clean the original solder from the contact, pass the wire through the hole and crimp it back against itself. This make a firm mechanical connection prior to soldering. Heat the connection and flow in enough solder to make a good connection on both sides of the contact. Let cool and reassemble into the motor being careful to align the brush assy. in the slots and gently push until the retaining tang locks into place. If you choose to solder #10 wire to the end of the #16 then be sure to heatsink the #16 so that the heat will not unsolder the wire from the brush assy or cause heat damage to the plastic brush retainer.

Last year, when I was testing my autonomous mode bin-hunting algorithm (servos + reflection sensors), there was still a bug in it. Whenever the robot didn’t have a ‘lock’ on something in front of it (like a bin), it would go straight backwards. So, it had a lock on a bin, but then it lost it, and went from full forward to full reverse, and one of the motors started smoking. We ended up having to replace that motor, as it was never as strong as it used to be after that. I recommend you start talking to FIRST about getting yourself a new motor.

And then I never got a chance to test my (fixed) autonomous mode, we never were sure that it worked, so we never had an autonomous mode. :frowning:

From Team Update 7 last year.

Cautionary Note About Skill-Bosch Drill motors!!!

DO NOT attempt to unsolder the wires that are attached to the Skill-Bosch motors. The plastic housing that holds the brush assemblies will be damaged if you do. The high temperature of the soldering process causes the plastic to deform and destroys the motor. Teams should make their electrical power connections to the motors’ pre-attached wires, not directly to the brush holders.

Regardless, letting out the magic smoke is always a bad thing. Most of the above posts have covered the various ways to do this.


My team just had this problem last night. We were driving the robot around for some testing, and about 3-4 minutes of driving it around on a cement area in the middle of our school, we noticed smoke from the motors. We checked it out and there was definitely smoke coming from the motors and a very strong smell of it. We have one large muffin fan mounted above each drill motor, although we noticed a large amount of escaped airflow, we thought this might be the problem, so today we are going to fabricate some air ducts. Does anyone else have any suggestions? We did not disassemble the motors and I do not believe there was any drilling on the chassis around the motors.

Also, we noticed that there was a lag with one wheel, so it skips three or four times at acceleration and then moves slower than the other wheel as we drive around. I know that the other wheel’s gearbox is greased up, and this one’s isn’t. Does anyone know what else might cause this problem? :confused:

This is very typical of some designs. You do not say what your configuraion is so I am going to assume four wheel tank or two wheel with non steering two front wheel. These types of drive systems use incredible amounts of current when turning. Again, if there is any friction in your drive train it will manifest itself as high current in the drill motors. Can you describe the drive train or include a picture?

Magic Smoke, Magic Smoke, Run For You Lives, You Released The Magic Smoke!!!

We have vertically mounted drill motors, connected to the kit’s gearbox with a 2:1 gear ratio. The output axle of the gearbox runs to one of the kit’s 12.5" pneumatic wheels. I will try to get a picture up soon, I have none with me at the moment.

Thanks for your help.