Motors burning out?

Hello,

I’m a first-time Vex IQ coach. The kids are having a great time experimenting with the robot, but recently one of their mechanisms stopped working. It’s a “slapper” that pulls back and slaps the disks into the scoring zone. Out of nowhere it seemed to stop having enough torque to pull the rubber bands back far enough, and after swapping in a new motor, it seemed to work again.

The next time we met, however, that motor seemed to be too weak as well. One of them touched it and said it seemed to be overheating.

Do these motors overheat easily? The only thing I can think is that they have a bit of code that pulls the slapper back so the disks can stack in a level pile before they begin shooting. The motor holds the slapper back against the tension of the rubber band, and it makes a low whining sound. Could this be the issue? Are there other ways to have motors lock in place without overheating them?

Thanks in advance!

The sound you describe seems bad.

I’m not sure there’s enough detail to provide great feedback, but a few thoughts.

  1. IQ motors aren’t terribly strong. Pulling against rubber bands could be a big load to them. Depends on the mech, gear ratio, etc.
  2. From the sound of it, the motors may be holding force for a long time. This could make any heating problems worse. I assume that most shooters wind something up and have a slip mechanism to release. Not sure.
  3. IQ motors shouldn’t get hot.
  4. Some sounds could be the shaft not all thecway inserted. It is possible to round out the part of the motor the shaft goes into.

Motors are hard to get, I hear
Probably wouldn’t encourage them to just replace them as they break without debug.

3 Likes

Not first time as last year’s Pitching In robot utilized rubber bands in the catapult. Did not have any issues at all. This year, we have a similar build using a catapult and also have a couple of motors as actuators for arms, etc. Over the last week, we’ve lost three motors. Not sure why and cannot find anything in the literature. I suspect the “hold” setting may be the culprit but, again, I cannot find anything that even hints at that being a problem. I’ve asked VEX support and am awaiting a response. You mention “debug” - do you have some process? We’d be grateful whatever you may have. The VEX debug process for motors does not address this issue.

If you find anything, please let me know @willjlong ! My older son used a similar idea for Pitching In and they likewise didn’t have any problems. Needless to say we can’t afford to burn through motors and replace them frequently.

Not heard from VEX. I did some further testing and , of the three motors tested, one was completely dead and the other two moved very, very slowly. All three motors were used in various ways that included the “hold” command. My builder said that, in each failure incident, the suspect motor got very hot and "the robot stopped working. " He replaced the motor and the robot started working. Agree that motors should not overheat, etc.

At this point, absent additional information, I’m going to encourage my builder and programmer to find ways to remove or minimize the need to command a motor to hold. I hate doing this in the middle of competition season as it will surely require drivers to adapt. I agree, we can’t afford to burn through motors.

I am in Vex VRC, and our motors burn out quite a lot. I have picked up a couple of tips along the way to help cool them down, but I have one favorite that I use all the time: canned air. Just canned air. You can get air dusters for keyboards and such at Office Depo, Office Max, Wally-Mart, etc. Just turn the can upside down and spray the motors, and it cools them down very quickly and they return to their regular power. This tip is very helpful especially during competitions when we have back-to-back matches. Hope this helps!

1 Like

Thanks! WIll give this a shot.

1 Like

Great idea.!!
I’ve seen a few (very few) replies offering “hot air.” Nice to see someone offering “cool air.” :slight_smile: Will absolutely get a couple of cans!!

2 Likes

I will say to be careful with canned air, most canned air uses tetrafluoroethane as the refrigerant (the cold stuff it shoots out when turned upside down) which, while not incredibly toxic to humans, if inhaled it acts as an asphyxiant, and if you get it on your skin it can cause frostbite in some circumstances. If you trust the student using the canned air, it should be completely safe, however, if the student is going to be messing around with it (I’ve seen some people spraying it at/on each other) I would suggest not letting them use it.

If you use canned air atleast look on the label and follow the safety guidelines they have on there (except the one saying don’t it turn upside down), and do some research into the chemical it uses as some refrigerants are more toxic and should be avoided (especially ones using butane, butane doesn’t mix well with hot electronics)

6 Likes

Thanks for the info on air can contents. Will check it out.

With respect to overheating and failing IQ Smart Motors, I’ve learned a bit more. Overheating and/or failing IQ Smart Motors appears to be a fairly common problem. Using the “Hold” or “Brake” modes to hold a load (e.g. a loaded catapult) can result in overheating. My understanding is that repeated episodes of overheating can cause deterioration in motor performance, ultimately resulting in near or complete failure. The programmer and builder on our team spent several hours yesterday identifying ways to reduce or eliminate the need to set motors to Hold or Brake. Not something that we really wanted to do in the middle of competition season but, at the end of the day, can certainly be classified as a “real world” exercise. Now our drivers need to practice the changed functionality.

1 Like

Perfect example of how iteration saves the day. Make sure all of the programmer / builder documents all the work (designs, testing, redesigns, etc) and gets it into the notebook. Judges just LOVE that kind of work.

1 Like

Absolutely! Already done!
Thanks for the reply.

How many rubber bands are being used?

Two. The catapult has sufficient power to put 3 disks into the “4” zone or 5-6 into the “3” zone. Our guys changed the code so that the catapult is not “cocked” for an extended period. The robot also has a gate (a la last year’s Clamp) that was held up and down using “hold.” As it was overheating (pretty minimal load), they added a simple rubber band to hold the gate up (eliminating the need for “hold” in that configuration) and then minimized the amount of time that the gate was held down using “hold.” These changes seem to have had an impact as the motors are running much cooler. Not really a “fix” IMO but hopefully the result is a tolerable solution.

1 Like

That was the Junior’s favorite prank to play on the underclassmen, my 2nd year of FRC. I remember sitting in the stands at a competition and my older teammates would see how long they could hold the spray on someone’s back before they noticed

There was someone on our team who would spray it on our shirts it was mine not even his so it was very annoying

Seriously, the spray was very helpful. We got through a tournament without any smoke or fire. I was the Keeper of the Can and, on two occasions, watched one of our team members cool down a motor. Worked like charm. Indeed, it got pretty cold and I would speculate that spraying it on skin might indeed be an issue.

Thanks, Jaden, for the tip!!

1 Like

No problem! Feel free to ask if you need any more of them! <3

A reply two weeks after the last post that doesn’t move the conversation forward, isn’t looked favorably upon.

If you have something that moves the conversation in a substantial way, then great. Otherwise, let these threads lie.

4 Likes

Sorry, I was on an offline break for those two weeks, and I didn’t want to be rude by just not saying anything if that makes sense

1 Like