NEO Motors Running Extremely Hot

Throwback to the time we ran our 2017 robot continuously for driver practice for over a half hour (stopping only to swap batteries). Someone finally noticed the radiating heat. Measured it at 300deg F externally.

We let it rest awhile and did something else.

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I’d doubt it. The outrunner is moving inside the shroud. What any high power brushless system needs is airflow across the stator, else the breakdown of the coil insulation starts to become a self-destructive system: Increased winding resistance leads to higher temps, which breaks down the coating, which leads to higher temps…

These motors don’t have any built-in mechanism to shed heat. I’d be VERY wary of running them near max for any reasonable amount of time.

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Couldn’t you argue the same thing about CIM style motors? But we’ve shown that they can be run in drivetrains for extended periods of time for practice. You shouldn’t be using any FRC motor for 40 minutes straight. But I haven’t seen anything posted here that would make them not suitable for use in a few back-to-back matches with field timeouts in between.

If the claims here and other places are true that the NEOs cool via their aluminum case, then it makes sense that adding a heatsink to that case should help dissipate heat. CIM motors specifically don’t dissipate heat through their case, so it makes sense that the heatsinks aren’t very effective with them.

(Note: I’ve never actually used the NEOs, just judging based on claims from other people who have)

I’m impressed by the 40min strait of drive practice already, great job. I would think by the nature of brushless motors, the aluminum casing probably dissipates alot of heat, maybe make sure the casing of the motor has room around it for some air ventilation.

Wouldn’t do harm to be measuring the temperature as well if you are using the Spark Max’s over the CAN bus. I’m impressed that you guys were able to run the motors for that long though, I don’t think I’ve ever had a straight 40 minutes of drive practice without having to take a break for some reason.

You will notice faster heating with a NEO because the heat generating components (the coils in the stator) are physically mounted to the face plate. On the flip side, this means they will cool off faster too.

The coils in a CIM motor are only contacting the outside through the bearings. After long periods of driving or large current draws, I’ve watched the external temperature of a CIM continue to rise in temperature for at least 10 - 15 minutes, getting too hot to touch.

As others have pointed out, running any FRC motor for 40 minutes will generate significant heat, causing some to fail.

@sam.mulvey747, could you send your robot logs to support@revrobotics.com. I am curious to know if this particular motor was drawing higher current than the others. If so, this could point to a mechanical issue within the gearbox or drivetrain.

We have temperature feedback coming in the next major firmware release for the SPARK MAX. A thermal cutoff wouldn’t necessarily help the problem, as other motors would then take the full load and heat up even faster. So, for the next release, we’re enabling the user to read the temperature and make their own decision on how to react.

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I’m wondering if a more viable setup for a practice robot would be removing the outer casing and blowing air across the uncovered motors. Adding thermal compound with a cleverly designed aluminum gearbox would also help.

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The steel sleeve you see around the outside of motors like the 775 are not for cooling purposes they are called a flux ring and it is to concentrate the magnetic flux and increase the torque output of the motor and make it more efficient.

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No, the thermal behavior of a rotor v. a stator is pretty different. See what @dyanoshak said in his post.

Yeah, this would change the temp quite a bit. I’d be mostly concerned with ensuring that the motor never reached a point where the stator’s coil insulation could be compromised. Once it goes, the motor will quickly fail.

We were attempting to use the NEOs for our lift on this year’s robot and broke one from stalling it for no more than 20 seconds. The motor started smoking and you could smell it from across the shop. Do not stall NEOs for any more than a couple seconds.

Did you have any current limiting in place?

@Jon_Stratis Yes, all four NEOs had a 40 amp current limit set in the Spark MAX Client.

Stalling at what voltage? What reduction? What load was placed on the motor?

General statements like this can be damaging without empirical information to back it up.

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I am sorry, the motor had a 12.75 :1 reduction, I am unsure what voltage because the spark max driving it was run by our test board (a PDP with a thrifty throttle to control motors). I would not be surprised if this accident was entirely my fault.

I’m not trying to assign fault, whatsoever.

Since we’re all still learning about the NEO, having failure modes documented and communicated is good for all of us. The voltage matters, as does the approximate load. A good analogue here would be a 775pro stalled. Stalling at 3v won’t do much, assuming the power output by the mechanism at that voltage is sufficient to hold the system static. Stalling at 12v will do damage.

Would a computer fan pass inspection? If so I would have one mounted to vent air up and away from your motors. Also what amperage are you running?

2019’s R34/table 10-1 allows (emphasis mine):

Hard drive motors or fans that are: included in any Kickoff Kit, distributed via FIRST Choice, part of a legal motor controller (including manufacturer provided accessories), or part of a legal COTS computing device

Assuming next year’s rule is similar, the fan would have to fit in this (or pair an otherwise legal motor with a fan blade). There are several fans of this size which have been available in the KoP and FIRST Choice in recent years.
Added: A few of the legal motors have built-in fans. I don’t see any rules against directing the airflow into or out of them across another component.

2020 this won’t be an issue, just dip the motor in the field.

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My reading of this rule says that you could pull the fan off an old Victor 884 or 888 and use it, right?

Check if the NEO is already pushing air through itself when it is spinning (both directions). An external fan that is “fighting” this airflow is not likely to help.

Note: I have not used a NEO yet.