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 email@example.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.