How to kill a motor?

[DaveG28]

Had a very nearly new Novak 5.5L conk out on me today, just stopped working at all!? Is it possible to kill them from overheating, you could smell the burning at the end of each race from the motor up to the round where it went pop, so wondered if I've killed it that way, or if it might be worth me sending it off to Novak or someone as its so new?

Alternatively, what else might have gone wrong!?

[jono83]

I think you answered that yourself

[Dagger Thrasher]

Yep, that sounds like you've fried the motor I'm afraid. It's easy to kill a brushless motor from overheating/overgearing. The rotor of any brushless motor has a maximum temperature that it can tolerate before it gets demagnetised...in the case of Novak motors, this is around the 175F mark. When a rotor begins to "de-mag", the motor has to pull more current to make up for the weaker magnetic field, so the motor gets even hotter, even more current is pulled and the rotor de-mags even more until the motor's dead. You're lucky you didn't fry your ESC, too; the current draw from a demagnified motor can be massive, and can kill a speedo very quickly before you notice.

Running a motor over its safe temp can also burn the windings, which is probably the burning smell you describe. Sorry... I don't think Novak are going to help you here. When you get a new motor it's always a good idea to frequently check the motor's temp while you set up its gearing to avoid this happening; ideally, you don't want the motor to be running any hotter than 150F.

[DaveG28]

No worries, my bad then, although I'll replace with a different motor type, unfortunately it was on pretty much the best gearing I could get with the available spur/pinion combinations on the car, the next downwards gearing step is a big one which left it a bit too punchy/too slow top end!

Good lesson learned though, I'd always thought the ESC would thermal before killing the motor, I'll take more care from now on!!

[ianjoyner]

Were you using a GTB? They are supposed to thermal if the motor or ESC gets too hot. I'm not sure if other controllers use the temperature sensor in the motor though.

Sounds like you fried the windings, definitely worth measuing the temp when exploring gearing options. Even without the thermometer though I'm guessing if you can smell burning that's too hot .

[Dagger Thrasher]

That's true, if it was a GTB then they're meant to shut down when the motor overheats...but that isn't always reliable. What car were you running it in, and what was your gearing? You shouldn't have a problem finding a ratio that allows the system to run cool, so perhaps there was some binding in the drivetrain you'd missed?

Thinking about it, it might be worth hooking up another motor, if you have one, to your ESC just to be sure that it's still alive and well.

A temp gun is invaluable when it comes to gearing BL motors.