Brushless motor repair

[andy fraser]

Is anyone doing brushless repair, I just toasted a het typhoon 98 850 kv blocked a water line and got HOT.

 

[RaceMechaniX]

Andy, you can see if Don Huff is willing to rewind it.

 

[donaldhuff]

Andy,

I got your motor today and tore it apart. On the inside, it is surprising similar to a TP 4070. The stator plates and stator assembly are identical to the TP, it is practically a TP part. The rotor is only slightly different from the TP, with the wrapping being the biggest difference.

The motor can is paper thin at only .012", and I bent it up some getting the thing apart, I've never seen a can so thin. I usually drill and tap the rear end before I take one apart so that it goes back in the same place, but the parts were so thin that I couldn't get them to hold threads. Even with an 0-80 screw, there were only a couple of threads to hold, and they didn't hold on the first tightening.

And not so much of a surprise is that the wire is the lower temp rated stuff that most of the motors from "over there" use.

I can rewind it, but because of the way it is made and the same goes for the TPs, I can't get it back as good as it was to begin with.

If I were you, I would replace the HET with a TP 4070!

 

[andy fraser]

did it fail from the short to the end bell. I assumed it was a cooling problem but that's fine. guess i have to bite the bullet and replace it with neu or 56.

 

[donaldhuff]

OH, I thought that you were positive that it failed because of no cooling.

Actually, on the I.D. of the stator hole where the rotor goes through. There was one strand of wire that had gotten out of the slot and gotten to the inside where the rotor could run against it. That will short one out, but doesn't always make one run extremely hot. It may have even happened after it got so hot from over heating. ALL the wire in the whole motor was baked, so I suspect something else caused it.

The short on the one lead wire would have surely burned it up, but then why was that wire naked? I think that had to happened after it got so hot.

Dead shorts like that usually burn one up to the point of not running rather quickly, and don't always build up so much heat before knocking off.

Sorry that I can't tell you exactly what happened, but when everything in there is burned, it's hard to tell what to point a finger at, and say "that did it".

 

[Mark Bullard]

Rewind these motors can be a problem with it getting very hot. Depends on the magnets and how hot it got. When a brushless burns the winding it will take a little of the magnets power from them. A simple test is to buy the smallest dial torque wrench you can buy that fits the torque of the motor. By putting a variable DC voltage on two of the winding leads and by measuring the current to the max current of the motor. Then take the torque wrench with a special device to be placed on the shaft that you can turn with the torque wrench. With the wrench set at zero and turning to the next pole position you will set the torque wrench pointer to the newton meters that the motor will produce. This is a cheap mans way of dyno the motor. If the motor will not produce the torque it says it will the magnets are bad. But this only works on a good winding. This is how I test all servo and brushless motors in house.

 

[RaceMechaniX]

I bought several of these mini Gauss meters to measure magnet strength and for multi-segmented axial magnets to check for magnet twist.
Very handy for checking magnets. Too bad they stopped making them.

Spin Doctor ER Gauss Meter

 

[Mark Bullard]

I bought several of these mini Gauss meters to measure magnet strength and for multi-segmented axial magnets to check for magnet twist.
Very handy for checking magnets. Too bad they stopped making them.

Spin Doctor ER Gauss Meter

We were testing a motor with our PDMA test package. The motor kept failing the test. After I found out what it was failing I check the stator with a gauss meter. The magnet pull in just the core iron left from running was what caused the motor to fail. Not something to be testing on a old winding that has been running.