MMM demagged my Novak motor

[SpEEdyBL]

While i was running my MMM/HV 4.5 in on a 4s NeuEnergy 4100 mah pack in my 8ight geared 10/49 today, I noticed the fan came on earlier than normal. The motor was only 160F so I kept on running. Then the oddest thing happend. When I drove down to the end of the street to do a pass, the motor had unusual insane speed going down the straight. I had to see that again so i drove back down to the end of the street again, a little further this time. However, the motor started to cogg pretty badly. First I thought it was radio interference, but as the car got closer it still cogged and had barely any power - as if an extremely weak battery were plugged in. I picked up the car, and the motor still struggled to start up even with the wheels in the air. I immediately turned everything off and the motor was 200F and probably hotter inside! It also had a pretty bad burning smell and the shaft would turn with almost no resistance. I figured rotor had demagged, but I am quite uncertain as to how. The magnet did not come apart from the shaft and the temps were no were near the 180 celcius (356F) mark that novak rates their rotors.

I am posting this here just find out if other people have had problems with the MMM demagging their motors, and if so, which motors they were. I know the novak motors weren't designed to run sensorless but they seem to run pretty well on the MMM otherwise.

[e-mike]

neu motor is your solution....

[What's_nitro?]

The 180*C is most likely the rating of the insulation on the magnet wire used in the stator coils. The magnets on the rotor won't be able to take anywhere near that before they demagnetize. I've demagnetized HDD magnets (same kind) and I could still hold them in my hand. I don't think anyone has ever had an HV rotor come loose from the shaft. The rotor isn't large enough in diameter to torque itself off. The MMM does allow more current to pass through the system, and so more power. Everything will get hotter, faster, so you just need to watch the temps more closely. If you have another HV motor, try adjusting your gearing.

[suicideneil]

The noobs on the idiot forum have managed to seperate the magnets from the shafts on a few hvmaxx motors. 160F isnt excessively hot, but hot enough really- when a magnet overheats in a motor it will loose its strength, and the effective kv rating becomes, but you then suddenly loose power at the same time. The MMM isnt at fault, its the 4.5 spinning toaster of death motor that cooked itself essentially.

[SpEEdyBL]

Originally Posted by What's_nitro?

The 180*C is most likely the rating of the insulation on the magnet wire used in the stator coils. The magnets on the rotor won't be able to take anywhere near that before they demagnetize. I've demagnetized HDD magnets (same kind) and I could still hold them in my hand. I don't think anyone has ever had an HV rotor come loose from the shaft. The rotor isn't large enough in diameter to torque itself off. The MMM does allow more current to pass through the system, and so more power. Everything will get hotter, faster, so you just need to watch the temps more closely. If you have another HV motor, try adjusting your gearing.

If you buy a novak rotor separately, the rating is 180C or 200C, so I am sure this is the temperature rating for the magnet itself, unless it was a typo and they meant farenheit. It is considered a "high temperature" rotor nonetheless.

I do plan on replacing this motor with a tamer 7.5 so i can use more pinion gears when the castle-neu motors become available. Meanwhile, I have my old 1/8" shafted rotor back in my 4.5 and it works fine.

[Hakan_J]

I used to have a Lehner 1940/8 with a mamba max. Unfortunately my MM died so I got the Monster Max instead. I had run my Lehner for about a year on the MM and it was working great. The first time I took my buggy to the track with the MMM my Lehner fried! Im not saying that my MMM killed my Lehner but it does seem a strange coincidence? I am now running a Tekno NEU instead.

Are the more people out there with a similar experience?

[kvrc]

you also have to remember that without using the novak esc you cant have the temp sensor working. i am sure novak uses the sensor because they know how much heat is too much.

[JThiessen]

180C/350F. That is extremely hot - just for the rotor, say its total length is about 100mm long, it will grow about .18mm in length for that temperature change. And the motor casing will grow about .4mm. Depending on how tight the rotor is shimmed, you have the potential for a fairly large amount of deviation just in the length. I'm not quite smart enough to calculate the change in diameter of the two, but there's quite a bit of room between the rotor shaft and the internals of the motor. Also, the epoxies in the motor will likely degrade very fast - especially if its been that hot once or twice before. Taking a anything to its extreme limits is risky business.

[Arct1k]

I don't see why this is the MMM's fault which the "MMM demagged my Novak motor" implies. The following thread provides great background on demagging and heat...

http://www.rc-monster.com/forum/show...301#post205301

The MMM has been documented to allow the motor to pull more AMPs (note it is the motor that pulls the amps) and hence this will result in more heat due to motor ineffeciency.

[phatmonk]

I thought you couldnt run a sensored motor on the MMM s

[Arct1k]

You just don't connect the sensors - It will run just like a normal sensorless motor...

[SpEEdyBL]

Originally Posted by Arct1k

I don't see why this is the MMM's fault which the "MMM demagged my Novak motor" implies. The following thread provides great background on demagging and heat...

http://www.rc-monster.com/forum/show...301#post205301

The MMM has been documented to allow the motor to pull more AMPs (note it is the motor that pulls the amps) and hence this will result in more heat due to motor ineffeciency.

Thanks for finding that Arct1k. That is probably what happened. Even though the temps weren't so high, I guess they added to the affect of the high current and cogging/phase misfiring, that combined, demagged the rotor.