I think i burned my motor up .

[rchippie]

As the title says . I was running a novak xbr esc with a ex 13.5 & trak power lipo's . My car is a tc4. I was running a 31/66 or 5.3 gear ratio for the first race . The temps were 175 at thermal . the second race i ran a 33/66 or 5.0 gear ratio the temps stayed the same & has a stutter at slow speed . So i tried a 29/66 or 5.8 ratio during practice the motor got hot quick & had a stutter at slow speed . The car had a stutter untill it got up to speed then it went away . But it came back when i slowed down to turn . I just took the motor apart the rotor still seems to be magnitized as it picks up the screws that hold the motor together with no problems . I switched to my speed passion 17.5r after & had no problems . So i know it's not the esc .

[lutach]

Originally Posted by rchippie

As the title says . I was running a novak xbr esc with a ex 13.5 & trak power lipo's . My car is a tc4. I was running a 31/66 or 5.3 gear ratio for the first race . The temps were 175 at thermal . the second race i ran a 33/66 or 5.0 gear ratio the temps stayed the same & has a stutter at slow speed . So i tried a 29/66 or 5.8 ratio during practice the motor got hot quick & had a stutter at slow speed . The car had a stutter untill it got up to speed then it went away . But it came back when i slowed down to turn . I just took the motor apart the rotor still seems to be magnitized as it picks up the screws that hold the motor together with no problems . I switched to my speed passion 17.5r after & had no problems . So i know it's not the esc .

You demagnetized the rotor. Even though it still has some magnetism, it'll make your motor hot as it needs more current now to turn the rotor. I have a lot of demagnetized rotors that I sometime use to magnetize some tools I use. You I used the 31/69 combo to hit 65mph in my TC3 which has the same diff ratio? With the 17.5r you have no problem and you should be able to use the bigger pinions as the 17.5r will needs it to be fast.Keep in mind if your ESC shut down because the motor got too hot, then the rotor probably went above the 175-180F mark. Most temps taken from outside the can will not tell you how the temps were inside. Open your 13.5 and check the magnet wires to see if they look ok and if they do just buy a new rotor and don't use such a big pinion or small spur.

[rchippie]

Originally Posted by lutach

You demagnetized the rotor. Even though it still has some magnetism, it'll make your motor hot as it needs more current now to turn the rotor. I have a lot of demagnetized rotors that I sometime use to magnetize some tools I use. You I used the 31/69 combo to hit 65mph in my TC3 which has the same diff ratio? With the 17.5r you have no problem and you should be able to use the bigger pinions as the 17.5r will needs it to be fast.Keep in mind if your ESC shut down because the motor got too hot, then the rotor probably went above the 175-180F mark. Most temps taken from outside the can will not tell you how the temps were inside. Open your 13.5 and check the magnet wires to see if they look ok and if they do just buy a new rotor and don't use such a big pinion or small spur.

what wires do you mean ?. What gear ratio & spur would you suggest for the 13.5 ?.

[lutach]

Originally Posted by rchippie

what wires do you mean ?. What gear ratio & spur would you suggest for the 13.5 ?.

The copper windings. See if there's any signs of burns. You were geared for 37mph and if it was me I would've started at 30/72 and taken from there, but I don't know how big your track is so all I'm doing is given you a starting point to check temps after you race a full 5 minutes. Your motor might've had something else go wrong that caused it to heat up like you said.

[rchippie]

Originally Posted by lutach

The copper windings. See if there's any signs of burns. You were geared for 37mph and if it was me I would've started at 30/72 and taken from there, but I don't know how big your track is so all I'm doing is given you a starting point to check temps after you race a full 5 minutes. Your motor might've had something else go wrong that caused it to heat up like you said.

the wires look a nice & even shinny red in color . This track had a straight approximently 140 - 150 feet long . This motor had the none sinterd rotor . I think i will just but the upgraded rotor for this motor .

[lutach]

Originally Posted by rchippie

the wires look a nice & even shinny red in color . This track had a straight approximently 140 - 150 feet long . This motor had the none sinterd rotor . I think i will just but the upgraded rotor for this motor .

Yes, just get the rotors and see how it goes. I was also under the impression the wires were supposed to have a yellowish color as most high temperature magnet wires have it. I've had wires turn that shinny red color after they had heat issues and went bad.

[BrianG]

Is the smell simply "that new motor" smell? Even when not new, the varnish does have a distinctive odor.

Coil windings are so short that they have very little DC resistance, so getting a reading with an ohmmeter is all but impossible. However, you could build a simple oscillator (555 timer based) running at ~20kHz. Add a little "current amplifier" to the output (1A max), and hook each motor lead to it with a precision 1ohm resistor in series. The voltage drop on the resistor should be equal on all phases.

[rchippie]

Originally Posted by BrianG

Is the smell simply "that new motor" smell? Even when not new, the varnish does have a distinctive odor.

Coil windings are so short that they have very little DC resistance, so getting a reading with an ohmmeter is all but impossible. However, you could build a simple oscillator (555 timer based) running at ~20kHz. Add a little "current amplifier" to the output (1A max), and hook each motor lead to it with a precision 1ohm resistor in series. The voltage drop on the resistor should be equal on all phases.

In all honesty it kind of has that burnt motor smell . But it's not a very stronge smell .

[SpEEdyBL]

I demagged my HV4.5 5mm shafted rotor. I put the orginal rotor back in and it worked fine. The motor had a burned smell too. You can always send your motor to Novak with the demagged rotor installed and they will replace it with less than the cost of a new motor.