Melting Motor?

[MauriceW]

Hello,
I have been lurking in the forums for a while, and have been really impressed with the r/c community here. I am a returning to r/c after about 5 years. I have an Associated RC10B4 Stealth buggy that I got about a month ago. I use it just to run around the grass in parks and such. I have been really happy with its performance and handling. It has the stock 15T motor and I have been using 2 different 1600 mAh NiCd packs and a new 3800 mAh NiMh pack.
The first time I noticed what I will describe was when I used the NiMh pack. When I plugged it in and turned on the power, the throttle was reversed, but the steering was normal. At this point, I probably should have thought more about it, but I just changed the throttle reverse switch on the transmitter.
After about 5 minutes of running, it started hesitating (glitching?) while accelerating. It got worse over the next minute, so I drove it back toward me. I noticed smoke coming off the end of the motor and a smell of melting solder. I then saw that the solder on the yellow terminal (not sure if that's + or -) on the end of the motor was liquefying, and the motor was so hot I couldn't touch it without risking a burn!
I touched up the solder and checked the spacing between the pinion and spur gears. I set them with a piece of paper between them. I tried running it with both of the NiCd packs today, and the throttle is back to working like normal. After about 5 minutes, the same symptoms appeared.
I'm not sure what to check now. It doesn't seem like the gearing should be a problem since I haven't altered it. The packs have all been very warm, but not so much that I couldn't hold them. I'm note sure what to do next. Any help would be much appreciated. Thanks in advance,
Maurice

[702nitro]

Hey whats going on? Glad your back into R/C. I think the reason your motor is overheating can be attributed to running your car in the grass. Have your car setup, then run it on pavement for a duration similar to your runtime in the park grass. See if it overheats?

[gizmoguy303]

The motor that comes with the Associated RTR's is known for overheating and it is probably the first thing you should replace. In addition to its lack of quality, it was probably getting severely worn as you were running the car. As the brushes and commutator wear, the rate at which they wear increases because of the increased vibration and arcing. It's a exponential increase of deterioration until either you cut the comm and replace the brushes, or the motor has a "meltdown" and is basically junk.

Most racers have a pit lathe which cuts the communator and restores the motor to perfect new running condition.

Get a quality motor that will last you a long time, like the V2 motors from Orion/Peak or a Checkpoint motor. A 19t V2 motor would probably be perfect for your situation. Decent power, low maintenance. Start by gearing it one tooth lower than what the manual suggests, since you're running in grass.

Also as a side-note, double-check the polarity of your NiMH pack...I've never heard of throttle reversing simply because you are using a different battery pack.

The paper-trick to set gear mesh works OK, but IMO it sets the mesh a little on the tight side. Experiment with your gear mesh until it feels nice and free without being too far apart.

Good luck!