My latest engineering challenge comes from an upgraded Ebay purchase GP-35. I added a DCC decoder that shorted out after running it a few minutes.
So I greased, and I oiled, and I got it to stop squealing. I ran it on the test track while I installed missing railing and redid the lights.
Last weekend, the motor squealed again and blew another DCC decoder.
Those decoders cost more than the engine.
I see I can buy another can motor on Ebay for $20, but me being an electronics engineer, I need to do a failure analysis.
When I disassembled the motor, the magnets came out with the rotor. They should be glued to the motor shell, but the glue job was full of voids and lack of a proper cure.
This is the first time I've seen a DC motor do this.
The squealing was definitely the rotor running against the faces of the magnets. I surmise that by constantly injecting lots of oil, it allowed the motor to run quietly for a while. You can see the wear on the rotor.
After cleaning out the bad glue with a dremel brush and needle file, I used JB Weld to glue the magnets back onto the housing.
Cure time for each magnet is one full day. It stays clamped.
To take the motor apart, I removed the flywheel away from the brushes by twisting using two pairs of pliers.
Then I pried open the crimps on the housing and slid the rotor (and magnets) out of the housing. Don't lose the plastic washer.
And for all that's Holy... DO NOT remove those brass spring retainers. Just leave them be.
Two days later, the JB Weld has cured and I can reassemble the motor. I power tested the motor. Then I used a small bench vise to crimp the corners. The other flywheel twists on by hand.
Every step I test the motor. I also ensured it's isolated from the frame. Installed a THIRD !!! DCC module on the shell with the lights.
The power draw went up to 2 amps, and the oil in the brushes went up in smoke. Then it calmed down. I let the motor run for 30 minutes at 12 volts, then I reverse the leads.
After cooling down for 3 hours, I tried it again and it wouldn't start. I had to dump solvent alcohol down the holes onto the brushes to clean the oil residue off. It runs reliably now. There is no easy access to clean the brushes, so I left that issue alone for now.
Do I hook up the DCC controller?? I'm not that stupid! I ordered qty:40 .75 Amp Poly Fuses.
A poly-fuse is like a fuse that self-heals after it cools down. These are useful in electronics where you simply don't trust the circuit.
If something goes wrong with the motor in the future, it will stop power to the motor.