DC MOTOR QUESTION

[DiodeDave]

Update

The smoking motor/gearbox had a bent axle and a loose magnet. The vendor made a quick exchange and I'm back in business. I have the two trucks shimmed and should be back in business. I'll find out Friday.

Thanks to all for your input.

Dave

 

[BobK]

The test I proposed in my only post was intended to determine if this was the case, as I suspected (one motor defective).

Bob

 

[DiodeDave]

The bad motor was replaced and the new setup with 24v motors wired parallel have been working well. The truck has been leveled using shims. So far, I've run about 5 miles without any problems. After one 2 1/4 mile run, the motors, gearbox and controller were nice and cool.

 

[duke37]

I think that the downward force is not the problem, there should be enough force unless you are going uphill.

The front wheels are smaller so the front motor is running faster, the back EMF is higher and the motor takes less current. It may even be running as a generator as explained previously.
The back wheels are bigger, the motor runs slower and the back EMF is less so the motor takes more current, gets hotter, and generates more torque, enough to spin the wheels.

The way to solve this is to have the wheels the same size or to alter the gearing to get the same rail speed for the same motor speed. As a rough guess matching to better than 5% will be needed.
Another way would be to run each motor off a separate power supply which is current controlled, not voltage controlled.

 

[DiodeDave]

Duke37

Thanks for the reply. The smaller wheels are on a separate truck. The two motors are on 2 axles on the same truck with the same size wheels. One motor was defective and replaced by the vendor/manufacturer. The new motor and balanced frame now works properly.

Yesterday I ran 6.25 miles. At the end of the run, the motors were barely warm to the touch and the controller was not warm at all. I was pulling 2 adults and 3 cars with a total load of about 875 pounds. Some of the track had a 3% grade. Wheel slip was nonexistent except for when the rails were damp due to sprinkles.

At the end of the run, my 2 12 volt series 24 batteries were producing 12.6 volts under an 8 amp load.

Overall, I'm pleased and think I have solved my issues.

Thanks for the interest.

Dave