Motor runs but will not start

I have a N scale Kato motor that will run just fine but will not start on its own even with full voltage. Give the flywheels a short spin and the motor will run fine at all speeds but if you stop it, it will not restart. I have a replacement motor on order but I am curious what may be the problem with this bad motor. Any ideas? Can it be fixed?

 

I have only seen one actual bad motor in a Kato locomotive, bad as in opened or shorted windings. From what you are describing I would suspect something is up with the brushes.

 

That what I was thinking. If a winding is bad then it cannot develop starting torque. Once it's running the momentum and torque generated by the good windings will keep it running.

 

Will open it up and look at the brushes. Kato sells replacement brushes if that is the problem

 

How hard are you pushing it to get the motor started? If you have to push real hard then there is a something preventing it from turning freely. The motor should move very freely when hand turning it. Sorry — I'm no electric guru!!!

 

To Check the problem motor do this- apply about 1/2 voltage (6 volts) to the motor. If it does not start just rotate the flywheel a little-( don’t try to spin it) a little at a time the motor may start and run. Shut off the power and try to re start.
The motor may start or not- depends on where the armature parked. If it starts just keep on stoping and starting, sooner or later if there is a bad segment it will park there and not re start. Means there is a bad or broken segment- BAD MOTOR. Can’t repair- just install the motor you have coming.
I have replaced two Kato motors over the last 10 years of doing DCC installs.

 

The above is a good method to check for open windings. Another way is to hold onto a flywheel while supplying voltage so the flywheel tries to turn within your grip. Slowly let the motor turn while keeping control of it with your grip on the flywheel. If the armature reaches a spot with an open winding, it will stop and no longer try to escape your grip.

i think you just have a problem with a contaminated commutator, however, as you seem to indicate the motor has normal speed and torque after it's running. In that case, you need to clean the commutator and brushes. Particularly look for oil contamination. Oil will burn exposed to the minute sparks always present with brush/commutator contact and a non-conductive film will form on the commutator segments.

Doug

 

Thanks for the help. Nothing worked so I have installed the new motor. Runs great.