It would still be at the motor RPM. The linear velocity of the brushes against the commutator is lower than the linear velocity of something touching the outside of the rotor, but they are all at the same RPM. A bump on a commutator segments would make a noise or vibration at twice motor RPM because it woudl hit both brushes, and any vibration would be in the plane of the brushes.
I did once have a kato that didn't run out of the box. The problem was that excess adhesive was used in assembling the commutator and had oozed all over one segment. If you turned the motor by hand, it would run, but poorly, and it almost always stopped with one brush on the bad segment and would not restart.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
SouthPennIt is a high speed vibration coming from the motor or drive line.
by high speed, do you mean at the RPM of the motor or faster?
commutator brushes are crossing commutator gaps at a faster rate than the motor. Could they be too tight?
greg - Philadelphia & Reading / Reading
If you have a "good" identical unit to the bad one(s), might you just open them and substitute good drivetrain parts to the bad one to determine what's ok or not? E.g, if you could substitute everything but the motor and flywheels and the problem was still there, that would narrow things down.
Maybe relatively easy in some cases, much more laborious if a custom DCC loco with the multitude of wires, etc that may need some disconnecting.
Paul
Modeling HO with a transition era UP bent
Usually if there is a bad winding or other electrical issue int he motor, it will stop at some point and you won;t be able to restart it unless you spin the motor by hand to get past the dead spot. No power in one motor pole won;t make a vibration, it's not like being down a cylinder in a car motor. If it varies with speed, it has to be one of the spinning parts, most likely the flywheel - or maybe a spot of glue or something is on one of the flywheels, it doesn;t take much to make it vibrate. Try running the motor with flywheels either witht he drive shafts disconnected or completely out of the chassis. If it vibrates - it's the flywheels or else a similar thing like a spot of excess varnish or glue on one of the motor poles. If the motor and flywheels are smooth, then it has to be somethign in the universals or drive shaft.
Vibration is usually mechnical, not electrical, although never say never.
Have you tried removing one driveshaft in any of these units then run it? Not saying this will solve the problem, but may give you some more ideas on diagnosis.
Mike Lehman
Urbana, IL
The majority of my engines are Stewarts with Kato drives. I have been purchasing them since the early 90s and continue to purchase them on EBay.
I have never had any problems with any of them until recently. I have three of them that vibrate and make some serious noise when running. You can feel the vibrations in the sub road bed. This vibration and noise is ten times worse than any blue box Athern I ever had. It is a high speed vibration coming from the motor or drive line. I have spent hours trying to find the cause of the vibration. I'm starting to believe that the motor armature has an open or shorted winding.
I ran the motor at slow speed looking for bent drive shafts. I made sure all the mounting screws were tight. I tried running with the mounting screws loose. I removed the motor and checked the fly wheels and they seem tight. I put a drop of glue on the mounting brakets to keep them tight to the motor.
I can order new motors but none of the couplings, u-joints, or drive shafts will work. Which means trying to find the right combination of parts to make everything work. Ugh. Been there/done that and I really don't want to do it again. But if the motor is shot....
Any suggestions? Time to break out the ohm meter?