Lurching by 4-4-0 at slow speed- below about 3 miles per hour.

[Andy Autry]

I installed a decoder with back electromotive force to achieve speeds down to about 2 miles per hour. At low speed the locomotive acts as though the motor is cogging.  Is the motor a three pole or five pole motor, and is the armature skewed?

[Yampa Bob]

There are several knowledgeable people here that can probably answer your question,  Jim Banner will likely be in shortly.

It might help to know what brand decoder you installed, and the model of your controller.  Also do you have the instructions for the decoder?  There should be a section addressing the back EMF feature.

I'm just starting to learn about CVs, I have the instructions for the Bachmann decoder with back EMF.  It says "CVs 54 and 55 may need adjusting to suit the motor".   

This might give you a clue of what to look for in your instructions, until someone better versed can help you.  Hang in there, at least this will bump you to the top so your post will be better noticed.

Bob

[richG]

I installed a decoder with back electromotive force to achieve speeds down to about 2 miles per hour. At low speed the locomotive acts as though the motor is cogging.  Is the motor a three pole or five pole motor, and is the armature skewed?

I just tried my Spectrum 4-4-0 with Micro-Tsunami decoder and mine appears to be doing the same thing. At 4.4 mph it looks ok. At 2 mph I would say it seems to hesitate a little. I did this with clean track and wheels on a five foot section of straight track.  I know the Spectrum motors are skewed armatures and five pole with flywheel.
The loco does not have much running time yet.

I have an old Mantua General with tender drive and can motor with a Lenz  LE077XF N scale decoder that runs much smoother at 2 mph.

I will have to take a closer look at the Spectrum.

Rich

[RAM]

Rich since you have a cam motor, it is a much better motor than the motor in the spectrum.