Hi!

I bought a pair of these wonderful locos last spring. Märklin item 36242.



So far so good.. BUT.. They have serious problems with the motor control. They run smooth and nice as long as the locos is running without cars on a flat track.
As soon as it is pulling cars and especially on track climbing, or even worse going down, they change speed like a "rubber band effect". It seems (without really knowing) that the decoder is over compensating the motor load, or compensating too fast, or possible keeping the compensation too long time.

I have never altered CV values for the motor load compensation on my CS2...

QUESTIONS:
1) Do you think the rubber band like motor drive problem can be corrected by altering the CV values?
2) If so. Which values should I be working with?

Please help.

Regards

Thank you Tom for this information!
I've learned a lot and the thread about the 3-pole motor was very informative.
Yes, I use CS2.

However..
I have now tried different K & I-values between 5 to 200 (Default was 64). Different value changed the properties of the motor characteristics as described in the excellent thread about 3-pole motors you refferred to, but no value seem to have an inpact on the rubber band (Push-Pull) effect when the loco is pushed by more than 6 cars in a 2-3% down ward slope.

I also tried to vary the CV for amount of compensation (Default was 29). Changes were noted. For instance values below 10 resulted in unability for the loco to climb 3% slopes with more then 2 cars. Values over 200 resulted in over powered shaky motion especially in low speed.

No setting of K, I or amount of compensation resulted in reduction of the rubber band effect in down ward slope with cars.
The variation between runs in the same slope with the same cars using unchanged CV values was greater than any change noted due to CV value settings.

I wish I could upload a short film to show you, but the motion precision on Youtube is so poor, so I don't think it's worth while.