sparking at commutator and wheels

Sparking at the brushes/commutator is normal. It may decrease as the brushes wear in and match the contour of the commutator. The brushes are now in a different position and rotation orientation than before you took them out. In the future, you could be aware of which tube they were in and what their orientation was and replace them the same way. But for now, you can just leave them alone and they will adjust themselves.

Sparking at the wheels indicates dirty/corroded wheels or track.

+1, what Roy said. Poor spring tension will also cause the sparking on the brushes or the center rail.  Its the same affect as being dirty,  not a good clear path for the electrons so they will jump resulting in the lightening show.

Thanks. What I did notice was that the springs are very strongly holding in the brushes to the commutator; I was surprised, and kept thinking that they were holding them in too strongly, and that was what was causing the problem. Of course I also polished the commutator before reassembly. After I ran one of the trains for about five minutes, and observing the sparking, I took the motor apart, and the commutator now had a lot of carbon residue on it, presumably from the brushes. But it might simply be that, as Roy pointed out, the brushes are now in different orientations and need to "wear down" into their correct contours to match that of the commutator.

As for the sparking pickup rollers, make sure they are turning freely. Perhaps a drop of DeOxIt, NeverStall or RailZip will lessen rollers sparking (not recommended for commutator & brushes).

Bill in FtL

Agree with all the above and well stated. Dirty track is always a place to look for and clean. You would be surprised how carbon'd up it can get in a short time especially if dealing with arcing. The engine's collector roller assembly may seem to ok but if one roller is dragging or grinding compared to the other may warrant replacement. Too much brush pressure - you should be able to feel by manually turning the wheels, hearing a squeak noise, or observing how quickly the engine comes to a stop. If too tight on the brushes - that engine will stop abruptly versus a slower more relative stop. Also, if using older copper brushes (original) they may be culprit even though there seems to be enough surface left. The engines wheels to my knowledge are lead and rolling surface is protected with tinned/chrome surface but not the inside of the wheel flange- make sure to keep that clean as well....

Humble opinion and fight the same problems..

John

Thanks everyone! I will try all of your suggestions and report the results.

You mentioned you polished the commutator it is always good pratice to clean off residue left on it even if using a very light sand paper as it leaves a residue which in turn may cause sparking.I cannot attest to it but i always use acetone sparingly to wipe it down afterwards same with after cleaning the brushes and rollers.

Just very careful around any plastic.

I'll dip a q-tip in acetone and clean out the brush well's works well and very effective on wheels been doing it for years with no problems.

Sparking on the commutator is normal.  The segments are at different potentials and when the brush crosses from one segment to another there is a spark.  Commutation can be improved by using brushes of the correct material and size. Smaller brushes short the segments for a shorter time.  Carbon brushes of the correct resistance reduce the amount of short circuit current that flows from segment to segment. Normally we leave it up the motor designer to get these details correct. Sparking can be reduced by ensuring that the commutator is smooth, flat, and square to the shaft.  We normally leave it to the motor designer to get the brushes in the correct location.  Just make sure you did not change the location of the brushes. Sparking can be reduced by increasing spring tension.  This also increases wear on the brushes and commutator. Again we normally leave it to the motor designer to get it right. You need to make sure you are using the correct springs and that they are in good condition.  You can play around with commutator and brush design features, just be prepared to deal with the consequences if it does not go well.