Prewar M10000 Problem

One trick to these engines is that there is not excessive downward pressure on the pick-up sliders. If there is too much tension on the stiff sliders, it will loose some tractive effort. Be sure the car vestibule wheels are oiled. This is a slippery set even when well tuned.

Are you losing power (i.e. wheels don't turn until you crank it up to 18v) or losing traction (wheels spin)? I agree with Chuck's advice about checking the sliders. Also check the vestibule wheels for any drag. Make sure the train rolls freely when assembled without the locomotive attached. Also check if there are any center rail pickups for interior lighting - those could also be dragging. 

Have you checked to see if you get any electrical sparks inside the armature area when running at a higher voltage? You may have; 1) weak brush springs or 2) not 100% clean motor contact area, residue left from a cleaning fluid, or 3) ruff brush area. The brushes have to be almost 100% flat across the armature contact area for best performance, just because they are new or replacement brushes don't mean they are in great electrical shape.

I have a 249E that I have reconditioned the brushes a little and it works good enough to run at slow speeds but needs new brushes. So it is sitting on a shelf until I get time and money to repair it better.

Lee Fritz

I loosened up the pressure exerted from the sliders.  The locomotive appeared to gain some traction after adjusting the pickup rollers.  I am successful in getting the locomotive to move the train every time.'

The brushes appear to be perpendicular to the commutator.  I probably could try ordering a new brush plate and see if that helps.

Thanks for the help!