Marx steam locomotive brushes overheating

[OhioZephyr]

I have a Marx motor that I have wedged into an old AF clockwork enging body.  The motor runs well at start up, but as it runs it slows down.  When I touch the brass tube that hold the brushes, it is very hot.  The brushes are probably original, but I have cleaned everything and see no sparks coming from the brushes and commutator.  I do see sparks coming form the side rods as they brush the wheels.  Could that be adding to the heat build up?

Thanks

[Mononflyer]

Sounds like you may have an electrical short somewhere.

[OhioZephyr]

I thought about that too.  But if there were a short, wouldn't the engine be dead form the get-go?  But I will check.

 

Thanks 

[ADCX Rob]

The brush tubes are warm, normally, but shouldn't be too hot.  The reason is there is some high resistance in the area. 

Clean the brushes and tubes, replace the brushes if they are oil soaked and the springs if weak. 

If you can source a set of shunted brushes, this will eliminate the resistance issues with the brush tubes:

[LL675]

not always. My 671 had a short in the wire going to the pickup, that would only happen once in a while. Had me baffled until I saw a tip in Ray Plummers column IIRC.

[OhioZephyr]

Rob,

Thanks for the new insight on brushes.No, I do not have a source for shunted brushes, any suggestions.

Best regards,

Jim