#41 Army Switcher running hot

Did you clean the slots between the commutator segments? These tend to fill with carbon dust from brush wear. This carbon dust shorts the slots and results in the motor drawing more current than it should.  A bar to bar meter test will also help detect problems, including shorted slots. On this motor I would be looking for a resistance of about 1.7 ohms bar to bar. Bar to shaft tests is also a good idea. This should be 400,000 ohms or greater.   These are not the most efficient motors. Maybe 75% or less. This means that 25% of the power going into the motor comes out as heat. So these motors do run hot.   There could be a problem with the collector spring tension. Somewhere there is a value for the force the roller applies to the center rail in the Service Manual. I do not recall what it is. You could compare the spring force on this loco with other locos you do not have problems with.

Thanks Dave, the commutator slots are clean, pretty sure my issue is the pickup spring tension. My question now is, what’s the easiest way to increase the tension on the existing pickup arms? I suppose I have to remove it and disassemble it in order to turn the spring one revolution tighter… ??? It’s in like new condition so I’d hate to take my chances with buying a new one…

Why not just use new springs and brushes, that will remove the issue of spring tension and defective brushes.  It's a cheap fix.

@gunrunnerjohn posted:

Why not just use new springs and brushes, that will remove the issue of spring tension and defective brushes.  It's a cheap fix.

Good Morning John, sorry, I may not have been clear in my post... I did replace the brushes and the spring tension on the brushes is fine. I was referring to the spring in the collector assembly... there is very little tension on the arms that hold the rollers to the middle rail, I believe this is adding to the excessive sparking and I was asking the best way to remedy the problem.

OK, that's different.

Looking at your picture, I'd say you need to consider replacing the pickup roller assembly!  Those are hopelessly pitted, and that will surely cause sparking!  It would be possible to clean those up with something like a Cratex polishing wheel, but I suspect easier to just replace them.

FWIW, virtually all of the small AC motorized units will have some sparking at the pickups, seems it's the nature of the beast.  However, with those rollers, I suspect that's a primary reason for excessive sparking.

It is the material the rollers are made from. All reproductions are not equal. Try to find a pair of original powdered iron rollers. And be sure the roller pins are clean. Yes too, too light spring pressure will cause arcing. Maybe just locate a new original pick-up assembly, they are out there.

Another thought is your power supply. Ones like a CW80 will cause more sparking than a postwar transformer.

I'm using a postwar KW... Going to work on it tonight again, thanks for the recommendations...

If I had that one, I'd probably start with a dremel stone, then the Cratex wheel and smooth them out.  If the springs are really weak, not much you can do about that except replacement.  However, something like Deoxit-D5 on the axles and hinge of the roller assembly will reduce any resistance and potentially help with the sparking.

I'm guessing Chuck has the right answer, find an original pickup assembly.

I have the PWC Picatinny Arsenal TMCC version and as you can see, my rollers look clean.  I've also recently cleaned the armature and lubed the engine.  However, this still has visible sparks running on a pure sine wave transformer, it's the nature of the beast.  I doubt they're nearly as bad as what yours produces.  Note that the rollers on mine are made from what looks like sintered brass, these are what Lionel supplied on these locomotives.

Those springs do lose tension after being exposed to excessive heat, as can result if the rollers are straddling the ends of blocks and there is a short elsewhere in one block.  Or if the loco has jumped the track, with one roller touching the outside rail and the other the center rail.