# Prewar Lionel 1688 - Hot Brushes?



## Gerard (Dec 26, 2010)

Hi everyone.

Just got my Christmas layout finished and have been running my 1688. There's something that has been concerning me though.

After about ten minutes of running, the bottom metal brush cover gets burning hot to the touch. I would guess the top one does as well, but only the bottom brush cover is exposed with the locomotive shell on, and I haven't run it with the shell off to test.

I did take the brush cover off and clean the commutator and brushes the best I could using a pencil eraser. They were pretty clean already and it didn't make any difference. There is still some minor darkening on the commutator where the brushes contact it, but I think I'd have to go for a sandpaper polish to get it any better. Brushes and springs seem fine to me, and have plenty of extra push on the commutator surface. I also measured resistance from the bottom brush cover to the frame, and got a reading as low as .2 ohms.

The locomotive runs strong and smooth with about 8-9 volts, 10 volts max even when pulling several cars. As far as I can tell, it runs every bit as great as it should. Is it just normal for the brushes to produce so much heat, or is it indicative of poor electrical contact, even though the locomotive runs great? I'm just afraid it might get hot enough to melt the commutator windings or something.


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## Big Ed (Jun 16, 2009)

If you burn your finger then it is too hot.
It gets that hot?

You check all the wiring?


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## pookybear (Feb 3, 2011)

Something is not right, you should not be burning the commutator faces
like that. Do you have carbon or copper brushes?

Also if you can take a spare piece of track, place the engine on this
extra track. Then do an ohm test from the outside rail to the center
rail. This will give you ohms through the whole circuit. Looking for not
much more than 1.6 ohms at the most.

If it is higher start looking at the pickups for high resistance or the e-unit
fingers if fitted with one.

Pookybear


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## T-Man (May 16, 2008)

Try cleaning the grooves between the copper plates on the armature. A carbon buildup produces a short.


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## Gerard (Dec 26, 2010)

After 5 minutes I'd call it warm, but after 10 minutes it's hot enough that I'd not want to hold my finger on it for more than a couple seconds.

What would be best for more thoroughly cleaning the armature and grooves? Maybe a toothpick?

I get approximately 6 ohms measuring from center rail to outer rail with the locomotive on a spare track piece.

I'm going to take the shell off again and see what I can find.


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## Gerard (Dec 26, 2010)

I was able to get readings as low as 2.2 ohms from center pickup to frame. Resistance seems to vary a lot rolling on track. I guess another wheel cleaning is in order. I might give that a shot first.

How does one tell carbon from copper brushes?


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## servoguy (Jul 10, 2010)

Whatever brushes are in the loco should be OK. If things are getting hot, there is either too much resistance just at the brush itself, or the loco is drawing too much current, perhaps due to poor lubrication. Do the wheels turn easily? If you put the loco on the track and push it, do the wheels turn or do they slide? They should turn. Is the inside of both brush holders clean? Are the brushes clean on the outside? Are the slots in the commutator clean? I don't mean **** and span, but has the majority of the accumulation of carbon from the brushes been removed. 

I am not sure that the brush holder is getting too hot. There is always some sparking where the brush contacts the commutator. Too hot to touch is only about 120-130 deg F. 

How much voltage does it take for the engine to run by itself? If it takes more than 7-8 volts, it needs lube. I have a 2333 that will run with 7-8 volts with 6-8 cars behind it. I have oiled the commutator of the 2333 to reduce the friction.


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## Gerard (Dec 26, 2010)

Thanks to everyone for all the suggestions. I just want to do my best to keep this classic going as long as possible.

I cleaned the brushes pretty good. The springs and holders looked pretty much spotless. The commutator I cleaned the best I could with a Q-tip, but could possibly use a more thorough cleaning to get into the grooves. I attached a picture of it in its current state.

Also cleaned the wheels and replaced a problematic pickup shoe, but I still got a lot of fluctuating high resistance readings when trying to measure it on track. On a live track, though, the engine seems to get very reliable electrical connectivity.

The wheels turns quite easily and smoothly by hand. With the locomotive shell on, the wheels get excellent traction - no way they'd ever slip. With the motor out of its heavy shell, the wheels do slide on track without a little downward pressure. I did lubricate all of the usual spots when I got the locomotive about a year ago, and it still runs the same overall as it did then. I'll probably add another drop of oil to all the usual spots.

It does sometimes need a nudge to get going... seems to have slightly more trouble in forwards than reverse for some reason. Might be a slight conductivity problem with the E-Unit? Once it's running, though, it's quite strong and smooth. A little fluctuation at slow speed sometimes, but almost perfect at medium speeds. The engine will run at a nice medium speed with about 8 volts, and about 9 volts pulling the tender and a few cars I believe.

I had it running again for about 15 minutes, and the brush holder eventually got too hot to hold my finger on. Aside from needing a small nudge to get going, it ran so great on 8.5 volts that I really couldn't imagine it having a significant issue. I really can't find anything functionally wrong, aside from maybe needing more commutator cleaning and a few more fresh drops of oil. Would brushes and commutator getting into the 120-130 degree range be nearing any potential harm to the armature? What would be a normal temperature for the brushes to reach with a typical amount of sparking/friction?

Thanks again. I really appreciate all the helpful people here.


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## T-Man (May 16, 2008)

You have to make sure the drum is clean and not broken.











To remove lines use 320 or crocus/400. Or both the smoother the better and remove the copper record grooves. This is not routine, once may last another 50 years.


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