# Help with DC motor problem?



## lownote (Jan 3, 2008)

These are probably dumb questions. I know very little about DC motors, and have never taken one apart. At least not since taking HO slot cars apart in 5th grade 

I have an old LGB 0-4-0 steamer in American profile--model #2117 D 

It ran marginally well but sometimes needed a nudge to start. Then it fell into a pond--kids!--and after that ran poorly and then not at all. I finally took it apart today--power pickup was fine, but when I hooked the motor directly to the transformer I got nothing. The worm gear and driveshaft turn freely with no apparent binding. It's a Buhler motor. 


So I sprayed a whole bunch of contact cleaner in there. Now it runs, but it still needs a nudge to start--just a little tiny twist of the worm gear. And it seems to run a bit unevenly--if the motor is rotated, it seems to hesitate a bit in some planes but not in others, It seems to run better in ne direction than in another. 

So what am I looking at--internal corrosion? Maybe some of the contact cleaner hasn't evaporated yet? Does it need to be lubed, and if so how? It can obviously be taken apart, but I'm not sure at all that I want to go there. Maybe it's just shot? Any suggestions? 

I have some other LGB 0-4-0s--two "stainz" engines--I could cannibalize. But obviously I'd rather fix this if I could. I assum an LGB replacement is going to be hard to find


----------



## Bill Swindell (Jan 2, 2008)

I would suggest that you need to really clean the commutator. Does the motor fail to start itself every time? You could have a bad winding.


----------



## lownote (Jan 3, 2008)

How do I clean the commutator? I've never taken one of these apart


----------



## Dean Whipple (Jan 2, 2008)

Posted By lownote on 07/09/2008 11:02 AM 
How do I clean the commutator? I've never taken one of these apart 


There is no need to take the motor apart I've cleaned lots of commutators, it's easy...get a piece of very fine wood type sandpaper the tan colored type *without any metal grit that would short out the commutator* cut it into a strip about a 1/4 of an inch wide, fold it over the tip of a pencil with a good eraser then with the motor running carefully touch the sandpaper to the commutator being careful not to disturb the wires on the armature...you'll see the dark copper brightens as it gets clean, if the dirty commentator was your problem the motor will start to speed up...your done, good luck...


----------



## lownote (Jan 3, 2008)

Thank you very kindly Dean, but I'm not sure we're taking about the same thing-I can't see any place where I could do what you describe. I cant see a disk or a place to insert sandpaper 
I did a scan--the copper colored business visible through the "window" is a coil which does not move


----------



## Dean Whipple (Jan 2, 2008)

I'm not familiar with the Buhler motor, but if you can find the brush or brush holder, you can remove the brush and rotate the motor by hand and sand it through the brush holder hole.....if not I hope someone who is familiar with Buhler motor can help you.....


----------



## lownote (Jan 3, 2008)

Well thank you Dean--I think I probably have to get a replacement if I can find one


----------



## Dan Pierce (Jan 2, 2008)

A lot of motors do not have the wires soldered internally, they go to a connector that pinches the wires. 

The motor problem described sounds to me like a contact is missing on one winding and that is why the motor needs to be nudged to turn. 

i have scrapped the wires and soldered these on several motors and made them operational.


----------



## bobgrosh (Jan 2, 2008)

I fixed one just like that one a few weeks ago. 
The big black part shown on the left is a brush holder. 
There is a red one on the other side. 
Mark the case with "R" and "B" so you don't get them reversed when you put them back in. 
Pull the brush holders straight out the side of the motor, (they have spring loaded clips and just snap right out.) 
Clean the carbon brushes and brush holder so they move freely in and out of the brush holder. 
Pop the brushes back in and test. 

If still not good enough. 
- Remove the brush holders again. 
- Use a "Q" tip soaked in LGB smoke fluid, insert it into the hole where the brush was removed to clean the commutator while rotating the shaft by hand. Use a good light and be careful you don't break any wires. 
Pop the brushes back in and test. 

If still not good enough. Repeat and clean the armature with an eraser, then blow out the motor with compressed air before you install the brushes. One drop of plastic compatible light oil might help. 

Those bueler motors are very tough, and easily cleaned. You may even be able to find some replacement brushes for them at some old LGB dealers. 


On one of mine, the fish pond had only left some algae in the brush holders so they were sticking and not putting enough pressure on the commutator. Cleaning the brush holder and carbon brushes might be all that you need to do. Avoid the armature cleaning steps if possible. 

B0B


----------



## lownote (Jan 3, 2008)

Bob Grosh--thanks, that was exactly what I needed. I could not figure out how to get the motor disassembled. Following your advice I got the brush holder off and found one of the brushes was cracked and the other had lost its springiness. I cleaned the one that was stuck and carefully reassembled it so the cracked brush was back in place and it worked fine. 

Probably I still want a new motor. That cracked brush can't be reliable. I'll go out to Star hobby today and see if I can find a replacement brush, although I doubt they'll have it.


----------



## bobgrosh (Jan 2, 2008)

Brushes are made of coal. Find one a little larger, with an suitable braided wire, and file or sand it down to fit. I used to do it all the time for NCR cash registers. 
LGB did sell brush assemblies. You should be able to find some somewhere, a lot cheaper than a new motor. Someone who has a bad motor might have some good brushes they would sell you, sorry, I don't have any bad motors. 
Or, take some measurements, and a better scan. Bueler motors is in the Carolinas I think. I found them once on the net and called them. Call and email them. They might be able to send you a new brush assembly. They were very helpful to me. 
The broken brush may last a lot longer than you would think. Unless the broken part falls out and jams, it will probably still run for years. 

Oh, I should have added to the earlier post... With the motor out of the loco, run it at 8 to 10 volts ( no load) for 1/2 hour after cleaning or removing the brushes.


----------

