# The HO Powerhouse, The DC Motor.



## T-Man (May 16, 2008)

Old engines have problems running, especially when neglected for long periods of time. Members want to get them running again. How often have we heard "clean and lube" . This one problem has a little twist.

I have an old AHM switcher. It ran Ok on the track but started to get slower until it stopped. I attacked and had no luck to bench test a startup. It did not burn up( I hope to disprove it). I did find something interesting with this particular motor design. Uncommon as it is the brushes stuck. AT least one did. When this happened the contact worked until the brush wore out and the connection ceased. How about that! The side opening is very small but I did manage to move the brushes up into the holders and back again. They are not that free moving and is the problem at hand. The springs don't remove and I can't figure out if the brushes are removable. A strange design. FOr now I am lubing the area and working the movement to free them up before trying again.

You can see the space in the second picture.











The brushes are housed in a plastic square but I don't think I can remove easily. The black plastic doesn't show any detail.









What led me to the find, is that during the bench test I got a spark from one brush. There was was a gap but because of the curvature it could not be seen. Only whe I tried to move a brush I noticed the resistance.


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## gc53dfgc (Apr 13, 2010)

It is really not that strange of a motor/brush design T. Those ussually just pop out and launch all over the room so they do come out eventually. Once you get them out sand the brushes flat so there is no curve to them at all. Then clean the comutator/armature/piece where the brushes touch with some 91 percent isypropol alcholo. Reassemble and it should run like new. I have done this on several of my AHM switchers and brought each one back to life doing this. I also do it on all of my other motors as well and it brings them to running just like new.


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## tjcruiser (Jan 10, 2010)

T-Man,

Interesting surgery.

I'm curious as to what transfers power from the brushes (or springs, really) to the motor wiring itself? Is there a metal cover plate (with soldered wire) that pushes up against the back of the spring?

You might need new springs and brushes here.

TJ


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## gc53dfgc (Apr 13, 2010)

tjcruiser said:


> T-Man,
> 
> Interesting surgery.
> 
> ...


You got the right idea TJ, the spring and brush pieces are held in place by a metal tab with a soldered on wire that goes over them. Very hard to put back on by hand and more dangerous when trying to get the springs out without loosing them.


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## shaygetz (Sep 23, 2007)

A classic AHM buzzer, a beast to work on...:thumbsup::thumbsup:


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## Massey (Apr 16, 2011)

If you have a R/C car hobby store near you, you may want to stop in there and ask them for a "comm brush". You want the fiberglass type if they have them. These brushes are designed to lightly scrape the tarnish and carbon off the commutor so the brushes have a nice clean contact surface again. ALso the brushes should come out the holes where the springs are but may be stuck due to debris or flashing that has formed on the trailing edge of the brush that makes the brush wider than the hole. This is common on motors that run one direction for long periods of time. If you can get a small xacto blade in there or a jewlers screwdriver and carefully scrape off the flashing you should be able to push the brush out for cleaning. 

Some brushes are supposed to have an arc to the where they meet the comm. This provides the proper amount of contact with the comm and also helps reduce wear on both the comm and the brush by having them fit to each other. This arc is not supposed to be lopsided, agian that happens when a motor is run one direction for long periods of time. 

The last thing to look out for and this could spell doom for the poor little motor is the condition of the end bell. The area that holds the brushes gets really hot and the plastic can melt around the brush. This will also prevent the brush from comming out of the motor and if this is the case the motor is prolly dead. If the brush cannot be held in place at the right angle or tightly the motor will not perform how it should and it will also generate more heat than it was designed to handle. Yes that means more melting and that is a bad thing. 

Hope this helps you out with your motor.

Massey


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## shaygetz (Sep 23, 2007)

I have one in my old motor box you're welcome to...it's complete, though I can't say if it runs. PM me if you're interested.


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## shaygetz (Sep 23, 2007)

tjcruiser said:


> I'm curious as to what transfers power from the brushes (or springs, really) to the motor wiring itself? Is there a metal cover plate (with soldered wire) that pushes up against the back of the spring?
> 
> You might need new springs and brushes here.
> 
> TJ


TJ, they get contact through trapdoor-like covers that you slide over the brushes. The wires for pickup are soldered directly to those covers that slide back and forth in grooves.


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## tjcruiser (Jan 10, 2010)

Thanks, guys!

TJ


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## T-Man (May 16, 2008)

This is a first time problem for me. Spring tension may also be an issue. They are old. I see from the discussion that I should be able to remove them. From the appearance of the case I wasn't sure it could be done. The motor wants to run, so more cleaning is in order.
Thanks guys!


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## T-Man (May 16, 2008)

TJ here is your picture with the cover plates over the springs. I got the brushes the out. They are shot after their extraction. So I will remotor with a new one. Thanks for the offer Shay but I wil go with a new one.


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## tjcruiser (Jan 10, 2010)

Thanks for the detailed pic, T. Good luck with the remotor.

TJ


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## shaygetz (Sep 23, 2007)

You're quite welcome...the nice thing about those drives is that new motors are almost a drop-in fit.:thumbsup:


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