Ask MAKE: Cleaning an old motor?

Ask MAKE: Cleaning an old motor?

Ask MAKE is a weekly column where we answer reader questions, like yours. Write them in to mattm@makezine.comor drop us a line on Twitter. We can’t wait to tackle your conundrums!


Andy writes:

Recently I acquired a vintage Leslie speaker cabinet. The speaker cabinet uses ac motors to turn baffles and horns to create a Doppler effect. Upon opening up the speaker, I found that the motors were working, but very dirty and coated with gunk. What is the best way to clean a motor with an excess of build up?

Congratulations on your acquisition! Since the motors seem to be working fine, my guess is that it might be best to clean them cosmetically, but not to try and take them apart and rebuild them. Even though they are electrical devices, you should be able to clean them like anything else, using some form of solvent and a brush. Just make sure to let them dry out completely before you power them up!

I would start a mild detergent (soap and water). If that doesn’t do the job (which it probably won’t), try mineral spirits or a specialized electric motor cleaner. The biggest things I can think to look out for when using a solvent to clean the motor are that it doesn’t damage the varnish on the motor windings or get into any greased bearings. The varnish is used as a coating on the motor windings, to keep them from touching each other and shorting out, so removing it would not be a great thing to do. If the motor does have greased bearings, you might want to lubricate them as well.

I’ve taken apart a few motors, but admittedly don’t have a lot of experience in this field. Does anyone have a favorite technique or solvent that they use to restore vintage machines like this?

20 thoughts on “Ask MAKE: Cleaning an old motor?

  1. Tim Lewallen says:

    I use tuner cleaner from Radio Shack. It works great for stuff like this.

    1. Gareth Branwyn says:

      Here’s a piece from my old tech website, Street Tech, from 1997, about the wonders of RadioShack tuner cleaner, written by a radio engineer friend of mine.

      1. Matt Mets says:

        That sounds like a great product! Thanks for the insight, Tim and Gareth :-).

        Also, that’s a sweet looking radio- do you still have it?

      2. RocketGuy says:

        There’s stuff that the old-school electronics shop has, expressly for cleaning electrical contacts (i.e. getting rid of crackles in stereo volume knobs and so forth), that would probably be good for the places you can’t get into, as it also coats/lubes.

        I agree with Craig though, get the commutator smooth!

  2. Alan says:

    Isopropanol (rubbing alcohol) is my go-to solvent for cleaning stuff like this. It dissolves lots of types of gunk, but doesn’t eat most paints, varnishes, or plastics the way other solvents can. It also evaporates quickly.

  3. craig says:

    Oh wow. Are those two circular hoop contact points (armature) for motor brushes in the middle of the photo? If so, that is the one point where visual dirt will be a problem. Once cleaned, getting it free of any rough rust/pitting is a must or your carbon brushes will get eaten to nothing in notime. Ultrafine emery paper while hand rotating will get it shiney, then wet-sand with another piece held against while hand turning it. you want it bright and smooth. And before trying to physically rid any grime from the rest of it, blast it with an air compressor sprayer all around and inside. Anything left is harmless.

    1. Matt Mets says:

      Hehe, I think the piece of machinery (generator) in the photo is probably long dead… it used to power the Vulture Mine near Wickenburg, Arizona. I didn’t have a photo of Andy’s motor, so I was using it as an example. A picture of the whole thing is here:

  4. says:

    Congratulations and good luck! You’ve just reminded me that I have a leslie of my own stashed away in a corner(next to the chest freezer awaiting PID modification). They are wonderful pieces of hardware, with awesome electronics, especially if your model contains a tube poweramp. The mechanics are very cool too. Some of these guys actually have clutches to change speeds. Mine has a motor that has two separate sets of windings on the same shaft to achieve the effect. It would be great to see pics, or at least to know what model it is… there is a wealth of DIY knowledge on the web pertaining to leslies and the hammonds that love them. A friend and I bought a hammond/leslie back in highschool (’98?) and he rebuilt the thing; they are beautiful beasts.

  5. Ernie says:

    I have found that a can of automotive starter fluid (ether) works great for this type cleaning. Just make sure it has dried completely as it is very flamable.

  6. gear head says:

    …on just how dirty the motor is. A really dirty or dusty motor can pull oil out of the oil-lite or ball bearings at either end of the rotor shaft. Once those bearings surfaces are ‘galled’ it can be difficult to re-oil them and expect the bearing to lubricate the spinning motor effectively.

    Those old motors were built well and were built to last. A little bit of preventative maintenance will keep them going for a long time yet. Simply spraying detergent or solvents into the motor case will move the dirt around and probably make the bearings fail sooner. Removal of dust accumulation keeps the motor running cooler too so you should consider an overhaul if they are badly choked with crud.

    Motor dissasembly and cleaning is pretty straightforward if you take a methodical approach and lay everything out carefully as you dismantle the motor. I have a 70 year old motor in a test fixture running 5 hours a day and it runs better than any of the new motors that preceded it.

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