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I've decided to have a look at an SCX RX42B motor that HL had been complaining about. I hooked it up to the test supply and it spins up ok, but it is wafting out a nice constant stream of smoke. I'm looking for suggestions of the sort of thing to look for before I open it up.

I plan to try burning off any oil on the brushes via the soldering iron. But what other suggestions do you have?

Dunk it in a alcohol bath and run it for a minute or two. That will help clean the brushes and the comm.

But yes, sounds like the Exxon Valdez had a spill inside. Clean up and re-test :)

Exxon Valdez paid this SCX motor a visit.

Once you clean it up - I would put it in a bath of Naptha, but get the motor running first. Do not start the motor up in Naptha, nor alcohol for that matter.

Once degreasing / desludging has been completed, take a close look at the comm. You might find more crude between the plates for the segments of the motor. An X-acto #11 blade will clean it out very nicely. It might require a cut of the comm to bring it back to full life.

If that does not work, it's time for rings and valve guides!

The big guy beat me to the alcohol bath suggestion. It's amazing what can get into the manufacturing process on even the highest quality operation (i.e. I had 3 Slot it orange endbells go "Post Toasties" on me in one evening).
The important thing, as we used to say in Air Force electronics, is to make sure you let all of the smoke out!

Marty did you make a typo? The rule, as far as I know, and the way I have done it for many years, and the way our tips section teaches, is dunk it all the way, then apply current. Water is only conductive on the surface, and the only way to ignite alcohol or naptha is to allow the bare wires with current passing through them to meet the surface at the same time. I find 91% isopropyl alcohol is much better because it doesn't stink, and it absorbs remaining bits of moisture from the motor's interior much more effectively. I only use naptha for my pipe lighter.

I believe he was actually doing a shellite/fuelite bath run in when the problem started.

Like Rob, I had always been told to ensure complete emersion of the motor before applying power.

I have another one that had been displaying some odd behaviour and causing a large voltage drain on the supply. Seem I just cleared it with a big amperage dose and some smoke. It's now working fine.

Not really sure I like this motor black magic.

Lynne, there is a terrific product here that is a spray for the commutator and brushes for cleaning and lubrication. It goes under several names here, but by the use and the smell they are all the same chemical spray. It takes only a tiny amount to do a great job. I also use it for my controllers. I believe it is intended for industrial electric motors.

What name does this magic spray go by? I wondered about CRC contact cleaner, but wasn't sure if it might damage the brushes.

electric contact cleaner is all close to the same you can get 1 thats very flammable and they make another that is not, they both work well, but you just cant beat an alcohol dip, heck you drink, give your motor a sniff :music-rockout:

Ahh... But whiskey or bourbon, Jon? :) Easy... Bourbon. Whiskey's for drinking. :D

This is exactly why I don't recommend an alcohol bath for toy car motors. It isn't that it doesn't work, it's that signals get crossed, somebody does the wrong thing, and *poof* somebody lights on fire. Use water, instead.

When the motor runs, it's sparking as electricity jumps across the air gap at the commutator. So if you start a motor and submerge it into alcohol or naptha, you have a spark, you have air, and you have fuel. If the motor passes through the right concentration of vapors on its way to the fuel, you have a pretty serious problem on your hands.

If the motor starts when it's submerged, you have no air, and combustion won't happen. There are still other accidents that can happen, and if the motor is pulled out of the bath while the armature is still turning, things can get pretty hot. Sure, the odds are low -- but why even take that chance? Use water.

I use water to do the work, then alcohol to dry the water out of there. It just means I don't have to poke around with a swab.

Lynne, the spray I was talking about is non-flammable. I didn't even know there was a flammable one. But that is what I use after the cleaning is done, just the tiniest little squirt of it.

Any chance of a brand name or chemical name for your non-flammable contact cleaner?

I'll give the motor a dunk in some methylated spirits today and see if that clears it's problem out.

I've used both water and fuelite to run SCX motors in. And I must admit, I feel safer with using water. But then there's the problem of getting it dry. Of course, there is also the problem of water not dissolving oil, which is why I started using the fuelite.

It never ceases to amaze me just how much carbon and junk one little motor can spit out over a few hours of a 'run in' routine.