Cleaning a Dirty Brushless Motor

Some times you biff a plane into the dirt.  Some people tend to do this a lot more than others.  I think I tend to land (pun intended) into that group.  This can really mess up an electric motor, especially if you keep trying to spin the propeller (if one still exists), or the shaft.  This can cause all kinds of damage to the magnets and stater coils.  So don't do it!  If you get dirt into your motor, just leave it until you get home and can clean it.  Brushless out runner electric motors are actually quite easy to clean out.

I recently had this issue with my Hobby King Club Trainer.  I came in over a freshly plowed field and didn't make the runway.  Of course it nosed over and the cowling scooped a large amount of dirt all around the motor.

Below is how I went about cleaning it up and getting it back into shape.

The first thing that I did was to take the nose cone and prop off.  All the while being careful not to spin the motor shaft (or at least as little as possible).  Then I removed the motor from it's mount and disconnected the power connectors.

Now you need to take the motor apart and separate the out runner and magnets from the stater coils.  A lot of times this is done by removing some Allen set screws.  In my case, this was held together with an "E" clip in a slot on the end of the shaft.  There are special tools for removing these, but I usually just use a small screw driver or pick.  Just be careful not to bend or gouge up this little item or you will need to find another.

Now separate the two parts.  This is not always easy to do as the strong magnets used will try to keep the iron stater where it is.  Just be careful and don't pull on the wires!  For mine, I was able to pull on the prop shaft and the bearing tube.  After some effort, it popped right apart.  Depending on how much dirt is in your motor it may cause it to bind up.  If this happens, first try tapping the motor with the bell facing down to see if anything will come out.  Then try to gently turn the motor just enough to free it up.  Repeat this process as needed until it can be taken apart without damage to the magnets or iron stater.

Now take the bell out runner side and tap it down on a suitable surface.  By a suitable surface, I mean something relatively soft.  Don't do this on a hard surface like tile or metal as you risk damaging your tile and the shaft.  This will dislodge most, if not all, of the non magnetic dirt.

Now take a stiff epoxy brush and start bushing out the rest of the bits that remain.  I thought I would have a tough time with the magnetic bits and iron dust with such strong magnets, but they came out quite easily.

As you can see, it's nice and clean once again with no remaining bits.

Now just reverse the process to put things back together.  Be careful putting the stater back into the out runner bell as it can come together quite violently and pinch fingers!  Once it's back together make sure that it spins freely again.  Of course you will still get the "coging" of the magnets and stater, but there should not be any grinding or gritty feel.  If you do encounter this, start over and clean it out again.

Argh!!! It happened again!

You can see that the mud actually mushed all the way through the motor.  I pulled everything apart and used some water to rinse most of the mud off.  Then I made sure that it was dried out to make sure it did not rust and then used these techniques to clean it out the rest of the way.  And yes, it did fly again.

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