Does this really work?
Why does this work?
Why doesn’t the motor short out?
Some info on why this is done. Seems idiotic to me, it’s just a matter of breaking in the brushes to get them to conform to the shape of the commutator. And who still uses brushed DC motors like those anymore anyway?
The video mentions distilled water, i.e. water with very little contamination. This is a very poor conductor, so the motor will not short out. If you put the motor in tap water (which has a substantial amount of dissolved minerals that enhance conductivity), there will be some leakage current, but the motor will still be operable.
If you drive your full-sized car into a lake, the headlights will continue to operate for a long time, and so will the electric windows and door locks (though perhaps not for quite as long as if the car were on dry land).
I’ve done this with regular tap water and it works fine. Apparently the water isn’t conductive enough to cause problems. I hooked it up to a standard D cell and just ran it down.
I was using a brushed motor because that’s what was required for the class of airplane it was going in.
R/C cars still commonly use brushed motors despite the brushless variety becoming dominant in model aircraft.