I have a couple of cute little robots from sometime in the 80's. Powered by a couple of AAs with a little DC motor.
When I put batteries in I got no action and finally it seems the motors themselves aren't working. I pulled one apart thinking to clean brushes maybe and to my surprise found a substantial amount of green goopy stuff on brushes and commutator.
I'm not planning to put it on my toast in any event but should I be evacuating the house? It just occurs to me that these little guys are from a simpler time when maybe some PCB-based dielectric lubricant might have been seen as a good thing.
Generally, the "brushes" on those little motors are strips of copper or brass; the goo is likely some form of petroleum jelly, and over time oxidation on the copper/brass forms the green (verdigris - Verdigris - Wikipedia), and probably mixed in with the grease, which was lubricating the rear "bearing" (if you want to call the plastic hole a bearing).
You need the grease, but you want new - so pull the rotor out, and carefully clean the commutator, the brushes, and the rear cover of the old grease. Be very careful around the commutator and brushes, as the commutator has thin wires soldered from the rotor coils, and they are easily broken off (inspect them while you are at it). Also, the brushes, if they are oxidized, will need to be carefully cleaned in some manner to remove the oxidation (I am not sure what to do here - because of the small size, it may not be easily possible - you might look into verdigris removal? Maybe there's a way using chemical action?).
Once everything is cleaned, reapply some new petroleum jelly (or silicone grease lubricant - like "Super Lube" brand lubricant) to the hole - just a small dab, and don't get it on the brushes, then re-install the back cover (not the slot behind the brushes: slip a piece of plastic or something the width of the slot or a little less, so that the brushes are spread apart wider than the commutator - install the back, then pull out this spreader to snap the brush back in place - this is important to do to keep from deforming the brushes).
Try running it - and good luck!
One last thing - these toy motors are one thing to take apart, but there are motors out there that you don't even want to attempt to touch the brush mechanism; I totally destroyed a couple of Pittman motors I had trying to replace the brush mechanism on one - I stay away from that end of these motors now (Pittman motors are really high-torque, high-precision DC gearmotors - that cost over $100.00 USD new! Fortunately, mine were cheap from surplus, so I didn't lose much - but there was no way for me to repair them; they're parts donors, now).
Just a guess but seems like copper corrosion probably mixed with water or lubricant from the motor. Could try cleaning it all up and it might work. Might just be a bad connection due to the "goo".
ok thanks for the tips - i knew what the greenish color was about but it didn't occur to me that there would have been substantial lubricant needed. the toys must have been lying so that the lubricant dripped down onto the commutator.
thanks for the assembly tip as well.
note the slot behind the brushes: slip a piece of plastic or something the width of the slot or a little less, so that the brushes are spread apart wider than the commutator - install the back, then pull out this spreader to snap the brush back in place - this is important to do to keep from deforming the brushes
That is SO clever!
I now notice that the driving gear is loose on the motor's shaft - 30 years is a long time!
