Kaptain Kleaver's Electric Mini Pickup : The Motor

This is the story of how I rebuilt the motor that's going into my electric Mini pickup.

I bought this motor from Paul Compton, and it was looking a bit sad when I first got it, even though electrically it was OK. I think it was originally made for a milkfloat, but it should easily be capable of moving a small car like a Mini pickup, especially if I use a higher voltage to make it rev up more.

Originally designed for 45 volts at 160 amps, I'm going to be running it at 120v... with currents of up to 400 amps or so, but this will be done with a Curtis 1221B motor controller. Electric motors are usually rated very conservatively, so you can get away with this kind of abuse if you're careful!

So where's the return path for the magnetic flux? Take a close look at the pictures, and you'll see the U-shaped pole pieces. These are bolted to the casing, and provide the return path for the magnetics - clever stuff! The ruler on the bench gives some idea of the size of all the parts.

I replaced the original bearings with new sealed ones - the old ones were full of rusty grease!
About a year later ( this is a long-term project! ) I took the motor back to Paul, to get his help in machining the commutator. It was making a distinct ticking noise as the brushes rode over some high segments. Since I don't have access to a lathe, and Paul knows what he's doing with EV motors, this seemed like a good plan. We mounted the armature into his lathe ( motors this size are quite heavy! ), and took a tiny skim off the surface to see how it was cutting.
Copper is difficult to machine, this was no exception, with some tearing - but it wasn't too bad, so we carried on and machined the whole length of the commutator.

After some sanding down with medium then fine wet'n'dry, the commutator looks really good! Since these photos were taken, I've very carefully chamfered the edges of the segments, to take off the sharp edges, and seated the brushes to match the commutator. The commutator must have been cone-shaped, because on the lathe the cut was getting deeper as we went along it! Not only was it out-of-round, it wasn't parallel ... it certainly needed doing!

Now all it needs is some paint ( I took advantage of Paul's homebuilt sandblasting cabinet) and it'll be as good as new - ready to go into the Mini !

I've also decided to beef up the brush rigging, some of the old bits of metal were looking rather corroded.And they were brass - yuck! Several times worse conductivity than copper! So I've replaced them with much thicker copper bar.the grotty-looking yellow wires will be replaced with much thicker braid, jacketed with fibreglass sleeving and PTFE high-temperature heatshrink.Finally, a good layer of 200 deg C conformal coating varnish will help keep corrosion from starting on the metal, and will help prevent the high voltages leaking to the casing ( can happen when the carbon dust accumulates from wearing of the brushes ).