On Sunday, 14 October 2018 02:04:13 UTC+1, Bob Engelhardt wrote:
On 9/8/2018 12:27 PM, Bob Engelhardt wrote:

With a small bit in a Dremel I excavated behind the segment, down to its
connecting wire.Â* There was no continuity from that wire to other
segments!Â* Then I noticed what had been staring me in the face all along
- the connecting wire exposed and broken:
https://imgur.com/a/jhIcgqf

Its connection to the segment also came loose, so I soldered in a jumper:
https://imgur.com/a/yiBcCit

It surprised me that the original connecting wire was steel.Â* I don't
know why steel would be used, but it made soldering difficult.

With it "fixed", it still sparked like crazy! It took a while, but I
finally found a transformer that I could re-purpose as a growler. With
that I discovered that the armature had shorted windings. Sigh.

I took it as an opportunity to do something new: rewind an armature.
There's a number of YouTube videos showing it and it doesn't seem too hard.

First, I needed the parameters: size of wire, number of turns in each
winding, and the connections of the windings to the commutator segments.
It was easy on the videos - you just unwind the old and record the
parameters. Not so on mine - the windings were potted with epoxy. With
some careful destruction I got some of it unpotted, but not the
connections to the commutator. So I trashed it.

Part of the commutator connections problem was that there were jumpers
from the commutator to the windings. Most (?) armatures have their
windings loop around a lug on a commutator segment and continue. I.e.,
each lug is the start point of one winding and the end point of another.
On mine there were 2 commutator segments per rotor slot; the jumper on
one connected to a winding wire, but the jumper on the other connected
to _2_ winding wires! How could there be 3 connections per slot?
Bizarrely asymmetrical.

I'm disappointed that it wasn't more doable.

motors with partial short can be run in series with a 3kW heater - but not now.


NT