This week I have mainly been rebuilding dynostarters.
I have ended up building 5 Sachs engines. Since my leg is not really doing to well at the moment it seemed a good time to raid the pile of not so good dynostarters and see if I could not restore some of them to functionality again. I did not have the kit for undoing set screws so the first test was to pull out those with stator coil faults. Then attempt to see if that was due to a surface insulation problem, or an internal failure. In the selection were several duffers, but two that I might be able to repair.
The amateur way of doing this, I have no growler, is to look for damaged areas first. If that does not work then the link joints can be undone in a systematic way, reducing the sections to isolate the fault. In one case this proved the fault was not on the visual damage, but elsewhere internally to a differing coil. That unit was set aside for another time. Leaving just one. It looked like it had been dropped. So i carefully pulled/levered the coils out to get an oval again. You can buy insulated paper that is impregnated with something. Having slid three sections in I tested the stator. It was now insulated. So a tidy up of the inserts and a careful adjustment of the coil. A retest. The problem then is that the coils outer cover has normally got destroyed. I have found that fine cotton cloth soaked in shellac does the job. A pair of scissors to get rid of flaps of cloth so the new surface lies low.
Several of the units needed new feed wires as the old ones had been cut off, or been damaged by melting, or chaffing. The scrap stators still supply enough good used wires that I can solder correctly marked tagged wires on in full. Its a soldering job. But making a new lead is no real difficulty. Just be sure the wire is of the correct quality. Put it through the rubber grommet before tagging, of course!
Then in all cases it was a clean up. I still have Trich, a banned substance, but one of few things that removes carbon. All the little screws, washers, paxoline etc are cleaned up. Then its assembly of brush holders. On the Schmitt they are all insulated. Sometimes it can be quite an effort to get the paxoline tube of the right length, in the right place and all snug. You think its there. tweak down and there is a leak to earth. Siba does seem to be easier than Bosch. Then a sort through the used brush box for good sets of brushes. Three engines were treated to new brushes. Another round of testing.
The flywheels, or commutators, are really not easy to repair. So its a straight test for leakage to earth. A check of the commutator surface for damage, or excess wear. I have found the stub end of a joss stick to be an excellent tool for cleaning the flywheel. You should not used steel on them as it will damage the insulation. Trich again comes in handy. You will be amazed at the amount of loose carbon even a clean looking flywheel can produce. Its dust that is a conductor, so you do not want it collecting in nooks and crannies where it might start bleeding current to earth. Cleaning the flywheel is actually included in most Microcars service schedules! A serious Micronaut is never without his dynostart puller, chosen for the best design of his favoured car.
Anyway out of the collection of rather mangy dynostarts have come 5 very good servicable units that should now last another lifetime. Plus I rather enjoyed the effort, which will save time later as I have good ones ready on the shelf if I am in a hurry.
