12V Model T Starter Conversion
As originally built the starter was made to deliver the proper torque from a 6V source. Converting to 12V increases the torque as well as the no load RPM. The first thing that I noted was a 6V starter operating at 12V really slammed into the ring gear. However there are a lot of T drivers out there running 12V with no serious consequences. Enter the culprit.... the snout bearing. The babbit on mine was almost non-existent. This allows the starter shaft to flex away from the ring gear causing the gear mesh to be reduced. Take this to the extreme (mine) and the gears can jump and chip. Now if the motor 'kicks back' because of too much advance plus the added torque of 12V.........the shaft bends and things go down hill from here. My shaft was bent over 1/10" out of round.
A quick trip to Chaffins Garage for parts ($45.00) where Dave straitened the shaft and I was ready to rebuild the starter and convert to 12V. New starter gear (one piece), bendix parts, bolts and keepers and a used transmission bushing covered most of the new stuff. Dave had found that there was a bushing with the proper I.D. to fit the Bendix shaft but required the starter snout to be bored out to fit. I took the bushing to a friends machine shop and had the bushing press fit after the hole was bored.
So far after three weeks it's working fine and sounds like a good running 6V starter on 6V.
The following article is from an Email by a friend who kindly shared his experiences with me. So I include his comments here with his permission.
I used 2
#10AWG stranded insulated wire to make connections. This is equivalent to a
#7 wire but easier to handle and to get. It is pretty close to matching the
copper bar normally used to "wire" up starters. Take a good look at the
field connections as they are for the 6 volt configuration. The current
comes into the terminal on top and splits, going to the left 2 coils and the
right 2 coils. At the bottom of each pair of coils, a soft wire cable goes
to one of the 4 brushes. These 2 brushes are opposite each other. The
other 2 brushes go to ground.
Conversion Schematic Diagram
This site was last updated 11/13/09