Ye Olde 3 brush Dynamos

[RobThomas]

Are there any sparkys round these parts who understand the dark arts enough to know how a 3-brusher would work with a regulator designed for a 2-brusher? It is for a 1932 model Morris Minor with the 6-volt supply. I want to use a RF95 type regulator (6V from a Morris series E) and an older 3-brush dynamo.

Will it still work or will it Ppppfffzt at the first turn of the key?

[bmcecosse]

I think the idea of the 3 brush arrangement was to give the option of high or low charging rate....... It's so long since I ran my 8Es......I really can't remember. You may be able to use a regulator just sticking to the 2 opposed brushes - but the reg is of course designed for 12 volts - not 6. I really don't know if this will work - no great harm trying.

[katy]

I'm not familiar with the generators and regulators that you're talking about, but I do know about 3rd brush generator as were used on early (20s, 30s, 40s) North American cars, and you'rs are probably the same basic system.
The 3rd brush is adjustable, it supplies power to the fields, you would have to disconnect the wire that connects the field coils to the brush from the brush and bring that wire out to connect to the field terminal of the regulator.
Hope this makes sense.

[RobThomas]

no great harm trying

...apart from the £100 for the 6v regulator and the £100 for the 6v dynamo.

[bmcecosse]

I was assuming you already HAVE the 3 brush dynamo and a 12 v regulator - hence the need to do the trial! Thanks for the heads up on the 3rd brush 'Katy' - I did wonder if that was what it is for.....

[RobThomas]

I have a 3 brush 6v dynamo and a selection of 6v regulators (CF2, CF3, RF91, RF95). I'm guessing it is the same story for 12v. The 91 and 95 have the ability to top out the dynamo current to keep the battery from being overcharged (second coil inside?).
Does anyone know if they are wired differently, other than just having an extra brush?

[bmcecosse]

I'm guessing a wiring diagram for a Morris 8 will show it?

[RobThomas]

Sadly, no. They show a full 3-brush or a full 2-brush system but there is nothing to help design a hybrid system. A nice fellow from the world of A7s suggested avoiding a 3-to-2 conversion since it is fraught with problems. I'd prefer to go 12v but there is a problem in trying to find a dynamo in 12v where it has the adjustment on the left side and the 2 pivot points to the right side (Opposite of later cars and not interchangeable). The C45 also has the bolt pattern spaced further apart so I'd need to find an elusive 12v C45 with the correct bolt pattern or otherwise fabricate a whole new system to hang the dynamo which would then look too modern. I wanted to have the car looking 1930's. The pre war has the dynamo swung over the head whilst the MMs had it hanging off of the right side. Does that make sense?

I didn't pick a good week to have my TIG welder go belly-up.

[bmcecosse]

Some interesting comments in this thread re use of 3rd brush with summer/winter (my low/high comment) to regulate the charge - no regulator required!