!930 car dynamo

[ex 2 Base]

Not sure if this is in the correct location. Has any one reconnected a third brush 12 volt dynamo to a two brush type so that a voltage regulator can be used, or can they point me in the right direction. Correct me if I am wrong, I propose to remove the third brush altogether and connect its lead to the F terminal on the regulator. the D to it correct terminal, E to frame and A to ammeter. your help will be much appreciated. Ted

[Murphyv310]

Something in the back of my mind tells me you won't get the required output. Is this a six volt system?
I did some work with a prewar dynamo when I was young about 18 but it's to long ago to remember.

[boater sam]

Basically you are correct, the 3rd brush wire becomes the field control to the voltage regulator.
But as well as voltage control, you need to limit the charging current or else you will get the armature too hot and the commutator will throw its solder.
There are solid state regs that will do this, and the old Lucas 2 and 3 bobbin regs too but you will have to set the max current down to a sensible figure.

[peter scott]

I think you could connect it to a normal control box but it might be better to disconnect the field from the third brush and connect it to the grounded brush instead.

Peter

[ex 2 Base]

Having had another think about it I'm sure you are right Peter. Connect one end of the field to the earthed brush other to terminal F. This is for my friend Riley car which I haven't yet seen,but I think will be 6 volt as most were those days. Some had preselector gear boxes as well. I have read that it is easy to covert a 6 volt dynamo to 12 volt using an electronic regulator. Ted

[The Philpott]

Only just seen this thread.

I think the vehicle will be 12 volt not 6.

The 3 brush dynamo historically has sustained a certain amount of flak from Riley owners, whether it is justified or not my father would be able to advise as he has been messing with them since well before decimal currency appeared! I can ask him if you wish. There will have been a lot of discussion re. setting them up in old riley register bulletins, which would be a good place to look.

There is potentially less demand on the dynamo these days with the development of more efficient lighting- which is nice.

The sheer physical size and weight of the dynamo compared to the output might well breed prejudice against it especially among those used to seeing the compact unit used on, say, a Triumph Spitfire.

Dave

[peter scott]

Fitting alternators to pre-war cars is a bit like fitting undisguised yellow capacitors to old radios. I guess it doesn't matter if you never look inside but that hardly applies to an engine compartment.

Peter

[Murphyv310]

Peter.
I'm sure you could fit a small alternator in the old dynamo housing, 22 to 30 amps would be fine on a pre war car as the demand is so low.
The idea of a solid state regulator on the original dynamo though makes total sense.

[peter scott]

Me thinks you are trying to wind me up Trevor.

Peter

[Murphyv310]

Hi Peter.
No actually I'm not. A few years ago I went to the Boness hill climb and I got chatting to a chap with a prewar MG quite a big car of which I don't know the type. He had fully stripped the dynamo and had got new coils made up and slip rings made for the shaft. As the old dynamo was long it was apparently quite an easy job so he said, he was able to use parts from a French alternator a Ducelleir (spelling?) from what I remember
Strange I bumped into him again a couple of years ago and discovered the car was found in Fenwick!! Which I didn't know on the previous chat.