1929 Model 75 generator

[BlueDevil]

What is going on here?

 

The generator on my 75 is a 955 model and it has an extra wire, a notch cut in the cover band for the extra wire and had a regulator.

[Bloo]

21 hours ago, BlueDevil said:

What is going on here?

 

Well... as you say, someone apparently added a voltage regulator. The second wire is to control the field. If done properly, the voltage regulator is a significant improvement. What are your goals for the car? If it's going to be a driver, I would leave that for now and try to set it up and use it and see how that goes. For show of course you would probably need to get rid of it.

 

There were factory systems that work about like this around 1934-38. The can has a traditional cutout and also a voltage regulator inside (2 relays). Current regulation (Amps) is still handled by the third brush. Make sure you still have a third brush in the generator. 

 

I'd set the third brush to the maximum current (Amps) that the generator can safely supply long term. Caution, that probably wont be in the manual, and it won't be much. The maximum spec (Amps) in the manual for cars of the 1929 era is usually a bench test setting intended only to check generator health and is WAY TOO HIGH for constant use. A safe setting is going to be much less current (Amps) than the test setting. Cars that came from the factory with a voltage regulator on a third brush generator usually do not have an adjustable third brush. It is riveted in place. Maximum current (Amps) is fixed in that case so you don't need to consider it. On cars that had only a cutout originally, like almost everything from 1929, the third brush is adjustable. You must still consider the third brush (Amps) setting when using a voltage regulator.

 

I'd set the voltage regulator (the relay that controls the extra wire) so you get 7.5 or 7.6 Volts at the battery at room temperature. This is with a fully charged battery, the engine revved up to a fast idle, and the can installed on the regulator. Don't check with the can off. The setting changes with the can on. Check a few times and be precise.

 

Never ever run a third brush generator with the battery disconnected. Some windings may burn. If it is unavoidable for some reason, disconnect the generator and ground it's output terminal. This applies only to third brush generators.

 

 

 

 

Edited December 8, 2023 by Bloo (see edit history)

[BlueDevil]

Bloo,

 

Great information. Thank you for taking the time to explain it.

 

More investigation is required. I will update when appropriate.

 

Bill

[BlueDevil]

Ok, i got it apart and just want to get it to function as original at the moment.

 

There is the field wire and the wire that goes to the cutout.

 

There are 3 brush terminals (marked in white), 1, 2 and 3. 3 is grounded. 

 

Question of the day, which wire goes on 1 and which goes on 2?

[BlueDevil]

I think 1 is the field and 2 is the cutout.

[Bloo]

The 2 brushes directly across from each other are the main ones. The armature windings are the ones that supply charge current. One brush is grounded, and the other goes to the cutout (in the regulator box). From the other side of the cutout relay, a big wire goes to power the car and charge the battery.

 

The field coils, the ones in the case that do not move, are controlled by the voltage regulator and the third brush. Those will be connected to the third brush and the field terminal in some way or another.

 

EDIT: 2 should be the field. Most likely 2 goes to one end of the field coils, and the voltage regulator connects to the other end.

 

Edited December 8, 2023 by Bloo (see edit history)