George, some Delco 3 brush setups used a 2-unit regulator- - - -cutout relay and voltage, no current regulator. I've got a Delco service manual from the early 1950's that covers that system and a bunch of others including the heavy duty 6-unit regulators used on the 24 volt military rigs.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!