Generator speed ?????

I just picked up a spare generator for my '55 Buick and I noticed the generator pulley was about 1/2" smaller diameter than the one I have on the car presently. I don't know what the installed gen came off of originally, but it seems to be working OK for the last few years.

Anyway, being a little*****, I started doing some figuring and calculated that at 2500 rpm engine speed, the generator in the car would be spinning at approx 4800 rpm and the spare would be running about 5900 rpm. That seems like a helluva difference, so I checked a friend's '59 Poncho with a 389 and at 2500, his generator would be running around 5800 rpm.

Does anybody know what the "ideal" generator speed to engine speed ratio should be ?? If around 2.3:1 is correct, what would happen by having it turn too slow - slower charging rate ?? Too fast and I'd expect prolly premature bearing failure or brush jump or ???

Thanks for your input,
-Bob

 

Do not take this as FACT......some old guy told me this when I worked at the salvage yard........

The smaller pulley generators came on AIR conditioned vehicles. They needed more juice at low RPMs. The old guy was looking for a generator.......and we came up with one......but it was a plain jane, no air car. That's when he told me the little story about the pulley.

He did know what he was talking about ?


I haven't a clue........but it sounds logical.



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Early Corvettes with mechanical camshafts, which made the engine rev higer, came with larger generator pulleys.
So I guess there is a max generator speed.

 

I looked at this a few years ago, and by a quick guesstimate of pulley sizes with an alternator pulley a 1/3 of the diameter of the crank pulley, I worked out them*****ers might hit 15,000 rpm when the engine is revved up to silly numbers

Hence the production of all sorts of aftermarket down speeder pulleys I suppose.