I am working on a project where I think I will need an alternator with a different configuration that what is traditional. I have in mind an alternator resembling the old style generators but even more streamlined. My idea is of an armature that is appx 3" in diameter and maybe 10-12" in length with the accompanying coils etc. Should make the overall OD of the unit about 4 - 4.5 inches.
My question is how will this alter the charging output. I think the smaller diameter will accomodate (or require) a higher rpm.
Any help on this is greatly appreciated.

 

Without a diagram, I have no clue what you mean by "old style".

The existing designs will be hard to beat, over 200 amps @13+ Volts in an object that would fit in an 8 inch cube box.

What do you think could be improved?

 

Smaller diameter is bad, it requires much higher RPM and then you start to get increased losses from both the eddy currents at high freq and from the gearing at high step-up ratio.

There's a good reason modern alternators are of a large diameter, and that skinny "old style generators" were last used in the 1960's!