A quick change gearbox isn't terribly difficult to add to an older machine. In general, engine lathes aren't rigid enough to machine drums and/or rotors- - - - -in particular, rotors which must have friction surfaces parallel within .0005". (1/2 thousandth).
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!