The 3100 Rule,
As long as the commutator doesn't have any shorted bars, it can be turned down and undercut many times. I have seen commutators turned so much I wondered how the generator could 'gen', but it did so just fine.
I don't know this for sure, but if the 6 volt armature has the same exact physical dimensions, most importantly, the armature proper is centered in the field shoes, It seems it would work fine. This is a non-engineer, backyard observation though.
Interesting project..you must be part mad scientist too!
Stuart
