You just need any old reduction system, gearbox or a set of sheaves to get
the speed you want and a nice plate on the end of the reduction with an
eccenctric pin to make the back and forth motion on the lathe will do fine -
sort of like a steam engine being driven by the flywheel.
While the treadle lathe in any of it's various forms is nice, they really
weren't that good for turning except to show for what the oldtimers back
then really had to put up with.
FWIW, the Woodwright Shop (PBS) does have a tape on doing a treadle lathe
and springpole lathes have also been shown in other episodes.
--
Why do penguins walk so far to get to their nesting grounds?