Below is a great video of a guy building a foot powered woodworking lathe which uses a flywheeel to maintain rotational force.
Personally, I would rethink the treadle construction and maybe use some bearings to give some longevity, but it’s just so awesome all the same!
I built a pole lathe years ago, which was connected to my lightweight shed to pull the pole back up after the down stroke from the treadle. This caused the whole shed to shake in unison with the lathe so that everyone knew when I was turning wood ;).
It looked something like this.
The idea behind a pole lathe is to use a treadle (and your foot) to push down causing the work piece to turn .
A rope is attached to the treadle at one end and a bendy pole or sapling at the other.
The rope is looped over the work piece to make it turn on the down stroke, which also tensions (bends) the pole or sapling.
During the down stroke you use your chisel to remove material from the work piece.
You take away the chisel from the work piece on the upstroke, which is provided by the pole returning to its untensioned (unbent) position.
A pole lathe works surprisingly well and can be made very cheaply.