Be aware of differences in treadle design. Those for sewing machines typically had a back and forth, heel -and -toe type action, designed for use by a sitting person, and higher speed with not much torque - how hard is it to drive a needle through cloth? Heavier duty ones for leather were designed to be used while standing.
Treadles designed for wood lathes provide a great deal of torque (needed when roughing) at low speeds, and higher speeds with less cutting being done on each revolution - sharper tools cut more, brake less, and typically have only an up (coasting) and down (power) motion, and if you have a really heavy flywheel, you can get them up to speed, and maintain the speed relatively easily. Stopping a heavy flywheel if the project comes loose, however, is another kettle of fish. Design in some kinda brake for the flywheel.
Think of bicycles in the 1880s vs modern ones - the basic design is the same, it's the refinements that make lots of difference.