Forget the hand crank and the bicycle, consider the treadle...

My grandfather had a  treadle powered grinding whetstone for axes and such.
The cylindrical stone rotated with a trough of water on the lower side below the axle.
The ax was held to sharpen on the upper side.
Cooling water helped avoid loss of  temper
The heavy stone was its own flywheel.
Diameter was maybe 1', 30'cm or so; width was maybe 10 cm or so.
It sadly disappeared from his barn.
I think in my lifetime he replaced the treadle with an electric motor.

If I could find someone (nearby) who's able to, and wants to, build such a machine I would like to try out a foot-powered kitchen blender (strong enough to make nuts into nut-butter). I do have the book on human-powered low-tech machines (the Dutch translation).
I like such things, but I don't have the right kind of handyness/skill to work with metal and wood ...

btw some bicycles now instead of a chain have a belt-drive. I think that would work well too on stationary human-powered machines.

Wow!!!
Truly amazing!!
I had no idea!!
Love the YouTube vids

I knew spinning wheels and old singer sewing machines were essentially this type of foot power but really didn’t understand the concept or realize how much one can do with this!

I think there is real potential for making a really efficient one that can saw wood or sand things, similar to the videos

Is there a way to make these work with hands/arms for those without use of legs/feet, I wonder?🤔

Thanks much for posting!!

tuffy monteverdi wrote:Wow!!!
...

Is there a way to make these work with hands/arms for those without use of legs/feet, I wonder?🤔
...

Sure there is!. But then I don't think of a 'treadle', but a handle to turn around or up and down (even better two handles for two hands alternately).