d,
I suspect, though I'm not positive your comment was kind of maybe directed at my post. I like treadles ( have two Red Eyes and a 9W-7 - so far ) and have occasionally taken the belt off and "hand cranked" them.
To use a hand crank machine I would need three hands. Two to guide the fabric and work the controls of the machine, and one to crank it.
I can see using a hand crank on those machines that can be set up for one ... as a manual test method to verify you've fixed it right. After that put the motor or treadle belt back on.
There, hope I answered your questions.
Joe