The treadle belt was shortened to run only from the motor's pulley to the handwheel.
From the en.wikipedia.org
The closer on a manual lathe is either lever-style or handwheel-style.
From the en.wikipedia.org
The add-on motor drives the handwheel by means of a rubber belt.
From the en.wikipedia.org
Each rotation of the crank handle produces three rotations of the handwheel, and hence three stitches.
From the en.wikipedia.org
If the handle is circular with the stem as the axis of rotation in the center of the circle, then the handle is called a handwheel.
From the en.wikipedia.org
In the first variant, the rotation was accomplished by a large handwheel, though later there would be gear drives and hydraulic actuators.
From the bbc.co.uk
To answer this, the modernized models 127 and 128 moved the bobbin winder up several inches where, with a suitable tire, it can run directly off the handwheel.
From the en.wikipedia.org
Driving the bobbin winder with a separate belt, hooked onto the motor pulley whenever needed, means that the standard V belt cannot be used to drive the handwheel.
From the en.wikipedia.org
More examples
A wheel worked by hand
Control consisting of a wheel whose rim serves as the handle by which a part is operated
Any wheel worked by hand, whether used to allow leverage, as of a valve or a handbrake, or to allow fine adjustment, as of a setscrew
A manual override device used to stroke a valve or limit its travel. The handwheel is sometimes referred to as a hand jack. It may be top mounted, side mounted, in-yoke mounted or shaft mounted and declutchable.
(nut , bolt ): A threaded nut or bolt which can be tightened by hand, usually in the form of a knob with a gripable (knurled) surface, or with protrusions (wings).