" fired this volley in news:cc5a1ba4-
:

I can not see well enough to tell, but I think the handle turns the
roller.



The hand crank turns an offset crank arm on the roller. The link pin
creates the offset, and carries the torque from the hand crank to the
crank arm. 'Tis a weak point of possible failure, methinks; but it
allows the mechanism to work, which it could not if the link were
attached directly to one side or the other of the hand crank. If the pin
is stout enough, it would be strong enough -- it just doesn't look very
big.

LLoyd