Info and drawings from an earlier thread about hand cranks
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=760998I've started a lot of old engines with hand cranks. One of the most important things with a long crank like these is having an outboard support bracket, see Denny's pictures linked in thread link above.
Also expect that the crank will be kicked backwards out of your hand, so keep thumb outside of the grip, let the handle be kicked easily out of your grip, and no locked elbows, keep it bent to reduce likelihood of breaking yourself.
With proper adjustments it'll never kick back, but always expect it.
Grigg