In general, I find those terrible. As a human I have large muscles and limbs capable of creating quite a bit of force. A 3.5 inch crank held between my thumb

In general, I find those terrible. As a human I have large muscles and limbs capable of creating quite a bit of force. A 3.5 inch crank held between my thumb and forefinger doesn’t seem like a great way to generate electricity. I would much rather lift 50lbs a few feet every half hour than spin a tiny crank.