Vroom!
Here you can see the Difference Engine running. The guy in the
red shirt was specially trained by the builders. I cannot remember
the exact number he quoted, but he has to maintain a fixed number
of revolutions per minute. If he goes too slow or too fast the
Engine will jam. The resistance on the power handle changes
throughout the cycle, so the power applied cannot be constant, he
has to vary it as he cranks.
