Hand Crank how to?

[jhendren]

I want to create a handcrank to spin a DC motor at 24000 rpm. The DC motor is an 18V hobby motor from radioshack. Is this possible?

[xxChrisxx]

Possible yes, practical no.

You'll never be able to crank it fast enough with practically sized gearing.

[Mech_Engineer]

If you figured you would be able to spin a hand crank at about 60rpm (1 rev/sec), that means you'll need a 1:400 gearbox to step up the speed (and it will reduce your output torque by a factor of 400 as well). My guess is most hand-crank generators utilize a motor which spins at a couple of thousand rpm at most, meaning the gearbox is on the order of 1:20 or so.