In this video at 0:40, what is the equipment he is using to power the motor? It seems to be some sort of torque leveraged device (forgive my ignorance).


  • 3
    \$\begingroup\$ hand cranked dynamo maybe \$\endgroup\$ Nov 6, 2012 at 19:46
  • \$\begingroup\$ Just a PM motor attached to a gearbox and a hand-crank. Essentially a duplicate of the demo around 0:20, but with a PM motor that is spun faster. \$\endgroup\$
    – HikeOnPast
    Nov 6, 2012 at 20:43
  • \$\begingroup\$ So it is the gears that leverage the force to torque. Is this process multiplying force from the muscle to the motor rotation or is the muscle force equal to the mechanical force exerted from the motor? \$\endgroup\$ Nov 6, 2012 at 21:54

1 Answer 1


The unit is a motor driven by a gearbox.
A driven motor is a genertor or alternetor (subject to cetain conditions), which is the point he is making.

The motor speed is increased by gearbox action so the voltage produced is greater than without the gearbox as Vout is ~ proportional to speed.

Re torques - it's a gearbox with a motor on the end.
Standard gearbox dynamics apply.
The force on the higher speed end - actually the torque, which is rotational force, will be LOWER at higher speed.

Power = k x torque x RPM. So

RPM_In x Torque_In x efficiency = RPM_Out x Torque_Out or

Torque_Out = RPM_In / RPM_Out x Torque_In x efficiency


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