HardWired II

[overkill]

Increasing the speed is very effective; the equation for kinetic energy of a spinning disk or bar is:

Kinetic energy = ½ × moment of inertia × angular velocity squared (where moment of inertia is basically the weight and angular velocity is the RPM).

That means a large reduction in weight can be made up by a relatively small increase in the RPM to give you the same amount of energy. The downside of a high RPM vertical bar is that the bot will gyro dance something wicked.

EDIT: since you mentioned Scissorhands, its weapon only weighs around 2Kg and spins at 2,400 RPM. If you doubled the speed on that it would have 4 x the energy. OTOH, the bar is spun by a Mag motor with a peak output of 2.2KW; doubling the speed will need a correspondingly larger motor.