Sunday, July 20, 2014

Windbot Muscles

Me with a newly-built windbot muscle.

A simple, muscle-like actuator for wind animated sculptures can be made by supporting a Savonius wind rotor on a taut thread. The thread needs to be very fine and strong. I have used Berkley Fireline of 1-lb test strength. A small Savonius rotor can be made by splitting two disposable cups and reassembling them with hot melt adhesive.

The wind rotor twists up the thread causing it to contract. When the wind dies down, the contraction slowly relaxes as the rotor spins in reverse.

The relaxation can be made very fast and controllable by using high-performance ball bearing swivels. Lazer Eagle Claw 75-lb test swivels work well enough with the windbot muscle shown here.

A Savonius wind rotor made from two disposable cups.

Detail of the wrap-around wire fitting that confines twist to the outboard sections of the doubled length of FireLine.

Suitable ball-bearing swivels for the muscle shown.

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