CoolIP index                                                          Most recent edit: Wednesday October 24, 2012

* See legal note below.

Plucking "Slip-Stick" Line Tug Dynamics

Novel AWES architectural principles continue to emerge. Plucking a kitestring to transmit power is a Brainstorm Special, crazy sounding, but curiously worth pondering. Friction is described as a "stick-slip" phenomenon where by a static load is tapped by a sudden release. A plucked or bowed violin operates by stick-slip power transmission to the resonant body. Plucking a string is like drawing and releasing a bow, naturally operating at high spring efficiency with potential to scale, which makes it yet one more way we might transfer energy down along a kiteline.

The useful property of the characteristic sawtooth pluck waveform is its sharp plunge phase whereby a surface load, like a high speed flywheel/generator, can naturally get a fast little kick, without a lot of step-up gearing. Practical conditions to meet- The string must be a quality elastic cell and properly tension cyclically (more tense the better), with sudden release. The plucking mechanism and line pluck point want to be at a fundamental harmonic node, with the line handling chafe resistant. Line-catching/releasing can in principle use low-wear high-duty components. Predictable losses to mitigate are at the upper kite lifting network (should be stiff within the pluck timescale) and there will be added aerodrag at the sweeping pluck point. Downwind line release is favored.

An exotic variant is high-speed water-ballasted wings with tow-hooks acting like "guitar-picks", plucking the line to send the power down, briefly hooking and decelerating to deflect the line at great tension, and suddenly releasing it, Rock-and Roll forever ;*)


CoolIP*                      ~Dave Santos                 20Jan2012                   AWES5430

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