Sharp VAWT Bird Windmill
Description
A nice wind toy that demonstrates the principle and capabilities of vertical axis wind turbines with pitch control (VAWTs). The toy consists of a simple lightweight planar wing mounted on a string. When exposed to wind, the wing demonstrates its self-starting capabilities - it begins to tumble and eventually starts to perform circular motions orbiting a virtual vertical axis. The design of the wing includes a counterweight mounted on a outrigger at the leading edge of the wing. The counterweight experiences a centrifugal force as the wing orbits. This force counteracts the torque generated by the wing. The result is a passive self-balancing system for the angle of attack, which dramatically improves the performance of the wing throughout the entire rotation. This system also contributes to the wing's ability to compensate for gusty winds. Unfortunately we had almost no wind the last few days. So I made a video of the wing in operation inside the house using a small fan. Assembly: For the assembly I used M3 hardware: short threaded inserts from CNC Kitchen and DIN 912 / DIN-EN-ISO 4762 M3x10mm and M3x6mm screws. You can use an M3 screw to attach the counterweight to the leading edge of the outrigger using the long hole. Please note that the counterweight is mandatory for the wing to operate as required. It must be approximately the same weight as the wing itself. When hanging from the cord line with the counterweight attached, the wing should remain horizontal (see photo). There is also an M3 sized hole at the front of the outrigger that allows you to mount your own fairing covers for your counterweights, if desired. To attach the wing to the cord, I printed two PETG washers and glued them to the cord to prevent the wing from sliding down the cord while still allowing it to rotate freely without tangling the cord. Happy Printing! Some background: A few years ago I was working on a DIY VAWT project and did some research on different types of VAWTs and their aerodynamics. I came across the concept of the self-balanced VAWT as introduced by Peter Allen Sharp. I got in touch with Peter and we had some really nice conversations where he explained his approach in detail and also sent me a homemade wing to play with and familiarize myself with its operation (see one of the pictures). I had a lot of fun with it and derived a scaled down, optimized, 3D printable version of it for the Wind Spinner contest. Peter has uploaded some videos of his creations on YouTube, check them out: https://www.youtube.com/@PASVAWT/videos
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