Vertical Axis Windmill Invention
Toronto Inventor Tom J. Gilmour recently published his conceptual designs for what he is calling Tom’s Whirligig. Patent applications have been made, and Tom hopes to reserve all rights and worldwide patents for his design. Tom believes his windmill plans to be the most complex ever devised. While he is not yet sure of the workability of this concept, he is optimistic about its feasibility and hopes to soon find the time to build a working model. His website provides detailed descriptions, illustrations, Google Sketchup files and a blog for visitor comments.
The focus of this new design is based around a continuously rotating carousel, which houses eight symmetrical airfoils. The entire carousel is mounted on a fixed vertical shaft. Each individual airfoil is meant to rotate 360° independent of the main shaft. A top mounted central weather vane keeps the cam shaft pointed at the wind. In high-intensity winds, the airfoils can be rotated to a zero angle of attack in order to prevent damage.
While tallest design that includes eight airfoils, he points out that the unit could theoretically work with more or less, as long as the tubular or central shaft is strong enough. Tom is recommending airfoils in multiples of 4, 8, 16, etc. for maximum efficiency. He believes there is no limit to the possible size and power output of his invention.
As far as strength goes, the main shaft, which is cemented in the ground, doesn’t move, so it can be as heavy as necessary to withstand any possible wind load. The carousel consists of a couple of wheels separated and affixed to each end of the tubular central shaft. Wheels can be made very light and strong (consider the wheel on a bicycle). The airfoils are attached to the carousel, at the top and bottom so that the main spar of the airfoils can be made much lighter. The weather vane and cam move very slowly and only with shifting wind direction. As far as the weather vane and cam are concerned, weight is not an issue. Hence, they could be made very strong. I would mount the airfoils so that their point of rotation was slightly forward of their center of lift so that they would have a natural tendency to weather vane. This would put a slight compressive force on the push rods and cam rollers. The force of the wind is transferred directly via the airfoil’s mounting bearings to the carousel. The push rods and bell cranks only control the attitude of the airfoils close to their center of lift, so they don’t need to be very heavy or strong. It would be possible to design this Whirligig with a fairly low rotating mass. Also, there is no chance of anything ever going supersonic unless you built a whirligig hundreds of feet in diameter (well maybe?). I have drawn the Tom’s Whirligig with eight airfoils but it would work with fewer or more. A carousel with only two airfoils might not start by itself. Three airfoils would work but probably wouldn’t be very balanced. I think a minimum of four airfoils would be practical. But 4, 8, 16, etc. (any even number above four) would probably work. One thing to note; it is possible at the low points on the cam, for the airfoils to go either clockwise or counterclockwise. It is very unlikely this would happen. An airfoil would go around backwards with its trailing edge pointing into the wind. But the perversity of mechanical devices says that if it can happen, it will. So I think it would be prudent, in considering the diameter of the carousel and the chord (width) of the airfoils, to design it such that the airfoils could pass each other, trailing edge to trailing edge, without interfering with each other. I don’t think there are any practical limits to the size of this whirligig. You could build one on the top of Mount Washington two hundred feet high.
Of all the possible uses Tom envisions for his invention, he is most excited about the possibility of mounting the windmill on top of a catamaran. He believes this would provide the boat with the ability to travel in any direction, including straight into the wind.
Tom is looking for other inventors working on similar ideas, and would love to see your inventions and sketch models, and hear your comments and suggestions. Here are some more resources for information about Tom’s Whirligig.
Tom’s Whirligig website:
Tom’s Google Sketchup Files:
Tom’s Whirligig Blog: