A New Vertical Axis Wind Mill
Hello: My name is Tom
J. Gilmour (t.j.gilmour@sympatico.ca) I live in
As of April 12, 2007, I am publishing this design on my website in the hope of creating some interest in this windmill.
I am the inventor of this Vertical Axis Windmill that I’m going to call Tom’s Whirligig. It is illustrated below.
I would like to reserve, for myself, all rights to any and all worldwide patents on the design of this illustrated Vertical Axis Windmill.
Papers documenting this design have been sent, in my name, to the Canadian Intellectual Property Office. (Patent Office)
Canadian Intellectual Property Office
I will freely admit that this is the most complex, Rube Goldfarb Windmill ever devised by mortal man. Having said that, I feel that it does have some redeeming features.
I don’t know if this windmill will actually work as I’ve never attempted to make a working model of this design.
I have been kicking ideas for it around in my head for a couple of years, but have not found the time to build it.
A brief description:
The windmill consists of a carousel (light Green) that, in
this case, carries eight symmetrical airfoils (darker green). The carousel rotates, continuously, about a
fixed vertical shaft that is cemented into the ground. The airfoils can rotate
360 degrees via the top and bottom mounting bearings in the carousel. Each
airfoil has a permanently-affixed bell crank at right angles to the center line
of the airfoil which, in conjunction with the cam, push rod and bell cranks,
control the rotation of each airfoil within the carousel. The oval cam (blue)
is locked to the weather vane. The
weather vane (blue) tracks the wind and is connected to the carousel by
bearings that allow it to rotate, freely, 360 degrees in relation to the
carousel. I’m going to restate this
because it is an important point. The top bearing of the cam and weather vane
is on the main shaft and allows rotation independently of the carousel. The
function of the weather vane is to keep the
A picture is “worth a thousand words”.
FRONT VIEW (see below)
TOP VIEW (see below)
Note that the oval cam’s high points push the airfoils past 90 degrees, giving the airfoil at the front (closest to the right edge of the picture) of the carousel a 12 degree angle of attack in relationship to the wind. The airfoil at the back (nearest the weather vane) also has a 12 degree angle of attack in relation to the wind. The airfoil at the front would have a moment of lift, pointing at the bottom of the picture whereas the airfoil nearest the weather vane would have a moment of lift pointing at the top of the picture, hence a clockwise rotation. (see below)
VIEW OF CAM (see below)
The oval cam (blue) is locked to the weather vane and is offset from the center of the carousel by a distance equal to the length of the bell cranks. The eight push rods have rollers that are held to the cam by a series of links (something like a bicycle chain) wrapped around the cam. I’m referring to the cam as an oval which it could be but it would be possible to make the cam as something more like a rounded rectangle. This rounded rectangle would have a more aggressive profile pushing the airfoils to a steeper angle of attack earlier. In a perfect world I could visualize an oil filled housing containing complementary cams, with the push rod ends riding on roller tappets. This would keep the cam and rollers and all that out of the rain and snow. I think there could a number of different ways of engineering this cam and roller arrangement.
A perfect windmill would be infinitely strong so as to withstand hurricane-strength winds and yet have zero mass so that it could move in the lightest of breezes. This is an impossible goal. The design must be a compromise between strength and weight. With propeller- type wind turbines, the blades are only held at the root, hence the blades must be strong enough to withstand a large wind force. In winds stronger than the maximum design allows, the blades are usually rotated to a zero angle of attack, thus stopping the windmill. With propeller-type wind turbines there is also the problem of the tips going supersonic in high winds.
Tom’s Whirligig Design:
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 is any practical
limits to the size of this whirligig. You could build one on the top of
In this design there is something else to consider. I have stated above that the push rods and bell crank arms push the airfoils to about a 12 degree angle of attack. For a symmetrical airfoil twelve degrees is close to the stall angle and is also close to the point of maximum lift. As the airfoils are attached to the rotating carousel they are also moving across the face of the wind. This tangential movement affects the effective angle of attack of the airfoils. This is basically the same as a fixed pitch propeller on an airplane. As the plane goes faster the effective pitch of the propeller is reduce to the point that no matter how much more powerful you make the engine, you can’t get the plane to go any faster. This is the reason that Aeronautical Engineers developed Variable pitch propellers for aircraft many years ago. The effect of this tangential movement is good in one sense and that is the whirligig would hit a maximum RPM even in a gale force wind even if there was no load on the carousel.
Another thought I’ve had, and would like to perhaps try some day, is to build a catamaran boat with a Tom’s Whirligig mounted on its deck. I would hook the rotating force of the carousel, via gears, belts, shafts and pulleys, to a conventional in- water propeller. The Whirligig presents a fairly small drag- profile to the wind, consisting mainly of the leading edge of the airfoils. It might be possible to create a wind- powered boat that could sail in a straight line at any point of the compass, including straight up into the wind.
If anyone out there would like to try and build a working model of this windmill, I would be very interested in seeing your pictures and hearing the results of your efforts. (see my e-mail address above)
I have also created a Blog if you would like to share your thoughts with me and the rest of the world.
http://whirligigwindmill.blogspot.com/
The pictures on this web page were created by doing a screen capture of my “Sketchup” model. For those of you not familiar with Google “Sketchup”, it is a very powerful 3D modeling software that is FREE.
This is the greatest piece of free software you will ever find anywhere. If you are into engineering, then I think it is a tool you should have.
If you want to examine Tom’s Whirligig in greater detail, then download and install Sketchup and get the model of Tom’s Whirligig from the Google 3D Library.
http://sketchup.google.com/3dwarehouse/search?q=Windmills&styp=c
Thank you for your interest in my Whirligig
Tom