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Whirligigs and Vollis Simpson


From: Jessica
Date: Wed, 14 Jan 1998 16:11:00 -0600
Subject: windmills


My name is Jessica, and I am building a windmill 
for a science competition.  I have to design a windmill 
that will get the maximum power. Do you have any 
suggestions as to how many blades I should use?
					Thanks,
					Jessica


Date: Wed, 14 Jan 1998 19:39:42 -0600 To: Jessica From: Natalie Rusk Subject: Re: windmills Dear Jessica- I just asked your question to J. Newlin who runs the Experiment Gallery here at the Science Museum. He suggests it depends whether you want high speed or high torque (force of rotation). If you want high speed, then the fewer blades the better. He said you could use just two, but it is usually easier to balance with 3. Are there wind power farms in Illinois? The windmills on windfarms generally use only 3 blades for maximum speed. (There's a picture of one at http://www.exploratorium.edu/learning_studio/wind_farm/lonemill.gif ) If you want high torque (stronger rotational force), then you'll want to add more blades. For example, windmills for water pumps often have 6 or 8 or more blades. Vollis Simpson the artist in N. Carolina told us he designed his first windmill ever to power his furnace. It looks to me like it has dozens of blades. http://www.sci.mus.mn.us/sln/vollis/theyard/furnace/furnace.html (But he said it never did work quite right on the furnace. Which is one reason he started making whirligigs for fun rather than to do work) And we saw the windmill turn towards the wind but not spin. So I guess you have to decide if you want greater rotational force or faster speed. Vollis pointed out to us that the amount you pitch (i.e.,tilt) the blades makes a difference too. He also said the most important part of making a windmill or whirligig spin is to get it centered. I'd be interested to hear what you find out--what does and doesn't work. Natalie Rusk Learning Technologies Science Museum of Minnesota

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