link to Home Page

icon Problems

A working model of the Nebraska Windmill could easily be made with a cardboard box. Make the turbine to fit your box. That would be a good way to test it. This should be held together with bolts and balanced so as to not fly apart under high wind conditions. Don't nail it together it will soon fall apart if you do. I estimate about 200 dollars to build it.

Offered by Darrell.

I took your idea on using a cardboard box to test out this concept. I stapled four blades of 8x16 inches to simulate four sheets of 4x8 feet of plywood to a 1/2 inch dowel, each 90 degrees apart. I then took two 2x4's and drilled a 5/8 inch hole, centered 8 & 1/2 inches from the bottom of each. Then I stapled one of the 2x4's to each end of the box, which was my bearing, crude but useful here. Before inserting the main shaft and blades I drilled two holes in the dowel, where I used washers and cotter pins to prevent lateral movement, and then coated the ends as well as the holes with axle grease. I have a small infrared tachometer that I use often here in my work. I attached a small stick-on reflector to one end of the shaft, set up my tachometer and waited for morning.

In an 18 mph wind at ground level we saw 22 rpm, not good at all! Then I thought "remove the back of the box" to lessen impeller impedance created by dead air in the box itself. Remember Newton's Law about an object at rest? Air is a fluid, and as such has all of the characteristics of water, just in a smaller degree. A cubic meter of air weighs in at about 2.34 kilograms per sq. meter at sea level. That's 5.24 lbs. per 1.3 cubic yards. The results were improved - in the same wind we saw an increase of 6 rpm at 28 mph. In my opinion this approach is not useful at all, especially when you can't yaw it into the wind. Also wind speed at ground level averages about 28% less than at 60 ft.

The problem here is there is no lift being created, only drag. It is only "drag" that moves the upward vane in the direction that the wind is blowing, while the same "drag" in smaller amounts impedes the free rotation of the others.

Offered by Jay.