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.