Hello Willi,Tom, and Harrie,
Hope you don't mind if I answer to all of you and not seperately.
I try to answer the questions about our 2 windmills.
One was wound up for 12 volts , the other for 24 volts. We think, that the 12 volt machine cuts in earlier than the 24 volt machine, and it works more efficient in lower winds. But this is only an evaluation, because we cannot measure correctly. In a storm we had a reading on the anemometer of 36 m/sec. The ampere meter showed more than 40amps. The cone shaped form on the hub plate is what I call a "spinner". It was made this way:
1 formed the outer shape with clay on a potters wheel (this because I am a potter as well). When the clay stiffened a bit (not hardened) I poured plaster on it until it had a layer of 1 ½" thickness. When the plaster was hard, I took the clay out, because it was still soft and easy to remove. After that I coated the inner side of the plaster form with wax und put a layer of glass fibre sheet in it with polyester resin. To release it, beforehand I had a hole drilled into the top of the form, and had closed the hole with a little clay. The hole makes it possible to help release the polyester form with compressed air.
The pins which hold the magnets are an industrial product of which I do not know the English name (German: Schwerspannstift), it is made of rolled spring steel and look like a slit Tube. Their shape results in has a high tension when they are hammered in to a fitting hole. The holes are exactly 3 mm wide and the diameter of the pins is 3.2 mm. Their sit in the disc is 8mm (that is the full thickness of the disc). They hold extremely tight, thus tightened, there is no possibility for the magnets to move...
To drill the holes I made a little gauge out of a flat steel with the 6 holes in it. (By now I think you could do with only three, one at the top and two at the sides).
The magnet disc has a hole in the centre (10 mm), and I bolt the gauge in the centre. The dividing marks for the magnets are the station marks for the gauge, when the gauge is in its right place, the nut is tightened and the drilling can start.
The magnets are glued with a two component epoxy of "Loctite" Nr. 3430.
The ball bearings are 6007, that means, they are 60 mm in the outer diameter and 35 mm for the shaft, and they are 15 mm wide.
They sit in a tube, two in the front and one in the back. They are sealed.
The plastic blades performed very well. They are a copy of the world famous "Jerry blades with the Zubbly and Woofer mods". They run very fast. My mistake was that I left the bolts of the stator a little bit too long, so the blades bent in a heavy storm and touched the bolts and that was the end of them.
At this time I was fighting with carving Hugh Piggotts blades. My poor English was the reason why I did not understand Hugh's advices. But it was a challenge for me and I never give up. In the end with the help of my wife, who speaks much better English than me, we found out how to make the blades and now I am very happy to have Hugh's blades on the machines. I think the plastic blades are very good and easy to make. But there are two disadvantages. They do not really have a correct aerodynamic profile, it is just a radius and so can cause turbulences and if it is very cold they may break into pieces.
I appreciate very much to be in contact with a community of friendly people with common interest in windmills (and renewable energy) who are willing to share their knowledge and experiences.Thanks to all of you!
Fritz
