The Model

I spent the last few months of 2008 researching wind turbines. I made many small scale models and experimented with many blade designs and arrangements.

In December 2008 I began building a life size replica model of a 1000 watt machine to better understand the design and assembly.




I found a large blue PVC pipe at the rubbish dump and carved three blades just under one meter long. This PVC is really tough material and is normally available at most respectable dump sites whenever needed. It is actually not bad machining it and it does not damage blades or clog up sanding belts. They work rather well as crude turbine blades and hold up to the out door elements pretty well, but the main advantage is that it is rather easy to make a blade in a hurry. The disadvantage of PVC blades is the weight and the shape. They work, but are not as efficient as properly designed blades. I would estimate them to be around 50% less efficient, give or take ten percent. But they do work. There are loads of Internet sites devoted to the constructing of the PVC blade.

I made wooden replicas of the rotors and stator. In my model their where 12 magnets per rotor and the three phase stator has four coils per phase, totalling 12 coils.

I decided to use the rear brake drum and stub axle of a VW Golf as the bearing hub upon which the turbine will be mounted. They are cheap, available and really more than strong enough to handle the thrust forces destines to be imposed during the turbines lifetime.

I copied the furling design from Hugh Piggots design manuals and welded up a mock version out of light weight metal to get to know the angles and idea behind this ingenious method of regulating the wind effect on the turbine. No springs are needed in this design and it is very effective and simple in concept.

After all the crude model parts where constructed I assembled them and headed off to the open fields to test the device.

Little did I know of what this model was capable of. Out of sheer ignorance and inexperience, I got the machine up in a gale force wind, as a storm was approaching, and had no load of the blades, they where free to go mad, which they really did.

These last two photos are the only ones I have of the assembled model. As soon as I released the beast, a gale came up and got the machine spinning so fast it sounded like a helicopter. My mounting was way to weak and the entire assembly came crashing down, doing some very expensive damage to a vehicle, which foolishly was down wind from the device. Humble apologies still go out to the effected party. No one was injured and the only damage sustained by the model was a broken tip of one of the blades.

It was a very expensive lesson in the power of the wind! I have learned that attention must be given to every aspect of safety and a warning to anyone who plays around with these turbines... they are really, really dangerous things if extreme care is not taken to avoid catastrophic failure.

After licking my wounds, I shortened and reshaped the blades and reinforced my test stand and attempted the test again in far lighter winds the next day

I did some rpm measurements and found the device could run up to 300 rpm in a slight wind. I don't know what the wind speed was but it was under 20 km/h for sure.

I also made sure the furling mechanism worked and that I had succeeded with that aspect of the design.

The model had served its purpose, and then some. Now I was ready to start with the real thing, with a few differences, particularly to the blades. But that is another post.