A Panemone (Drag-Type Windmill)


This project has been through 4 revisions so far, with 3 actual constructions completed. Each of the three has been blown apart by the wind, but the latest one has been standing (and turning) for more than 12 months.


A "PANEMONE" is defined as a device which derives its energy from the wind in such a way that the wind-catching vanes move IN THE SAME DIRECTION as the thrusting force of the wind (this is called "DRAG"). This is in contrast to the motion of a propellor, whose blades move AT 90 DEGREES to the thrust of the wind (this is called "LIFT").

The only problem is that most panemones, when they are turning, have some component of DRAG, as well as some component of LIFT. So, a rather better definition of a Panemone is: The axis of rotation is at 90 degrees to the direction of the wind. (The rotating shaft lies ACROSS the wind, whereas with a propellor, for instance, the shaft points directly INTO the wind.)
You can see from the diagram above, that the wind will push against the panels when they present themselves across the wind, and the panemone will rotate in the direction shown. When a panel reaches the furthest downwind point, it will "jibe" like the sail of a boat when it turns across the wind. Then, on the "upwind" beat, the panel will remain feathered into the wind, until it reaches the most upwind position again. Then the panel stops feathering, because it reaches the stop peg which forces it to present itself across the wind again for the next "downwind" beat.... (and so on).

My panemone has FOUR arms, and looks like a cross between a rotary clothes-line and a square-rigged sailing boat. My daughter Jean has painted the panels in wonderful psychedelic blue, purple, red and yellow swirling patterns, (blue/purple on one side, red/yellow on the other) - and they make a striking display when the wind blows them round and round....

I had thought that this design was unique, until one day I was browsing in the Massey Uni library, and found that the Chinese have been building panemones very like my one since about 800 AD.... (for pumping water).
Oh, well - I guess a Good Idea is one which gets re-discovered many times!

One of my favourite pastimes is to sit on a deckchair by the windmill with a cold glass of homebrew in my hand, in a stiff breeze....

The entire structure is supported by a central steel pole (3.5m tall) braced with eight guy-wires staked firmly into the ground. The pole rests on the top of a fence-post driven all the way into the ground.

The top of the pole is capped with a steel washer, which has a 16mm steel rod through it. This supports a conical thrust bearing (from a motor car hub), which in turn supports the entire rotating structure.

Most of the central support structure is made of 100 x 50 framing timber, and each pair of arms is made from four lengths of the same timber, 6m long. (Two lengths to support the top and two lengths to support the bottom of each panel.) Everything is nailed together as shown in the diagram.

Each of the four panels is made of 75 x 25 timber for the frame, and a sheet of 3-ply (which has been painted wonderfully as you can see from the photos.) Each panel is 1.2m high by 2.4 m long.

The panels are fixed to the arms by a steel rod and bearings as shown, and they swing freely until they stop against the flexible plastic stop pegs. The stop pegs hold the panel into the wind in a moderate to strong wind, but allow the panel to "break away" when the wind is too severe. The panel then feathers, to prevent damage to the structure. (Neat, hey?)


I haven't connected the windmill to any power generating sytem yet, but I've got a couple of ideas about how to do this.

I have a permanent magnet washing machine motor (just like the one I used for my pelton wheel - see that project), which works as a generator nicely. The generator needs to spin at around 400 revs per minute, and since the windmill goes round at a stately 4 revs per minute, I need a pully and belt system which steps up the rotational speed by 100 times!

I hope to do this with two steps of 10:1 each (which makes 100:1). But I'll write more about this here, when I've done it.


Disaster Struck!

After my panemone had been working for a year or so, we had a VERY strong wind (which blew down lots of old trees in the district and did a lot of damage to buildings and powerlines), and my poor panemone couldn't cope. The panels all feathered, just like they were supposed to do, but then they began to oscillate madly from side to side, the whole structure weaving crazily as if it had a life of its own! Then a guy-wire snapped, and it was all over...

Sob...

A couple of homebrews later, a new idea and a new panemone rose from the ashes
This one is a HORIZONTAL AXIS Panemone. It looks like a ferris wheel, or perhaps an upside down paddle-steamer :)

The idea is to place a wind-shield around the base of the structure, so that the wind only blows on the TOP HALF of the machine, and blows the paddles round. Our wind almost always comes from the North-East, so the panemone faces that way.

I've built the paddles from blue tarpaulins which will tear off in a very strong wind. This hasn't happened yet!
I'll put more pictures up here when I've built the wind-shield....


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