Why Windmills?

The windmill is a symbol for our times.

We of the cities have largely forgotten them, how they were a symbol of water and life.  But they are still standing all over the country, supplying the water, withstanding the storms, an occasional saviour for lost travellers.

Windmills are rooted in the depths of the earth, planted over a bore.  The fan is engineered to catch the smallest breeze.  As the wind strength increases, the fan swings out of the breeze, so that even a gale will not damage it.

Building is long, hard, and sometimes dangerous. We dig down at least four feet, maybe seven feet for each of the three or four legs of the mill.  And then we build from the ground up.  The base plates go in to the holes with the first piece of the heavy legs. By the time the second piece is in place, it is time to link the legs together with the first of the horizontal bars.  Then another vertical. We are always building above ourselves, balancing heavy angle iron as we bolt pieces into place.

By the time the second horizontals layers are ready the bracing pieces are put in place as well, triangulating and strengthening the structure, which will stand for 50 years and more, in the worst of winds. The parts of the puzzle are being pulled up by ropes now, too far below, and too heavy to be safely handed up. The ladder that will allow people to service the fan maybe loosely bolted on as we go.

Nothing is bolted in too tight, until there is a level or two bolted in above.  All the pieces are slightly out of line, the tower a little wobbly, until we reach the cap, that last, heavy block of cast-iron which will bear the weight of the head and the fan.  It's levered into place over the uprights, and the last bolts are pushed in. It can take an hour of pulling and twisting, levering through the holes with heavy screw drives before the last braces and uprights line up well enough to allow the bolts through.  Then all the bolts of the tower art tightened, and re-tightened. The tower is ready to be positioned.

By eye it is shoved and bullied so the cap is directly over the bore casing.  A long line will be used as a plumb bob to make sure the position is correct.  Then a spirit level will be used at the top of the mill, to make sure it is completely upright.  Grunting and swearing in the holes, the builders scratch out under a heavy foot-plate, or pack flat rocks under another to apply the last few millimetres of correction. No matter how carefully the holes are dug and checked before building, things are never quite level.

If the levels are not correct, and the bolts are not tight, then all the building which follows will be at risk.  We finished late one night and left the tower standing in its four holes, ready to concrete in the morning.  The gully winds of the night blew it out of the ground, where it lay twisted, waiting for our morning arrival.  After undoing every last bolt, we heated and welded and reinforced, and then began again.

Concrete is the best; at least several feet poured over the base plates.  Then we can make up fill with rocks.  But concrete all the way to the top, rounded above ground level to stop pooling and rust, is ideal.  Scratch in the date, and the builders, before it sets.

This head of the windmill supports the fan, which can be six, or eight, even thirty feet in diameter. The head is also a gear box. It converts the power of the spinning fan into the up and down motion that will pump water to the surface, perhaps from  hundreds of feet down.  It is dangerously heavy, sometimes over two tons, and must be lifted above the tower top. 

Heavy piping is lashed to the side of the tower, a jury rig with which to hoist the head. The biggest heads need a bore casing, six or eight  inch pipe,  to be raised and lashed along side the tower, so that this temporary tower can stand on the earth itself. A twenty four foot Comet fan has a two and a half ton head.

The little windmill at Wamikata. You can see Andrew's hat between the legs of the bloke at the right!

More to come....