French water mill engineering

Having ploughed through the lengthy list of topics, I have defaulted here.

A friend showed me a picture of the centrifugal governor in a now-defunct water mill in central France:

The ball-operated mechanism has no direct effect on the mill machinery: if it runs too slowly the balls cause the little bell to ring and, if too fast, they bang on the board - the miller then, presumably, regulates the flow of water accordingly.

The unfortunate coda is that the property owner wished to restore the mill wheel, etc but was refused permission to resume taking water from the now sadly-depleted river.

Wonderful!

What a shame the planning officials could not see that restoring the mill would not deplete the river.

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I have seen, externally, a much smaller, restored mill in the French Pyrennees; with an unusual type of turbine. Unfortunately I have no photos of it. The mill was closed on our visit when we spotted it by chance, but I was able to paddle into the short tailrace to see that the power-plant was two crude, open-construction reaction-turbines on vertical shafts. Each runner was a cast-iron cylinder with four vanes inclined at 45º, as spokes / blades, to catch the water from spouts directly above them. The give-away of restoration were big, gleaming stainless-steel bolts in the iron-work! The head was a good 3 metres, I think I judged from the dam directly behind the small, stone building.

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I helped friends return Upwey Mill, near Weymouth, to flour-milling condition, back in the 1990s I think. He had to obtain an abstraction-licence but it was really only a formality because the river itself was not affected.

This mill though did suffer from curious stream surges enough to break the cogs (proper mill-wrighting term for the hardwood gear teeth), which at about £11 a go was not wanted. The cause was traced to automatic borehole pumps about a mile up-valley from the spring, which itself is only about 100 yards upstream of the mill, responding to the normal fluctuations in public water demand.

Clearly we could do nothing about that, but we realised the cure would be a choke-board to keep constant the remarkably shallow layer of water flowing over the sill into the wheel; and to divert the surplus over the weir.

After we, both members of our local model-engineering society, had sketched assorted arrangements of gears, screws etc. he came up the with the ideal solution. He stood the plank on pairs of blocks of wood, each pair of a given height according to what the water would power. It worked perfectly!