Reassembly is the opposite of disassembly

Nether Alderley Mill, is a water powered corn mill, which some members of the team at Quarry Bank also help to look after. Our ongoing conservation work at Nether Alderley Mill has taken a new ‘turn’ lately. Over to volunteer Bruce Williams for more details.

At Nether Alderley once the waterwheels are in action, they turn the Great Spur Wheel which drives the mill stones.

To turn the mill stones, the Stone Nut has to be lowered to engage with the Great Spur Wheel.  The Stone Nut sits on a collet, which is a conical shaped lump of cast iron firmly attached to the shaft which turns the runner stone.

The runner stone being lifted from the base stone.
Mill stones at Nether Alderley, the runner stone being lifted during previous restoration work.

Earlier this year it was evident that the Stone Nut was lower than it should be, implying that the collet had somehow slipped down the shaft. The collet is attached to the shaft by means of an iron key wedged into a keyway on the inside of the collet. On inspection, it was discovered that there were two cracks in the collet either side of the keyway.

Crack on the collet at Nether Alderley Mill
Crack visible on the collet

Subsequently these cracks evidently widened, as one of our millers discovered that the Stone Nut was turning without turning the shaft – in other words, the collet was no longer firmly attached. This required fixing so we could continue to run the machinery.

Our friends from the Norfolk Millwright Alliance came to remove the damaged part for repair. This involved removing all the “furniture” – the Hopper, Shoe, Horse, Damsel and Vat – from the stones, then lifting the runner stone to one side in order to be able to remove the upper bearing of the shaft from the middle of the bed stone.

The 'furniture' under which the millstones sit at Nether Alderley Mill
The ‘furniture’ under which the millstones sit at Nether Alderley Mill
The large runner stone has been moved to one side
Runner stone moved to one side

Once this was done, the shaft could be lifted using a chain hoist so that the collet could be removed from the bottom of the shaft.

Shaft suspended on a chain hoist
Shaft suspended on a chain hoist
Bottom of shaft free of its bearing
Bottom of shaft free of its bearing
Collet removed from shaft
Collet removed from shaft

The shaft and collet were then taken away for repair, and the mill made safe by securing the Stone Nut with a chain hoist and straps to ensure that it could not move.

Stone Nut secured while shaft and collet are missing
Stone Nut secured while shaft and collet are missing

When the millwrights returned to refit the parts, it was seen that the cracks in the collet had been expertly welded together.

Welded repair on collet
Welded repair on collet

Also a new internal keyway had been milled in the collet, some distance from the original, in order to avoid any strain on the welded repair, and a matching keyway milled in the shaft so that in future the collet would not be able to turn without the shaft.

Keyway in shaft
Keyway in shaft

As it says in all the best workshop manuals, reassembly is the opposite of disassembly. Thus the shaft was lifted up into position, and the collet slid on from the bottom. The shaft was then fitted into its bottom bearing, and the upper bearing was refitted into the bed stone.

Upper bearing refitted in bed stone
Upper bearing refitted in bed stone

Then the runner stone was lifted back onto the shaft, and the tentering mechanism used to lower the runner stone until it was nearly touching the bed stone. The Stone Nut was then engaged with the Great Spur Wheel, so that the collet could be positioned correctly on the shaft before the key was hammered into the matching keyways to attach the collet firmly to the shaft once again.

Stone Nut engaged with Great spur Wheel to position collet
Stone Nut engaged with Great spur Wheel to position collet

The furniture was then replaced round the stones, and the mill was ready for action again.

Furniture being reassembled
Furniture being reassembled

Thank you, our ability to conserve Nether Alderley Mill and to keep it running, is down to the support of our visitors.  Nether Alderley Mill is open every Thursday, Saturday and Sunday until Sunday 4 October, please check the website before visiting.

Thank you to Bruce for this blog, all images ©Bruce Williams

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