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Dredging the Mill Pool - Watermill Blog



Dredging the mill pool was one of the maintenance tasks that got mentioned in the last blog.
It became obvious through the summer months that we didn't have enough water in the pool to do more than short periods of milling.

The problem dates back to the awful rain of 2007 that caused flooding throughout the country and damaged the hillclimb track here at Shelsley Walsh.

The extreme weather washed many tons of silt into what was then the newly dredged millpool. When the pool is full it looks fine but the water was only a few inches deep in large parts of the pool. This was a problem that would not go away by itself.

We managed to find a contractor who was prepared to tackle the job at a price we could afford so we drained the pool and they arrived on site on the 20th September with a digger and a large dumper truck. The first day seems to have gone reasonably well but disturbing the silt in the pond had the effect of re-plugging the drain and partially blocking the pipe to the waterwheel.

What happened next was captured on video. Nothing dramatic, but you can watch as the team struggle to unblock the drain before calling in the experts.
 
The following week we were able to use a full pool of water to finally dislodge the blockage in the penstock pipe. The clang from the waterwheel as the 'plug' emerged echoed round the farmyard.

The delays cost us an extra day's hire of the digger, but the pool now has a much greater capacity and we have found and removed an obstruction in the penstock pipe that must have been there for many years.

Another essential task that came to light during the summer was to consolidate the great spur gear. This is the wooden wheel that takes the drive from the centre shaft to the stone nuts under each pair of millstones.

This wheel is almost certainly contemporary with the centre shaft so must be over 300 years old. We had trouble all summer with the wooden cogs, the gear teeth, coming loose. Any cog that protruded too far from the circumference of the wheel would hit an upright and break off with a scary bang.

The timber of the gear wheel is mostly sound but very wormeaten in places. After some research we decided to follow the suggestion from the Society for the Protection of Ancient Buildings, SPAB, and use a resin filler. We sourced a specialist wood hardening resin that soaks into the wood before it hardens. Using this will preserve the wheel as it is but strengthen the timber to withstand the occasional use that we need to be able to demonstrate how everything works.

The two part resin is mixed and then just applied with a paint brush. Not a difficult task  but getting to the inside surfaces of the gear does require some contortions. There is no way of cleaning the brushes after they have been in the resin but the cost of few brushes and the resin is small compared with the cost of getting a new spur made. We would much rather preserve the original anyway.

We need just one more mix of resin to finish the job but we are waiting for a supply to arrive from America. It's a job we want to finish so that we can replace all the wooden cogs before they get muddled up. We might even try some milling to see if the dredging has made any difference to how long we can continue.


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