Further work on No 2 stone

Today we continued to work towards our goal of milling with the No 2 stone before the end of the season. The tun is a two-decker structure, the upper section being detachable mainly to make it easier to get it in and out of the limited space.
Ray made good progress with the tun, putting in the cross bracing timbers which will support the top and help it to support the horse ...
... and built the top, made like the rest of the tun from tongue and groove floorboarding. All that remains is to finish trimming the edges of the top, cut the central hole for the grain to enter, finish the internal reinforcing, and finish and stain the wood.

Bob and Richard worked on the stone nut disengaging mechanism. The vertical bars have had to be modified as the holes in the tentering beam through which they pass are no longer vertical. To give a little flexibility, the bars are no longer fixed into holes in their bottom plate - instead they have collars which rest on the plate. Today's task was to fix the collars by drilling and fitting spring pins, and then refit the bars.

Finally we made a second hole in the cement dressing on the top of the runner stone and filled it with molten lead to balance the stone.

Repair to the Dump Valve

As previous blogs will relate (once I get round to entering them - I am blogging most of this stuff retrospectively), we have a sort of "emergency stop" lever for the mill. It works by dropping a board out of the bottom of the launder close to the wheel, stopping the flow of water much more quickly than closing the diverter. We call this the Dump Valve.

During Sunday 19th June's operation, we found that the dump valve was not closing properly, spilling a lot of water. It then failed to open properly and stop the wheel at the end of the afternoon.

Investigation showed that there was a lot of algae and other green slimy stuff in the works, but once this was removed it became apparent that the arm that works the valve flap was not fixed securely to the operating shaft. In fact the coach screws were in soft, wet timber and could not be tightened.

The Dump Valve operating arm,
showing the rigid link

We therefore bored out the holes in both the arm and the shaft to take 12mm studding, made and drilled 2 plates from 3mm mild steel, and reattached the arm. We also removed a bit of the timber cladding where the operating lever comes through the end of the wheelhouse to allow the lever to move further.

After we had adjusted the operating chain, the valve worked perfectly until the drop board jammed in the hole.

12 July 2011 fitted a rigid arm so the lever now pushes the drop board open rather than allowing it to fall under its own weight..