Working on the details

Having done all the big construction jobs, progress appears to slow down while we complete the details that will enable us to mill for the first time.

The spring and cords attached to the shoe

Today we made and fixed a rigid metal pointer to indicate on the tentering rod how far the stones are separated. We made a spring from a thin piece of ash which pulls a string to return the shoe when the damsel pushes it. A cord holds the shoe at an adjustable angle to regulate flow. We have installed a shutter on the hopper outlet to control grain flow and Richard has made a neat screw control for it.

The hopper outlet shutter and screw control

We also began to make an adjustable carrier to hold magnets above the shoe to remove any bits of metal mixed in with the grain.

This week's work

The horse and shoe

On Monday this week Ray and Richard made more progress on the grain feed, completing the woodwork of the hopper, including the slide shutter, and the shoe. Richard and Bob then made some steel brackets to support the hopper from a hoist while its best position was determined. Once we had sprayed these and fitted them, we offered the hopper up to the horse and left it in what we judge to be the best position.

Richard fits brackets to the hopper

We also discussed whether all the wooden parts that contact flour actually need to be coated with shellac as advised by the SPAB booklet, or whether there is some modern alternative. This needs further investigation.

Bob guides the hopper into position

Weekly restoration work

Today Ray made further progress with the stone furniture. The horse is complete and the grain hopper is being constructed.

There is a snag here - the chamfer angle for the ends of the boards for an inverted pyramid is difficult to estimate. By trial and error we arrived at an angle of 36.5 degrees (the outer angle of the hopper being 60 degrees). I did manage to find a mathematical solution on the web (http://www.slyman.org ... PyramidAngleCalculator) which gives an answer of 35.3 degrees, but I guess we will go with what works.

Meanwhile, Bob and Richard were looking at the tentering for no 2 stones. This depends on a bracket fixed with a long bolt through the hurst frame, which is rather insubstantial at this point, due to woodworm and mortises from former use of the timbers. At present the tentering beam is supported by a car scissor jack. The bracket leans forward at a few degrees, but seems otherwise quite sound at the moment.
We decided to make a tapered washer out of 2 old iron wedges to compensate for the lean in the bracket, and keep an eye on the set-up for any deterioration.

Visit to Lode Mill, Anglesey Abbey

Today we visited Lode Mill, part of the National Trust's Anglesey Abbey estate. This is another big, multi-storey mill, again mainly built of wood but with a large, iron 4 o'clock breastshot wheel.

The mill wheel

The stone floor

Once again we found the person in charge, in this case Chris Stimson, was generous with his time and knowledge and showed us round the mill and millwheel, including parts not normally open to the public.

He agreed with the thought that it was illogical to mill flour NOT for consumption. We would, however, have to sort out the lifting of delivered grain to the upper floor.

There was a suggestion that if you mill on four days or fewer in any five week period, there may be exemptions from some of the food hygiene regulations - but this may conflict with tea room use, of course.

Lode Mill also offers a hand quern and the opportunity to handle grain and flour - in general both mills had excellent educational facilities and interpretation.

Un-greased wooden cogs

Chris stated that you should NOT grease wooden cogs, as they pick up dust and debris to form an abrasive mixture that wears the wood too rapidly. maybe a better option for us would be to smooth the surface of the stone nuts.

Lining of grain boxes can be achieved with sheet aluminium as a Houghton, or metal gauze as at Lode. Other containers are mainly plastic Really Useful Boxes, one with a hole cut for the flour chute - on a table, not at floor level.

There are some issues around cleaning up after every milling, stone speed and tentering all of which we need to resolve - the input of a miller was stated to be essential, so Nic Jones' input needs to be obtained.

Visit to Houghton Mill near Huntingdon

Today we (Bob and Glenis) visited the National Trust's watermill at Houghton. We were made extremely welcome by Phil O'Donohue and Steve (sorry, can't remember his surname), who spent two full hours showing us round and discussing some of the issues around milling.

Houghton Mill is a rather bigger affair than Acorn Bank, being on 5 floors and powered by a "4 o'clock breastshot" wheel about 15 feet in diameter and 16 feet wide. They produce flour in one operating session each Sunday afternoon, which is sold at the mill and makes a valuable addition to the economics of the property.

The main lesson was that if we are milling flour, we ought to sell it, otherwise the public will (rightly) ask why we are bothering. They suggested that we should get the local authority food hygiene people involved as soon as possible. Their flour is also used in their tearoom scones, and it was suggested we should consider doing the same.

They also have a hand and a rotary quern to show the concept of milling - I think we should have at least one of these.

The design of our tun needs some extra consideration, as the uprights will form pockets in which flour can become trapped. This photo shows the Houghton solution of fixing internal boards across the angles.

They always un-tenter the stones after each milling session, as the flour can pack down into a dense, cement-like substance if left under pressure.

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..