Thursday, April 20, 2006

Mill Architecture


Form and function

Evidence suggests that corn milling at Crabble goes back to thirteenth century. Most likely there was a natural spring-fed pond or a widening of the river at this pont. It being an ideal site, mills have been built there ever since.

Being functional structures they were built, not to look pretty on the landscape, but a practical utilitarian job to do using whatever materials were available locally and cheaply, often reclaimed, secondhand timbers and so on. Certainly, in our Crabble Mill there still remains some timbers which pre-date the Mill, most likely older ships timbers.

Our Mill was build in a number of stages and the 1812 version did not look like this. Certainly there was no annex (the two storey extension), it could have been five storeys not six, and it had a different waterwheel configuration. This Mill originally co-existed with the previous little mill (mentioned in a previous post), and as business grew and technology improved the Mill grew and was extended a number of times.

The rooves were made of tar and papier mache as they had to span large areas with small internal roof supports, and also the pitch of the rooves were very shallow. Therefore, slates or tiles were unsuitable. Paper would have been plentiful, probably sourced from the paper mills down stream. Now, in our Restoration in 1990 we replaced tar and papier mache with a more practical solution and covered the rooves with a coated stainless steel.

The building structure of this 'machine' comprises 2.5 storeys made from brick in order to provide a strong and solid base to house the prime movement of the waterwheel, the main internal gearings and the millstones. There is a massive about of weight and movement for it to 'hold'. The upper 3.5 storeys are timber framed with weather cladding. This is not because they ran out of bricks! It's because this has to be much more flexible and be able to move and absorb the energies more of the mechanisms contained within i.e. the seperators, cleaners and graders. It also has to contain all the different storage bins. So, you can see that the upper storeys had a different function that the lower.

The brickwork is laid in 'Flemish Bond' which contrasts from modern style brickworks. There's no cavity walls. Some of the headers are a metallic purple which is caused by vitrification in the kiln.

The windows are sash with the tradition of twelve panes and set in an approximate symetrical configuration. Shutters are required for practical purposes.

The lucam is the top housing projecting out, which protects the hoist gear. Almost beneath it on level 4 a hood covers the vent extractor system. On the opposite side of the Mill on the top level there's another vent which is connected to the smutter. Our old pictures show that the smuts were not just blown out into the atmosphere but were taken down a long trunking to the river.

The most recent necessary alterations to the Mill are the stairtower and the bridge. Both were added in the 1990's Restoration in order to meet modern requirements (and convenience) to allow public access into the Mill and up through the Mill tower.

The entrance to the Tea Room, previously was simply a door to enable the miller to access the waterwheel enclosure and also up the centre bank ("bund") to use the regulating sluice between the pond and river which probably had to be done twice a day.

The weir is zig-zag shaped to allow a slow 'overflow' of surplus energy with minimum disturbance. As well as the dam walls which need maintenance, there are also 4 sluice mechanisms. The main waterwheel sluice to power the Mill is located at the midpoint of the wheel (hence the it being a 'breastshot' type). There should be a sluice to control the flow between the millpond and the river, there are also two sluices regulate the water levels of the both the river and the pond.

The built waterways are a 'headrace' to feed the waterwheel, a 'by-pass' to take away energy surplus to requirement, a 'tailrace' to guide the outflow from the Mill downstream to the point of convergence meeting the by-pass.

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