Tuesday, October 07, 2008

Thanksgiving / Hals setup

Taken with the earlier discussion on the possible layout of the Icelandic smelter at Hals:
This is was the situation at the smelter work area at the beginning of the week. You can see that our last (June 08) clay cobb smelter remains in excellent condition. By intent, I had set up the area with our working smelter to the right side. This was so that a second smelter could be installed to the left hand side of the block retaining wall.

Next is a simple plan view of the existing situation with some of the significant measurements, with a theoretical layout of the Icelandic smelter indicated. I have taken two of the available rail road ties and used these to block in the 2 m x 2m size. On the actual above ground sod construction, this would be a log crib. With the length of the ties actually a bit more than required (and lots of stones!) I set the rear dimension using a row of rocks. By removing three stacks of the retaining wall blocks, I end up with about the correct opening for the front V of a working area leading back to the smelter front wall. Measuring from the current work surface to the tops of the two rail ties, you end up with about the correct height proposed for the Icelandic construction.

the next drawing is an plan view of my proposed set up for the Thanksgiving smelt as it overlays the existing area. As outlined in the last posting, Work Dynamic is the primary thing being explored in this experiment. The position of the hand powered bellows is indicated, and will be blocked in with a plywood cut out for this smelt. The space between the V of the concrete block walls is the length of a standard brick (about 25 cm).

After much grunting and groaning (about 6 hours worth).
You can see in the photograph that I have cut back the bank to create the V shape work area. The concrete blocks have been used to secure the walls. I suspect that in the historic smelter, these could be a combination of wood (towards the front) and stone slab (at the smelter surface). Our own past experience has shown that any wood within about 40 cm or so from the smelter wall will certainly catch on fire from the radiant heat. At this point I had to scrounge a few more blocks for the left side, so the top surface has not been copletely packed or leveled. As usual for Wareham, the larger rocks (about head size) seen on the left were of course just sticking out an inch or so from my digging lines! As of today (Tuesday 7 AM) I have not actually cut down the cylindrical hole for the smelter itself, which is marked by the plastic pail.

The next illustration is a section through the centre of the smelter roughly S-N. Our standard Norse Short Shaft smelter construction will be used. You can see that it comfortably fits into the earth banking, with its top about flush with the upper work area. One overall question that remains is how to construct the area of the smelter that will be exposed to open air (tap arch, tuyere and the 'heat zone'). Given the relative scarcity of clay in Iceland, I suggest that the historic smelters would have used stone slab with an inset clay bellows plate construction.

The last drawing is a section (cut E-W) I have laid out the working position of the current smelter bellows. Oour tested angle of 23 down for the tuyere is extended along the length of the bellows (about 100 cm) plus the length of our normal ceramic tuyere tube (30 cm). This is shown with the tuyere inserted at 5 cm proud of the smelter interior wall. If the blow tube method is undertaken, the whole workings of the bellows and tuyere would be moved back about 10 cm away from the front edge of the smelter wall. Michael Nissen normally uses a less pronounced angle on his smelter set ups, so the combination should retain a correct working height for a potential bellows operator.

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February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

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