The Champlain valley was once a major source of very high quality ore... so clean in fact, that it was specified for the cables of the Brooklyn Bridge by the designer, John Roebling. The ore was roasted & then brought by train to a depot and unloaded over a period from the 1850's to the 1950's. Lucky for me they spilled a lot. :) It will be interesting to compare the results of smelting different ores in, say, pattern welding...
I built the first set of bellows with the expectation that I would discover flaws and make another.
This set is about 3.5 x 2 feet and rises about 2 feet. It was decided that not enough air was being produced.
This was due to several issues:
* Not enough volume.
The next set in production is approx. 6" x 3".
* Too much flexibility in the bellows fabric. (Oiled canvas.)
Solution is to add supporting ribs.
* Air leakage around nozzle connection.
Inspect & eliminate all small leaks.
The several historical illustrations depict air inlet valves on the top paddle of the bellows. While the thick leather flap I used on the trial bellows worked, it is much more efficient to place the inlet valve on the bottom paddle where gravity may assist in the crucial production of an effective air seal. I rather suspect that if every bellows depicted and produced after the Viking Age is constructed in this manner, we may begin to wonder if the hole depicted on, say, the Ramsund carving, isn't there to help imply "bellows," rather than realistically depict them. Here I will depart from convention and place my new inlet valves on the bottom paddles.