a MEDIEVAL Double Bag Bellows

- This just a short piece, cut and modified from an ongoing conversation about iron smelting bellows over on Don Fogg's Bladesmith Forum.

Now, something you see on Early Medieval illustrations of blacksmith's set ups is stuff like this:



(sorry, I can't cite the sources. I have been preparing lectures and just did some scavenging via Google)

The Early Medieval blacksmith forge is using an extension of the twin chamber bellows from the earlier Viking Age. The chambers have been increased in size. The forge is now at table height. Most commonly the smith is shown working standing at the anvil.

The historic illustrations are never clear on this system, though the cross shaped bars and ropes are often illustrated.

These images stuck me as most useful, as you can see more easily how this lever system might work. A long bar set in a diagonal, likely mounted to the building, can rotate down its axis. There is a cross bar set on to this pivot. From the cross bar two ropes or chains attach to the top plates of the pair of bellows. One side of the cross bar extends towards the operator. There is a handle hanging down from this free end.
I suspect you would place some large weights on top of the two bellows top plates.
Pulling down on the handle would raise the opposite side bellows chamber. This also would free the close side chamber to drop and exhaust under the action of the weight. Releasing the handle would allow the far side chamber to drop under its top weight, the ropes would raise the close side chamber at the same time.