The Air Pump

The Air Pump

he discovery of a bellows device under the snorkel in the first crew station was a major surprise. None of the surviving diagrams show any sort of pumping mechanism, although written accounts mention one.

Bruce Kinsey asked about the bellows during the 2007 member appreciation tours. He learned that it was attached to the side of the hull and had the hose running from the bellows to a valve on one of the snorkel pipes in the air box. The bellows was used to pump fresh air into the cabin. Stale air left via a valve on the second pipe. I've seen no additional information on where the bellows was attached. It's possible it was mounted low on the wall and operated by foot power, not unlike many bellows used for forges and other functions.

The interior drawings below show a possible position of the bellows from the side and top. It was uncovered in a more horizontal position with the longer cross-member up, so the mounted position may have been rotated 180 degrees from the illustration. Oriented that way, and mounted a little lower, the cross-member might have served as a kind of pedal for pumping. (The interior of the air box in the drawing is completely speculative.)

Bellows position, side elevation - speculative

Bellows position, plan view - speculative

Here's some additional speculation:

A standard bellows is a two-cycle device: Filled through the inlet valve on one stroke; emptied through the exit valve on the reverse stroke. Unless this is a double bellows, it seems likely its purpose was to draw fresh air into the sub and not to expel stale air. So long as the cabin exhaust vent was physically separated from the pump outlet, expulsion need not have been powered. The fresh air would mix naturally with the stale air in the cabin, recharging the oxygen content.
Did the crewman power both strokes, or was the return stroke aided by a spring?

The bellows is part of the snorkel system, so we should consider the entire system. Alexander’s drawing shows a lever mechanism for raising and lowering the air pipes. (I have not yet shown this lever in my reconstruction.) The crewman at this station would operate this lever. It is likely that one pipe was for drawing in fresh air and the other for exhausting stale air. There are other possibilities for exhaust, but this is the simplest. Both pipes would have stopcocks to close them for completely submerged operation. These would likely be in or just below the snorkel box or could be part of the lever apparatus. The bellows mechanism would draw in fresh air on its expansion stroke and blow this air into the cabin on the compression stroke. It would of course have flapper check valves to direct the fresh air correctly on each stroke. The bellows inlet would be connected to one of the snorkel pipes via wood boxes. The bellows exhaust was apparently piped via a hose away from the opening for other pipe. It would not be necessary to pump out the stale air since increased air pressure as fresh air is pumped in would exhaust it naturally.

The following section is mostly out of date and incorrect. I'm temporarily retaining it only for historical reasons.
At first thought to be a wooden bench set high in the cabin, the discovery of the leather bellows fabric hinted at its real function. Sketchy reports described only two wooden boards connected by a leather diaphragm, and a long, possibly rubber hose. In web cam views and the 2001 photo of its removal, the bellows presents a massive, complex, confusing image. A 2005 photo of the bellows undergoing conservation, published in the Post and Courier, is much clearer but the apparatus is small compared to the earlier photo. The newer photo may show only the bellows component of a larger air pump system, or the earlier photo may include additional, unrelated block-lifted material.
The graphic at right shows a possible reconstruction of the air pump. An early press report mentions a hose attached to the bottom and perhaps running under the bench. The bellows position and some details are speculative (see above for better position information).

	The Post and Courier photo shows a relatively small wood and leather device – perhaps a foot wide by a foot and a half long. Assuming the object is right side up, the wood fittings on top probably connected to similar fitting in the air box on top of the hull. I’ve made several other assumptions: The bellows is hinged on one of the short sides. It is relatively intact – that is, it has been cleaned but not dismantled.

The box on top is probably the air inlet. The small tab may attach to the flapper valve. The long piece of wood on the bottom board is in the Post and Courier photo but may not actually be part of the bellows. If it is a part it may have been a pump handle mount or may have served to lock the bellows closed. If the bellows included a spring to close it automatically, the handle could have been just a simple rope to pull it open. The following early speculation has been superseded by new information.

     I'd initially positioned the bellows with its long dimension athwartships as in the lower graphic at right. At the time, this seemed to be closer to the position in which it was found. In this position, an operator at the station would pull it toward himself to work it.
     The fore and aft position depicted in the upper graphic, however, fits nicely and seems a better design to me. Oriented this way an operator in either this station or the the first cranking station could reach forward to operate the mechanism.
     Bellows details are so hard to see in the early photos it really isn't possible to determine the position with any certainty. Since the bellows apparently fell or floated from its mounted position, its archaeological context may not be related to its mounted position.

Speculative Position 2

What do you think?

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