The Gear Train
|ut of necessity, the hand crank is offset from the cabin centerline. There would be no room for the crew if it were connected directly to the propeller shaft.|
|There has been much speculation about this linkage and now the excavation is beginning to reveal details. The older, speculative schematic at right illustrates the descriptions of a chain joining the gears and a large flywheel. A flywheel serves the general purpose of smoothing rotational motion. The propeller would resist speed variation as the crew cranked as well as induced motion from waves or currents. As depicted, the crank has a larger gear than the propeller shaft so the propeller turns slightly faster.||
|This recent rendering of the area under the aft hatch lends depth to the speculation. I'm continuing to refine the view based on a study of released images.|
The reconstruction above is based on early photos
that provide glimpses of this area behind an archaeologist or conservator at
work, a photo shown during the Smithsonian Seminar, and the interior
panorama on the Friends of the Hunley web site. I updated and
added detail to the aft sea-cock, visible on the upper right side. In
addition to other errors, the image erroneously shows the pump canted at a
large angle. See the tanks pop-up for more up-to-date information.
The last crank of the shaft is attached to the hull at its forward end only. This business end of the shaft must be attached somewhere near the gear, but no obvious structure showed up in photos until early 2008. A photo taken during removal of the aft pump assembly reveals what may be a horizontal bar running across the cabin between the gear train and the flywheel. This is a logical attachment for the ends of both the propeller and crank shafts, providing stability where it is most needed.
What do you think?
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21 Jan 08