#54672, "RE: Vertical sliding Watertight Door system" In response to In response to 1
TTSM pg.113 is the best picture of H&W's WT door mechanism. That's the picture with a man in it. The description is already very good.
Door movement: Let's call the shaft with the gear above the center of the door the main shaft. That gear is fixed on the shaft. The shaft can move left-right by a small amount. The worm gear at the side of the door frame is free to spin on the main shaft. That gear would have a bearing surface on its left side. The main shaft has a head like a nail to the right of the worm gear. A friction material (B) would be placed between the main shaft head and the worm gear. The weight arm (C) pivots on a rod in the casting next to the head of the main shaft. Beneath that pivot rod is a bolt tip that pushes on the main shaft head pressing it against the friction material and the worm gear.
So when the weight presses down, the main shaft is clamped to and obeys the worm gear, stopping or moving with it. When the weight is up, the main shaft is free to let the door fall by gravity.
The friction area could actually be built of several layers like a multi disk automotive clutch. Maybe the main shaft doesn't slide sideways, the head could be a splined casting that slides on it. As the Stone hydraulic door system became more popular there is probably not much in the period texts. A patent search might lead to better details.
In the final assembly the two gears and the friction area are covered.
Control: A small vertical rod (E) runs down from the large magnet box (A) at the top to the float at the bottom. The magnet is wired by thin conduit mounted on posts above it (pg.112 left). The magnet is energized to lift the control rod and thus the weight. Nowadays that would not be considered fail safe. A hand release lever (D) on the bulkhead can also lift the control rod. At the bottom the float sits in an enclosure. When the float lifts it works through a lever on a bracket to lift the control rod. The lever and bracket show in this picture.
For opening the door the vertical shaft (G) through the worm gear can be cranked by a bevel gear (F) at the bottom. The L shaped gear handle is hanging on the bulkhead. The shaft can also be cranked from an upper deck. These routes can also be used for slow or remote closing of the door.
Cataracts* (old name for a flow slowing passageway): The two hydraulic style cylinders above the door have a closed fluid circuit. The small pipes at the side only allow fluid to move from beneath the pistons to above them at a rate slow enough to give a controlled descent of the door. When the pistons pass the extra pipe connections 2/3's of the way down more fluid can pass into the upper part of the cylinder and the descent rate becomes quick enough to let the door slam home.
*I think cataract is an alternative to the word rapids as in river rapids. Much as we think of them as being fast water the rocky, restrictive bottom makes them slower than a smooth bottomed passageway making the same descent. Hence the period use of the word here for a slowing mechanism. In my time the word dashpot was used for this sort of mechanism.