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Turret sealing tube
By 1942, Germany had some experience in modifying tanks for travel under shallow water. Their technique was to add external rubber seals to the outside of existing tanks. This had the disadvantage that the seals could become damaged over time.
Very early in the Tiger's design a decision was made to enable it for underwater travel, as the vehicle's great weight meant that many bridges would not bear it. The tank's armoured shell had already been designed; now, it was modified so that all joints had integral rubber seals.
The turret ring, containing the ball bearings on which the turret rotated, was fixed inside the lower walls of the turret (standard German practice). This is a cutaway model of the Tiger's turret ring. At the extreme right of the picture, you can see the sealing mechanism that was added to the ring. It is an inflatable rubber tube. Before underwater travel, the turret would be locked in the forward position. The rubber tube would then be inflated, pressing against the outer wall of the turret and the seating ring which was bolted to the hull top.
This diagram shows the rubber tube and some of the surrounding mechanisms. The tube's dimensions are indicated. It was inflated by hand-pump via a small tube leading up from the hull interior; this inflator tube is also shown in the diagram.
It was expected that some water would collect in the turret ring mechanism despite the inflated tube. Therefore a drain pipe was fixed in the turret ring, allowing this water to be drained into the hull. This diagram from the Turret Manual shows the drain pipe. The pipe is screwed into the turret base. There is a screw cap on the bottom of the pipe.
The inflator tube and drain passed through holes at the front left of the hull roof. They are the mid-sized holes in this photo [3] . The largest hole is for the turret's lock.
When the turret was installed, these holes could be reached only from inside the hull. Here, we are looking upwards at the hull roof from below [3] . All equipment has been removed in this photo; the odd-shaped plate is welded to the hull roof and serves to locate the holes precisely.
Note that a small flange and a rubber seal have been bolted into the plate from the previous photo, ensuring a watertight seal.
In September 1943, the Tiger's submersion ability was deleted [2] . The inflatable rubber ring disappeared from the design.
Sources
[2] DW to Tiger 1
[3] Survey of vehicle 250122, Bovington, by David Byrden
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