Sealing the turret ring
By 1942, Germany had some experience in making Panzers capable of submerged travel in shallow water. External rubber seals were added to joints on the vehicles. But those seals were permanently fixed to the outside of the tank and could become damaged.
Very early in the Tiger's design process a decision was made to enable it for submerged travel, as the vehicle's weight was too much for small bridges. The tank's armoured shell had already been designed. Now the relevant welds were required to be watertight, and integral rubber seals were added to unwelded joints.
The joint between turret and hull presented a major problem. The two assemblies did not touch except via the ball bearings in the turret ring. The gap between them could not be sealed with grease like that of an axle or torsion bar. It was decided to use an inflatable rubber tube.
The sealing tube
This is a cutaway model of the tank's original turret ring. The ball bearings sit inside the 2-part ball bearing race. That is placed upon the toothed base ring. That ring has a vertical outer flange with a channel, and a rubber tube is placed in that channel.
The toothed ring is fixed to the hull, while the turret's armoured wall (at the right of the image) moves around it. By inflating the tube, you force it to press against the flange and the wall, sealing that gap. The turret had to be locked immobile to help the seal.
The rubber tube had a nominal diameter of 30mm when not active. It had a single inflator valve on a thin tube [1, see plate 8] .
While inserting the inflatable tube into the channel on the toothed ring, you would push the inflator valve into this small hole.
The drain
It was anticipated that the rubber sealing tube might fail or deflate, allowing water into the ball bearing race. So, at the inner surface of the turret ring, there was a secondary seal as a backup. But water would then remain trapped in a U-shaped channel in the toothed ring, causing rust. Therefore, this channel had a drain. The largest hole in this model is the drain hole.
The drain and the inflator tube both had protective sleeves leading down through the hull roof into the crew compartment. They were positioned together in the front left quadrant of the toothed ring. This model shows both of them. The sealing tube is visible also.
This "exploded" model shows the parts of the submersion gear.
In September 1943, the Tiger's submersion ability was deleted [2] . The inflatable sealing ring and the drain were no longer built into Tigers.
[2] Germany's Tiger Tanks, volume 1 : DW to Tiger 1
[3] Survey of Tiger 250122, at Bovington museum, by David Byrden