Under the Tiger's gun there was a structure called the Beam ('die Brücke'). It supported the gunner's seat, the elevation handwheel and the turret floor.
There were two designs for Tiger's turret, and each had its own Beam. The diagram above shows the first kind (in turrets with a drum cupola)
The first kind of Beam was made of two tubes, joined in the middle. The right-hand tube was attached to the 'Bock'. This diagram shows a view from above.
The tube had a sleeve at its right end, and the rear side of this sleeve was opened up. This photo shows the opening. The elevation gearbox enters the opening, and the drive shaft runs inside the tube. At lower left, you can see the top of a leg that supports the turret floor.
The sleeve was welded to a curved metal bar, and this was bolted to the 'Bock' as shown in the diagrams and photo above.
At the other end of the tube was the gunner's elevation handwheel and firing trigger. The bearings for them were welded to the end of the tube.
The left-hand side of the Beam was a 50mm-diameter tube. It was made of two parts, joined by a welded ring. One end was flattened and welded to the upper 90mm tube. The other end was welded to a small plate, and that plate was bolted to the turret support ring.
This photo shows how the tubes were joined. Notice that the flattened section is made of two castings welded together.
The design of the Beam was greatly simplified when the turret was redesigned. The 90mm tube and sleeve were eliminated. The left-hand tube was expanded to 80mm diameter and was extended all the way to the 'Bock'. This diagram shows the new arrangement, including the gunner's seat.
The angle of the Beam is known from German manufacturing diagrams.
The new Beam was bent slightly to meet the 'Bock'.
This photo shows the right-hand end of the later Beam. The floor support leg and elevation handwheel are attached awkwardly so that they retain their original positions as in the old turret. An electrical junction box is added.
[2] Survey of vehicle 250122, Bovington, by David Byrden