The Tiger's turret sat upon a flat machined seating ring that was welded to the hull's top plate. This ring had holes for the bolts that locked the turret in place; the bolts were accessible from inside the tank and had to be removed before the turret could be lifted off.
This is the forward left corner of the seating ring on the Bovington vehicle [1] . (At this time, the vehicle had been sandblasted and repainted.) The smallest two holes are bolt holes for affixing the turret; the other three holes (all shown in the diagram) have special purposes.
This diagram shows a section through the ring, with a bolt hole. The 25mm hull roof plate is shown at the left. Dimensions in green ink are reliable because they are quoted from German drawings.
This photo, taken from within the hull, shows the bottom of the ring and two of the bolt holes. Weld was applied in the notch.
This is a model of a hull top. The three special-purpose holes are shown. The large one is for the turret lock; there is a hole for draining water out of the turret ring mechanism, at the right of the picture; and a hole for inflating the sealing tube, at the left [4] .
The Tiger had a persistent problem in that these bolts tended to break when the turret was hit by enemy rounds. The first solution was to redesign with stronger bolts. Later, starting with the 201st turret, the number of bolts was approximately doubled [7] . The new bolts were interspersed with the old so the turrets and hulls remained interchangeable.
The turret had 8 internal screws which would have collided with the new bolts. Therefore, the new bolts at the 8 octant positions were moved outwards to a radius of 1065mm. But some of these positions were still unusable; the front and back ones were on the weld line of the hull top plates; the left and right ones collided with the walls of the ammunition bins; and the front left bolt interfered with the submersion equipment. These 5 bolts were therefore omitted. The diagram above shows the remaining 43 bolt positions that were present in all Tigers after the 200th turret.
This diagram, taken from the Tiger Turret Manual, shows the ring and the turret mechanism that sits upon it. The ring is represented as flat without a deep rim on the inside; this is an error. See my earlier diagram for the true profile.
The diagram shows both an inner bolt and an outer octant-position bolt, although these never occurred together. Also notice the screw in the turret mechanism; this is why the inner octant positions were unusable.
The turret was difficult to align when being replaced on the hull. Therefore another improvement was made; two locating pins ("Einbaudorn") were added to the turret bottom, and holes for them were made in the ring on the hull. This feature was added during or after April 1943, possibly at the same time as the extra bolts; it was certainly present by the 236th hull. The same pins were used on the Tiger B.
This diagram of the hull ring shows the new holes for the locating pins. At 30mm diameter, they were slightly larger than the bolt holes; it would, of course, be undesirable for the locating pins to fit in the bolt holes.
In the Tiger B turret, the locating pins were placed centrally fore and aft. These positions were not available on the Tiger E because of structures within the hull. The pins were placed on the left side of the Tiger E turret, perhaps allowing a single person to watch them both as the turret was lowered.
This is a diagram of a pin. It can be screwed into a dedicated hole in the bottom of the turret. After the turret is replaced on the hull, it can be unscrewed and removed from inside the tank. I don't know if these pins were carried in the Tigers; they may have been kept by the workshops. I have found only one clear photograph of these pins in use.
The redesign of the turret in July 1943 [7, see 3.4.2.20] brought another improvement. Washers were placed on all 40 of the inner bolts. The idea was that if the turret was struck, the washers would deform rather than the bolts breaking. The change was successful; photographs prove that when these turrets were torn off by explosions the mechanism would rip open at the ball bearings rather than the bolts.
This diagram from the Turret Manual shows the washer on the inner bolt.
This photo was taken in the Saumur museum vehicle, just behind the commander's seat. You can see the turret fixing bolts and their washers. Also notice the large hole; this is for the rear locating pin. These bolts should have metal strips to prevent them vibrating loose; the hull strips are all missing in this tank.
The new turret did not need the plunger-type travel lock in the hull [7, see 3.4.2.20] . But I don't know if the lock and its hole in the hull roof were deleted at that time.
The Tiger's submersion ability was deleted in September 1943 [7, see 3.4.1.5] . The two relevant holes in the hull top must have been deleted also. For the rest of the production run, the turret mounting ring looked like this.
This photograph was taken in the Late Tiger at Saumur museum. This is the underside of the hull roof, forward of the loader's seat. [A] is one of the 40 bolts on the inner ring, with its washer. [C] is a bolt for the splash-guard ring outside of the turret. [B] is the forward right outer bolt position for the turret mounting ring (see my diagrams above). Here, the bolt itself is missing.
[1] Survey of vehicle 250122, Bovington, by David Byrden
[2] Survey of vehicle at Saumur, by Hilary Louis Doyle
[5] Survey of vehicle 251114, at Saumur, by Jean-Charles Breucque
[6] Tiger in Action, Squadron Signal # 27
[7] DW to Tiger 1