Some Info on the IS-2U Designs

In 1944 an informal competition began to develop between the ChKZ and Factory №100 to improve the armor protection of the IS-2. Two solutions were presented to solve this problem,  P.P. Isakov suggested that the front hull be comprised of a downward pointing wedge. The sides would not be vertical like other tanks instead the sides would slope upwards. The bottom of the hull would be flat and instead would be sloped upwards as well. This design would've require removing the torsion bars and placing ribs along side the hull for bogies that would be used for the spring suspension. This solution also did not leave adequate room for ammunition and fuel.

G.N. Moskvin suggested that part of the hull remain vertical and that floor remain flat. This solution did not require abandoning torsion bar suspension. The fuel would stored in between sheets of armor at the bottom of the tank. However this complexes welding and is not consistent with the all wedge hull that was originally envisioned. However G.N. Moskvin was replaced by S.V. Mickevich and worked further on his solution.

The IS-2U in its final form