of the Object 236, and eventually the SU-152, which concept was later continued and further developed with the ISU-152. The ISU-152 followed the same design as most other Soviet self-propelled guns. The fully armoured hull was divided into two compartments: fighting compartment for the crew, gun and ammunition in the front of the hull, and engine and transmission in the rear. The gun was mounted slightly to the right of centre with a limited traverse of 12 degrees left and right. The crew consisted of four or five men placed in the superstructure. Three of the crew were to the left of the gun: driver to the front, then gunner and last the loader. The vehicle commander and lockman (who operated the gun breech) were to the right: commander to the front and the lockman behind. When the crew consisted of four men, the loading was carried out by the lockman. The suspension consisted of twelve torsion bars for the six road wheels on either side. The drive sprockets were at the back, and the front idlers were identical to the road wheels. Each track was made up of 90 links. There were three internal fuel tanks, two in the crew area and one in the engine compartment. These were usually supplemented with four unconnected external fuel tanks. 12- and 24-volt electrical power supplies came from a 1 kW generator feeding four accumulator batteries. For observation from the interior, all roof hatches had periscopes and there were two gun sights: telescopic ST-10 (СТ-10) and panoramic. For crew communication a TPU-4-BisF intercom was fitted, and for inter-vehicle communication there was a single 10R or 10RK radio. These were better than Soviet equipment at the start of the war but still inferior to German equivalents. The crew were given two PPSh submachine guns with 1491 rounds and 20 F-1 grenades for short-range self-defence. The ISU-152 was armed with the same gun as the SU-152, but it used the hull of the IS-1 tank instead of the KV-1S. Later in the war the ISU-152 was further improved. It used the hull of the IS-2 or IS-2 model 1944 tank, the armour of the mantlet was increased, the gun was replaced by newer variants, a 12.7×108 mm DShK anti-aircraft machine gun was installed by the right forward hatch and later its ammunition capacity increased, the 10R radio set was upgraded to a 10RK and