KV-7 “Object 227” self-propelled artillery installation SAU
The KV-7 was a prototype design that never made it into production. It was an early attempt to increase firepower against light defensive positions. The first iteration was a triplex design with a single 76mm gun flanked by two 45mm guns. This approach performed poorly in trails and it was decided to evaluate twin 76mm guns and drop the 45mm entirely. Trials didn't go to well for the twin mount either and the project was eventually cancelled. The effort wasn't a total loss, the concept eventually evolved into the SU-152.
In the first few months of World War II, many advantages and disadvantages of Soviet weapons and military equipment appeared. Something showed excellent results, and the performance of other types in a combat situation did not meet expectations. For example, existing tanks, including heavy KV-1s, did not always cope with the tasks assigned to them. Reservations and driving performance were sufficient, but sometimes lacked firepower. The troops needed a new armored vehicle with more serious weapons. In addition, the soldiers would not mind getting a tank with a comfortable fighting compartment.
In the fall of the 41st, all the problems encountered were gathered at the Chelyabinsk Kirov Plant. Designers L.I. Gorlitsky and N.V. Kudrin initiated the start of work on the creation of a new tank. The project was named "Object 227" or KV-7. As a basis for the new armored vehicle, the KV-1 tank chassis already mastered in the series was taken. The layout of the original tank decided not to change and also to place the fighting compartment in the middle part of the armored hull. Where big problems arose with weapons. In the fall of 1941, the 76-mm F-34 and ZIS-5 had the largest caliber among all the tank guns available. However, as it turned out from the combat use of T-34 and KV-1 tanks in the first months of the war, they were insufficient weapons for a heavy breakthrough tank. The Chelyabinsk engineers did not have the opportunity to wait for a new instrument of a larger caliber.
A heavy KV-4 breakthrough tank was assembled on the principle of a two-tiered weapon layout, which was typical at that time for Soviet multi-turret tanks T-35 , SMK, T-100 , T-28 , T-29 , American M3 "Lee" (M3 Lee ) , French Char B1-bis and others. At the same time, the armored hull was divided into three compartments: the control compartment in the bow, the fighting compartment in the middle part of the hull and the turret, and the engine-transmission compartment in the stern of the hull. It is also worth noting that the distinctive specifics of the layout of the KV-4 was that the combat compartment and the control compartment were partially mated with each other, since a 107-mm caliber gun had to be installed in the front of the hull.
Initially it was assumed that the crew of a heavy tank breakthrough KV-4 would consist of 9 people. Of these calculations, at least 4 people should have served a 107-mm cannon and at least two 76-mm cannon. In addition to them, it was planned to include the commander, driver, his assistant or radio operator in the crew. For landing and disembarking from the tank, the crew could use four main hatches, two of which were located in the roof of the upper turret and two - in the roof of the curbstone hull.
First, it was proposed to equip the “Object 227” with three 76 mm ZiS-5 cannons at once. According to the designers who proposed this, a battery of three guns could give the new tank sufficient firepower without requiring a significant reorganization of production and logistics. However, three 76-mm guns could not fit into the rotating turret. After a series of unsuccessful attempts to re-arrange the combat compartment or turret, the engineers decided to abandon the latter. Under the new proposal, the three ZiS-5 were to be located in a fixed armored wheelhouse. Thus, the KV-7 became not a tank, but a self-propelled artillery mount. Designers with ChKZ did not set as their goal the exact observance of terminology and continued work on the topic "227" already in the form of an SAU.
Nevertheless, even the rejection of the rotating turret did not give any sense in equipping the new SAU with three ZiS-5 guns. The size of the breech and recoil devices of the guns required not only removing the turning mechanism, but also expanding the wheelhouse to indecent sizes - its side walls in this case should have been almost beyond the level of the external tracks of the tracks. Of course, after such a result of the preliminary design, the three ZiS-5 were rejected for futility. The second version of the KV-7 self-propelled weaponry was to install one F-34 76mm gun and two 45mm 20K guns. It was proposed to install all three guns on one supporting block, indicated by the U-13 index. A common cradle with three “sets” of fasteners for recoil devices was mounted on a single frame. The design of the U-13 allowed to simultaneously target all three guns in both horizontal and vertical planes. The possibility of providing each gun with its own means of guidance was considered, but this possibility significantly complicated the design.
It is noteworthy that when designing the KV-7 for the first time in the Soviet Union, a so-called frame system fastening tools. Subsequently, similar mechanisms would be applied on almost all Soviet self-propelled guns of the time. Frame fastening had great advantages over the previously used so-called. Tumbov, in the first place, in the ergonomic aspect. The used U-13 mount allowed to direct all three guns within 15 ° to the sides of the longitudinal axis in the horizontal plane and from -5 ° to + 15 ° in the vertical. The aiming of the F-34 and 20K guns was made with the help of the TMDF-7 telescopic sight. Additional weapons self-propelled consisted of three machine guns DT. Two of them were located in ball installations in the front sheet of the hull and aft sheet of the cabin.
In addition, at the disposal of the crew of six people was another similar machine gun, which, if necessary, could be used as a spare or anti-aircraft. Self-propelled gun ammunition was 93 76-mm projectile, 200 45-mm, 40 disks for machine guns and 30 grenades. which, if necessary, could be used as a spare or anti-aircraft. Self-propelled gun ammunition was 93 76-mm projectile, 200 45-mm, 40 disks for machine guns and 30 grenades. which, if necessary, could be used as a spare or anti-aircraft. Self-propelled gun ammunition was 93 76-mm projectile, 200 45-mm, 40 disks for machine guns and 30 grenades.
The armored cabin was made of rolled armor plates with a thickness of 75 mm (fore) to 30 mm (roof). The forehead and sides of the wheelhouse were located at angles to the vertical plane. The gun mask had a thickness of 100 millimeters and was made movable. In addition, the gap between the mask and the cabin was equipped with additional shields. The design of the armored hull of the undercarriage of the KV-1 base tank did not undergo any changes, except for modifications to the deckhouse installation. On the prototype KV-7 with three guns installed 12-cylinder diesel V-2K with a capacity of 600 horsepower. The transmission was completely copied from the KV-1. Similarly, the situation was with the fuel system, suspension, tracks, etc.
The assembly of the first prototype of the SAU of the project “Object 227” was completed as early as December 41st. Then the tests began. The driving characteristics of the new self-propelled gun did not differ much from the KV-1 tank — the applied chassis and the new engine had an effect. But on trial shooting there were serious problems. As it turned out, the KV-7 self-propelled gun simply could not simultaneously fire from all three guns, which did not allow producing more than 12 rounds per minute. Due to the different calibers and ammunition capacities, each gun or at least each type of gun required a separate sight. Thus, one TMDF-7 sight, intended for use with an F-34 gun, could not cope with its duties. Another design problem emerged from the shooting of the extreme 45mm cannons. Due to the peculiarities of the U-13 system mounts, a shot from a 20K gun shifted all the guns and knocked down a tip. Finally, a single system of fastenings for all three guns did not allow simultaneously to fire at more than one target. It was decided to continue upgrading this version of the KV-7 to increase the effectiveness of the fire.
Simultaneously with the three-cannon variant of “Object 227”, a two-cannon was created in the design office of ChKZ. As if anticipating problems with aiming guns of various caliber, Gorlitsky and Kudrin proposed to develop a version of the self-propelled gun "227" with two guns of the same caliber. As weapons for the KV-7-II project, the same ZiS-5 was proposed. On the basis of the fixtures of the U-13 system, the installation U-14 was made, designed for the installation of two three-inch guns. Two guns ZiS-5 on the installation of the U-14 were mounted on the second prototype of the new SAU. At the same time, the design of the cabin was almost unchanged - only the mask of the guns and a few other details had to be redone. Also had to redo the laying of ammunition for guns. The use of two identical guns made it possible to simplify its “organization” and to place 150 shells in the fighting compartment.
Creating a two-gun self-propelled gun mount took more time and tests of the KV-7-II began only in April 1942. A single caliber of both guns greatly facilitated the work of the crew, and in the future could simplify the supply problem. After several days of training, the crew of testers was able to achieve a combat rate of fire at 15 rounds per minute. This was more than the first version of the KV-7. However, this superiority over the three-gun machine and limited. The running performance of the KV-7-II was exactly the same, and the ergonomics of the crew compartment, if improved, is not much. Similarly, the situation was in comparison of the KV-7 self-propelled guns of both versions with the original KV-1 tank.
At the end of the spring of 1942, the question of the fate of "Object 227" reached the highest level. During the discussion of the test results and the prospects of self-propelled guns as a weapon for the Red Army, a phrase was voiced that put an end to its adoption. Someone from the military leadership of the Soviet Union asked: “Why do you need two or three guns? One, but one good one, will be much better.” A number of sources attribute these words to Comrade Stalin. However, other Soviet military leaders also did not see any advantages over the existing equipment in the KV-7 project. Installing more powerful guns also could hardly make the KV-7 a promising system. According to the results of the discussion at the top, the project was closed. The first copy of “Object 227”, equipped with three guns, was disassembled and later was used as a platform for testing other equipment.
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