Sunday 7 June 2020

An Intermediate Step

The road to a new tank often goes through a number of intermediate prototypes. The Germans took this road to the Tiger and Panther, the American Pershing also evolved in a similar fashion. Soviet tank building also followed this road. For instance, the KV-13 tanks may not have gone into battle but they served as a foundation for the IS-2, the best Soviet tank of the war. The T-43 tank was also such an intermediate step. This interesting tank fell victim to trials that dragged on and a rapid increase in tactical-technical requirements in the second half of 1943.

Bigger turret

The T-43 program was contradictory from the start. This is generally linked with the fact that the GBTU changed its requirements for tanks several times in 1942-43. The T-43 started out as an ideological successor to the T-34M and turned into more of a heavy tank. At the very least, the T-34M 1942 tank and the KV-13 were built to the same technical requirements: a fast heavy tank with a mobility and mass of the T-34. A.A. Morozov, the chief engineer of factory #183, himself repeatedly compared the T-34M tank developed in 1942 and the T-43 that grew out of it to a heavy tank. However, the KV-13 quickly started moving towards a true heavyweight, while the T-43 increased in mass much slower, remaining close to the weight of the T-34.

Overall view of the reworked T-43, May 1943.

Production plans ran into some difficulties. In the summer of Stalin gave the order to increase T-34 production to maximum, even at the cost of heavy tanks. As a result, the T-34M developed in 1942 never made it past a scale model and the T-43 that evolved out of it was no longer seen as a replacement for the T-34. The GABTU also looked on some of the decisions made by factory #183's design bureau with mixed feelings. While they could be made to reconsider some items (such as the initial commander's cupola design) Morozov stood up for the reuse of T-34 components. The 1420 mm wide turret ring was one of them. It is often said that the factory couldn't produce a larger turret ring, but that was not the case. It could be produced if the equipment was converted. It would take time, but more importantly the T-43 and T-34 turrets would no longer be interchangeable. Morozov also linked the increase in the turret ring to increase in mass, which already grew over 30 tons.

Sectional view.

The turret ring debate ended in favour of Morozov in the fall of 1942, as a result of which the T-43 prototype built in December of 1942 had a 1420 mm wide turret ring. The commander's working conditions still improved thanks to changes to the turret and the introduction of a commander's cupola. Nevertheless, Senior Assistant to the Chief of the 6th Department of the GBTU BTU  Engineer-Major P.K. Voroshilov criticized the turret and commander's station, and rightly so. Despite the improvements there was a drawback to placing the commander behind the gun as on the T-34M developed in 1941. It took several steps including lowering the brass catcher to enter his station without using the commander's cupola hatch. The commander's height was also limited. In other words, a new position for the commander's cupola and a 1600 mm wide turret ring were the first requirements in the improvement of the T-43's design.

The improved T-43 had a completely different turret. The turret ring diameter was enlarged and the commander was moved to the left.

Work on a modernized T-43 began in April of 1943. It proceeded alongside various experiments with the T-34. Even though the 3-man turret and commander's cupola of the T-34 was rejected, work went on. This work also influenced the T-43. For instance, two experimental cupolas with MK-4 observation devices were tested in the spring of 1943. These were copied from the Infantry Tank Mk.IV, the Churchill. As a result, the T-34 received a commander's cupola with a two flaps by the summer of 1943. As for the T-43, it received a hatch with one flap without observation slits along the sides.

The design of the commander's cupola was vastly different compared to the one designed for the first T-43.

The requirement to enlarge the turret ring and move the commander out of the turret bustle resulted in a redesign of the turret. The new design was only slightly reminiscent of the old one. Only the gun mount was taken from the old design, and even that was changed slightly. Since the commander was now on the left side of the turret, the gun mount was moved forward and to the right. The ventilation fan moved to the back of the roof. The gunner no longer had a hatch and had to enter through the commander's cupola. Since the turret was now larger, there was room for ammunition. 76 mm round racks were installed in the bustle and on the right wall. The factory #183 design bureau met the requirement for increased ammunition capacity.

In addition to turret platform changes the new T-43 had a full sized driver's hatch.

The change to the turret ring also influenced the design of the hull. The turret platform had to be widened to the width of the air intakes. Important changes were also made to the front of the hull. The machine gun to the right of the driver returned (it was present on the T-34M 1942, but the T-43 lost it). The second change was the addition of a driver's hatch. The driver having to enter through the fighting compartment was considered unacceptable. The driver's hatch reduced the toughness of the front plate, but the GBTU considered this tradeoff worth it.

Hull machine gun mount.

Morozov's main argument against increasing the diameter of the turret ring was that he was trying to avoid an increase in mass. This is exactly what happened to the new T-43. According to calculations, the tank would weigh 33.5 tons (to compare, the T-34 weighed 31 tons by May of 1943). This had an effect on the ground pressure and mobility of the tank. Calculations showed that the speed of the T-34 and T-43 would be the same, which the GBTU and NKTP had their doubts about. In any case, the requirements for a larger turret came from the GBTU and NKTP and there was no arguing with them, especially as the situation on the front lines worsened.

Catching up to requirements

The spring of 1943 was a time of many changes. One of the causes was the capture of two Tiger tanks on January 18th, 1943, near Leningrad. They arrived at the NIBT proving grounds in April, but the GAU renewed work on 85 mm tank guns that had been going on since 1940 in March. Tactical-technical characteristics for 85 mm guns in the KV-1S and IS (the second variant of the KV-13) were prepared on March 26th, 1943. The T-43 was not included, but a memo attached to the design of the S-31 gun developed by the TsAKB mentions the T-43 as a potential carrier for the weapon. The TsAKB did not design an S-31 mount for the T-43 in detail, but this was the first indication. The memo was dated May 14th, 1943, by which point the T-43 was already finished. It's doubtful that Morozov expected anything larger than an F-34 to be installed in it. As for the D-5 (a gun developed at factory #9 and the S-31's main competitor) the T-43 was not even mentioned in its documentation as of May.

The first improved T-43, August 1943.

An additional factor was the GBTU's vision of a modern heavy tank. While factory #183 continued to work on the T-43, Chelyabinsk designed and produced two heavy tank prototypes. The IS tanks elicited a mixed reaction. Even though they were more reliable than the first KV-13, they had a number of drawbacks. The concept of a heavy tank with the dimensions of a medium one was one of them. The IS-1 now weighed 37.1 tons and the IS-2 37.9 tons. Frequent breakdowns of running gear meant that it had to be redesigned.

The concept of a highly mobile heavy tank was killed by the requirement of installing an 85 mm gun. The TsAKB had a solution in the shape of a turret they designed themselves, but this was no more than the artillery design bureau's initiative. The GBTU and NKTP knew that the IS needs a radical reworking, especially since calculations made at factory #9 showed that an increase in the turret ring diameter was necessary to install the gun. The result was the Object 237, a heavy tank in every sense of the word. The T-43 was no longer a competitor of the IS and could only be compared to the T-34. 

The tank was built to blueprints made in the spring of 1943, but its weight went over 34 tons.

Documents describing the production of pilot tanks show that factory #183 was already in the process of building the T-43 as of May 7th, 1943. At least three tanks would be built: one hull was already finished and two more still had to be built. There was also enough parts for one T-43 tank with the exception of the turret, turret ring, and final drive covers. In practice, not a single T-43 tank was built in May of 1943, and the total number of tanks was reduced to 2. I.M. Zaltsmann gave order #307s on the comparative trials of the T-34 and T-43 on May 29th. The trials would begin on June 10th. The tanks would travel between Nizhniy Tagil and Moscow, a distance of 2000-2200 km, in no more than 20 days.

The turret was the biggest change from the 1942 production tank.

The two prototype tanks built in June of 1943 were even heavier than originally thought. The mass of one T-43 tank without crew was 33,780 kg. Considering that one crewman would weigh about 80 kg, the combat mass would reach 34,100 kg. A small delay moved the start of the trials to June 20th, but this was just the beginning. On the orders of People's Commissar of Tank Production V.A. Malyshev the sending of the tanks was postponed. The tanks remained in place through July. The GBTU was somewhat baffled, as they expected the tanks to be sent to the NIBT proving grounds, as trials of the first T-43 were only performed at the factory. The improved tank had to be checked at the proving grounds, especially as production tanks already underwent warranty trials there.

The First Secretary of the General Committee of the Communist Party in Nizhniy Tagil Ye.F. Kolyshev wrote a letter to Stalin on July 20th, 1943, arguing that the T-43 should be put into production. This resulted in a letter from Beria dated July 27th, instruction Malyshev and Fedorenko, the commander of the Red Army's tank and mechanized forces, to speak with him urgently. The T-43 had not gone through nearly any trials by that point, only breaking in runs and firing trials of the machine guns.

A comparison with the T-34.

Beria's involvement kicked the process into gear. Malyshev signed order #460s/085 on the execution of T-43 trials on August 1st, 1943. However, instead of Kubinka they would be held at Sverdlovsk. The trials program was approved on that day. The tanks would travel for 2000 km, of those 500 on rocky terrain, 900 on dirt and country roads, 600 off-road, and 100 on special trials. They also had to perform a 100 km march on a dirt road and 75 km on a cobblestone road without stopping. Gunnery trials (both the cannon and machine guns) were also involved. 

Like the first T-43, the improved tank had boxy external fuel tanks. Trials showed that the T-43 had a lower range than the T-34 due to carrying less fuel.

Trials deviated from the initial plans. The trials of the first prototype began on August 2nd, 1943. The route taken was also different. The first outing from was from Nizhniy Tagil to Sverdlovsk to Chelyabinsk and back. The second outing was from Nizhniy Tagil to Rezh and back. The first T-43 tank covered 2669 km during trials, of those over 2200 in August of 1943. The second prototype covered 1348 km. The average speed was 26.1 kph on a highway, 20.2 kph on a dirt road, 18.6 kph off-road (this was nearly the same as the T-34's speed off-road). The fuel expenditure was 203, 237, and 250 L per 100 km respectively. This was about the same as a T-34, but since the T-43 carried 318 L of fuel and the T-34 had 400 L the T-43 had less range. The conditions of driving were also the same. Both the T-34 and T-43 could drive in 3rd or 4th gear off-road.

The driver's station was more comfortable than on the T-34, but there were still issues.

Obstacle trials results were also similar. The maximum slope 10 meters long that the tank could climb was 31-33 degrees. The limit was the power of the tank's engine. The T-34 showed the same performance. The tank could drive at a tilt of 27-28 degrees. The testers recommended the installation of a handbrake on the T-43 like the T-34 had. These high results were obtained because the weather was dry. Knowing how the T-34 behaves in mud, the commission recommended that the designers work on improving traction.

Special trials showed that the mobility of the T-43 was on the level of the T-34.

There was one way the T-43 was clearly superior: armament. The use of a torsion bar suspension improved the smoothness of travel, which in turn improved the gun's accuracy. The enlarged turret ring also improved the rate of fire. The T-43 had a rate of fire of 13 RPM. The T-34 had a rate of fire of 10 RPM in the same conditions. There were also complaints about the gun mount. The design of the mantlet made access to the recuperator difficult. The attachment of the mantlet with 8 bolts was also questioned. There were complaints about the electric trigger. Nevertheless, the tank passed gunnery trials after firing 317 shots.

Visibility from the altered commander's cupola.

The visibility of the T-43 was considered high, and it would be improved further by adding 5 vision slits into the cupola. The crew positions were also rated highly. The commission required a back to be added to the commander's seat and noted that the gunner shifted to the left during movement. The loader had neither a seat nor a perch and also hit his head on the torsion bar of his hatch.

As with the first T-43, there were complaints about the driver's station, albeit fewer of them. The driver had less room than on the T-34. There were also complaints about his controls. The driver's hatch was smaller than on the T-34. There were issues with reliability. Some of them were growing pains, but there was also a warning bell in the form of breakdowns of the road wheel tires. The T-34 had the same problem, but the road wheels taken from the T-34 were clearly overloaded, especially the 2nd, 3rd, and 4th wheels.

The increase in weight had an effect on reliability, although the T-34 had similar issues.

Despite the defects that were discovered in trials held from August 2nd to August 29th, the overall conclusion was positive. The commission led by Chief Tester of the NIBT Proving Grounds Kulchitskiy and Chief Engineer of factory #183 Morozov proposed that the T-43 should be put into production as soon as possible. The commission was right, but time didn't stand still and it was not in favour of the T-43.

The cost of a missed year

The results of trials were sent to Moscow in early September. Two important events took place before that. One was the Battle of Kursk, a pivotal moment in Soviet tank building. It was clear that the USSR fell behind Germany in tank building and a number of experimental tank developments were expedited. The second was that the SU-85 SPG and KV-85 heavy tank were accepted into service on August 8th, 1943. They were armed with the D-5 85 mm gun developed at factory #9. The possibility of using this gun in medium tanks was also investigated. 

The T-43 tank with a dummy D-5T gun, early September 1943.

The D-5T gun was also mentioned in the conclusions of the T-43 trials commission. Item #4 practically approved the 85 mm gun as the weapon of the production T-43 tank. It turned out that the turret was roomy enough to fit it and the crew felt better than in the T-34 with the F-34. However, the loader's job was made more difficult since the D-5 used longer and heavier ammunition. The commission inspected the installation of a dummy gun in the turret of a T-43 tank and ordered production and trials of a real prototype.

While Nizhniy Tagil was hard at work, Moscow was discussing the fate of the T-43. Factory #183 director Yu.Ye. Maksarev was sceptical about putting the new tank into production. He estimated that production could start no sooner than January of 1944, and even then required the delivery of 390 new tools and hiring 5000 workers. Two pilot T-43 tanks were to be built by October 15th, but on September 30th the GBTU delivered a crushing verdict: the T-43's armament was insufficient, 75 mm of front armour was no longer enough, and the running gear was unreliable.

While conclusions regarding the armament were fair, the complaint about the running gear raised questions. As noted before, the T-34 and SPGs on its chassis had the same issues. The GBTU also suggested that the turret ring should be enlarged further, to 1700 mm. Chief of the 6th Department of the GBTU TU Engineer-Colonel Rozengard made calculations for an improved T-43. According to his calculations, a T-43 tank with a 1700 mm turret ring, 90 mm thick front hull and 110 mm thick front turret would increase the tank's weight by 680 kg.

T-34 tanks with T-43 turrets, fall 1943. Improved commander's cupolas with vision slits are installed.

The GBTU approved tactical-technical characteristics for a new T-43 with thicker armour and a D-5T gun on November 5th, 1943. According to the characteristics, the mass of the tank was 33-34 tons. These requirements were a death sentence for the T-43. It would not be possible to fit the tank into these requirements. Priorities shifted further and further towards the T-34.

Factory #183 produced two T-34 tanks with turrets from the T-43 in the fall of 1943. One tank received the turret with an F-34 gun and the second a turret with a D-5T. The second variant was higher in priority. The T-34 tank with a T-43 turret and a D5-T-85 gun was trialled at the Gorohovets proving grounds from November 20th to 23rd. The trials were a success, which meant a green light for the T-34-85. The T-34-85 received a different turret in production, and early T-34-85 tanks at factory #112 had two-man turrets. Turrets with three crewmen were introduced in March of 1944. Instead of the D-5T they had a different gun: the S-53 developed by the TsAKB.

Trials of a T-34 tank with a turret from the T-43 and a D-5T gun at the Gorohovets ANIOP, late November 1943. Successful trials resulted in production of the T-34-85 tank.

Experiments with the T-43 continued at factory #183 up until November of 1943. It was clear by then that the tank would not go into production. The biggest cause for this was the loss of the most precious resource: time. Factory #183 had a chance at getting the tank to an acceptable state in the fall-winter of 1942. The cause of failure was various delays and Morozov's refusal to follow requirements, especially regarding the turret ring. The chance of the T-43 being accepted into production in the spring of 1943 were low, and after the Battle of Kursk they totally vanished. An increase in requirements led to an increase in mass and a drop in reliability. The GBTU understood this, and requirements for a new tank were composed on November 27th, 1943. With the same requirements for armour and armament as the improved T-43, this tank would weigh 30 tons. This kicked off the work on the T-44 tank, but the only thing it had in common with the T-43 was the turret, and even then only in initial stages of development.

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