Monday, 19 April 2021

On the Way to the King Tiger

There is an unwritten rule in tank building: start working on a replacement for the tank that you just built. This rule is especially true in wartime. In some cases, work on the replacement began before the predecessor left the drawing board. This is how work started on the Tiger II, the heaviest mass produced tank of WWII. Formally, development began in 1941. The tank named VK 45.02(H) gained a lot of weight during development and changed its name and designs multiple times.

A bigger gun

Formally, the story of Germany's heaviest mass produced tank started on May 25th, 1941. A meeting was held with Hitler present, where he raised the question of armament of future tanks. This was not the first time this idea came up. In February of 1941 a proposal was made to use a 105 mm gun instead of an 88 mm gun with the ballistics of the Flak 18 AA gun. A second 88 mm gun appeared in April of 1941; in addition to the existing one there was an idea to make one with higher muzzle velocity. Finally, on May 26th the idea of an 88 mm L/71 gun was put forward. This gun was based on the 88 mm Flak 41. One issue was that the new gun would not fit into the turret of the VK 30.01(P), but Hitler still wanted a gun that could penetrate 100 mm of armour at 1.5 km. The proposal was made again and again until work officially began on a turret that could fit this gun. The turret was compatible with two tanks, the VK 45.01(H) and VK 45.01(P), although in practice neither Krupp nor other subcontractors put much effort into development.

An 88 mm Flak 41 gun. This was the priority candidate for tank gun development as of the spring of 1941.

Things started moving towards the end of November of 1941 when the Tank Commission visited Mtsensk and inspected T-34 and KV-1 tanks. This trip had a significant impact on the whole German tank development program, although at first the changes were only made to medium tank development. Work on 30 ton medium tanks began in December of 1941. As for the heavy tanks, the VK 45.01 program was not touched, as it would threaten successful completion. Only two bidders reacted to the changing requirements: Porsche K.G., responsible for the chassis, and Krupp, responsible for the turret. Krupp was also working on the VK 70.01 project, which was reworked after Soviet tanks were inspected.

The situation began to clear up on January 30th, 1942. A large meeting was held between Porsche and representatives of the Ordnance Directorate, including the head of the 6th Department Sebastian Fichtner and Heinrich Kniepkamp. Krupp representatives including Heinrich Muller, the chief designer, were also present. The meeting established that starting with the 101st VK 45.01(P) the hull would be changed to have a front plate sloped at 60 degrees. On February 4th, 1942, this variant was named VK 45.01(P2). This index didn't last for long, and by the end of March the tank was called VK 45.02(P). The names were changed multiple times. Internally, Porsche called the tank Typ 101 verstärkt (Type 100 strengthened), but on March 23rd the name was changed to Typ 180.

Typ 180 or VK 45.02(P) as of October 1942.

The name change and decision to change the upper front plate were relatively minor in the long scheme of things. The design evolved into a vehicle that had little to do with the VK 45.01(P). This included the overall design of the hull. Similar processes happened to many German tanks developed during the war. This was largely due to the influence of the 6th Department in general and Kniepkamp in particular. Work on the VK 30.01/VK 30.02 was actively moving forward in early 1942. Since this vehicle (the VK 30.02(M) was developed under Kniepkamp's patronage), its hull was taken as the foundation. Work on the VK 30.02(M) also affected the VK 70.01 in the spring of 1942. It's no wonder that initially both tanks had very Panther-like observation ports and machine gun mounts. The overall layout of the engine compartment was the same as on the VK 45.01(P).

Two 310 hp 15 L air cooled Typ 101 diesel engines powered two Siemens-Schuckertwerke aGV 275/24 generators. As with the VK 45.01(P), elements of the electromechanical transmission were located in the rear of the tank. Initially, the running gear was likely the same as on the VK 45.01. According to calculations the top speed of the tank was 35 kph.

The variant with an electromechanical transmission had the highest priority.

The situation around the turret was more interesting. Until the VK 45.02, German tank turrets were developed following the same processes: a square design with nearly no bustle. The VK 30.02(M) didn't have one either, as it was based on a Rheinmetall design made back in 1941. As for the VK 45.02, work began in early 1942 and followed the example set by the T-34. The resemblance is clear: a large turret bustle with a hatch to remove the gun, characteristic shape of the side plates and curve of the front. Krupp also applied the T-34 concept to its superheavy tanks, including the final Lowe and first drafts of the Typ 205. Even the final turret of the Maus had something from the T-34 in it. This concept solved two issues: fitting a large gun and making space for a ready rack in the turret bustle.

Porsche Typ 101/4 engines coupled to generators. This engine was the primary choice for the VK 45.02(P) and also its downfall.

The link to superheavy tanks was no coincidence. This applies not just to the turret, but also elements of the hull. Krupp was responsible for producing the hull of the VK 45.02(P), and so the production process was the same as on the Lowe, including its unusual front armour. Unlike the VK 30.02(M), the front was made from one 80 mm thick plate bent into shape, similar to the very first T-34s. This was not a very rational solution, but not so strange considering that the sides of the turret (110 mm thick) were also bent into shape.

An alternative variant, the Voith hydromechanical transmission. It was used on the Typ 181 variant.

The Typ 180 chassis did not keep its initial form for long. The first change was made on April 20th, 1942. Hitler ordered the thickness of the roof armour of the VK 45.02(P) to be increased to 40 mm during an inspection of the VK 45.01 prototypes. An order was also given to install special deflectors on the upper part of the hull front and bottom part of the turret to reduce the possibility of shells striking the turret ring. More improvements followed, which naturally increased the tank's mass. The 45 ton weight class was just a suggestion, as the mass of the VK 45.01(P) was estimated at 52.5 tons in the spring of 1942, and its successor was no doubt going to be heavier. Another option also turned up in addition to the electromechanical transmission.

The Typ 102, a Typ 101 with a Voith hydromechanical transmission, appeared in March of 1942. Its mass would have been lower. Half of VK 45.01(P) tanks were supposed to be built in this form. This transmission was also considered for installation into the VK 45.02(P). Porsche K.G. indexed this variant Typ 181. No blueprints of this tank survive to this day, but we can assume what it looked like based on the layout of the Typ 102.

A late variant of the suspension bogey that will later be used on the Jagdtiger with the Porsche suspension.

Work on the VK 45.02(P) and its turret did not just take place on paper. Contract SS-210-5806/41 for 100 hulls and 100 turrets was signed with Krupp on February 4th, 1942. As with the VK 45.01(P), assembly would be done at Nibelungenwerk. The first 8 hulls were expected in August of 1942 and then 15 hulls monthly starting in September. Deliveries of turrets would begin in November and 15 per month would be produced starting in December. The contract then expanded to 200 tanks with serial numbers 150101-150300. The first 100 VK 45.01(P) tanks had a direct impact on its ancestor. The Typ 101 engines had a ton of problems, including overheating. The tank also turned out to be much heavier than anticipated. The tracks had to be widened. Meanwhile, the VK 45.02(P) was going to be even heavier due to its larger turret and more powerful gun. Work on the Typ 180 and Typ 181 slowed down significantly.

An observation port replaced the driver's observation slit in the fall of 1942.

Porsche K.G. understood that the situation with the motor was far from ideal, and alternatives were proposed in the fall of 1942. The Typ 180 received Typ 101/4 engines, and the Typ 181 had three whole options for engines. The Typ 181A had the same Typ 101/4 engine, the Typ 181B had a pair of 370 hp 16 cylinder 19.8 L Porsche-Deutz Typ 180/1 engines. Finally, the third variant, the Typ 181C, had a 16 cylinder 37 L 700 hp Porsche Typ 180/2. This engine later evolved into the Porsche Typ 203 or Simmering-Graz-Pauker Sla 16. The tracks of the Typ 181 were also widened to 700 mm. The suspension was also likely changed around this time, as it was now somewhat different from the Typ 101. The overall layout with the parallel shortened torsion bar bogey suspension remained. In the fall of 1942 these were only desperate attempts to rescue the tank. 

Simmering-Graz-Pauker Sla 16, further development of the Porsche Typ 180/2 engine that was supposed to be used on the Typ 181B.

The Typ 180 projects that are well known today are dated October-November 1942. In early October the driver's station was reworked. The observation hatch was removed and a small periscopic observation device was added. It was still a weak point in the front armour, but there was no other option. The layout of the VK 45.02(P) with its forward turret and massive turret ring deflector did not allow for a periscope on the driver's compartment roof. An alternative to the VK 45.02(P) turned up around this time. Like the superheavy Typ 205, it had a rear fighting compartment. This layout offered many benefits. The overhang of the enormous gun was greatly reduced. The load on the chassis was more even. The driver's compartment hatches could now be placed on the roof, and instead of a "fish eye" for the driver he could get a proper periscope. There were also drawbacks, chiefly linked to firing backwards.

Typ 180 with a rear fighting compartment. The observation port vanished from the front of the hull, but the plate is still bent into shape.

Work on the VK 45.02(P) ended on November 3rd, 1942. There were many reasons for this, both political and technical. Porsche K.G.'s engines were rather unrefined, and Henschel's entry in the VK 45.02 program had a higher priority. As for the experimental VK 45.02(P) prototypes, correspondence with the 6th Department reveals that they were built. At the very least, there is information that Nibelungenwerk built three VK 45.02 (P) (Tiger 2) chassis. Nevertheless, this project had some consequences. For starters, Porsche K.G.'s prototypes now had the Voith transmission as their primary option. The VK 45.02(P) running gear was built in metal and a small series of vehicles was even built with it. As mentioned above, the Porsche Typ 180/2 engine also evolved into a design that was eventually built in metal. The situation with the VK 45.01(P) repeated itself. The tank may have been a failure, but the turret was much better, even though it went into production in a different tank.

A victim of unification

While Porsche K.G. and Krupp worked jointly on the VK 45.02(P), Henschel had a different approach. They didn't have time for another prospective heavy tank, as there were already three of them. In addition to the VK 30.01(H) which was moving towards a predictable finale and VK 36.01 that was still in limbo, they had the VK 45.01(H) to worry about. This tank was high in priority and took up the company's resources. It's surprising that until March of 1942 Henschel had no connection with the VK 45.02 program.

As strange as it sounds, the VK 45.02(H) looked like this in draft blueprint W 1461.

The call to adapt the VK 45.01(H) for a new turret sounded on March 5th, 1942. This meant that the VK 45.01(H) would use a turret developed for the VK 45.02(P) by Krupp. Like the VK 45.02(P), the turret would be installed after the 100th production vehicle. Initially, this only took the form of installing the new turret on the old chassis. Schematic W 1461 showing this layout survived to this day. This minimal plan did not survive for long. It was clear that the hull of the VK 45.01(H) needs to be improved at least by sloping the front armour. A new project began on April 16th, 1942, reusing the components of the VK 45.01(H). The 6th Department indexed this tank VK 45.02(H).

Both VK 45.02 tanks had the same turret. Interestingly enough, the blueprint is marked as belonging to the Tiger H3.

Initially, the VK 45.02(H) concept did not differ too much from the VK 45.02(P). The VK 45.01(H) chassis would undergo minimal changes to the engine, transmission, and running gear. This made the job simpler and accelerated putting the tank into production. The biggest changes affected the hull which was redone like the VK 45.02(P) and VK 70.01. Like with these tanks, the VK 30.02(M) was the object of imitation. The upper and lower front plates were sloped, and openings were added in the upper plate for a machine gun and the driver's observation port. Initially the machine gun was fired from a port like on the early Panther tanks. Drawings of the first variant didn't survived to this day, much like the VK 45.02(P). Significant changes were introduced in the summer of 1942.

An early variant of the VK 45.03 hull with a driver's observation port. The upper front plate is still 100 mm thick.

The 6th Department began considering unification of the new heavy tank and the VK 30.02(M) that was already being referred to as the Panther in August of 1942. According to the initial plans dated August 19th, 1942, the 201st production tank (or 101st production VK 45.02(H)) would have a Maybach HL 230 P30, the same as on the Panther. The cooling system was also taken from the medium tank. This required changes to the hull. The project was named Tiger II in September of 1942, but the index VK 45.02(H) was still in use. This transformation also led to more ideas about further development of the tank, and on October 12th, 1942, another tank was born: the VK 45.03 or Tiger III. This was not a brand new tank and merely intended as the final variant of the production VK 45.02(H). The Tank Commission vetoed the idea. Another transitional tank was just too much, so only the VK 45.03 survived.

The VK 45.03 hull as of November 1942. The front hull armour was increased to 150 mm.

The potential replacement for the VK 45.01(H) was vastly different compared to its predecessor by the fall of 1942. The mass kept increasing and there was no longer a possibility of using the VK 45.01(H) chassis with the new hull. All that was left was the road wheels (and even those were simplified) and the Maybach OLVAR OG 40 12 16 gearbox as one option. Other variants were considered, including the 7-speed mechanical ZF-Alklauen AK 7-200, 3-speed hydraulic gearbox from AEG, and a 10-speed electromechanical gearbox.

The concept of a center fighting compartment was retained, and the hull had to be lengthened, now surpassing 7 meters. The hull looked similar to that of the Panther, but the sides were made from one piece and there was a slope in the lower section like on the VK 45.01(H). This idea was later used on the Panther II, from where it migrated to the Jagdpanther and Panther Ausf.G. As the mass kept increasing, 9 groups of road wheels were used per side. These were no longer pairs: each suspension arm now carried a bogie with 4 wheels on it instead of 2. The wheels were under constant scrutiny from the 6th Department of the Ordnance Directorate. According to Kniepkamp, these wheels would not allow the tank to reach a speed higher than 25 kph. A new wheel with steel rims and internal rubber lining had to be developed. The track links also changed. Their thickness expanded to 760 mm by October of 1942 and the design was more reminiscent of the Panther.

A truly mad layout with four doubled up wheels.

The armour of the VK 45.03 was close to that of the VK 45.01(H) in the fall of 1942. The hull was 100 mm thick in the front, but sloped. This armour was potentially impenetrable even for its own gun at medium ranges. The sides were still 80 mm thick, but the upper sides were sloped. This was adequate protection not just for 1942, but for 1943. However, another armour boosting event took place in the fall of 1942. The Panther's armour was thickened, which led to an overloaded chassis. The same thing affected the VK 45.03 in December of 1942. Officially the thickening took place on January 3rd, 1943, but blueprints with a 150 mm thick upper front plate were ready by January 1st.

An alternative observation device for the driver, similar to the one used on the Typ 180.

In this situation the driver's observation port was a clear weak spot in the upper front plate. A periscopic device like the one developed in 1942 for the VK 45.02(P) was one potential solution. Changes to improve the tank's armour continued. The idea of unifying medium and heavy tanks came up once again, leading to the Panther II project that was in turn more similar to the Tiger III. The final decision regarding unification was made on February 10th, 1943. The transmission, engine, cooling system, and parts of the running gear were the same. The tracks were widened to 800 mm, and the 640 mm wide transport tracks were to be used on the Panther II. The unification did not continue for long, as the Panther II was cancelled in May of 1943. Even so, a portion of ideas such as the road wheels with steel rims remained on the heavy tank. It changed its name several times in this period. In March of 1943 it once again became Tiger II, and gained its final name on June 2nd, 1943: Pz.Kpfw. Tiger Ausf.B.

The first Pz.Kpfw. Tiger Ausf.B, the final stage of evolution for the VK 45.02. This was the heaviest mass produced tank used in WWII, whose mass was a significant drawback.

The results of the epic tale with multiple redesigns was mixed. The final variant was way too heavy, 68 tons, especially considering that the chassis was designed for a lower mass. This constant stream of changes also cost a lot of time. Of course, no one waited until it was approved, and the replacement didn't take place on the 101st or 201st tanks. Henschel continued to produce the Pz.Kpfw. Tiger Ausf.E, which managed to be a dangerous enemy in the right place at the right time without sloped armour. The first Tiger B was only built in October of 1943, and mass production began in January of 1944. Delays in the chassis did not mean that the contract for turrets was cancelled, and so the first 47 tanks with 150 mm thick upper front plates received turrets with thinner front armour. The new simplified and better protected turret was installed only starting with June of 1944.

Original article by Yuri Pasholok.

5 comments:

  1. The new simplified and better protected turret was installed only starting with June of 1944.

    But it apparently didn't take long for these to reach the front, as the Tiger IIs captured by the Soviets at Sandomierz were of the 185 mm thick flat turret front.

    In fact, any idea which units received the original 100 mm cast turret? I don't recall seeing any photos of these by either Soviet or Allies.

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    1. I can't recall seeing any in Soviet photos, but there were definitely some in Normandy, like the tank captured in Plessis.

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  2. Actually, the tiger 2 was not the heaviest mass produced tank of WW2. The actual heaviest mass produced tank of WW2 was the Jagdtiger. Weighing at over 80 tons and armed with a 128mm Pak 44 naval gun, this tank destroyer could penetrate any allied tank of the war. Unfortunately for the germans, most of the Jagdtigers in their arsenal suffered from their own problem and failed to even set their tracks on the battlefield except for a battle between shermans and two Jagdtigers where the Jagdtigers managed to knowck out 11 shermans in total and then eventually had to be destroyed due to the shermans and allied infantry overpowering the positions the Jagdtigers held.

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  3. I am afraid you are mistaken about the real tank that was the most heaviest mass produced. It was in fact, the Jagdtiger heavy tank destroyer. It weighed over 80 tons which was more than the tiger 2. More than 70 or 80 of these vehicles were made which is why most people do not consider it to be mass produced.

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  4. The actual heaviest mass produced tank of the war was the Jagdtiger. It weighed over 80 tons and the numbers it was built in was more than 70 or 80 vehicles. This is why most people do not consider it to be mass produced.

    ReplyDelete