Saturday 16 June 2018

Porsche's Leopard

Rumours and fabrications surround the history of tanks developed by Porsche K.G. Many of them were caused by incorrect information that appeared in reports made by American and British militaries right after the war. Later, they were supplemented by rumours and spread by not particularly thorough authors. Among others, this is the case with the history of the VK 30.01(P), the first tank independently designed by Ferdinand Porsche's team. This article will attempt to trace its history based on credible sources and archive documents.

An alternative from Stuttgart

Before we begin the tale of Porsche K.G.'s first tank, let us briefly cover the history of Ferdinand Porsche and his company. Many publications dedicated to German tanks created a general confusion regarding what Porsche K.G. actually did and what its production abilities were. Some readers imagine a massive organization that built tanks and turrets. It is easy to imagine that a tank called "Tiger Porsche" was built at Porsche.

In reality, Dr. Ing. h. c. F. Porsche GmbH, formed on April 25th, 1931, could not build tanks no matter how much they wanted it. This was an engineering company, which dealt in the development of automobiles and automotive components. The modern Porsche AG also actively works on designs for other companies.

Otto Zadnik's patent for an electric transmission. Later, his designs served as the foundation for electric transmissions designed at Porsche K.G.

The company's involvement in the tank industry was no accident. Ferdinand Porsche started working on tanks in the mid-20s, while he worked at Daimler-Benz. As of 1926, together with engineer Rudoph Mertz, he directed the development of the Grosstraktor medium tank, which was tested at the Osoaviakhim "Technical Courses" proving grounds at Kazan (TEKO). Another one of Porsche's designs was tested here, the four-axle Daimler-Benz Achtradwagen (Mtw 1). Despite the fact that Porsche worked alone since 1931, he maintained a warm relationship with Daimler-Benz. It is while working at Daimler-Benz that he received the nickname "professor".

Porsche was far from the only designer at Porsche K.G. The company was composed of a collective of talented engineers and designers. One of them was Karl Rabe, Porsche's right hand. It was he who pioneered the use of torsion bar suspensions of tanks. He designed it in 1933, and such a suspension was first used on the Landsverk L-60 Swedish light tank. This suspension was later used first on the La.S.138 (PzII Ausf. D/E) and then the Z.W.38 (PzIII Ausf. E). It was because of Porsche K.G.'s engineers that the troubles with the PzIII's suspension finally came to an end.

Another notable character working at Porsche's firm was Otto Zadnik. He worked on electric transmissions. However, he was not a pioneer here. The first use of an electric transmission in tanks was on the French Saint-Chamond tank in 1917.

The first sketch of the Porsche Typ 100 tank, dated December 9th, 1939.

Before we tell the tale of the VK 30.01 (P), let us shed some light on the organization known as the Panzerkomission (Tank Commission). This organization was created at the behest of Hitler and Todt, the minister of armament and ammunition. It was headed by Porsche, with Oskar Hacker, the head of the Steyr company, as his deputy. This was the formation of the so called "Austrian group". In addition to the Austrian ancestry of a lot of the commission's members, many of them formerly worked for Austro-Daimler. The Panzerkomission had its own manufacturing base, the Nibelungenwerk factory built by Steyr after the Anschluss. This factory built a number of German tanks. Several German manufacturing giants, including Krupp and Steyr, were also in this circle.

The point of the Tank Commission was the creation of a tank development group that was independent of the Armament Directorate. Creating a competitor for the 6th Department made sense. Some of the programs led by Heinrich Kniepkamp either idled or resulted in completely different results than requested by the military. Recall the Z.W., which only Porsche K.G.'s engineer managed to push through to completion. However, independent design was only one of the commission's tasks. It was also used in the analysis of the designs made by the 6th Department and actively offered consulting services in the field of development of armoured vehicles.

A competitor for the VK 30.01 (H)

Initially, the commission dealt with external developments. A task to design its own tank was only given in early December of 1939. In part, the program, titled Typ 100 or Sonderfahrzeug I (special vehicle 1) appeared due to the slipping of the D.W. heavy tank program. The continuation of this project received the index VK 30.01, and the chassis, developed jointly by Henschel and Kniepkamp, was in constantly flux. German brass understood that delays in work on a 30 ton heavy tank could have negative consequences.

The 88 mm KwK 36 L/56 tank gun, which forced the initial Typ 100 project to change.

On December 5th, 1939, Porsche K.G. began work on a new tank. Karl Rabe headed the development. His goals were very vague. The mass of the vehicle was to be 25-30 tons, with either a 75 or 105 mm gun. The mention of a 105 mm gun indicates that the customer was worried about yet another of Henschel's projects, the A.W. (Artilleriewagen), which later evolved into the VK 36.01 (H).

Franz Xaver Reimspiess, another former Austro-Daimler employee, who worked on the Mtw. 1 armoured car along with Porsche in 1929, worked on the initial concept of the tank. He became a key figure in Porsche K.G.'s tank design wing. Like other engineers, Reimspiess was a jack of all trades. Primarily, he was an engine man, but his portfolio contains work on suspensions, including torsion bars. Reimspiess' 30-ton tank design became the starting point for the future Typ 100. According to calculations, the length of the hull was about 8 meters, the length of the contact surface was 4.5 meters, the overall width was 3 meters, and the tracks were 0.5 meters wide. Overall, the tank was designed with the VK 30.01 (H) in mind, which can be seen in its armour and mass.

Blueprint K4432 dated March 5th, 1941, which shows an 8.8 cm KwK 36 L/56 in the turret of the Typ 100. This is the first version of the turret with a 1900 mm turret ring. A different design was built in metal.

Design work on the Sonderfahrzeug I continued for the first half of 1940. In that time, Reimspiess and other Porsche K.G. engineers finalized the overall concept of the new tank. In July of 1940, Hitler ordered that designs of new tanks were to be mothballed. In August, Walter Roland came to lead the Tank Commission, who had a different set of priorities in mind: increasing the volume of production. Roland represented the steel lobby, as the head of the Deutsche Edelstahlwerke Krefeld (DEW) company. While Porsche and other members of the "Austrian group" remained as members of the commission, the Typ 100 was forgotten for half a year.

Porsche regained his place at the head of the Tank Commission on June 21st, 1941. The Sonderfahrzeug I was remembered in early 1941. The VK 30.01 (H) program yielded no results, and Kniepkamp began his trademark juggling of transmission elements. It also turned out that the armament of the VK 30.01 (H) was too weak to deal with enemy tanks. An alternative was found quickly: the 88 mm Flak 18 AA gun. However, the VK 30.01 could not fit such a gun, and the chassis was ill-suited for it. Porsche's design finally came up.

Another reason for increasing the armament of the German tank, according to some sources, was the behaviour of the Soviet delegation in Germany in the summer of 1940. Soviet delegates expressed doubt that the PzIV was the heaviest tank produced in Germany, and requested that the Germans show them real heavy tanks. This demand made the Germans suspicious that the USSR was developing new heavy and medium tanks. Even though the Germans had no precise information, it was better to play it safe due to the approaching invasion of the USSR.

This is what the turret looked like in May of 1941, when a wooden model was constructed. The turret ring diameter shrunk to 1800 mm, and the sides were no longer symmetrical.

Work on the Typ 100 renewed in February of 1941, but the tank changed radically. The new gun required a new turret, one with an impressive turret ring diameter for the time: 1900 mm. There were even more ambitious plans of installing a 105 mm L/52 gun, like on the Pz.Sfl.IVa. Taking the drafts made by Krupp, Porsche K.G. prepared a reworked variant of the Typ 100 by March 5th. The hull of the tank became much shorter (6.3 meters), but widened around the turret ring to fit the necessary diameter.

The thickness of the front armour of the turret was 80 mm, and the sides were 60 mm thick. As for the hull, the precise thicknesses are not known, but based on the minutes of a meeting recorded on May 26th, 1941, the sides were 60 mm thick. Likely, the front of the hull was 80 mm thick, enough to protect the tank from the 50 mm Pak 38 from the front. Based on calculations, this tank's weight surpassed not only 30, but 45 tons. This was a heavy tank in every sense of the word.

An illustration of the new type of suspension. Later, this design was used on other Porsche K.G. tanks.

The powerful gun was not the only defining characteristic of Porsche's new tank. The vehicle, named VK 30.01 (P) starting with March 6th, was radically different from tanks designed under the supervision of the 6th Department of the Armaments Directorate. For starters, Porsche's engineers rejected the idea of the torsion bar suspension that they themselves created. A new torsion bar suspension was designed, with its elastic elements moved out of the hull. The result was a mix of a traditional bogey and a torsion bar suspension. Like on the B.W., the wheels were paired up. A shortened torsion bar was used as an elastic element. This design made the hull simpler, since there was no need to introduce multiple openings for torsion bars. If the tank was knocked out by a mine, all one had to do was swap out the bogey.

The diameter of the road wheels, 700 mm, was also more optimal. These road wheels were a lot less prone to shedding their rubber rims at high speeds, a defect which the Z.W.38 suffered from.

The VK 30.01 (P) track link, identical to the one used by the first VK 45.01 (P).

The biggest distinguishing feature of the VK 30.01 (P) was the transmission. For starters, instead of one liquid cooled gasoline engine, the Typ 100 was powered by two air cooled gasoline engines. Together, the two V-10 type motors produced 420 hp. Porsche considered diesel engines. However, he was not the only one to think about using diesels on tanks in Germany. MAN and Daimler-Benz were also working on such projects.

The electric transmission designed by Otto Zadnik together with Siemens was much more original. The engines were grouped together with generators that supplied power to electric motors at the front of the hull. The drive sprockets were also positioned in the front. The track links were left over from the initial Sonderfahrzeug I, still 500 mm wide.

Intermediate result

The reworked Typ 100 became the starting point for further work. On March 6th, the Armament Directorate ordered three hulls. Krupp was tasked with their production. The plan was to complete work 7 months after receiving blueprints. The development of the project documentation was the exclusive responsibility of Porsche K.G. This arrangement did not frighten its staff, since creating end-to-end projects was their speciality. The project was financed by the 6th Department.

Experimental VK 30.01 (P) on trials, late 1941.

One important question that had not been answered yet was the choice of armament. Krupp was responsible for the gun and turret. On March 13th, during the discussion of armament, another index was used in regards to the Porsche tank: Pz.Kpfw.VI (Porsche). As of April 2nd, three guns were considered as potential weapons for the tank: one 105 mm and two 88 mm, differing in muzzle velocity. The choice of the 8.8 cm KwK 36 L/56 was finally made on April 4th.

A contract with Krupp for 6 turrets with armament and other equipment was signed on the same day. Each turret cost 110,000 Reichsmarks. A full scale wooden model was also built at the cost of 5000 Reichsmarks. Finally, three hulls were ordered, costing 75,000 Reichsmarks apiece. The turret changed slightly by early May. The step on the roof was deleted and the sides became asymmetric. The gun mantlet also changed. The wooden model was built to reflect this.

Trials of this tank helped Porsche's team with the design of the VK 45.01 (P).

Krupp was not the only party interested in receiving a contract. Steyr made the most profits. In addition to engines, the Austrian company was tasked with assembling the VK 30.01 (P). Assembly was performed at Nibelungenwerk. Siemens-Schuckertwerke received the contract for electrical equipment. Finally, Skodawerke was responsible for the running gear. The appearance of Skoda in this list should be no surprise. The Czech company came under the jurisdiction of the SS after Wilhelm Foss was put in charge. Porsche was a member of the SS and the NSDAP since 1937. Nazi party membership opened many doors in Germany.

Passing through a forest road.

Krupp received an order from Nibelungenwerk on May 13th. It clarified the number of items needed: 6 turrets, 3 hulls, and a full sized model of a hull and a turret. The turret model was ready on May 20th, after which it was delivered to Nibelungenwerk, not without trouble. Later, the model hull arrived as well. The plan was to complete the first turret in November of 1941. Hulls would be delivered from November 1941 to January 1942 at a rate of one per month. As for engines, the first was assembled by Steyr on July 7th and trialled on the 14th. The second engine was ready on July 30th. After trials, the engines were also sent to Nibelungenwerk.

The tank drove confidently off-road. The issue was that the requirements for protection increased in the early summer, which resulted in increased mass. In its current state the VK 30.01 (P) chassis was not needed.

Issues began cropping up starting with May 26th, 1941. On this day, Hitler demanded that the front armour of the tank be increased to 100 mm. The armament was also to be improved to penetrate 100 mm of armour at 1.5 km. The gradual increase of appetites eventually led to the creation of the tank known as the VK 45.01 (P). This was the Porsche tank referred to as "Tiger", which first happened on August 7th, 1941. This scenario had no room for the VK 30.01 (P). In July of 1941, the contract for the pilot batch changed. instead of three hulls, only one was built, and from mild steel at that.

Porsche personally participated in the testing of his tanks. His trademark hat can be seen in many photographs. The man in the beret is Otto Zadnik, the man behind the electric transmission.

The precise date of the production of the only prototype of the VK 30.01 (P) is not known. Thomas Jentz and Hillary Doyle, famous German tank historians, estimate that it happened somewhere in October of 1941. The tank was not cancelled entirely, as it was very valuable for Porsche K.G. This was the first tank designed entirely by Porsche's team, and its chassis was a perfect test platform. A large volume of useful information was extracted from its trials that later came in handy when designing the VK 45.01 (P). The turret was never installed on the chassis, only a dummy weight was used.

Pz.Kpfw. Leopard during the trials of the VK 45.01 (P), summer of 1942.

Trials of the VK 30.01 (P) began in late 1941 and continued until the summer of 1942. It was also used to escort the much more successful VK 45.01 (P) during its trials. By the spring of 1942, Porsche's first tank received the designation "Pz.Kpfw. Leopard". This was little more than a formality. The tank stopped being interesting to its customer nearly a year prior. A much better protected tank with a much more complicated fate came to replace it.


  1. As a tank transmission fanatic I can see the appeal of a electric drive. The ability to perfectly regulate the speed of each track as opposed to jerky/clunky turns from many transmissions. Indeed had Germany built a turretless 40 ton Porsche design with the early 88mm gun, I suspect it would of made a good tank destroyer. Not to mention they could of gotten a small number to the front quickly. At least those engines would not of burned out like those of the 70 ton Elefant did when used at Kursk.

    1. ...and then you run into the problem that all that electrical gear A) weighs quite a bit B) eats up a lot of copper which was a strategic resource outright indispensable for a great many other things (mostly electricity-related).
      Tanks, by comparison, work fine without so cue the chopping block.

      Porsche's persistent fascination with the petrol-electric drive really did his sales no favours under wartime shortage conditions.

    2. I very much agree with you about the limitations of electric drive being strategic resources. Hence the reason I felt they should of just hobbled together the 10 to 15 hulls they had laying around and strap a simple forward firing 56 cal. 88mm on them and sent them to the front. I'm sure the Wehrmacht could find some stagnant part of the line with large open fields where this this SP Gun would do fine. PS your point is also valid when people insist that it would be easy to replace all our cars and trucks with electric power. I've been in copper and rare Earth mines and believe me, most environmentalist would not be happy if we dig a lot more of those huge holes.

    3. Yeah, the Ferdinand took 2 tons of copper to make the electrics, I doubt this tank would use significantly less. Definitely not feasible economically for Germany.

    4. Another detail that made the system less than sensible in applications that don't seriously need it (think trains and large ships for the more worthwhile uses) is certain degree of sheer inefficiency due to conversion losses. You're first converting mechanical energy into electricity and then that electricity back again into mechanical energy - according to Wikipedia that's ballpark 19% net loss (10% at each step so 0.9 x 0.9) with today's technology and I'm going to go out on a limb and guess Forties generators and traction motors weren't nearly as efficient...

    5. As I said I agree with the wastefulness of all electric drive. The flip side was Hitler was demanding more and more huge tanks and any tank over 40 tons with a conventional clutch and brake system caused excessive heat and wear on the front brakes, which required frequent changing. I did this only once and it took us all morning. The British Merritt-Brown type was regenerative and eliminated the brake problem. But the transmission broke down, often. So the German's were doomed no matter what type of transmission they put on their 50 plus ton tanks. The solution was not to build super heavy tanks.

  2. It's very interesting to see that large diagram of the horseshoe-shaped VK3001 turret. It has obvious similarities to the VK4501 Tiger (P) turret that was designed later.
    I have very detailed knowledge of the Tiger E turret's structure so I analysed the diagram in that light. I found that the similarities are more than superficial; the Tiger (P) turret is actually a modification of this one, just as the Tiger (H) is in turn a modification of that.
    Some fundamental dimensions of this VK3001 turret carry over unchanged into the Tiger E turret !
    As a result, I can tell you the following;
    that VK3001 turret's side armour is 50mm.
    the external radius of the turret (the rear is circular) is 1130mm.
    the cupola's radius is 780mm

    David Byrden ...