E-50 and E-75: A Story of Failed Unification

Panther II, the first attempt to unify medium and heavy tanks.

The next attempt to create a universal tank platform was made five years later. In April of 1942, Henschel began working on the VK 45.02 (H) tank, also known as the Tiger II. During development, a decision was made to share components with the VK 30.02 (MAN) medium tank. In November of 1942, the VK 45.02 (H) turned into the VK 45.03 (H), which is also know as the Tiger III.

On February 17th, 1943, the minister of armament and ammunition Alber Speer approved the unification of the VK 45.03 (H) and the prospective Panther II tank. This time, the idea was not to build the tanks on one chassis, like with the B.W. and Z.W. The heavy tank would use a suspension with nine pairs of road wheels, the medium tank would use seven pairs. The Tiger III had a longer hull. The engine, transmission, cooling system, and road wheels would be the same.

Meanwhile, the Panther II was delayed, and the VK 45.03 (H) turned back into the VK 45.02 (H). It had nothing to do with the tank that was previously developed under that index. Finally, the VK 45.02 (H) was accepted into service as the Pz. Kpfw. Tiger Ausf. B. As for the Panther II, the project did not progress past a test chassis. The reason for this was that MAN was too busy producing the regular Panther. The decision to use the hull of this tank for the Jagdpanther tank destroyer also played a role.

In May of 1942, Kniepkamp started thinking about a new universal tank chassis. Unlike the Tiger III/Panther II, his idea was closer to what he did five years beforehand. Instead of unifying the parts, the heavy and medium tank would share a chassis. While the Tiger III/Panther II were still in development, this idea was not taken seriously. Nobody was going to work on an even more controversial project in parallel. Kniepkamp had to wait until the spring of 1943 when it became clear that the unification of the Tiger III and Panther II was going nowhere.

A curious series of events preceded the work on a unified chassis. As we know, the VK 45.02 (H) and VK 45.03 (H) were not the only projects for a new generation of German heavy tank. In early 1942, Porsche K.G. began working on a heavy tank that was indexed Typ 180 or VK 45.02 (P) in March. Like the Henschel competitor, the armour of this tank was sloped.

As for the technical "filling", Porsche was true to himself. Porsche's designers did not share Kniepkamp's love of a front transmission, gasoline engine, or torsion bar suspension. The elements of the Typ 180's suspension, just like its predecessors, were moved out of the hull, and the drive sprocket was in the rear. Porsche's tank had serious issues with the engine. Air cooled diesel engines never reached an acceptable state. The military was also suspicious of the electric transmission. As a result, the Typ 180 was never even built as a prototype, and the turret that was designed by Krupp for this tank was "inherited" by the first 50 Tiger B tanks.

The E-50's chassis. Given a mass limit of 50 tons, only 10 remained for the turret.

It would seem that Kniepkamp's concept won. The Panther and Tiger B were both built according to the traditional German concept, which dated its way back to the interbellum Carden-Loyd tractor. However, the E series program launched by Kniepkamp in April of 1943 (Entwicklung, "development") departed from this concept.

Aside from the air cooled engine and electric transmission, it would appear that the 6th Department's chief developer copied his competitor's ideas. The E series had external suspensions and any kind of spring elements aside from torsion bars. Another feature of the E series was a rear transmission. The only prospective tank that would have had a front transmission was the superheavy E-100, but that had an obvious reason. The E-100 was a reincarnation of the earlier Tiger-Maus project, which had a spring suspension.

Two variants of the E-75. The Adler version was deemed more promising.

There were several reasons for moving the transmission back. The Carden-Loyd layout became complicated to service at a certain point. One can only imagine the headache that German repairmen got when a Tiger's gearbox in the middle of a field. In order to extract it from the tank, one had to take out a good half of its internals. Considering how heavy the turret was, this was no easy task. The Panther and Tiger B had an easier time of it, since there was a removable roof section around the driver's compartment, but the job was still far from easy.

Compared to this, the removal of the gearbox on Soviet medium and heavy tanks was a piece of cake, especially on the T-34 and IS-2. Another advantage of Soviet tanks was that if a shell or mine destroyed the front idler, one could temporarily wrap the track around the front road wheel. The tank partially retained its mobility as a result. On German tanks, where the drive sprocket was in the front, this trick wouldn't work.

Like with Porsche's designs, the suspension of the E-50 and E-75 was outside the hull.

Aside from the E-100, the E series contained the light E-10 tank destroyer which would serve as a replacement for the Jagdpanzer 38(t), a medium E-25 tank destroyer (replacement for the Jagdpanzer IV) and a "unified chassis". The medium E-50 and heavy E-75 tanks would use this chassis.

Krupp and Henschel worked on the E-100, but the suspension was worked on by Adlerwerke. Engineers from Klöckner Humboldt Deutz AG, or Magirus, worked on the E-10. Argus Motoren Gesellschaft m.b.H. worked on the E-25.

As for the E-50 and E-75, this is a more difficult topic. Adlerwerke is often named as their developer, but that is not the case. As with the E-100, this company worked only on the suspension. Information on the "unified chassis" is incomplete, and largely the product of speculation and fantasy.

The Adler suspension used springs instead of torsion bars.

Another little known fact is that the E-50 and E-75 duet was not the only alternative for the Panther and Tiger B. In April of 1944, Vereinigte Apparatebau AG, Rheinmetall-Borsig AG's design bureau, proposed its own suspension. It was essentially a modernized version of Aleksei Surin's suspension, which was used on the AH-IV tankettes, light Praha TNH and LT vz. 38 tanks, as well as a number of other CKD vehicles.

The difference between the two suspensions was that now the paired road wheels were interleaved. The difference between the prospective running gear for the Panther and Tiger B was the distance between the bogeys.

A diagram of the kinematics of the prospective Adlerwerke suspension.

The idea of Adlerwerke's engineers, led by Karl Jenschke, was different. Their design was closed to the suspension that was designed by Porsche KG. The difference was that Porsche's designers used a torsion bar, and Adlerwerke used springs. Jenschke claimed that this suspension was tested at MAN and gave good results.

Prospective Panther suspension by Vereinigte Apparatebau AG

The wheels here were also interleaved. The question of how many wheels there were per bogey has no answer. Most sources copy the sketch made by Jenschke in the spring of 1945, after he was taken prisoner by the Americans. There, he drive single road wheels. However, this decision was suboptimal from the point of view of weight distribution, and Porsche and Vereinigte Apparatebau AG doubled up their road wheels. It's likely that the E-50 and E-75 also had double road wheels.

A new suspension for the Tiger II. There's minimal difference between this variant and the one on the Panther.

According to the concept, the E-50 and E-75 would have nearly identical hulls, distinct only in armour thickness. There are no concrete numbers about what this thickness would have been. The numbers in the names indicated the weight class of the tanks, and since the E-75 would be 1.5 times heavier, the number of bogeys increased to four per side.

The information received by the Americans said that the weight reserve of the E-75 chassis meant that SPGs in the 80 ton class could be built on its chassis. This information gives additional room for speculation. There's no shortage to the vehicles that were "designed' on this chassis, but we must disappoint the "designers": a reserve and its use are two different things. As for the SPG with a 149 mm L/52 gun that is brought up when this project is discussed, its real mention dates back to documents from 1941 and applies to a completely different project, the VK 70.01.

Maybach HL 295, one of the descendants of the E-50 and E-75's engine.

The parameters of the E-50 and E-75's engine are also known. The V-shaped 12 cylinder Maybah HL 234 would be used. It was based on the HL 230, but the HL 234 output 900 hp at 3000 RPM. In order to make the engine more reliable, it could have been lowered to 850 RPM. The HL 234 had a special feature in the form of direct fuel injection. A turbocharger could also be installed, raising the power output to 1000 hp. The Maybach HL 234 R engine could serve as an alternative, but there is no data on it.

The engine would have been connected to a hydraulic 8-speed gearbox with a preselector and a 2-radius turning mechanism. The name of this gearbox was mentioned in the report on the Maybach HL 234: OG 40 12 16 B. A special feature of the E-50 and E-75's transmission was that the gearbox, turning mechanism, and final drives would have been built as a single unit. This saved up to a ton of weight and shortened the time to build the tank by 25%. According to calculations, the top speed of the E-50 was 60 kph and the top speed of the E-75 of 40 kph.

While there is some data on the engine, suspension, and hull of the E-50 and E-75, there is no information about the armament. This let the imagination of fans of alternative history run wild. However, if we take into account what little information we have and the overall tendencies of German tank building from the time, it turns out that most of these fantasies have few roots in reality.

One of the long guns that are frequently "mated" with the E series.

For starters, we must disappoint the daydreamers who put the Schmalturm, or "narrow turret" on the E-50. It was initially designed for the Panther II, and its significantly altered version would have been installed on the Panther Ausf. F. Those who put the Tiger B turret atop the E-75 will also be disappointed. Neither turret was going to be used on the E-50 or E-75.

According to information obtained by American intelligence, Krupp was supposed to design a new turret for these tanks. Like the hull, the turret designs for the two tanks would have been identical, with the only difference being the armour thickness and the armament. There is no other information about the unified turret, only that it would have an electric turning mechanism.

The latest "long arm". As with the previous weapon, it was never built in metal.

Let us discuss the topic of guns separately. British intelligence, which received information in a highly distorted state, created the myth that the Germans were developing new super-long tank guns. A typical example of this was the mythical 7.5 cm KwK L/100. There is also mention of an 88 mm gun with a 100-caliber barrel. There are three news about these guns: one good one and two bad.

Let's start with the good one. Research in the Bundesarchiv revealed designs of guns with barrel lengths of up to 130 calibers. This is the end of good news. These guns are labelled as "Pak" in the blueprints, so they were anti-tank guns. The date when these guns were designed is also striking: early 1943, whereas the main activity around the E-50 and E-75 dates to late 1944. Krupp's engineers also designed a 105 mm gun with a 100-caliber barrel, but it was also not a tank gun. In other words, these "grosse Schlange" have nothing to do with the E series tanks.

Installation of the 88 mm KwK 43 L/71 gun into the Schmalturm turret. You can't tell from the diagram, but the factory blueprint shows that in this case, the commander would have to sit on top of the gun breech.

Even if we assume that the aforementioned turrets were installed on the E-50 and E-75, this brings few good news to German tankers. Krupp worked on the installation of the 88 mm KwK 43 L/71 in the Schmalturm turret in November of 1944. It fit, of course, but the turret didn't get any roomier. The turret ring diameter was only 1650, and the gun barely fit, according to the factory diagram. The commander must have sat directly on top of the gun breech. The issue of loading was not discussed. The longer barrel would also have needed a counterweight in the rear of the turret.

Overall, Krupp's design was similar to the work done by TsAKB, led by V.G. Grabin, who managed to shove the 100 mm LB-1 gun into a stock T-34-85 turret. The results were the same as with the Schmalturm and the KwK 43: you can fire it, technically, but the crew was uncomfortable. Considering that this invention didn't move further than paper, the opinion of the German and Soviet militaries about such experiments must have been the same.

Sketch of the Tiger II with a 105 mm KwK L/68 gun. In order to get it to work properly, the gun would have to have two piece ammunition and a second loader. The Germans deemed both of those things unacceptable.

The situation with new armament for the Tiger B was even stranger. In November of 1944, Krupp prepared a draft for installing the 105 mm KwK L/68. As with the new gun for the Panther, the gun fit, barely. However, the one piece round for the 105 mm gun refused to do the same. The only way of shoving it into the turret would be to introduce a two piece round. This worked, and 20 shells could be carried in the turret. The rate of fire dropped drastically. However, this could be solved by adding a second loader.

Having though about this, the 6th Department decided not to build this tank in metal. This prospective gun for prospective tanks could only work in alternative history and in computer games.

Many military history "experts" have the opinion that the Germans had high hopes for the E-50 and E-75. In reality, the Germans had better things to focus on than the E series in early 1945. The development of a unified chassis was in such early stages that it had no chance of mass production. According to the plans of German high command, the Pz.Kpfw. Tiger Ausf. B and Pz.Kpfw. Panther Ausf. G remained the main tanks of the Panzerwaffe. The Panther Ausf. F would have gone into production to replace the Ausf. G at some point in the future. In reality, the Germans were stuck in 1943, trying to polish up the same tanks, which were gradually overtaken by the enemy's designs.

Even if we imagine that the war in Europe lasted past May 9th, 1945, and that the E-50 and E-75 made it into the army, the Germans wouldn't have gained much, especially on the Eastern Front. In the best case scenario, they would have faced the T-44 and IS-3. If we include prospective Soviet tanks, the Germans' future turns grim. The first prototype of the T-54 tank, immune to the 8.8 cm Pak 43 from the front, entered trials in January of 1945. The decision to put either the IS-3 or the even more protected IS-4 into production was made in the spring of 1945. This isn't even including projects like the Object 257. 

One must note that Soviet tank designers made huge steps forward when it came to protecting their tanks without increasing mass. Their colleagues in Great Britain and the US were behind, but they were catching up quickly. One must recall that there was no shortage of funding in wartime, and new British and American tanks would have arrived much quicker had the war continued. In any case, the E-50 and E-75 were far from Wunderwaffe and would be, at best, no better than their opponents.

T-54 prototype, NIABT proving grounds, Kubinka, March 1945. Immunity to the Pak 43 from the front, a 100 mm D-10T gun, mass of 35.5 tons, and all of this was not just on paper.

More proof that the Germans designed themselves into a dead end comes from the history of the French AMX 45 medium tank. This tank, which later turned into the AMX M4, was a direct descendant of the E series. The French did not use its suspension, but the Maybach 295 engine was a relative of the HL 234. The dimensions of the hull were also similar. German engineers worked on the project. The result was a dead end. Even the engine power had to be decreased from 1000 to 850.

The Germans themselves went down a different road in the early 1950s. The new German medium tank project was much more humble than the massive E-50. The 30 ton tank had a torsion bar suspension, a crew of four, and very thin armour, even by late WWII standards. The concept behind the tank was closer to being a product of the American tank school than the German. Its dimensions were closer to that of the Soviet T-54 and T-10. The 37 ton Standardpanzer, better known as the Leopard 1, was built by the same companies that designed the German wanks of WWII.