Monday, 14 June 2021

Germany and the T-34

The Wehrmacht was stuck at Moscow in the winter of 1941, and leadership of the Reich had time to think while its troops developed frostbite. The first encounters with the T-34 and KV-1 tanks showed that Soviet engineers were much better at implementing thick shell-resistant armour and powerful tank engines. A whole commission arrived on the front on November 18th, 1941, to survey the situation. The commission included the head of the Tank Commission Ferdinand Porsche, his deputy and director of the Steyr company Oscar Hacker, head of Department #6 of the Ordnance Directorate colonel Sebastian Fichtner, the civilian head of Department #6 engineer Heinrich Kniepkamp, and high ranking representatives of leading arms companies: Krupp, Daimler-Benz, Henschel, MAN, and Rheinmetall. They examined Soviet tanks and evaluated the harsh conditions of winter and the lack of roads.

No one doubts that this examination had a significant effect on further development of the German tank school. But what were their conclusions? How did Soviet tanks influence German tank building? There are many different opinions about this, right down to calling the Panther a poor copy of the T-34. What was the real change to the German way of building tanks after the fall-winter of 1941?

German diesels and the V-2

The myth that Germany was in awe of the Soviet V-2 diesel engine but was not capable of creating either a copy or its own analogue was born way back in the Soviet era. This is why German tanks continued to use gasoline engines until the end of the war. This myth is based only on the fact that Germany used gasoline engines in their tanks and is not based on any research into German engine development.

The BMW VI engine was built in the USSR under the index M-17. It was not just used in aircraft, but also in tanks. The Germans were not thrilled with this engine.

There was a lot that Soviet specialists and historians didn't know about Nazi Germany. No one explored this topic seriously until Walter Spielberger, and his works were not published in the USSR. With a lack of concrete facts, one can handwave away any argument. Why were the Germans unable to create an analogue of the V-2? Because they used gasoline engines until the end of the war. Why did they use gasoline engines until the end of the war? Because they were unable to create an analogue of the V-2.

Let's consider some concrete facts. The Germans first considered building a 30 ton heavy tank with and a 600 hp engine for this new weight class in 1935. Old BMW VI aircraft engines were unsuitable for this. They gave maximum power output at low RPM (1400-1600) and high torque. This required the use of heavy and bulky transmissions. The Ordnance Directorate held a meeting with Maybach and Daimler-Benz in October of 1935. This meeting did a lot to set the direction of tank engine development until the end of the war.

At the time Daimler-Benz was working on the new DB 600 engine that put out 1000 hp at 2400 RPM. It was much more powerful than the BMW VI, but it had an inverted A-shaped layout. Servicing carburetors through a hatch in the floor of the hull was too much even for the Germans, and so the engineers proposed a V-shaped 600 hp engine offshoot. This idea remained on paper, since the Germans decided to go with Maybach tank engines.

Daimler-Benz did not give up and began working on even more powerful engines in 1936. Two A-shaped engines were designed for aircraft, the gasoline DB 603 and diesel DB 607. There were also V-shaped engines for use on tanks and motorboats developed on their basis: the gasoline MB 503 and diesel MB 507. The "junior" MB 507 42.3 L engine put out 850 hp at 2350 RPM, and the "senior" MB 507 44.5 L variant put out 1000 hp at 2400 RPM. In 1937 Department #6 of the Ordnance Directorate responsible for motorization of the Wehrmacht ordered the MB 503 and MB 507 for trials, which were successfully held in the spring of 1938. However, interest waned quickly. Perhaps Department #6 considered them to big and too powerful. 

The MB 507 diesel engine was proposed for use in tanks in the late 1930s but there was no interest in it.

As you can see, German engineers considered using powerful water cooled V-12 engines back in the 1930s. After examining the T-34 Daimler-Benz proposed the MB 503 and MB 507 once more, especially now that they proved themselves in the Karl Gerat SPGs. Tanks were getting heavier and heavier, and so the 44.5 L MB 507 was no longer that excessive. The Germans started working on a standardized lineup of air cooled diesel engines in the summer of 1942. This led to the development of the X-shaped 16 cylinder Sla 16 diesel engine. Even after examining the V-2 German engine development still went its own way.

Was the Daimler-Benz Panther a T-34 clone?

Some still hold the opinion that the Germans only decided to replace the Pz.Kpfw.III and Pz.Kpfw.IV after meeting Soviet tanks. In reality, work to replace these medium tanks began long before that. Initially the Pz.Kpfw.III was supposed to be replaced with the Z.W.38 variant, but the early Pz.Kpfw.III Ausf.E and Ausf.F were difficult to produce and unreliable due to the number of technical novelties the Department #6 insisted on. In October of 1938 Daimler-Benz was permitted to develop the VK 20.01 (D) medium tank as it saw fit.

Layout of the hull and turret of the VK 20.01 (D). Note the indentations in the sides to support the leaf spring suspension. The Pz.Kpfw.III Ausf.B/C/D had something like this too.

The new medium tank had wheels grouped into bogeys on a leaf spring suspension, like on the Pz.Kpfw.III Ausf.D. The 700 mm diameter road wheels overlapped one another. Instead of a Maybach engine Daimler-Benz used their own MB 809. Like the MB 507 there were several variants of this engine.

The "junior" 17.5 L variant was used, which gave 360 hp at 2400 RPM. It was lighter, more powerful, and more efficient than the gasoline HL 120. The MB 809 design was finished in June of 1940. The engine went through bench trials in February of 1941 and was installed in a tank a month later. The VK 20.01 (D), Germany's first tank with a diesel engine, was finished before the invasion of the USSR. By the end of the war the test chassis had travelled more than 6000 km.

A wooden model of the VK 30.01 (D).

MAN and Krupp also took part in the VK 20 program, but their designs were left on paper. This was due to constant changes in requirements that Daimler-Benz's competitors could not handwave away. The fate of 20 ton tanks was called into question in December of 1941, after the T-34 tanks were examined. Some called for scrapping the whole program and building 30 ton class tanks, which could surpass the characteristics of Soviet tanks. Others maintained that the nearly finished VK 20 should be put into production as soon as possible, especially since the 20 ton tank was supposed to be cheap and easy to produce.

As we know, the decision to switch to 30 ton medium tanks won. Daimler-Benz presented the VK 30.01 (D) tank, similar to the T-34 at first glance. The transmission was now in the rear, the hull and turret were sloped, and the tank was powered by a powerful diesel engine. Some call the VK 30.01 (D) a copy of the T-34, but is this a fair appraisal? 

Diagram of the VK 30.01 (D) suspension. It is not radically different from the VK 20.01 (D), just one extra wheel has been added.

Look closely at the Daimler-Benz Panther. Interleaved large diameter wheels are grouped into bogeys on a leaf spring suspension, the diesel engine is water cooled, there is an 8-speed gearbox. All of this was tested on the VK 20.01 (D) before the invasion of the USSR.

As for the transmission compartment, the VK 30.01 (D) is very different from either the MAN Panther or the Soviet T-34 and KV-1. Daimler-Benz developed an 8-speed shaftless gearbox where gears were engaged with multi-disk clutches. The layout was a mix between gearboxes used on the Pz.Kpfw.III Ausf.E and Tiger H1. The problem was that shaftless gearboxes are difficult to install perpendicularly, and so the gearbox was installed beside the engine. A similar layout was used on the Grosstraktor. It's unclear how one can accuse this solution of being a copy of the T-34.

The hull of the VK 20.02 designed by MAN after inspecting the T-34. Later it would be used as the starting point for the VK 30.02 (M) and VK 16.02.

The VK 30.01 (D) can be described as a further development of the ideas first used in the VK 20.01 (D) upgraded to the 30 ton class with significant influence from the T-34 and requirements set by Department #6. The MAN Panther has the same story: further development of the VK 20.02 with Soviet characteristics. The hull with sloped armour was first used on the VK 20.02 (M) and this was an original design. The T-34 had an effect on the Panther's development, but one should not overstate it.

Sloped armour

The reader can see that German tank engines developed in their own way even after inspection of the V-2, and the Daimler-Benz Panther was anything but a copy of a Soviet tank. However, the T-34's influence on protection is strangely underappreciated. A gearbox hidden inside the tank is one thing, but a hull and turret define the shape of the tank. However, let's not get ahead of ourselves.

The Germans no doubt knew about sloped armour even before inspecting the T-34. A number of hulls for armoured cars and halftracks with sloped armour were developed in the 1930s. One can use the Sd.Kfz.252 munitions carrier as an example. The 7,5-cm Selbstfarlafette L/40,8 tank destroyer project that began back in 1934 is another good example. The reverse slope of its hull plates makes it somewhat reminiscent of late Soviet heavy tanks.

The 7,5-cm Selbstfarlafette L/40,8 hull and turret speak for themselves.

However, German tanks of the era are described as "a box on a box". For a long time, the Germans saved on armour to minimize weight and retain high mobility. The tanks were only protected from bullets and shell splinters. There was no reason to experiment with geometry. It was easy for engineers to lay out their components and use the internal space of their tanks.

Early German tank hulls consisted of several parts: the tub (Wanne) and superstructure (Aufbau) as well as an engine deck superstructure. This made it easier to assemble the tank and also perform refurbishments. Let's take production of the Panzer III as an example. The suspension, engine, transmission, and other components were installed in the hull tub, and then the superstructure and turret were installed. This is much simpler than threading the transmission through the turret ring, and few changes are needed to make the tank into an SPG: just replace the superstructure with a casemate. This layout would not have worked with the T-34 since a vulnerable joint would land right in the upper sloped armour.

Assembly of the Pz.Kpfw.III Ausf.G at Daimler-Benz

The Germans gradually moved to whole hulls. The VK 30.01 (H) and VK 36.01 had the superstructure and tub in one piece, although the shape was still the same. They used observation devices and machine gun mounts already developed for armour sloped at a small angle. Only examination of the T-34 forced the Germans to reconsider this approach. It is unfair to say that the Germans didn't know about sloped armour and if they had known, they would have used it. There are many cases where a good implementation served as an inspiration. For instance, the USSR began assembling tank hulls with welding after examining German designs. Does this mean that no one in the USSR was capable of joining two pieces of metal together with an electrode? Of course not. Here we see a similar case.

The T-34 had a different influence on different companies. MAN built a hull with sloped armour for the VK 20.02, but used an original design. The Daimler-Benz Panther hull looked similar to the T-34's, but with a number of notable differences. Krupp, on the other hand, was influenced much more strongly. The early T-34 tanks had their front hulls made from one curved plate. This feature was quickly dropped, but Krupp was still interested. The front hull of the Tiger H1 consisted of four plates, the front hull of the Tiger P consisted of six. Producing the whole front hull from just one piece would be much simpler and would reduce the amount of welding to a minimum.

The Pz.Kpfw.Lowe from the front. Note that the entire front hull is made from one plate bent in two places.

Krupp already had experience with bent armour plates. The VK 30.01 (P) had a cylindrical turret where the sides and rear were made from one horseshoe shaped plate. It's not surprising that they decided to implement the idea they saw on the T-34. Ferdinand Porsche suggested remaking the hull of the Tiger P to use sloped armour in January of 1942. In response, Krupp prepared the VK 45.02 (P) hull with a single bent front hull plate positioned at 55 degrees. This solution was to be used after the 101st tank built, but since the Tiger P was cancelled it never happened. The superheavy Lowe tank had a similar change made, and its hull front was made from one bent plate.

The significant impact of the T-34 on the tanks designed at Krupp is largely ignored. To this day one can see drawings and models of the VK 45.02 (P) and Lowe tanks with separate upper and lower front plates joined by welding. In reality there was no welds on the blueprints. The front hull was made from one bent plate.

Turrets: before and after

The early T-34 influenced German tank building not only with the shape of its hull, but also the shape of the turret. This issue deserves a separate examination. The Germans approached building turrets in a fairly simple way for a long time. The turret ring was surrounded with armour from all sides, creating a square or round shape when seen from above with wide fronts.

An early T-34 tank. The front of the hull and front of the turret are made from single curved plates.

The T-34 turret was different. It had a narrow front, small gun mantlet, and turret bustle. These solutions were important for the Germans, who widely used different thicknesses of plates. It's obvious that the weight of a plate is proportional to its area, and so if the thickest armour plates can be made smaller then the tank can be made lighter. The thickest armour is usually in the front, and so the T-34's narrow turret front was an interesting solution. The turret bustle was also important. It could be used to balance the tank's gun, which became increasingly heavier and more powerful, and also offered a good place to put a ready rack.

Having examined the early T-34 Krupp engineers had a small epiphany and radically reevaluated their turrets. As a result, the turret of the VK 45.02 (P) combined the best Soviet and German ideas: sloped armour, a narrow curved front, compact gun mantlet, large turret bustle with an ammunition rack, and a commander's cupola with periscopes instead of observation slits. Despite the thicker armour, more powerful gun, and ammunition rack the new turret was only two tons heavier than the old Tiger P and H1 turret. That's the power of well thought out geometry! Krupp also designed a similar turret for the early Maus tanks. Even the final variant had a turret front made from one curved piece of armour like on early T-34 tanks. 

Early VK 45.03 turret blueprint. It is similar to the VK 45.02 (P) turret but it has a hydraulic traverse instead of an electric one.

Not all was ideal. Eight out of fifteen VK 45.02 (P) turret front plates cracked during assembly. Their contours looked nice on paper, but ease of production was a different question. Meanwhile the requirements for protection kept increasing, and so Krupp thickened the turret front to 180 mm and dropped the idea of a curve. This is how the King Tiger's turret was born, old turrets with 100 mm thick fronts were only used on the first 50 tanks. 

Daimler-Benz also designed a T-34-like turret for its VK 30.01 (D) with a narrow front turret and small gun mantlet. Unlike Krupp, it rid itself of some problems and used a flat turret front from the start. Generally the Daimler-Benz turret was more progressive than the Rheinmetall one, but it was also 3-4 months late. The turret rings were also incompatible (1600 mm vs 1650 mm). This design was dropped and production Panthers used Rheinmetall turrets with wide fronts.

New turret for the Panther II. As you can see, the gun mantlet is completely different than on the Panther tank. The Schmalturm turret front was even narrower.

The new approach won out. Rheinmetall reworked the turret of the Panther II, making the front much narrower and using a new gun mantlet. This turret is known as the Turm-Panther (Schmale Blende) or "turret with a narrow mantlet". When work on the new tank hit a dead end the designs were transferred over to Daimler-Benz.

The company evolved its old ideas and designed the Schmalturm or "narrow turret". It was cheaper and easier to build than the old Panther turret, weighed 100 kg less, had better protection (the front was 20 mm thicker, the sides and rear were 15 mm thicker) and could also support a rangefinder. Work began too late and so production of the Panther Ausf.F with the new turret never took place.

The VK 16.02 turret was inspired by the early T-34 turret. This is most obvious when looking from above.

In addition, Daimler-Benz produced a T-34-like turret for the VK 16.02 light tank. Later it was supposed to be used on the Luchs reconnaissance tank, but the plans remained on paper. A lighter version of the turret was used on the Sd.Kfz.234 armoured car. The conclusion is obvious: the T-34's effect on German turret development was significant.

Tigers in a hurry

The topic of German heavy tanks is overgrown with myths. We won't even seriously consider the idea that Germany did not work on heavy tanks until after the invasion of the USSR, as it goes against too many known facts. However if one keeps in mind that the Germans were working on heavy tanks since 1937, one may ask a new question: what were they doing all this time? Some say that heavy tanks were incompatible with the Blitzkrieg concept and the work on them was low in priority. As soon as the Germans were bogged down in defensive fighting, they came up with the heavy and clumsy Tiger. This question can be rephrased: how did Soviet tank building influence German heavy tanks?

To start, let us say that the Germans did not slow down their own heavy tank development intentionally. The D.W. heavy tank was developed in parallel with the Z.W. chassis for the Pz.Kpfw.III. Design work was performed in 1937, prototypes were tested in 1938. Work on light tanks progressed at about the same rate. The issue is that the D.W. was very raw and poorly thought out. Necessary changes meant that mass production would have to be delayed. By the time the VK 30.01 (H) was made into a viable design it was already hopelessly obsolete. Excuses about low priority and Blitzkrieg are reminiscent of the fable of the fox and the grapevine. If there was no result, that must mean the result was unnecessary. 

This is what the VK 30.01 (P) looked like in May of 1941. One last step separated it from the Tiger.

Let's take a look at how the Germans changed their approach to heavy tanks after the invasion of the USSR. It is known that the Tiger H1 was the result of changing the VK 36.01 hull to support a turret with an 88 mm gun initially designed for the VK 30.01 (P). Krupp and Porsche actively discussed the armament of the future tank from February to May of 1941. Long 88 and 105 mm guns were considered. Finally the choice was made in favour of the 88 mm L/56 gun. The concept of a heavy tank with an 88 mm gun was finalized before the invasion of the USSR. The decision to thicken the armour to 100 mm as also made then.

The evolution of the VK 36.01 and VK 30.01 (P) into the Tiger H1 and Tiger P began in July of 1941. The Germans planned on finishing the design and starting mass production within a year. On May 28th Henschel received an order for the VK 45.01 (H) and the design of the new cooling system was finished by July 28th, so the new hull was already finished by then. Meanwhile, Porsche was busy designing new 15 L engines for the Tiger P. Documents included a stamp noting that work on the Geraet 4501 P was closely following the established schedule. The conclusion is that the work on the Tigers was well underway before the Germans were bogged down near Moscow and the appearance of the T-34 and KV-1 had no effect on their characteristics.

A blueprint of the Tiger H1 cooling system dated July 28th, 1941.

As for the King Tiger, the claim that it was designed in response to the IS-2 is absurd. The topic of installing an 88 mm L/71 gun on the Tiger surfaced in September of 1941. This project borrowed heavily from the Soviet tank building school, as during the development of the VK 45.02 (P) with the new 88 mm L/71 gun Krupp designed the hull and turret with inspiration from the T-34. The VK 45.03 or King Tiger appeared so late not because it was an answer to the IS-2, but because it was the victim of another attempt to rationalize two designs, this time the Panther II. 


Let us tally up the conclusions. The effect of the Soviet V-2 engine on German tank building is overblown, as is the claim that the Germans couldn't develop a diesel engine. German engine designers went their own way both before and after inspection of the V-2. The Germans were very capable of creating diesel engines for their tanks, even though they were bad at putting them to use.

The T-34 had an effect on German tank development, and a large one at that. It was after the Germans inspected the new Soviet tanks that they switched to the new 30 ton weight class. Don't overestimate this influence, however. The VK 30.01 (D) is visually similar to the T-34, but it's a completely different tank with its own nuances such as the transmission layout and gearbox design. This is anything but a copy.

The Germans knew about sloped armour before encountering the T-34 and used it actively on armoured cars. For a number of reasons, development of tank hulls and turrets was a step behind. After examining the T-34 the Germans reconsidered their approach and Krupp became fascinated with curved plates.

The early T-34 also had an influence on turret development. Many German tanks used T-34-like turrets, from the light VK 16.02 to the superheavy Maus.

The impact of Soviet tanks on the development of the Tiger is overblown. The Germans already considered heavy tanks weighing over 45 tons armed with a long 88 mm gun before the invasion. Development of Tigers began in July of 1941, although surviving documents don't allow us to fully trace their development history. As for the more powerful 88 mm L/71 gun, that was Hitler's desire and not a consequence of the commission's examination of Soviet tanks.

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