German tank development followed a very predictable course. This included engine development. After experiments in the 1920s and early 1930s, German tanks settled on the Maybach V-shaped series. These gasoline engines that worked at high RPM (about 3000) were characteristic for German tanks. They were used until the end of the war, although some began to think about an alternative as early as 1941-42. Ferdinand Porsche was among those who had his own idea about what a tank engine needs to look like.
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Simmering-Graz-Pauker is best known as a producer of train cars and locomotives. |
The first attempt to build a diesel engine was undertaken by Daimler-Benz in 1940. The MB 809 and later MB 507 were unlucky. Work on diesel engines was not abandoned. Porsche K.G. picked up the relay, working closely with Austrian companies. The new team created a brand new engine known as the Simmering-Graz-Pauker Sla 16. This was an X-shaped air cooled diesel engine which opened a whole new direction in development of tank engines. However, Germany did not have time to make use of the fruit of this labour.
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The predecessor of the SLa.16 was initially developed for the Typ 205, shown here in its configuration as of October 1942. |
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The engine without a cooling system. |
Cooperation between Porsche K.G. with Austrian and Czech companies was notable. This was especially clear when it came to engine designs. The presence of Oscar Hacker, the head of Steyr-Daimler-Puch, on the Tank Commission was no accident. Porsche also worked with Tatra on air cooled engines, who had a lot of experience in this, although the closest cooperation was with the Austrians. The Typ 100 tank engine was built at Steyr. Based on this engine, the company developed a number of gasoline and diesel engines, but none were successful due to cooling issues.
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It was 2.5 meters wide with cooling. |
Cooperation between Porsche K.G. and Simmering-Graz-Pauker began during the work on the Typ 101. The Austrian company is best known for its participation in the Maus project, as they had experience building special railway cars. However, the company also worked on engines. The experimental Typ 190 engine used a pre-ignition chamber design developed at Simmering-Graz-Pauker. Porsche K.G. continued to work closely with the railway company after that. A new project began in 1942 after clear issues arose with prospective engines for the Typ 180. The fact that a pair of engines was a mistake became obvious.
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An air filter was located above the engine. |
Initially the Typ 203 engine would have 18 cylinders. It was based on a Typ 192 2.3 L cylinder. It is best known under another name, Typ 205/2. This 41.4 L air cooled engine put out 780 hp at 2000 RPM. The first and last mention of this engine was made in October of 1942. It quickly disappeared, making room for the X-16 Typ 212 engine. It was based on the 3 L Typ 213 cylinder. The engine volume increased to 48 L and power increased to 1500 hp at 2500 RPM. Even this engine remained on paper. The Daimler-Benz MB 509 was chosen for the Maus in the end. However, work on the X-shaped engine continued.
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Trials of the engine were performed without a cooling system. |
According to the new concept, the engine was developed as an alternative for the Tiger II and Typ 180/181, although the latter option was soon discarded. Engineer Zeiberl led the work from the side of Simmering-Graz-Pauker. Porsche K.G. did not work on this engine for long. Cooperation with Simmering-Graz-Pauker ceased in August of 1943, although by that point the components were worked through in detail. For instance the cooling system and cylinders were developed in Stuttgart. Nevertheless, it was a joint effort. There was plenty of original ideas from Simmering-Graz-Pauker, including the aforementioned pre-ignition chamber design. The name SLa.16 is a fair one.
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The SLa.16 was far from a simple design. |
As with the Typ 100/Typ 101, the new engine was coupled together with the cooling system in one unit. Earlier engines had the cooling system straddling the motor while the Sla.16 had it on the sides. Two cooling fans were used with two separate fans to cool the oil. The engine turned out to be a lot larger and heavier than its competitor, the Maybach HL 230. The overall width with the cooling system was 2520 mm. The engine weighed 2250 kg, more than twice as much as the Maybach HL 230. There were some positives. The SLa.16 was 1150 mm tall, a little less than its competitor. The dry weight of the Maybach HL 230 also doesn’t include the cooling system, so overall the SLa.16 was also a little lighter.
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The pre-ignition chamber developed by Simmering-Graz-Pauker. |
Work on the engine was done in stages. A Typ 192 cylinder was built in the fall of 1942. In November it went through 48 hour long trials, developing a power of 47 hp at 2100 RPM. This would make the projected power of the SLa.16 752 hp. The engine received two Brown Boveri VTaS-200 turbo compressors. The engine built in early 1944 was supposed to be able to go into a Tiger II or a Jagdtiger with no changes to the transmission. A reductor gear was added for this purpose. This kind of unification made work on the engine more difficult.
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Installation of the second variant of the engine into the Tiger II, December 1944. The engine deck and exhaust system had to be converted. |
The need for a reductor gear was not the only issue. One could not simply swap the engine and frame. The SLa.16 was noticeably wider than the Maybach HL 230, plus its design required changes to the hull, engine deck, and exhaust system. An air intake was placed in the centre of the engine deck, above the air filter. The air intakes for the cooling system were also different, which would have made for a very different rear hull. No data exists that would show what it would have looked like, but a tank with an SLa.16 engine would be visibly different.
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The second variant of the engine. |
The experimental SLa.16 was installed on a stand and tested in late 1944. No one questioned the need for a diesel engine by that point. Even Maybach was working on a diesel variant of their own engine. The Maybach HL 230 demonstrated a normal power of 600 hp. The SLa.16 beat it with 770 hp at 2200 RPM in bench trials, but only without power going to cooling fans. When fans were hooked up it was clear that the engine needed work. Output dropped to 685 hp and fuel expenditure climbed.
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The same engine from the rear, |
Simmering-Graz-Pauker urgently began to rework the cooling system. Everything was done in agreement with Henschel and a draft for installation of the improved engine into the Tiger II was presented in late 1944. This diagram created the myth that the engine was going to be installed in this tank. That is quite unlikely, if only because there were no tanks built in Austria. However, the Jagdtiger built at Nibelungenwerk had the same engine compartment. That is where the second prototype engine was installed in April of 1945. The second prototype itself was finished at the beginning of the year.
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The Jagdtiger where the engine was installed. |
The second variant of the engine received a cooling system developed by Simmering-Graz-Pauker. Unlike the first variant developed at Porsche K.G., the new system was quite simple. Fans were located in the centre and four smaller oil cooling fans were used instead of two large ones. Interestingly enough, while only diagrams of the first engine survive, the second was photographed extensively. The engine went through bench trials, after which it was installed in a Jagdtiger. The foundations for the engine deck around the cooling fans had to be trimmed so it could fit.
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The engine as installed in the Jagdtiger. |
According to some sources, the SLa.16 was scheduled to go into production in June of 1945. The engines would be produced at Steyr. This date is unlikely, as it was necessary to first carry out a full spectrum of trials in a Jagdtiger. The tank destroyer only ran for 5 hours before the war ended. Nibelungenwerk ended up in the Soviet occupation zone and in 1945 all equipment was dismantled and taken to the USSR. The Jagdtiger went to Kubinka. Its further fate is unknown.
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This is just a diagram, but it shows how the engine would have been installed. |
No doubt the engine was studied in the USSR. A lot more information was received this way than through British and American intelligence. Experience from German engineers served as a foundation for work on Soviet X-shaped diesels. Interestingly enough, X-shaped diesel engines also came up as a part of the Czechoslovakian TVP program. In this case, this was due to German rather than Austrian influence. Tatra actively worked with Porsche K.G. and clearly retained something from the relationship. Even though a Czechoslovakian X-shaped diesel engine didn’t move past paper projects, the fact that it existed in the first place is interesting on its own.
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