Mercedes-Benz T 80 record car, 1939

Mercedes-Benz T 80 record car, 1939

In the second half of the 1930s, the legendary Grand Prix races with single-seater formula racing cars did not play the only leading role in motorsport. The ruling powers in Germany at the time supported the prestigious and headline-grabbing record-setting runs, in which the protagonists Daimler-Benz and Auto Union fought a stubborn duel on closed-off stretches of motorway.

The pronounced competitive situation between the two rivals, culminating in the staging of the record week in 1937, entailed a host of new class and world records in the years from 1934 onwards. However, the absolute land speed record, which had already been nearly 485 km/h in 1935 - a speed that was no longer feasible on public roads, taking into account a safety minimum for drivers - was not on the radar. 'Lone wolves' such as the Britons Sir Malcolm Campbell, George Eyston and John Cobb spurred each other on to ever new world speed records, which they set in vehicles that they themselves had designed, powered by one or more aircraft engines. The venue since mid-1935 has always been the Bonneville Salt Flats in the US state of Utah, which covered the site of a dried-up salt lake. They offered ideal conditions to push into such extreme speed ranges.

In Germany, one figurehead of motorsport in particular was watching the international happenings surrounding the improvement of the absolute land speed record - not least out of a healthy self-interest: Auto Union factory driver Hans Stuck. The number 1 of the Zwickau works team saw his position increasingly endangered by the successful performances by the beaming young star Bernd Rosemeyer and left for other fields of activity. Stuck developed the idea of activating his excellent contacts to the National Socialist political elite and, in cooperation with Daimler-Benz and Ferdinand Porsche's design office, to build a world record vehicle powered by an aircraft engine, with which he wanted to bring the speed record to Germany.

Daimler-Benz board member Wilhelm Kissel, who was always keen to emphasise the leading role of the company he headed in both automobile and aircraft engine construction, and Ferdinand Porsche, who was on the lookout for new orders, were enthusiastic about Stuck's idea - especially as the latter had succeeded in getting access to a Daimler-Benz type DB 601 aircraft engine. This was an unusual process, as all aircraft engines produced in Germany at the time were under the exclusive authority of the Luftwaffe's Technical Office. Stuck had had a personal connection with its head Ernst Udet for many years.

The initial target for the world record vehicle project was to reach a speed of 550 km/h - a figure that ultimately was increased to 600 km/h and finally 650 km/h as more and more new records were reported from the USA. Porsche's design office, which had already been commissioned with the realisation of the project on 13 January 1937, calculated that an engine output of around 3500 hp/2574 kW would be required to reach the 650 km/h mark. This was based on Porsche's concept of a three-axle record-setting car, which was to be considerably sleeker and lighter than the vehicles of the British competitors, some of which were equipped with two engines and produced over 1000 hp/736 kW more.

However, in terms of performance they still had a long way to go to compete with the current record-breaking vehicles, but also to reach the level of performance they hoped to achieve for their own project. The DB 601, a supercharged V12 aircraft engine with a displacement of around 34 litres, provided a maximum output of only 1100 hp/809 kW in its standard version. In addition to the classic design features of Daimler-Benz engine construction, the engine with a cylinder bank angle of 60° also had a number of performance-enhancing technical characteristics. Above all, these included petrol direct injection, but also four-valve technology and dual ignition.

The potential of the DB 601 was clearly demonstrated by the special versions called DB 601 Re V, which were specified in 1937 especially for aircraft speed records. With its higher compression ratio, more performance-oriented camshaft timing, modified supercharging and explosive high-performance fuel, the V12 delivered a peak power of up to 2770 hp/2037 kW.

In parallel to these tuned versions of the DB 601, Daimler-Benz had been working on a more powerful engine with the same technical basis since autumn 1936. Called the DB 603, the engine had a displacement of more than 44.5 litres and was intended as a power unit for larger and heavier military aircraft. Although the political-military leadership had already prohibited further development of the DB 603 until further notice in the spring of 1937, a test engine bought back from the Reichsluftfahrtministerium (Reich Air Ministry, RLM) was used for performance measurements on the test stand and provisional installation in the chassis of the new record-breaking vehicle.

The figures determined during these test bench runs proved promising: without any special performance-enhancing modifications to the technology, but using racing fuel, a maximum output of 2800 hp/2059 kW was recorded for the DB 603. The stated target of 3500 hp/2574 kW was thus within reach - provided that the use of the package of measures already employed on the DB 601 Re V to increase power had been approved by the RLM.

Above all, the chassis of the record-breaking vehicle designed by Ferdinand Porsche's office, which was given the designation T 80 (Type 80) in accordance with the Porsche nomenclature, clearly reflected the technical credo of the prominent designer. The mid-mounted arrangement of the gigantic power unit, the position of the driver well towards the front, but also the front axle design with double trailing arms in the shape of a parallelogram and the two rear swing axles, together with the use of torsion bars throughout, showed Porsche's signature.

One striking feature was the decidedly narrow design of the ladder-type frame, which was supported by oval longitudinal tubes and multiple transverse bracing. The track widths were 1300 mm at the front and 1320 mm and 1180 mm at the rear - the aim was to keep the frontal area of the body as small as possible in the interest of optimal aerodynamics. The engine, positioned directly behind the driver's back, managed without a gearbox - there wouldn't have been one to withstand the V12's massive forces anyway. Instead, the crankshaft of the engine, which was installed overhead as in an aeroplane, fed directly into a huge, oil-mist-lubricated triple-plate clutch with centrifugal governor.

The targeted speed level of 650 km/h naturally also required fundamental considerations concerning the brakes with regard to the frictional heat generated during the braking process. The tendency to warp, which is always present in drum brakes, threatened to become particularly pronounced in view of the drum diameter of 500 mm intended for all six wheels and the high number of wheel revolutions. The development team suggested using the turbo-cooled brake drums on the T 80 record car that had already been used successfully since 1939 in the W 154 3-litre Formula racing car, and which generated very efficient heat dissipation thanks to their special ribbing.

The tyres themselves were special treadless designs from the manufacturer Continental. With a diameter of 32 inches, the tyre width was only 7.00 inches in the interest of minimising rolling resistance. The main focus of the tyre designers had naturally been on the high-speed strength of the carcass. While the highly stressed tyres did not cause any problems during tests on the roller test rig, the spoke rims proved to be less resistant to speed. At speeds of around 500 km/h, deformation of the rims occurred, as a consequence of which discussions took place between Continental and the rim manufacturer, Hering AG.

Apart from the engine power, the key to the success of the project lay in the design of the bodywork. Compared to the Mercedes-Benz record-breaking vehicles based on the formula racing cars, the design of the T 80 broke new ground. The lowest possible air resistance owing to its flowing lines, a small frontal area thanks to the narrow vehicle width and large-format stub wings on the car's flanks, whose purpose was to produce high downforce values, characterised the outer shell, which was supported by a graceful tubular frame. The dimensions of the T 80 were impressive: with a length of 8240 mm, the width of the body without the stub wings was only 1740 mm. The driver's seat, which had been moved well forward, was covered by a completely enclosed, slim cockpit in the style of an aeroplane.

Until the beginning of 1940, Daimler-Benz considered the successful deployment of the T 80 possible. The car was sitting on its six wheels, almost all technical components as well as the body were almost ready for use. But some central questions that ultimately remained unanswered led to the project failing. The ban on further development of the DB 603 imposed by the RLM remained in place until almost the end, so that apart from a few test stand runs and a provisional installation in the chassis, there was no opportunity to bring the engine up to the targeted power level of 3500 hp/2574 kW. Of even greater importance, however, was the changed world situation: with the commencement of the war in September 1939, Daimler-Benz no longer had access to routes where the T 80 could have tackled the absolute land speed record. Closed sections of motorway were no longer suitable for speeds of around 650 km/h, even if the section near Dessau, which had already been used for record runs in February 1939, was initially still considered a possibility, and the Bonneville Salt Flats in the USA were also not an option under the given circumstances. Thus, all development work on the promising T 80 was stopped in February 1940.

The engine was removed and the vehicle laid up. The project, which by its nature had been carried out in secret, came to public light shortly after the end of the Second World War: after a visit to the Daimler-Benz plant in Untertürkheim, the British automotive journalist and motorsport enthusiast Laurence Pomeroy presented the vehicle in an article published in November 1945 under the title "A 450 m.p.h. Car" in the specialist magazine "The Motor". An even more detailed description of the extraordinary car was published in 1948 under the title "Investigation Into the Development of German Grand Prix Racing Cars Between 1934-1939 (including a Description of the Mercedes World's Land Speed Record Contender)". This very comprehensive document presents in clearly structured, technically very detailed form the findings of the British intelligence officer Cameron Earl, gathered by him with respect to the racing cars of Mercedes-Benz and Auto Union during a four-week trip in April/May 1947. The top speed figures of 450 and 464 mph (724 and 746 km/h respectively) stated in the two sources were clearly too high - the Daimler-Benz AG interview partners visited had probably given overly optimistic estimates here.

As early as the beginning of the 1950s, the spectacular record car was exhibited at the then Daimler-Benz Museum and made accessible to the public. When reports appeared in the British trade press in March 1952 that Mercedes-Benz intended to launch an attack on the absolute world speed record with the T 80 in that same year, the company hastened to deny these rumours and to state that the spectacular vehicle "will not leave its stand in the Daimler-Benz Museum in Stuttgart-Untertürkheim in the future either."

This remained the case. When the museum was redesigned as part of the anniversary "100 Years of the Automobile 1886-1986", the T 80 was no longer placed standing on its wheels but hanging on the wall. For this reason, the body including its tubular frame structure was separated from the chassis with drivetrain, fitted with wheels and attached to the museum wall. The original chassis, which weighs several tonnes, has been in the "sacred halls" of the vehicle collection ever since. In 2017, the idea was developed to make this impressive exhibit accessible to the public again. For this purpose, it was fitted with specially made new tyres, while to give a more realistic impression of the vehicle's appearance, an original cutaway model of the DB 603 aircraft engine and a faithfully reconstructed tubular frame construction were also mounted. The newly created exhibit was officially presented in this form at the Goodwood Festival of Speed in July 2018. Since then it has been possible to admire the T 80 - in the form of its original body with wheels - not only in the museum, but - with a bit of luck - as an original chassis during one of its appearances at exhibitions and events. However, it can be ruled out that the T 80 will one day be actually driven.

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