No other manufacturer is as closely associated with the history of the diesel engine as MAN. After all, it was at Maschinenfabrik Augsburg – later to become MAN – where Rudolf Diesel developed the world’s first engine to bear his name. Intensive promotion of diesel technology is still part of the company’s visionary orientation. The MAN Nutzfahrzeuge Group continues to build on its diesel competence. Its range of products centers on the most modern diesel engines for commercial vehicles, autobuses, yachts and rail vehicles.
Just 150 years ago, few scientists could have imagined engines that would propel automobiles, trucks and enormous container ships all around the world. The 19th century, the era of the Industrial Revolution, was characterized by the steam engine. Its steady pounding could be heard coming from machine shops, ships and locomotives. But the end of the steam engine and its huge boiler plant was already approaching.
Rudolf Diesel was born on March 18, 1858, the son of German parents, in Paris. The young boy had a scientific leaning and was sent to Augsburg to attend the Royal Bavarian Vocational School, now the Holbein High School. Following that he studied at the Munich Polytechnic under Professor Carl von Linde, for whom, after graduating, he returned to Paris to set up a factory for ice machines. But he was more interested in building a “rational heat engine”, an idea that led to the invention of the diesel engine.
Eventually, on February 28, 1893, he was awarded a patent for an “internal combustion engine” by the Imperial Patents Office in Berlin. He wanted to find alternatives to the steam engine, which needed a lot of maintenance and only worked with efficiency of 10 per cent at the most. To achieve this he needed partners, but those he approached were sceptical. All they saw in him was a young 34-year-old engineer with an invention that aspired to take the place of the omnipresent steam engine.
But Diesel persisted until, finally, he managed to convince the president of Maschinenfabrik Augsburg of his plans. The risk was considerable, but Heinrich von Buz agreed to go ahead with the idea. Maschinenfabrik Augsburg – a forerunner of MAN – and the Friedrich Krupp company made the necessary means available: manpower and equipment, an experimental station and financial resources to get the project going.
In April 1893 already, Rudolf Diesel started setting up an experiment in Augsburg. After a number of initial difficulties a first measurement of power was performed in June 1895. But the efficiency of only 16.6 per cent was disappointing. It was not until February 17, 1897 that Diesel’s invention worked satisfactorily for the first time. The similarity with a steam engine could hardly be overlooked. The massive steel construction was three metres in height; the A-frame with the cylinder mounted on a crosshead and flywheel at the side, powered by kerosene, managed an impressive 18 hp and quite astonishing efficiency of 26.2 per cent.
Diesel’s rational heat engine thus outclassed all other forms of propulsion. It worked without an ignition device, needed no boiler plant, and no coal bunker. Compared to the gasoline powered or spark ignition engine, the diesel engine possessed three decisive advantages: it was more robust because it consisted of fewer parts; it was able to burn heavy oil, which was cheaper than gasoline; and its efficiency was far superior.
Selling success
Very soon the diesel engine embarked on its triumphal course around the world. But things would not have reached that stage without the support of Maschinenfabrik Augsburg. The engineers at the Augsburg works improved details and eliminated many teething troubles. Just after the turn of the century the engine was finally regarded as safe to operate and ripe for the market.
Initially, Rudolf Diesel showed himself to be very adroit in how he marketed his product. Worldwide licences made him a millionaire. By 1903 already, ferry boats with diesel engines were crossing the English Channel. In 1913 there were some 300 diesel-propelled ships on the world’s oceans. By 1912, co-operation with the Borsig works in Berlin had produced the world’s first diesel locomotive, delivered to the Königlich Preussische Staatsbahn.
Rudolf Diesel died on September 29, 1913, under tragic circumstances while travelling to England. He fell overboard during the night from the packet ship Dresden – something that has remained a mystery ever since.
Engines on wheels
Among fast running diesel engines it is MAN Nutzfahrzeuge that sets the pace with ground-breaking developments – direct injection, exhaust turbocharging, the most modern forms of combustion and many pioneering technologies are developed by MAN engineers.
In the early years of the 20th century MAN engineers achieved ground-breaking developments. Doing away with the crosshead, which was adopted from the steam engine, produced a substantial cut in the weight/horsepower ratio.
In 1898, Maschinenfabrik Augsburg and Maschinenbau-Actiengesellschaft Nürnberg agreed to combine their activities – the newly established Vereinigte Maschinenfabrik Augsburg und Maschinenbaugesellschaft Nürnberg AG soon afterwards became Maschinenfabrik Augsburg Nürnberg or M.A.N. In 1915 the Armed Forces Administration was pressuring the production of trucks because of the enormous war requirements. The Nuremberg works was contracted for something that President Anton Rieppel had long wanted: “MAN must be put on wheels”.
On July 12, 1915, MAN concluded a license agreement with the Swiss automobile factory Adolph Saurer and became a truck manufacturer. A diesel engine was still out of the question, because it was too heavy and its fuel compressor injection made it too complicated.
The first truck manufactured in Nuremberg went onto the market under the double name MAN-Saurer. A 37-hp gasoline engine propelled the chain drive and gate-type gear control of the solid rubber tyres on wooden wheels. Its load capacity was four to five tonnes.
After the end of World War I, the engineers at the Augsburg works resumed development of the diesel engine. The focal problem, the injection of the fuel with compressed air and the necessary high-pressure compressor, was solved by MAN technicians through direct injection. Fuel was injected straight into the combustion chamber under high pump pressure. This very much simplified the engines and their maintenance. At the same time, the way was opened for small engines and higher engine speeds.
While other manufacturers stuck to the concept of the precombustion chamber engine, MAN decided to go its own way. At the German Automobile Show in Berlin 1924, MAN presented the first diesel truck, which was soon being manufactured in small series. The four-cylinder, now produced by the Nuremberg works, delivered 45 hp at 1050 crank shaft revolutions, consumed only 200 g/hph, and was barely heavier than a conventional carburettor engine. The first customers trusted in MAN’s good reputation and its new engine design – Bavaria’s postal administration, for instance, which ordered a number of engines for its autobuses ahead of the Berlin Show.
In 1925 the MAN trucks were again among the special attractions of the show in Berlin. The most modern diesel truck was without doubt presented by MAN – engine, clutch and gearbox for the first time in a single block, and the engine power transmitted to the rear axle by a propeller shaft.
In 1927, MAN answered the demand for high engine power with a six-cylinder diesel. Multiple-jet nozzles, an optimized piston head and four valves per cylinder achieved 110 hp. At the same time, specific fuel consumption dropped. In 1930, in the course of its basic research, MAN developed the K principle with an oblique combustion chamber, air accumulator and 400 bar injection pressure. That allowed the use of a piston with a smooth head.
The master stroke
The year 1923 saw the breakthrough – fuel was injected direct under high pump pressure into the combustion chamber. The highly complex compressed-air injection by compressor was no more. Smaller engines and higher engine speeds were now possible. While competitors chose the pre-combustion chamber technique of the engineer Prosper L’Orange for their heavy-oil engines, MAN stuck to the principle of direct injection for its diesel engines.
Typical features of the direct injection diesel were undivided combustion chambers and, compared to pre-combustion chamber or swirl chamber engines, the smaller combustion chamber surface. This was accompanied by lower losses of heat and flow, resulting in less consumption and higher efficiency. Today virtually all diesel engines in commercial vehicles worldwide use direct injection.
MAN developed a series of trucks that, in a two-axled version, was capable of handling payloads of three, four, five, six and a half and – for export – eight tonnes. The year 1926 already saw the first MAN three-axle truck, extending the system of type rating to 10 tonnes. However the long bonnet still concealed a 150 hp six-cylinder gasoline engine, which was not replaced by an equally powerful diesel engine until 1932.
The three-axle heavy-duty S 1 H 6 was the most powerful diesel truck in the world, its six-cylinder engine with 16.6 liters capacity producing 150 hp – ideal for long distances and heavy loads. But the presentation of the world’s most powerful three-axle diesel came at the time of the Great Depression, which was also a difficult time for the commercial vehicle manufacturer MAN. Consequently only few examples of the impressive heavy-duty truck appeared on the roads.
Truck production did not really get going again until after 1933. The construction of motorways and various procurement programs created heavy demand. The legislature increased admissible vehicle weights – two-axled trucks may now weigh up to 15 tonnes. In 1934 MAN attracted attention through a triumph of a special kind: the International Automobile Diesel Engine Rally, conducted through large areas of the Soviet Union, was won by a vehicle with a MAN engine in the face of tough competition.
In 1937 the engine designers in Nuremberg came up with a revolutionary innovation in the spherical combustion chamber and the flat-seat jet. MAN spoke of the G principle (G standing for globe) – the eccentric hollow sphere in the piston head reduces the heat losses, the rugged flat-seat jet, offset from center, avoids the elaborate multiple-jet nozzle. More fuel burns in a short time, performance improved from the 100 hp of the forerunner six-cylinder to 120 hp.
World War II
In 1938, by order of the Army Ordnance Office, production of a standard diesel was commenced, designed by MAN, Henschel and Humboldt-Deutz. Behind this was an attempt by the Armed Forces to reduce the diversity of its truck models. MAN was called upon to produce a 4.5- and a 6.5-tonne model. But the focus in armaments was on building battle tanks – the building of trucks and buses was later halted, with the exception of spare parts in Nuremberg.
Quite apart from this production, the company continued the development of high-performance diesel engines. Together with a partner enterprise, MAN presented an air-cooled V16 diesel engine with an exhaust turbocharger that produced unbelievable 900 hp at 2200 rpm, for a sensational weight/horsepower ratio of only 1.7 kg. The 4.5-tonner developed for the forces, named SML, became the prototype of a modern semi-forward-control truck, and the basis for post-war production.
On April 16, 1945, the US Army arrived and confiscated what was left of the MAN works in Nuremberg. War damage here was especially severe. Nevertheless, at the end of 1945 already the first 4.5-tonners of the type ML 4500 rolled out of the patched up factory shops, and in 1946 the output was all of 129 units. Working away under the short bonnets of the two-axle trucks were six-cylinder inline engines, using the G principle to produce 110 and 130 hp, and consuming only 18 litres of diesel to travel 100 km fully loaded.
In 1950, MAN presented its first post-war heavy-duty truck in the F8. The nucleus of the imposing 10-tonner (10 tonnes payload) was Germany’s first water-cooled V8 diesel, generating 180 hp from 11.6 liters cubic capacity and capable of handling the heaviest truck trains. The cab was just as generously scaled as the engine, and a special design feature of the F8 was the headlights integrated in the wings.
In 1951, MAN surprised visitors to the IAA in Frankfurt by presenting the first German truck engine with exhaust turbocharging. This technology, already adopted in marine engines, locomotives and stationary diesel engines, made it possible to achieve higher power with more injected fuel, and to make better use of the energy. The six-cylinder of the two-axle MAN MK 26 was named D 1546 GT, and instead of the usual 130 hp the engineers produced 175 hp from 8.72 litres displacement, a remarkable 35 per cent more. But for the moment the turbocharged six-cylinder was a prototype – its technology showed the way for the future however, and features today in every diesel engine.(To be concluded)
