by Vaclav Smil
German Trio and the First Car Engines
The next critical stage in the history of internal combustion engines continued to unfold in Germany, and we have already met all three protagonists, Benz, Daimler, and Maybach. Karl Friedrich Benz (1844-1929; figure 3.1), was born in Karlsruhe to a family whose men were smiths for several generations. After his technical studies, Benz set up an iron foundry and a mechanical workshop, and in 1877, with his main business struggling, he began to build stationary engines. Gottlieb Daimler (figure 3.6) worked for Otto & Langen (later Deutz AG) between 1872 and 1882 and left the company after disagreements with Otto. And Wilhelm Maybach, whom Daimler recruited to N. A. Otto & Cie. in 1873, improved designs of both Otto’s two patented engines and brought them to commercial production. Independent efforts of these three men had eventually resulted in the first practical high-speed four-stroke gasoline-fueled engines.
FIGURE 3.6. Gottlieb Daimler. Photograph courtesy of DaimlerChrysler Classic Konzernarchiv, Stuttgart.
After leaving Deutz at the end of 1881, Daimler, soon joined by Maybach, set up a shop in the Gartenhaus on his comfortable property in Canstatt, Stuttgart’s suburb, and set out to develop a powerful, yet light-weight engine fueled by gasoline (Walz and Niemann 1997). Gasoline, by that time readily available as the first volatile product of simple thermal refining of American and Russian crude oil, was an obvious choice. With about 33 MJ/L (nearly 44 MJ/kg), the fuel has about 1,600 times the energy density of the illuminating gas (which could be used in transportation only if highly compressed), and its low flashpoint (– 40°C) makes it ideal for easy starting. At the same time, this very low flash point also makes it very hazardous to use. By 1883 the two engineers had a prototype of a high-revolution (about 600 rpm) gasoline-fueled engine with a surface carburetor and inflammation-prone hot-tube ignition (heated by an external gasoline flame) that caused repeated flare-ups.
In 1885 Daimler and Maybach fastened a small (about 350 W) and light, air-cooled version on a bicycle, creating a prototype of the motorcycle, which was driven for the first time on November 10, 1885, by Daimler’s son Paul just 3 km from Canstatt to nearby Unterturkheim (Walz and Niemann 1997). Figure 3.7 shows this, still a rather unwieldy, machine as well as its subsequent transformation into a modern-looking motorcycle with electric engine starter that became fairly popular just before WWI (O’Connor 1913). Going a step further, in March 1886 Daimler ordered a standard coach with four wooden wheels from a Stuttgart coachmaker and mounted on it a larger (0.462 L, 820 W), water-cooled version of the engine (figure 3.8).
FIGURE 3.7. Daimler and Maybach’s unwieldy 1885 motorcycle with subsidiary wheels compared to a tandem machine of 1900 and to standard motorcycles of 1902 and 1913. Reproduced from O’Connor (1913).
Daimler and Maybach’s inelegant vehicle, with passengers precariously perched high above the ground, made its first rides in Daimler’s garden, a trip from Canstatt to Unterturkheim sometime during the fall of 1886, and the first extended journey in 1887 from Cannstatt to Stuttgart at about 18 km/h. Their early engine had only a single opening for inlet of the charge and the exhaustion of gases into the cylinder. Gasoline was supplied from the float chamber to carburetor, and the engine was cooled by water. Remarkably, their achievements were being independently anticipated and duplicated by Karl Benz working in Mannheim, about 120 km northwest from their Canstatt workshop (Walz and Niemann 1997).
On January 29, 1886, Karl Benz was granted the German patent (D.R. Patent 37,435) for a three-wheeled vehicle powered by a four-stroke, single-cylinder gasoline engine; this date is generally considered as the birth certificate of the first automobile. This was Benz’s goal all along: once he decided in the late 1870s that engine construction is the best way to save his business, he concentrated, as already noted, on developing a two-stroke engine that he intended from the very beginning to use in vehicles. As described in this chapter’s epigraph, he was successful just before the end of 1879. By 1882 he had fairly reliable two-stroke gasoline-fueled, water-cooled horizontal engine with electric ignition, and in 1883, after securing an investor, a new company was finally set up. After the expiry of Otto’s patent, Benz began designing four-stroke gasoline engines.
FIGURE 3.8. Daimler and Maybach’s first motor car. Their engine was installed in a coach ordered from Wimpf & Sohn in Stuttgart for the 43rd birthday of Daimler’s wife Emma Pauline. Image courtesy of DaimlerChrysler Classic Konzernarchiv, Stuttgart.
The first three-wheeled motorized carriage was driven publicly for the first time on July 3, 1886, along Mannheim’s Friedrichsring. The light vehicle (total weight was just 263 kg, including the 96-kg single-cylinder four-stroke engine) had a less powerful (0.954 L, 500 W) and a slower-running (just 250 rpm) engine than did Daimler and Maybach’s carriage, and it could go no faster than about 14.5 km/h. The vehicle’s smaller front wheel was first steered by a small tiller and then by a horizontal wheel; the engine was placed over the main axle under the narrow double seat, and drive chains were connected to gears on both back wheels (see the frontispiece to this chapter). The car had to be started by turning clockwise a heavy horizontal flywheel behind the driver’s seat, but water cooling, electric coil ignition (highly unreliable), spark plug (just two lengths of insulated platinum wire protruding into the combustion chamber), and differential gears were the key components of Benz’s design that are still the standard features in modern automobiles.
The first intercity trip of Benz’s three-wheeler took place two years later, in August 1888. Benz’s wife Bertha took the couple’s two sons and, without her husband’s knowledge, drove the three-wheeler from Mannheim to Pforzheim to visit her mother, a distance of about 100 km (DaimlerChrysler 1999). After their arrival, they sent a telegram telling Benz about the completion of their pioneering journey. That trip was made in a vehicle with a backward-facing third seat that was placed above the front wheel, and by 1889 other additions included body panels, two lamps, and a folding top. But these machines were seen largely as curious, if not ridiculous, contrivances, and before 1890 only a few three-wheelers were actually made for sale, and the same was true about the 3-hp Victoria, Benz’s first four-wheeler, which went on sale only in 1893.
Meanwhile, in 1889 Daimler and Maybach introduced a new two-cylinder V engine (angled at 17°) that displaced 0.565 L and ran at 920 rpm. Although they mounted the engine on a better chassis and used steel wire, rather than wooden spokes, the vehicle with larger back wheels still retained a decidedly carriagelike look. But the design pioneered the modern concept of power transmission through a friction clutch and sliding-pinion gears. A year later, in November 1890, when new partners were brought in and the Daimler Motoren Gesselschaft (DMG) was set up, they produced their first four-cylinder engine. At this point, their engines had much more power than needed to propel a carriage, but Daimler and Maybach did not take that step: after disagreements with new partners, they left the company and turned to a collaborative design of new engines that produced a new two-cylinder Phonix before they returned to the DMG in 1895.
And so it was a French engineer, Emile Levassor (1844–1897), who designed the first vehicle that was not merely a horseless carriage. As a partner in Pan-hard & Levassor, he was introduced to the German V engine by Daimler’s representative in Paris, and in 1891, working for Armand Peugeot (1849–1915), he designed an entirely new chassis. Cars with Daimler and Maybach’s engines took the four out of the first five places in the world’s first car race in July 1894 (a steam-powered De Dion & Bouton tractor beat them). A year later—when Levassor himself drove his latest model to victory in the Paris—Bordeaux race (roundtrip of nearly 1,200 km) at average speed of 24 km/h (Beaumont 1902)—the car’s Daimler-Maybach 4.5-kW engine weighed less than 30 g/W, an order of magnitude lighter than Otto’s first four-stroke machines.
A momentous event in the company’s history took place on April 2, 1900, when Emil Jellinek (1853–1918), a successful businessman and the Consul General of the Austro-Hung
arian Empire in Monaco, set up a dealership for Daimler cars (Robson 1983). He placed the initial order for 36 vehicles worth 550,000 Goldmark, and then doubled it within two weeks. His condition for this big commitment: exclusive rights for selling the cars in the Austro-Hungarian Empire, France, Belgium, and the United States under the Mercédès (the name of Jellinek’s daughter) trademark. Maybach responded to this opportunity by developing a design that Mercedes-Benz (2003) keeps describing as the first true automobile and a technical sensation and that Flink (1988:33) called the “first modern car in all essentials.”
Being basically a race car, the Mercedes 35 had an unusually powerful, 5.9-L, 26-kW (35 hp) four-cylinder engine running at 950 rpm with two carburetors and with mechanically operated inlet valves; the vehicle had a lengthened profile and a very low center of gravity (DaimlerChrysler 2003). Shifting was done with a gear stick moving in a gate. What was under the hood was even more important: Maybach reduced the engine’s overall weight by 30% (to 230 kg) by using an aluminum engine block, and the much greater cooling surface of his new honeycomb radiator (a standard design that is still with us) made it possible to reduce the coolant volume by half. Consequently, the mass/power ratio of this powerful engine was reduced to less than 9 g/W, 70% below the best DMG engine in 1895, and the vehicle’s total body mass was kept to 1.2 t.
Within months the new car broke the world speed record by reaching 64.4 km/h, and a more powerful Mercedes 60, with unprecedented acceleration and more elegant bodywork, was introduced in 1903. This combination of performance and elegance, of speed and luxury, has proved to be the most endurable asset of the marque: the company advertised it as much in 1914 as it does today, and it continues to charge the buyers a significant premium for this renown (figure 3.9). Introduction of the Mercedes line could be seen as the beginning of the end of Germany’s automotive Gründerzeit. During the first decade of the 20th century, the center of automotive development shifted to the United States as all three German protagonists left the automobile business. Daimler died in 1900, Benz left his company in 1906, and Maybach left DMG in 1907.
Before leaving this early history of German internal combustion engines, I should clarify the subsequent joining of Daimler’s and Benz’s names. In 1926 Benz & Cie. and DMG joined to form Daimler-Benz AG, uniting the names and traditions of the two great pioneers of internal combustion and automaking. Interestingly, the two men who lived for decades in cities that were just a bit more than 100 km apart never met during their long lives. And in 1998 Daimler-Benz AG bought Chrysler, America’s fourth largest automaker (ranking behind General Motors, Ford, and Honda) to form DaimlerChrysler (Vlasic and Stertz 2000). That I have said so far nothing about the U.S. automakers has a simple explanation. As the leading British expert put it (Beaumont 1906:268), “progress in the design and manufacture of motor vehicles in America has not been distinguished by any noteworthy advance upon the practice obtaining in either this country or on the Continent.” Matters changed just two years after this blunt and correct assessment with the arrival of Ford’s Model T.
FIGURE 3.9. Ludwig Holwein’s elegant pre-WWI advertisement for a Mercedes. Courtesy of DaimlerChrysler Classic Konzernarchiv, Stuttgart.
The Diesel Engine
Rudolf Diesel (1858–1913), the man who invented a different internal combustion engine, set out to do so as a 20-year-old student, eventually succeeded (although not in the way he initially envisaged) nearly 20 years later, but ended his life before he could witness his machine in all kinds of road and off-road vehicles as well as in all modes of shipping (figure 3.10). Diesel’s account of his invention, written in 1913, explains how the idea of a better engine dominated his life since he was a university student (Diesel 1913:1–2):
When my esteemed teacher, Professor Linde, explained to his audience at the Munich Polytechnic in 1878, during his lecture on thermodynamics, that the steam-engine transforms into effective work only 6–10% of the heat value of its fuel, when he explained Carnot’s theorem, and pointed out that with isothermic changes of condition all heat conducted to a gas would be converted to work, I wrote in the margin of my college notebook: “Study whether it is not possible to realize in practice the isotherm?” Then and there I set myself the task! That was still no invention, not even the idea of one. Thereafter the wish to realize the ideal Carnot cycle dominated my existence.
FIGURE 3.10. Rudolf Diesel, who did not succeed in designing a near-Carnot cycle engine, but whose new machine became the most efficient means of converting chemical energy of liquid fuels into motion through internal combustion. Reproduced from Scientific American, October 18, 1913.
Diesel’s invention belongs to the same category as Charles Parsons’s steam turbine: both had their genesis in understanding the laws of thermodynamics. Consequently, both of these developments are excellent examples of fundamental innovations that appeared for the first time only during the Age of Synergy: inventions driven and directed by practical applications of advanced scientific knowledge, not discoveries arrived at random, or by stubborn tinkering and experimenting. There is, however, an important difference: Parsons had realized his initial goals almost perfectly. Diesel’s main objective, inspired by Carl Linde’s (1842–1934) lectures, proved to be technically impossible, and he had to depart fundamentally from his initial idea of a near-ideal engine, but he still designed a prime mover of unprecedented efficiency.
Diesel also had an explicit social goal for his machine that he described in his famous programmatic publication (Diesel 1893): he wanted to change the fact that only large factories were able to invest in large efficient steam engines by introducing a prime mover whose affordable operation would make small businesses competitive. After his studies in Munich, Diesel became employed by Linde’s ice-making company in Paris in 1880 and spent most of the 1880s in perfecting and developing various refrigeration techniques, including an ammonia absorption motor in 1887 (Diesel 1937). After several years of experiments, he filed a patent application for a new internal combustion engine in February 1892, and in December of the same year he was granted the first German patent (Patent 67,207) for the machine.
Thanks to the interest by Heinrich Buz (1833–1918), director of the Maschinenfabrik Augsburg, and with financial support by Friedrich Krupp, the difficult work of translating the idea into a working device began soon afterward. The engines were to follow the four-stroke Otto cycle, but their operating mode was to be unique. Air alone was to be drawn into the cylinder during the charging stroke, and then compressed to such an extent (Diesel’s initial specifications called for as much as 30 MPa) that its temperature alone (between 800°C and 1,000°C) would ignite a liquid fuel as it entered the cylinder, where it would burn without exceeding the pressure of air and oil injection.
But, as Diesel was eager to stress, to claim that the self-ignition of the fuel is the most important attribute of his design would be an incorrect and superficial view: it would be absurd to build a much heavier engine merely for the sake of ignition when the machine is cold, because once the engine is warmed up self-ignition takes places at lower pressures. The engine’s principal goal was the highest practical efficiency, and this necessitated the use of compressed air (Diesel 1913). Diesel’s initial goal was to achieve isothermal expansion: after adiabatic compression of the air, the fuel should be introduced at such a rate that the heat of combustion would just replace the heat lost due to the gas expansion, and hence all thermal energy would be converted to kinetic energy and the temperature inside the cylinder would not surpass the maximum generated during the compression stroke.
As the conditions close to isothermal combustion could not be realized in practice, Diesel concluded in 1893 that combustion under constant pressure was the only way to proceed (Diesel 1893). But even then, it took more than three years of intensive technical development, and steady downward adjustments of operating pressure, before a new engine (German Patent 86,633, U.S. Patent 608,845) was ready for official acceptance testing. Th
is took place in February 1897, and although the pressure—volume diagram bore little resemblance to Carnot’s ideal cycle, the engine was still far more efficient than any combustion device (figure 3.11). Official testing results showed that the 13.5-kW engine, whose top pressure of 3.4 MPa was an order of magnitude below Diesel’s initial maximum specification, had thermal efficiency of 34.7% at full load, corresponding to 26.2% of the brake thermal efficiency (Diesel 1913).
FIGURE 3.11. Pressure-volume diagrams and details of cylinder heads from Diesel’s U.S. Patent 608,845 (1898) of a new type of internal combustion engine.
By the end of 1897, brake thermal efficiency reached 30%, and 15 years later a much larger (445 kW) diesel engine had mechanical efficiency 77% and brake thermal efficiency 31.7% (Clerk 1911). In contrast, typical brake efficiencies of commonly deployed Otto engines at that time were between 14% and 17%. Diesel’s dream of a Carnot-like engine was gone, but expectations for a machine whose efficiency was still twice as high as that of any other combustion device were high. Licensing deals with potential manufacturers were struck soon after the acceptance testing, but actual commercialization of diesel engines ran into problems associated above all with the maintenance of high pressure and with the timing of fuel injection. The latter challenge was solved satisfactorily only in 1927 when, after five years of development, Robert Bosch (1861–1942) introduced his high-precision injection for diesel engines.
