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 Development 1
1921 MAN single cylinder, 16 kW (22 HP), approx. 5.000 kg
kfz-tech.de/PDM15
Anyone who believes that with an invention and its realization, the inventor's luck will forever be on their side and that the product will find its way will unfortunately be
disappointed. It's the same then as it is
now. The bigger the hype surrounding something, the more sudden the disappointment. People simply don't realize that the world can't change overnight.
Want an example? A factory was founded specifically for the construction of diesel engines. Rudolf Diesel was initially against it and had to watch as people initially scrambled
to buy the shares, but after
incredibly poor management and many defective engines were delivered, they quickly lost value. He himself was ill, but still tried to compensate the owners a little by buying the
shares.
However, this significantly damaged the reputation of the diesel engine. And then came the scorn of those who didn't invent the engine. Even worse, that of competitors. It was a
good thing that the diesel
engine was initially built in small numbers for power generators, ships, and railways. Nevertheless, Rudolf Diesel suffered a setback: the value of his acquisitions of companies
producing diesel engines and oil wells in Galicia, which were not profitable, declined.
With that, we leave Rudolf Diesel. For him, a difficult period of apparent wealth began, but also illness and early death, or rather, suicide. He lived to see the worldwide success
of his engine. However, his death
spared him from the worst possible misfortune in diesel engine development.
In 1914, one year after his death, the world teetered on the brink. It was the beginning of the First World War, and industry had long since shifted to armaments production. MAN
received the contract to
develop a 12,000 hp marine engine. Despite its power, it was only supposed to have six cylinders and therefore be double-acting, meaning the pistons would be fired with
combustion pressure from both above and below.
To achieve this, the connecting rod had to be split into an upper, straight section and a lower section that pivoted with the crankshaft. The 'crosshead' design allowed a kind of
partition to be inserted beneath
the piston, generating compression or combustion pressure. Whether two- or four-stroke, the power was essentially doubled.
An experimental engine was built, already with three cylinders. The engine was particularly tall because of the long connecting rod. Above all, the cooling of the pistons, which
were now insulated from below,
was problematic. Everything was missing. For the test run, all the water available in the factory had to be diverted to the (wooden) test bench. And then it happened, the engine
exploded and the hall caught fire.
The consequences were enormous. No one had thought about the workers' oil-stained overalls, which caught fire in an instant. A total of 10 people died. At least the fire
department managed to protect a
neighboring pressure tank. But the reputation of this construction method was lost, despite a new beginning with only one cylinder. It was completely abandoned sometime in
the 1930s.
Of course, we are not so much looking at the large diesel engines here. These were successfully built at the Augsburg plant soon after it was spun off. Only hesitantly
Nuremberg plant, which was suffering
from emaciation, approached the construction of trucks. No, not what you might think now. It was practically the takeover of the production of the Swiss Sauer-Werke and its
products all had gasoline engines.
The impetus again came from the military administration, and since the Swiss also supplied Germany's wartime enemy through a French factory, they couldn't operate in
Germany themselves. Of course, the military guaranteed purchase, but after the war, with inflation and rising unemployment, this was no longer the case. The diesel engine
could have achieved cost-saving effects here, but truck production probably suffered from modest production numbers, and not only at MAN. The then most modern Reichsbahn
network in Europe dominated the transport system too much.
Nevertheless, work continued on a vehicle diesel engine, which, of course, had almost nothing in common with those built previously. Only Daimler worked with the traditional air
injection system, but abandoned this principle upon its merger with Benz in 1926. There, the pre-chamber process developed by Prosper L'Orange began its triumphant
advance. And although MAN was already working on direct injection at that time, the secondary combustion chamber dominated the diesel world in trucks until the 1960s and in
cars until the 1990s.
Now, one shouldn't imagine the first MAN four-cylinder with 7.3 kW (10 hp) at 700 rpm too romantically. It, and its successors for a long time afterward, barely met the most
basic standards for being near it. Even if it didn't emit soot, it still stank horribly from its fuel combustion. The breweries that were later the first to be supplied noted only a third
of the fuel consumption of the gasoline engine, but also a slightly different taste of the beer they delivered.
Additionally, one must consider the power-to-weight ratio, as the permissible total weight was at least 4 tons from the beginning. After all, the diesel engine in five-ton trucks
developed to 40 kW (55 hp) by 1925. The mileage of the diesel engines, however, was astonishing. One is known to have covered 600,000 km, albeit over a very long period.
And so, for years, MAN's direct-injection engines, later with their legendary center-ball system, competed with the Daimler-Benz pre-chamber. And although torque was now becoming more of a focus in heavy trucks, MAN
launched its first 10-ton truck with a 150 hp gasoline engine as early as 1927. The diesel engine with equivalent power didn't arrive until five years later.
It's fair to say that from 1933 onwards, MAN's buses, in particular, were almost exclusively equipped with diesel engines. However, given the low production volumes achieved in the truck sector, the diesel engine's
presence in public transport until World War II was rather sobering.
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