Invention Of The Internal Combustion Engine

The Beginnings of Mechanical Transport for the Millions

Silently, too engrossed to jeer, the small boys watched him. It was a warm summer’s day, a soft breeze was rolling in from the vineyards across the Neckar. Bad Cannstadt was at peace; the year was 1885.

Yet, somehow, even the street urchins, anxious to disturb it themselves, were aware that this was about to be shattered, and for ever.

Bicycles were common in Cannstadt, but they were expensive and this particular one looked more expensive than most. The crowd, it wasn’t entirely small boys, their elders were wandering up to the top of the hill, the steep slope up from the River Neckar, was arriving as if by accident; no one would admit having walked any distance to see a middle-aged gentleman try out a bicycle.

And suddenly, Herr Daimler was off. With considerable agility for a man of over fifty, he ran a few paces with the bicycle, holding it by the handlebars, and as it began to nose over the hill, hopped on board, began to pedal. Then the small boys and their elders could see him lean down to fiddle with the “engine” he had bolted to the frame.

He stopped pedalling.

With the noise of a hundred firecrackers and an explosion of deep blue smoke which all but obliterated machine and rider, the engine started. There was a confused cheer from the small crowd, confused because no one was sure what was happening. The bicycle had started off downhill by gravity and pedals; it was still going down, in the middle of its private cloud, but now to the accompaniment of a truly frightening noise and at a frightening speed.

A minute later, Daimler was returning, ascending the slope from the Neckar, and his feet, but surely, they couldn’t be?, his feet were stationary on their pedals. The world’s first motorcyclist had gone down to the river and come up, alive.

Gottlieb Daimler, whose name lives on with the Daimler-Benz firm of Germany, and a famous motor-car firm in England, has been credited with the invention of the motor-car as well as the motor-cycle; but this is contested. As the first man, though, to use the internal combustion engine for his own transport, if only with a humble “bike”, he has earned a niche in history. From his motorcycle he went on to make the world’s first motor-boat, to terrify innocent men and women sailing on the Rhine.

The engine he made so popular, the internal combustion engine, gets its power from fuel. Like its predecessor, the steam engine, it belongs to the group of “Heat Engines”, but it differs from the steam engine in that its fuel is consumed in the cylinder itself, with air, and the working pressure is produced by the sudden expansion of air which this causes. It can obviously be made less cumbersome than a steam-engine and it has other conveniences which have made it supplant the steam engine for many tasks. It is compact, it can minister automatically to its own needs, adjust its own intake of fuel and air; and it can start instantly, without the delay of lighting a fire, raising steam.

Probably the first internal combustion engine was made by the talented Dutchman, Huyghens, in the seventeenth century. He had already made improvements in clocks and optical instruments and was busy exploring the secrets of the universe with a telescope when suddenly he became earthbound: he had been struck, as if by lightning, with the idea of constructing an engine, which would work by gunpowder. He made it. The powder was ignited in a large cylinder under a tightly fitting piston, and this piston was forced violently up the cylinder by the explosion. Most of the resulting gas was allowed to escape through a one-way valve and the bit that remained shrank, when it cooled, so that a vacuum sucked the piston down again.

In fact, of course, the piston was forced down by the pressure of the atmosphere acting above it, against the vacuum below. There is no record of this terrifying engine having a practical application; its movement must have been violent, noisy and spasmodic. But, as an idea, it was a big step forward.

Rather over a hundred years later, in 1824, Samuel Brown produced a version which did useful work in pumping water. Instead of a rigid piston plunging up and down in a metal cylinder, Brown moved a column of water by his explosion, and achieved with this method a highly effective pump. When rotary movement was required, he simply pumped the water to a height, used it to work a water-wheel. Not, perhaps, the best arrangement for a moving vehicle, though it is amusing to picture one; a huge charabanc perhaps, with engine, water-tank and wheel at the back. The internal combustion engine became practical in 1876 with Professor Otto’s version. This had a “four-stroke” system of operation, a system which had been invented some years previously but which, until Otto, had never worked satisfactorily. The basic design of the four-stroke I.C. engine has hardly changed since Otto made it work; it provides the power for most of our cars, a proportion of our trains, ships, aeroplanes.

In Otto’s system, a mixture of fuel and air is sucked in through a valve at the top, by the first, downward, “suction” stroke of the piston (which has to be performed by hand). “When the piston reaches the bottom of the stroke, that “inlet” valve closes automatically, and during the second, upward or “compression” stroke the mixture is compressed, squeezed into a small space at the top of the cylinder. (This compression makes the mixture more combustible, so that a smaller proportion of fuel is needed.) At the top of the compression stroke an electric spark is introduced to ignite the mixture, and the resulting explosion forces the piston down in a “power” stroke. For the last, “exhaust”, stroke the piston ascends, borrowing momentum from its power stroke by means of a flywheel and a crank, like a bicycle pedal, and drives the burnt gases out through a second valve, the “exhaust” valve, also at the top. This closes automatically at the top of the stroke. The engine is then ready for a second four-stroke cycle of, suction, compression, power and exhaust strokes.

As we can see, only one of these strokes provides power, and it is usual to have other cylinders connected to the same crank, their “firing order” being arranged so that the power strokes come one after the other; with a four-cylinder engine, one of the cylinders is always on a power stroke, giving a smooth impetus to the nonproductive strokes of the other three.

But we must still remember, however many cylinders we decide to build into our engine: the first cylinder will still have to achieve a suction stroke and a compression stroke before it is able to fire. We must therefore rotate the engine for at least these two strokes, by hand, or as is now universal, by a small electric motor, a “starter”.

In 1881, Dugald Clerk designed an engine which worked on two strokes, not four: each descent of the piston was a power stroke; only the ascending ones were non-productive. In theory, this might be twice as efficient as the four-stroke engine, but such was far from the case, and two-stroke engines have only a limited application, in the smaller sizes, for things like motor-cycles and lawn-mowers. Basically, the “two-stroke” admits and compresses its mixture below the piston, not above (so, obviously, does it on a descending stroke), and then transfers it ingeniously through a “transfer port” to the space above, where it is ignited when the piston has returned to the top. Despite this doubled rate of power-stroking, the two-stroke engine is inefficient; the pumping, compressing, efficiency of the space below the piston is poor, and as the exhaust gases are driven out by incoming mixture, there is always some intermingling so that a small residue of useless, burnt gas remains in the cylinder, reducing the power of the explosion.

The two-stroke engine has tended to be neglected by designers, but its extreme mechanical simplicity, it can be built with only three moving parts, is a considerable asset.

All these early internal combustion engines from Otto’s on were powered by coal-gas. This was convenient for stationary models, but not ideal for those intended to move, like Daimler’s motorcycle. He was therefore the first man to use a liquid, a product of petroleum distillation which he called “benzine”, which we know as petrol or gasoline. Daimler’s principle, of mixing a little of the liquid with a larger volume of air, in a “carburetter” and then sucking the gaseous mixture into the cylinder, is the one still used for petrol engines.

Petrol, gasoline, benzine, by any name it is fairly expensive. Many inventors tried to use cheaper, cruder, oils. None were successful until Rudolph Diesel produced his “diesel” engine, and now these cruder oils are widely used. They will not ignite satisfactorily with an electric spark, but Diesel discovered that if a great deal of compression were used, if the engine were really heavily built, and the piston were then forced almost to the very top of the cylinder, leaving a very small space for fuel, the oil would ignite spontaneously, in the heat of compression. The general practice today is to inject the fuel as a liquid into the top of the cylinder, just as the piston is nearing the top of its compression stroke.

Diesel engines tend to be more economical of fuel than their petrol-driven counterparts, and the fuel is cheaper, but the engine is heavy, it accelerates badly and runs roughly at low speeds. These disadvantages have to be weighed against its economy, and although it is popular for heavy lorries it has found no favour with the ordinary motorist.

As we have seen with our four-stroke petrol engines, all these various types of internal combustion engine have a major disadvantage: an inability to start unaided. The modern electric starter is highly efficient, but it needs, for the few seconds it is running, a very great deal of electricity, and this presents problems of battery and generator which add to the weight and complexity of the engine. Another disadvantage of the I.C. engine is its narrow range of efficient operating speeds: unlike the steam engine it cannot shift a heavy load from rest, it requires a complicated system of gearing enabling it to “run fast and work slow”. In a car, the efficient range of engine speeds is narrow.

We can only start off from rest if we run the engine at the same speed as if we were travelling at forty miles an hour in top gear, and then engage a low one. But in this low gear the car is incapable of moving fast, the engine just can’t go round that rapidly, so we must change gear, perhaps two or three times, to reach the cruising speed we want. In this way we keep the engine running at much the same speed for all gears and most speeds.

It is this need for changing gear which has restricted the I.C. engine’s use for railways. A gear-box to deal safely with the huge power and torque of the engine required to move a train just wouldn’t be practical, and at present diesel engines on trains are used to generate electric current which then powers the considerably more flexible electric motor. A great deal of power is wasted in the transfer. This is why many railways, including our own, have been investing a huge capital outlay in overhead wires to operate electric trains direct.

And quite probably, by the time all lines have been electrified, an internal combustion engine will have been developed, either with a new gear-box or just in itself capable of working over a wide range of speeds.

The simplest form of internal combustion engine, though the title is usually reserved for the reciprocating, two- or four-stroke, variety, is the rocket. In this, the gases of combustion escape through a nozzle at the rear and drive the rocket forward. The gases can be used, instead, to drive a turbine-wheel, and this “gas-turbine” is now widely used in aircraft and may soon be used in cars. But most designers are confident that, although there are signs that the normal I.C. engine may some day be replaced for motor vehicles (as it largely has for aircraft), it is capable of further development. One interesting and hopeful experiment has been the German rotary-piston engine; this is claimed to be but a fraction of the size of a normal I.C. engine, so that the engine of a small car could be accommodated in the glove compartment.

Certainly, in the second half of the twentieth century, we can see that the internal combustion engine, whether or not it will be replaced, has revolutionized our lives. No modern farm could run without tractors and our lives would be difficult, at the very least, without cars, trucks and buses, the diesel trains on our railways.

If man lost the secret of the internal combustion engine, if Otto’s and Daimler’s work had been in vain and their secret vanished overnight, we would find ourselves in a far worse position than that of our ancestors, a century ago. They had never considered the horseless carriage, were not dependent on it. We are, and much as we may sigh for the peace, the silence of the day before the day Gottlieb Daimler mounted his motor-bike, we would find our lives unlivable without his internal combustion engine.