Early diesel engines

Rudolph Diesel’s intention was to replace the steam engine as the primary source of energy for industry. Diesel engines in the end of the XIX century and early twentieth century used the same form and layout as industrial steam: high-stroke cylinders, external valve, cylinder heads per cylinder and crankshaft without Carter, coupled to an enormous flywheel. Soon, there will be smaller engines with vertical cylinders, while most industrial motors large and medium sized were all horizontal cylinder, and just as steam engines, had more cylinders.

Highest early diesel engines were replicas of the steam, with impressive length, the top few meters. They operated with a very low speeds, mainly due to diesel injected with compressed air, but also because it had to meet most industrial equipment built for steam engines, where normal operating speeds fell between 100 and 300 revolutions per minute. Engines started using compressed air, which was introduced in the cylinder and rotated the engine, while the lowest could be turned on manually.


In the first decades of the twentieth century, when larger diesel engines were installed in ships, they were as steam engines, pushing a piston rod coupled to a rod that rotated shaft engine. Following the model steam engines were built with double-acting engine, where combustion take place on both sides of the piston to increase the strength. They had two sets of valves and two fuel injection systems. The system allowed also change reversing, changing times of injection. Therefore, the engine can be directly coupled to the propeller axis, without the need for a gearbox. Although they had great power and were very efficient, large double-acting engine problem was the combustion chamber and lower segments. In 1930 it was found that fitting turbochargers was an easy and effective solution.

Modern diesel engines

Diesel or petrol engines are in 2 stroke or 4 stroke. Most engines are 4 stroke, but bigger ones work in 2-stroke, mainly those on the ship. Most modern locomotives use in 2-stroke diesel engines coupled to electrical generators that act as electric motors, eliminating the need for transmission. To increase pressure cylinders used overeating, especially two-stroke diesel engines with two races per rotation of the crankshaft useful.

Normally, the cylinders are multiples of two, but can use any number of cylinders, as long as any excessive vibrations are eliminated. The configuration used is the 6 cylinder in line, but and 8 cylinders in V or 4 in line are used. Small capacity engines (especially those under 5000 cc) usually have 4 (majority) or 6 cylinders, used cars. There are 5-cylinder engines, a compromise between the smooth operation of one of 6 cylinders and  a small scale of one to 4 cylinders. Diesel engines for current uses (boats, generators, pumps) were 4, 3 and 2-cylinder or a small capacity single cylinder.

The desire to improve the ratio weight / power have brought innovations concerning the arrangement of cylinders to get more power per displacement. The best known engine is the Napier Deltic with three cylinders arranged as a triangle, each cylinder having 2 pistons with opposite action, all engines with crankshafts 3. Commer, a truck company in the UK has used a similar engine for its vehicles, designed Tillings-Stevens, member of the Rootes Group, called TS3. TS3 engine had 3-cylinders, horizontally inclined, each with 2 pistons acting opposite connected to the crankshaft through a mechanism type rocker arms. Although both technical solutions produced a higher power for their engine capacity, the engines were complex, expensive items and maintain.

Watch tweets on: