Seven cylinder engine

from Wikipedia, the free encyclopedia

The seven-cylinder engine , just seven cylinders , is a rare type of reciprocating - combustion engines . It is available as an in- line engine - then usually as a diesel engine , and as a radial engine - usually petrol engines . The in-line diesel engines are usually water-cooled , while the radial engines are air-cooled .

Types

In-line engine

In-line engines with seven cylinders, preferably two-stroke diesel engines , are used to propel ships. Well-known manufacturers of such marine diesel engines are MAN Energy Solutions ( B&W brand ) and the Finnish company Wärtsilä , but engines of this type were also manufactured under a MAN license by VEB Dieselmotorenwerk Rostock for the DSR of the former GDR. Their elongated design made them unattractive for installation in cars, but they are manufactured by the Finnish engine manufacturer AGCO Power (formerly SISU Diesel) as drives for tractors, combine harvesters and heavy trucks. In the 1950s, Krupp also built a seven-cylinder two-stroke diesel engine as an in-line engine for a heavy dump truck, which consisted of a three- and four-cylinder engine block.

Radial engine

Air-cooled seven-cylinder radial engine Siemens Sh 14

As early as the First World War , many types of aircraft were fitted with air-cooled seven-cylinder rotary engines in which the crankcase , cylinder and propeller rotated around the rigid crankshaft . Seven-cylinder radial engines of conventional design were used as aircraft engines for a long time because they offered the best possible ratio of number of cylinders, structural stability and engine performance. However, the structure ( valve control with cam drum , crankshaft with seven connecting rods ) and thus maintenance is more complex than with in-line engines.

Constructive features

The moderate running smoothness of seven-cylinder in-line engines, which is also a reason for their almost complete lack of use in motor vehicle construction, results from the odd-numbered crank offset, similar to that of five-cylinder engines. Additional difficulties arise in the manufacture of the mechanical core components (crankshaft in a seven-cylinder in-line engine or cylinder block and connection points of the secondary connecting rod to the main connecting rod in a seven-cylinder radial engine) from the difficult division of the full circle angle by seven (360 °: 7 = 51.428571 .. . ° or 51 ° 25'42.857142 ... ") , this can only be approximate. The construction of seven-cylinder engines is therefore only possible with the use of the permissible error tolerances and the best possible approximation of the desired result Even if the number of cylinders is even or divisible by three, even if seven-cylinder in-line engines are occasionally still built and used as ship propulsion systems.

Trivia and curiosities

  • The Dutch Navy, for example, equipped the submarine UD3 (Onderzeeboot 25 or O25) with two seven-cylinder in-line engines (two-stroke diesel).
  • An American type of tank from World War II, the M3 Stuart , was equipped with a modified air-cooled seven-cylinder aircraft engine (radial engine).
  • Custom bike manufacturers, such as JRL from the United States, build motorcycles with original seven-cylinder radial engines from aircraft construction.

supporting documents

  1. General information about the UD3 submarine