X motors are reciprocating piston motors with four rows of cylinders arranged in an X shape. They were used as aircraft engines, for example the Italian Isotta Fraschini Zeta and the US Packard 1A-2775 . These were 24-cylinder engines, as well as the American Allison X-4520 , the German Daimler-Benz DB-604 and the British Rolls-Royce Vulture . However, the last three examples can be classified more precisely as in-line star engines with 24 cylinders, since the cylinder bank angles are each 90 ° (symmetrical).
There are several forms of X-motors:
- One is symmetrical - i.e. H. all four cylinder banks are at 90 ° angles around the crankshaft (90 ° / 90 ° / 90 ° / 90 °). This form is due to its symmetry - analogous to the symmetrical V-type engine (180 °) and the symmetrical Y-motor (120 ° / 120 °) - better than a star or series of radial engine to look at.
- Another design, on the other hand, has the two opposite cylinder banks arranged at angles different from 90 ° (e.g. 120 ° / 60 ° / 120 ° / 60 °).
- In the third variant, three cylinder banks are arranged at the same angle - e.g. B. 45 ° / 45 °, the third and fourth cylinder bank angle in this case being calculated as 135 °.
The advantage of the X-engine design compared to in-line, boxer, V, W or Y-engines is that a relatively large number of cylinders and thus a lot of displacement and power can be accommodated per engine length.