Basically it’s for vibration control. Just as a straight six auto engine is naturally balanced, so are radial engines with an odd variety of cylinders.

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To save the engine running smoothly.

From Wikipedia:

Four-stroke radials have actually an odd variety of cylinders per row, so that a continuous every-other-piston firing order deserve to be kept, giving smooth procedure. For example, on a five-cylinder engine the firing order is 1, 3, 5, 2, 4 and back to cylinder 1. Additionally, this always leaves a one-piston gap in between the piston on its combustion stroke and the piston on compression. The energetic stroke straight helps compress the following cylinder to fire, making the movement even more uniform. If an even variety of cylinders were provided, an equally timed firing cycle would not be feasible.<1> The protoform radial Zoche aero-diesels (below) have actually an also number of cylinders, either four or eight; but this is not problematic, because they are two-stroke engines, through twice the number of power strokes as a four-stroke engine.

en.wikipedia.org
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Radial engine

The radial engine is a reciprocating kind interior combustion engine configuration in which the cylinders "radiate" outward from a central crankcase prefer the spokes of a wheel. It resembles a stylized star as soon as perceived from the front, and is called a "star engine" in some languages (German Sternmotor, French moteur en étoile, Japanese 星型エンジン (hoshigata enjin), Italian motore stellare). The radial configuration was typically supplied for aircraft engines prior to gas turbine engines ended up being preleading. S...


Pratt and Whitney engine that powered the Thunderbolt, Hellcat, Corsair, and also the B-26 Marauder – 18 cylinders.

Pratt & Whitney enginesupplied by the P-40, F4F, DC-3, B24 - 14 cylinders.

However, each of these engines had 2 rows of cylinders and also each row had actually an odd number, however still …


Boyo_Jim:

Pratt and Whitney engine that powered the Thunderbolt, Hellcat, Corsair, and also the B-26 Marauder – 18 cylinders.

Pratt & Whitney engineoffered by the P-40, F4F, DC-3, B24 - 14 cylinders.

However before, each of these engines had actually 2 rows of cylinders and also each row had actually an odd number, but still …

Not to mention the R-4360 which had actually 4 rows of 7 cylinders: en.wikipedia.org

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Pratt & Whitney R-4360 Wasp Major

The Pratt & Whitney R-4360 Wasp Major is an Amerihave the right to 28-cylinder four-row radial piston aircraft engine designed and also developed throughout World War II, and also the largest-displacement aviation piston engine to be mass-produced in the USA. It was the last of the Pratt & Whitney Wasp family members, and the culmination of its maker"s piston engine technology, however the battle was over before it could power airplanes right into combat. It did, yet, power many of the last generation of large piston-engined aircraft ...


Brian


Nefario February 25, 2016, 6:18pm #6
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Richard_Pearse:

To store the engine running smoothly.

From Wikipedia:

https://en.wikipedia.org/wiki/Radial_engine

Ignorance defeated! Thank you! From a lifelong motorhead…


Morgenstern February 25, 2016, 6:19pm #7

See the F4U Corsair Bird cage. 4 rows of 9


Qadgop_the_Mercotan February 25, 2016, 7:36pm #8

Wow, a question so excellent someone else had to ask it again appropriate away: http://jiyuushikan.org/sdmb/showthread.php?t=785150

Seriously, it was a great question. My old airplane had actually a Continental 220 HP radial engine (7 cylinders), and also that kitten might purr! “Powerful as the Nation!”


Boyo_Jim:

Pratt and also Whitney engine that powered the Thunderbolt, Hellcat, Corsair, and the B-26 Marauder – 18 cylinders.

Pratt & Whitney engineprovided by the P-40, F4F, DC-3, B24 - 14 cylinders.

See more: Why Is A Plowed Field Feathered Game ? Why Is A Plowed Field Like Feathered Game

However, each of these engines had actually 2 rows of cylinders and also each row had actually an odd number, however still …

Yes, it’s essential that each row has an odd number, the full doesn’t issue on multi-row engines.