Individual rows are always an odd number of cylinders. Why is this?
rsa
February 25, 2016, 1:52am
2
Basically it’s for vibration control. Just as a straight six auto engine is inherently balanced, so are radial engines with an odd number of cylinders.
To keep the engine running smoothly.
From Wikipedia:
Four-stroke radials have an odd number of cylinders per row, so that a consistent every-other-piston firing order can be maintained, providing smooth operation. For example, on a five-cylinder engine the firing order is 1, 3, 5, 2, 4 and back to cylinder 1. Moreover, this always leaves a one-piston gap between the piston on its combustion stroke and the piston on compression. The active stroke directly helps compress the next cylinder to fire, making the motion more uniform. If an even number of cylinders were used, an equally timed firing cycle would not be feasible.[1] The prototype radial Zoche aero-diesels (below) have an even number of cylinders, either four or eight; but this is not problematic, because they are two-stroke engines, with twice the number of power strokes as a four-stroke engine.
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is called a "star engine" in some other languages.
The radial configuration was commonly used for aircraft engines before gas turbine engines became predominant.
Since the axes of the cylinders are coplanar, the connecting rods cannot all be directly attached t...
Pratt and Whitney engine that powered the Thunderbolt, Hellcat, Corsair, and the B-26 Marauder – 18 cylinders.
Pratt & Whitney engine used by the P-40, F4F, DC-3, B24 - 14 cylinders.
However, each of these engines had 2 rows of cylinders and each row had an odd number, but still …
N9IWP
February 25, 2016, 6:08pm
5
Boyo_Jim:
Pratt and Whitney engine that powered the Thunderbolt, Hellcat, Corsair, and the B-26 Marauder – 18 cylinders.
Pratt & Whitney engine used by the P-40, F4F, DC-3, B24 - 14 cylinders.
However, each of these engines had 2 rows of cylinders and each row had an odd number, but still …
Not to mention the R-4360 which had 4 rows of 7 cylinders:
The Pratt & Whitney R-4360 Wasp Major is an American 28-cylinder four-row radial piston aircraft engine designed and built during World War II. At 4,362.5 cu in (71.5 L), it is the largest-displacement aviation piston engine to be mass-produced in the United States, and at 4,300 hp (3,200 kW) the most powerful. First run in 1944, it was the last of the Pratt & Whitney Wasp family, and the culmination of its maker's piston engine technology.
The war was over before it could power airplanes into c...
Brian
Nefario
February 25, 2016, 6:18pm
6
Ignorance defeated! Thank you! From a lifelong motorhead…
See the F4U Corsair Bird cage. 4 rows of 9
Wow, a question so good someone else had to ask it again right away: Why do aircraft radial engines always use an odd number of cylinders? - Factual Questions - Straight Dope Message Board
Seriously, it was a good question. My old plane had a Continental 220 HP radial engine (7 cylinders), and that kitten could purr! “Powerful as the Nation!”
Boyo_Jim:
Pratt and Whitney engine that powered the Thunderbolt, Hellcat, Corsair, and the B-26 Marauder – 18 cylinders.
Pratt & Whitney engine used by the P-40, F4F, DC-3, B24 - 14 cylinders.
However, each of these engines had 2 rows of cylinders and each row had an odd number, but still …
Yes, it’s important that each row has an odd number, the total doesn’t matter on multi-row engines.