WesWorld

Hi!

Radial engines with 14 cylinders often had their roots in 7 cylinder models, sometimes they were even like two 7er stars clued together. A 28 cylinder engine then resembles four 7er...

IIRC there also have been 5 or 9 cylinder radials but I can´t remember if anybody put together a double-5 or double-9. and if they were sucessful. Were there any? What defines how many cylinders were sucessful, made sense?

Can you help?

Sure, there were 18 cylinder radials: some of the more famous are the Wright R-3350 and Pratt & Whitney R-2800, along with the Bristol Centaurus, the Shvetsov ASh-73, and the Nakajima Homare as examples. The BMW-802 had 18 cylinders, but was never produced in quantity. I'm not sure that anyone ever did a 10 cylinder two-row radial for production, it was probably easier to just do a 9-cylinder. 4 row radials were NOT common, the R-4360 is about the only one I know of that got into production.

The R-4350 is the one used for the Connies, right?

No, the Constellation used the R-3350. The R-4360 was used on a fair number of post-War cargo aircraft, the C-97, the C-74, the C-124, the C-119, the Spruce Goose, etc. It was also used on the B-50, the P4M, the B-35, etc.

Its to do with balancing a number of factors. Realistically there is an upper limit on cylinder size, usually only odd numbers of cylinders for balancing reasons, not usually more than 9 per row from space considerations, try and have as few cylinders as possible to ease maintenance.

From memory, a 7 cylinder radial has about 92% the frontal area of a 9 cylinder so theres not a great deal between the,. Max cylinder bore is around 6" so if you want lots of power you have to go with lots of cylinders as with the R-4360.

One of my favourites would be a 3 or 4 row Bristol Taurus as you've got small frontal area and not much weight with lots of power. But its more complicated and more maintenance intensive than the 18cylinder Centaurus of similar power.

Adding cylinders and rows makes the gearing more complicated as well so it isn't really possible to stick with 4 valves per cylinder which eats into performance a bit. The sleeve valve is the best solution.

So would a 10- or 15-cylinder engine make sense (5er-stars in rows)? Are there historical examples?

Historically, there are very few engines with 3 or more rows that made it into production: the R-4360 is the only one I'm aware of (the Jumo-222 and the BMW-803 both had 4 rows, but neither one made it into production). I'm not aware of any 10 cylinder engines ever being put into production.

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Originally posted by HoOmAn
So would a 10- or 15-cylinder engine make sense (5er-stars in rows)? Are there historical examples?

I wouldn't recommend it as a 9 or 14 cylinder radial would offer similar performance but would be simpler.

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the Jumo-222 and the BMW-803 both had 4 rows, but neither one made it into production

There's also the Alfa Romeo 1101 28 cylinder type which will appear at some point here.