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Question; Radial Engines; why an odd number of cylinders?

L

Lionheart

SOH-CM-2014
Hey all,

You ever wonder why Radial Engines are always in odd numbers of cylinders and never even numbers? For instance, you always see 3, 5, 7, 9... Never seen a 6 or 8 cylinder....

Anyone know by chance?


Bill
 
I think it has to do with the firing order.

A 9 cyl radial fires in this order ..... 1 3 5 7 9 2 4 6 8

Every second cylinder in the rotation.

Pete.
 
Lionheart said:
Hey all,

You ever wonder why Radial Engines are always in odd numbers of cylinders and never even numbers? For instance, you always see 3, 5, 7, 9... Never seen a 6 or 8 cylinder....

Anyone know by chance?


Bill
Click to expand...

Does it also follow that the multiple rows are even numbers? The R1830 has 14, the R4360 has 28 etc.
 
to understand the concept, just re arrange 2 or 3 of the spark plug wires on the distributor on a v-8 and see how much it likes it
 
i know what has been said is true BUT!!! there was a 16 cylinder radial made ie 2 rows of 8. it was a DOHC Per cylinder.. (british desighn) i also seen a few model aircraft 2 cycles that have the same thing going on with 8 cylinders

so i wonder if you can get away with a even number of cylinders such as 8
 
There were quite a few radials with an even number of cylinders, the P & W Wasp Major, for example. Each single row of pistons usually had an odd number of cylinders, though, for the reasons stated above.
 
grumpos said:
There were quite a few radials with an even number of cylinders, the P & W Wasp Major, for example. Each single row of pistons usually had an odd number of cylinders, though, for the reasons stated above.
Click to expand...

And, the ones with more than one rows always had the cylinders staggered, the Hydra being an exception (this is a Major):

View attachment 4744

Staggering the cylinders had roughly the same effect as an odd number of cylinders.

-James
 
THIS THREAD!!!!!
1228206413316.jpg


Is the coolest thread I've seen anywhere in a long time. I'm impressed with some of the knowledge thrown out there. Any time a thread about something I don't know in aviation gets technical, I'm all for it.
 
grumpos said:
There were quite a few radials with an even number of cylinders, the P & W Wasp Major, for example. Each single row of pistons usually had an odd number of cylinders, though, for the reasons stated above.
Click to expand...

Yes, but always with an even number of rows. I never saw a 21 cylinder engine (3x7) for example.(Fully expecting someone to step in and prove me wrong! ;) )

More cylinders and then more rows of cylinders was the easiest way to increase power in those days. Making the cylinders larger would make the engines bigger, increasing the frontal area and drag. The Hydra was originally designed as a V-4 apparently, and the design worked so well they just quadrupled it to a sixteen cylinder engine.
 
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