6 cylinder radial

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H Pearce

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Hi all,

Thought this was interesting. I was under the impression that radial engines always had an odd number of cylinders. Was visiting a museum this afternoon and they had a 6 cylinder anzani. Sorry for the quality of the picture. If there is some real interest I can go back and get some more.
One thing that has just occurred to me is that the cylinders look to have a fore/aft offset, is it maybe a double row 3 cylinder setup?
 

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Hi all,

Thought this was interesting. I was under the impression that radial engines always had an odd number of cylinders. Was visiting a museum this afternoon and they had a 6 cylinder anzani. Sorry for the quality of the picture. If there is some real interest I can go back and get some more.
One thing that has just occurred to me is that the cylinders look to have a fore/aft offset, is it maybe a double row 3 cylinder setup?
Would that then satisfy the odd number of cylinders theory? Was that a harmonic issue? What number of cylinders per bank were the wasp engines?
 
Would that then satisfy the odd number of cylinders theory? Was that a harmonic issue? What number of cylinders per bank were the wasp engines?
I assume it would then be a “standard” odd number radial. So far as I know all radial engines were odd numbers of cylinders. Although I’m sure there must be at least one even one somewhere!
 
My understanding is the engines with an even number of cylinders are rotary engines. A different animal where the crank is fixed and the cylinders rotate with the prop.
 
4 stroke radials have odd numbers of cylinders to keep the firing equally space - i.e. for a 7 cylinder: 1-3-5-7-2-4-6 back to 1....)
An even number of cylinders results in 2 cylinders firing beside each other, introducing an uneven power pulse and vibrations (1-3-5-2-4-6 ->back to 1, 1 and 6 are next to each other)
That Anzani looks like it is offset front to rear so likely has a 2 throw crankshaft, so effectively 2 x 3 cylinders.
FYI - a 4 stroke rotary where the cylinders spin still has the issue with needing to fire every 2nd cylinder for even power distribution.

2 strokes radials or rotaries can have any number of cylinders as each cylinder is firing on each rotation (they just have a different challenge - induction)

Mike
 
4 stroke radials have odd numbers of cylinders to keep the firing equally space - i.e. for a 7 cylinder: 1-3-5-7-2-4-6 back to 1....)
An even number of cylinders results in 2 cylinders firing beside each other, introducing an uneven power pulse and vibrations (1-3-5-2-4-6 ->back to 1, 1 and 6 are next to each other)
That Anzani looks like it is offset front to rear so likely has a 2 throw crankshaft, so effectively 2 x 3 cylinders.
FYI - a 4 stroke rotary where the cylinders spin still has the issue with needing to fire every 2nd cylinder for even power distribution.

2 strokes radials or rotaries can have any number of cylinders as each cylinder is firing on each rotation (they just have a different challenge - induction)

Mike
I had read once that the early rotary's thin, light cylinders were machined down from around 2000lbs of billet steel, as they didn't have spin casting technology at that time. I wonder if a rotary would have a mild supercharging effect from the spinning assembly, the mixture within the intake tube being centrifugally flung away from center?
 
My understanding is the engines with an even number of cylinders are rotary engines. A different animal where the crank is fixed and the cylinders rotate with the prop.
All single bank rotaries that I know of have an odd number of cylinders. The only rotary that I know of with an even number had two banks of seven cylinders, the Oberursel UR III.
 
All single bank rotaries that I know of have an odd number of cylinders. The only rotary that I know of with an even number had two banks of seven cylinders, the Oberursel UR III.
I stand corrected. Not sure how I came to think rotary engines had an even number of cylinders. Admittedly I am not very knowledgeable about them.
 

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