6 cylinder radial

[H Pearce]

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?

 

[Klrskies]

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?

 

[H Pearce]

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!

 

[danallen]

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.

 

[ninefinger]

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

 

[Jasonb]

The Anzani does have the rear cylinders offset, there were some castings about at one time that used many of the same parts as the Cherney design Y configuration also the W configuration

https://modelengineeringwebsite.com/Anzani_6_cylinder.html

 

[Klrskies]

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?

 

[timothysielbeck]

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.

 

[danallen]

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.