X-Mozilla-Keys:                                                                                 
Vance Jaqua wrote:

Don Sherman wrote:

This is neither a trick question nor a Wankel

question:  why do virtually all

rotaries [radials] (piston type) have an odd

number of cylinders in each bank?

(Yes, I
know about the master/slave connecting rod designs

within.)  Air & Space asked

me this poser a couple of years ago and I have not

yet found a credible

answer.  DS

Strange as it may seem at first - the radial 4 stroke
engine requires an odd number of cylinders per row to
have an even firing order. typically the cylinder
adjacent will fire 360 degrees plus the cylinder angle
after it's neighbor. With an even number it would seem
to be the first cylinder's turn again - which cannot
be since it is on the exhaust stroke - Curtiss Wright
built a radial that was called 6 cylinders but was
really two rows of 3.  Go around the bank with your
pencil - skipping a cylinder each time and that should
help clarify it - Vance

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