Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site decwrl.DEC.COM
Path: utzoo!watmath!clyde!burl!ulysses!bellcore!decvax!decwrl!dec-rhea!dec-raja!merrill
From: merrill@raja.DEC
Newsgroups: net.physics
Subject: Odd number of pistons on planes
Message-ID: <735@decwrl.DEC.COM>
Date: Mon, 27-Jan-86 10:29:03 EST
Article-I.D.: decwrl.735
Posted: Mon Jan 27 10:29:03 1986
Date-Received: Tue, 28-Jan-86 06:22:25 EST
Sender: daemon@decwrl.DEC.COM
Organization: Digital Equipment Corporation
Lines: 16



Walt Hanstein proposes the following explanation for why piston driven
airplanes use odd numbers of cylinders:

Rotary engines have essentially a single crank per cylinder bank.
If you had seven cylinders in one bank you could also make a two
bank 14 cycle engine, 21 cyls., 28 etc.  Because these engines are two
stroke engines, they require two complete revolutions to fire all
seven cylinders once.

So a reasonable firing order might be 1 3 5 7 2 4 6 and then 1 again.
That would provide reasonable smooth torque.  I wouldn't know how to
get as smooth a torque using an even number of cylinders.

-------------------------------------------------------------------------