cower@garfield.UUCP (01/24/86)
i saw the discussion on the yaw of airplane engines...and was wondering if anyone knew why the number of cylinders on rotary airplane engines seems to be an odd number? i've asked a couple of people who i thought would know, and have never gotten an answer. granted - you don't see rotary engines much on planes (at least where you can count the cylinders)..but i'd still like to know. thanks...rich cower
farren@well.UUCP (Mike Farren) (01/27/86)
As to why radial aircraft engines have an odd number of cylinders, suppose
there was an even number. This implies that each cylinder will have another
directly opposing it. Since the cylinder fires at or nearly at Top Dead
Center, the connecting rod of it's piston will be nearly aligned with the
connecting rod of the piston opposing it, and the result is enormous stress
on both rods.
--
Mike Farren
uucp: {your favorite backbone site}!hplabs!well!farren
Fido: Sci-Fido, Fidonode 125/84, (415)655-0667doug@terak.UUCP (01/31/86)
> i saw the discussion on the yaw of airplane engines...and was > wondering if anyone knew why the number of cylinders on rotary > airplane engines seems to be an odd number? I don't know about rotary engines, but on radial engines the reason is that these are 4-stroke engines with a single crank throw. Since each cylinder on a 4-stroker fires once every two revolutions, the odd number gives a smoother power flow. By the way, to be more precise there are an odd number of cylinders *per bank*. On the more powerful radials, there were multiple banks on the same crankshaft. For example, a 36-cylinder radial can be created by using a 4-throw crankshaft and mounting 4 9-cylinder radials back-to-back. The conceptual difference between a radial and a rotary is that in a radial the cylinders are mounted to the plane and the crankshaft turns with the propellor -- on a rotary the crankshaft is mounted to the plane and the cylinders rotate with the propellor. P.S. If you want still more info, try net.aviation -- lots of folks over there with lots of good scoop on this sort of stuff. -- Doug Pardee -- CalComp -- {hardy,savax,seismo,decvax,ihnp4}!terak!doug