| From: Dave Collier-Brown via talk <talk@gtalug.org> | When I was a motorcycle mechanic I had a circular slide rule, with a | permanent mark at the coefficient for computing a catenoid, as I did a | lot of 2-stroke exhaust systems. Some hilariously wrong, some which got | me a reputation as a wizard. I know what a catenary curve is. The standard example is of a chain hanging between two posts (that's where the name comes from). Or a hydro wire. <https://en.wikipedia.org/wiki/Catenary> I understand that a catenoid is a surface of revolution of a catenary curve: <https://en.wikipedia.org/wiki/Catenary> I don't know what the coefficient for computing it would be. I don't even know what the inputs to this computation would be. How is this applied to 2-stroke engine exhaust systems? Is this related to back pressure or resonance? Maybe you are a wizard. [I hate 2-stroke engines because they pollute so much. I'm only exposed to them running lawn maintenance equipment.]