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Ed Anderson wrote:
The rotary is also pretty sensitive to back-pressure, so what kills the noise generally does the same to the power. There was one design I tired that used 3" dia SS disc in a tube with "Paddles" bent on the outer permimeter. The ideal was that the shock wave would see solid metal and be reflected - but the exhaust gas would cruve and flow around the paddle blades.
It worked (while it worked) , I flew from NC to Florida and it measurably reduce the exhaust note (by something like 8 db), the problem was the discs and the jam nuts I had holding them on a 3/8" dia SS rod (I don't weld) I had through their center. At some point, some of them (I had 5 discs in each tube) worked loose under the pounding . They then began to act like a windmilling propeller (yes, they were spinning at high speed). The effect was to expotentially increase the drag on the exhaust gas and imped gas flow.
Tracy was kind enough to use his arc welder to weld the discs to the rods (that lasted for about two weeks).
I think you gave up to early on that one Ed, but I can see how you felt like you did your part with so many others under your belt. The way I'm seeing it, the 3/8" torque arm was just way to small for the 3" disks torque arm. What you needed was some rosette welds on the perimeter of the discs to tack them to the will of the tube.
Make the discs last, and we can feed the exhaust through that Swiss muffler that Neil is talking about.
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