04-12-2022, 11:33 AM
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Contest, Sport, it's all good......
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Join Date: Jul 2008
Location: West of Minneapolis, MN
Posts: 760
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Quote:
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Originally Posted by tbzep
I enjoyed the videos. What material are the piston tubes made of? The B6 Egglofter flight put a lot of side force on it. It bowed like a spring but came right back.
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18mm paper body tubes from BMS. That is why they look white.
That B6 eggloft piston was 68" long (two 34" tubes, with a 19mm external coupler. And the inside edges sanded with a cone of sandpaper to round the lips so the piston head slides thru as though there is no joint at all).
It seems as it sepped, the exhuast helped to deflect the top sideways, acting upon the flat face of the top ring. The mass of the top centering ring helped it "twang" like that (plus the initial deflection cause), as I have not noticed that effect on any other 68" pistons that did not have those centering rings. Indeed that's the most extreme "twang" I've seen in flight test videos. Also, there is a chance that the piston tube also bowed some from the vertical acceleration, given the mass it was pushing and possibly the egglofter not being dead center. |