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M Roberts wrote:
Doug,
About the two VS one piece manifold flange. The reason for the RB single flange is to prevent fatigue failure of the studs in the rotor housings. The block of course is very rigid and does not move. Expansion and contraction of the header from thermal cycling can eventually break the studs off. First it will crack the exhaust/welds, if you keep making the header stronger to the point where it no longer fails, it will break the studs off. A lot depends on how the header is made. The worst case scenario is a Log type manifold with short stubs to the rotor housings and two separate flanges. The short stiff header has very little flex and will place a load on the studs. If you have nice long looping header primaries, there is enough flex in them to absorb the expansion and contraction without damage to anything. The best bet is to make sure things can move around a bit. If you use a log manifold, put a slip joint between rotors etc. Then you can use two separate flanges without any problems.
Monty Some work has been done to improve the retention of wood props by using belville washers. The wood expands and contracts with moisture, requiring periodic torquing of the bolts. Belville washers will keep the proper tension while allowing a bit of movement from the wood.
Would the same technique work to attach a header? Several hundred pounds of pressure. High enough to keep the header where it belongs and keep exhaust gas from blowing through, but low enough to allow some thermal variance?
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