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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?
Ernest,
If you had a slot in the flange running
horizontally or a loose clearance hole instead of a tight clearance hole, it
might work. I say might because we are dealing with what has more friction, the
washer on the flange or the gasket on the flange.
The wood prop is a different load case. Involving
axial loading of the stud. The wood gets crushed by the washer when the
wood swells, then when it contracts the nut comes loose. In the header case
the separate flanges load the studs in bending, a condition which is very
bad for a fastener with threads on it in a thermally cycled, corrosive
environment. All ugly from a fatigue standpoint.
I would personally not want the flange working on
the gasket or the stud. Best to put a slip joint in the header, clamp the flange
and gasket down tight and solve the problem for sure.
Monty
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