From the pictures of his exhaust
system, it appears that the pipes were supporting the muffler can. My
understanding, is that the entire exhaust will glow red, and the metal will
soften (as in almost melt) at high power settings.
The melting point
of inconel is over 2500F. Things will start to glow at about 1000F if
the light isn’t too bright. It is still quite strong at our exhaust
temps. It is worth noting that one of the features of expanding the gas
into the large tube is that the temperature drops (Charle’s Law of expanding
gases); the temp of the large tube is somewhat below the temp in the header
(how much lower depends on too many factors that I don’t know) and depends on
backpressure and engine rpm.
Al W. brings up a
good point. I had been primarily considering thermal stress, but stress due to
vibration from the engine (aside from exhaust pulses) could be a major
factor. Some high frequency resonance with engine vibration could
do a job on the welds where joe’s broke; or a resonance with the unsupported
exit pipe?
I guess I’ll learn
some more as I accumulate some hours on my plane. Now a real challenge
is coming up with some kind of damping support . . . .
Al
G.