So I am trying to plan my muffler
installation. I just bought a hushmaster II to hang under the cabin.
I want the exhaust the exit where it currently does mid cowl.
The question is how to make the
connection. It seems that if I make rigid connections then I will get
fatigue cracks in the exhaust, even if I support the weight of the
muffler. Do the pipes themselves just absorb the vibration of the
engine?
I need to use either a slip fit or a
v-band clamp to remove the pipe to get the cowl off. Will either of these
provide enough play in the system.
That seems better in terms of
flexibility, but is more costly and will probably let more heat into the cowl,
and will need a larger cowl opening (would prefer the slip or v-band
joint).
Am I worried about
nothing?
--
Dave Leonard
Turbo Rotary
RV-6 N4VY
David,
You are most definitely not "worried about
nothing". When I worked with rocket engines, there was a tremendous amount of
effort placed in making sure that there was no stress imposed on the piping due
to temperature changes and vibration. Granted rockets see much larger extremes
in temp due to cryogenic temps and very high stoiciometric combustion
right next to it. But the principles are the same.
In the ideal world you would use very thin inconel
and place a slip joint at each length between any fixed object (turbo,
engine block, muffler). Any bend would also have a slip joint before and after
it so that both torsion and expansion is eliminated. Each slip joint gets a
metal bellows to seal it and allow relative motion. Then you have to look very
closely at how you mount and constrain each piece of plumbing. Your exhaust
would cost $5K
In the real world, most of what we use is heavy
enough that you don't have to go to such lengths. In auto use the pipe is so
heavy and the stresses low enough that these are usually not a
concern. We are closer to the Auto than the rocket.
I would mount the muffler so that it can move a bit
using silicone or wire rope isolators. Then I would use a stainless or
inconel metal bellows with the wire mesh constraint (front wheel drive
auto) to let the engine move around also. I really like V-band clamps for
joints. How the mounts are placed and muffler oriented really determines the
detail design here.
Post some pics and drawings.
Sorry about your engine woes.
Monty
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