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