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
================================
Hi David,
I kinda copied Tracy Hush II installation. Come
off the exhaust stack with a peice of SS flex tube about 12 inches long into
the muffler. Hang the I hung the muffler from two places with battery/ ground
strapping material and then attempted to isolate it when I fastened it at the
beefed up floor.
Can send some pictures if you are
interested.
Bernie