So I am trying to plan = my muffler=20 installation. I just bought a hushmaster II to hang under the = cabin. =20 I want the exhaust the exit where it currently does mid = cowl.

The question is how to = make the=20 connection. It seems that if I make rigid connections then I will = get=20 fatigue cracks in the exhaust, even if I support the weight of the=20 muffler. Do the pipes themselves just absorb the vibration of the=20 engine?

I need to use either a = slip fit or a=20 v-band clamp to remove the pipe to get the cowl off. Will either = of these=20 provide enough play in the system.

Flowmaster also sells a = ball-and-socket type of joint. http://www.flowmastermufflers.com/products/index.phpmain_page=3D= product_info&products_id=3D2317=20

That seems better in = terms of=20 flexibility, but is more costly and will probably let more heat into the = cowl,=20 and will need a larger cowl opening (would prefer the slip or v-band=20 joint).

Am I worried about=20 nothing?

--
Dave = Leonard
Turbo Rotary=20 RV-6 N4VY

You are most definitely not "worried = about=20 nothing". When I worked with rocket engines, there was a tremendous = amount of=20 effort placed in making sure that there was no stress imposed on the = piping due=20 to temperature changes and vibration. Granted rockets see much larger = extremes=20 in temp due to cryogenic temps and very high stoiciometric = combustion=20 right next to it. But the principles are the same.

In the ideal world you would use very = thin inconel=20 and place a slip joint at each length between any fixed object = (turbo,=20 engine block, muffler). Any bend would also have a slip joint before and = after=20 it so that both torsion and expansion is eliminated. Each slip joint = gets a=20 metal bellows to seal it and allow relative motion. Then you have to = look very=20 closely at how you mount and constrain each piece of plumbing. Your = exhaust=20 would cost $5K

In the real world, most of what we use = is heavy=20 enough that you don't have to go to such lengths. In auto use the pipe = is so=20 heavy and the stresses low enough that these are usually not = a=20 concern. We are closer to the Auto than the rocket.

I would mount the muffler so that it = can move a bit=20 using silicone or wire rope isolators. Then I would use a stainless or=20 inconel metal bellows with the wire mesh constraint (front wheel = drive=20 auto) to let the engine move around also. I really like V-band clamps = for=20 joints. How the mounts are placed and muffler oriented really determines = the=20 detail design here.