Monty, that is great info. 

 

The turbo - engine is good.  I use the stock manifold that is very beefy iron and a very short moment arm. 

 

From the turbo outlet I currently have a 16G 321SS down pipe that is about 18" long going right down out of the cowl.  Easy enough.

 

I plan to hang the muffler under the cabin, so all I need is one bend going from the current down pipe to the muffler, about 2' away (with another small bend just before the muffler for alignment).  I was thinking a slip joint onto the down pipe, then another onto the muffler. 

 

Can v-bands be used INSTEAD of slip joints?  That would work great and be easy to do.

What is a manifold?  Can you send me a link to one?

 

Thanks for your help.

 

Dave Leonard

 

On 2/12/06, M Roberts <montyr2157@alltel.net> wrote:

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.

 

Flowmaster also sells a ball-and-socket type of joint. http://www.flowmastermufflers.com/products/index.phpmain_page=product_info&products_id=2317

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