"Schertz, William W." wrote:

Paul,
Attached is a scan of a sketch (pdf file) showing my comments on muffler
expansion.

Finn noted that is original "tangential" muffler failed after only 25 hours
at the welds to the can with the short stacks.

I believe that this is due to differential thermal expansion between the
muffler can which goes to 1600-1700 F, and the engine block which is
controlled to ~200F.  Each time the engine fires up or changes power, the
welds at the can are subjected to flexing, leading to fatigue failure.

On the other hand, if the tangential muffler with wrapped tubes has the
tubes _separate_ from the can until they merge after wrapping around the
can, then there is a lot more length to take up the expansion, and less
stress will be put on the joints.  However, if the square tube version uses
the can wall as one wall of the wrap-around tubing, then you are back to
having a short stack with the weld being stressed. I don't think you need
the telescoping square tubing as much as handling the expansion /
contraction of the muffler can, and the stresses it applies to the welds.
The short stacks can move the can in-and-out from the engine to relieve
stress in that dimension.

Bill Schertz

Thanks Bill. I converted it to a gif for instant viewing.

Paul Lamar
 
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