Paul,
After some more thought on the exhaust bracket and header tube - going
the Powersport route is more complex than most builders would
contemplate without ready access to parts. So I thought about the header
tube problem (breaking at the exhaust flange junction) and figured that
the problem could be overcome by using thicker pipe in this are rather
than light tube (compared to flange), welded to heavy flange material.

Even a short section 2" to 3" with a flexible joint after that wouldn't
add too much to the overall weight. One could even go further and weld
small triangular inserts to strengthen the connection from short header
to exhaust flange.

Do you need a drawing?
George ( down under)


DWGs always help.

Paul Lamar ...No rotor no motor.

Paul,
As requested.
George ( down under)

We tried using thicker pipe wall (600 series stainless in incremental
increases in thickness up to almost 1/8" wall ) and even those would
eventually crack.  The problem was not cracking at the flange, but rather
cracking of the pipe wall itself itself whenever pipes from each port were
merged outboard of the exhaust ports without any provision for a slip
joint
or other.  Before we came up with the idea of the ball joint welded
directly
to the port, we first used short stub stacks welded to the four stud
flange,
with a slip fit pipe over that and it completely eliminated the cracking
problems even using .035  wall...but we never came up with anything close
to
elegant in terms of securing the stub pipe to the slip tube.  To test the
approach we retained the exhaust tube to the stub stack using safety wire
looped through small 'L" brackets welded to the outboard tube with a hole
drilled in the 90degree leg for the safety wire...and the other inboard
"L"
brackets  held on the stub end by each of the four nuts that secured the
exhaust flange/stub stack to the rotor housing.  Looked cheesy and not
meant
for long term but the approach did work and led us to the ball joint.   It
is simple and cheap if you could come up with an effective, safe way to
retain the tubes.

Steve Beckham

Steve,
Thanks for the response, I agree the pressed exhaust flanges are the most
elegant option, but there are a degree of complexity for the average
builder - whereas just welding may be easier. See attachment for what may be
options. This isn't as you described (but similar) with a heavier tube as
the stub I believe it would be quite robust- drawing by Bill Jepson.
George (down under)