Not that I'm going to jump on this right away, but
it seems that it would be relatively easy to rosette weld the tips of the discs.
Drill 1/8" (or slightly bigger) holes through the tube at the center of each
disc tip.
Mark,
Since you have not gotten to the muffler part of your
design, here are some thoughts (Yes, I did do 6 muffler experiments - don't
ask me why)
The one design that was "almost" totally successful
in achieving my goals is attached. Hard to make out the details, but
enough to give you the general ideal.
My objective was trying to decided how to muffler the
shock wave (which creates most of the ear problems) but let the exhaust gas
flow freely. My conclusion was that reactive design muffler was the only
acceptable choice given our constraints.
What I came up with was the idea of stuffing (I
put five but I think three would make a considerable difference) disc with
outer parts cut into blades and bent at a 45 deg angle into a tube.
Looked a bit like an old farm windmill.
The idea behind this approach was if you looked
head on at the fan-disc - you see basically a solid metal front. That is
what the shock wave would see and most (a lot?) of the energy would be
reflected back toward the engine (actually to the next disc in the
tube). The bent blades on the other hand would permit exhaust gas to
flow with minimum restriction.
It really did deaden the sound where folks could stand
by the wing tip with no problem hearing someone else talk. I was
thrilled. It also met my minimum restriction as I could still get
my 6000 rpm static.
Ok, what went wrong - well, not being a welder I
resorted to other methods - which ultimately failed.
Two things occurred -
one if the disc broke loose of the small 5/8" thread SS
shaft from the Jam nuts on each side holding the disc, well, the disc could
(and did) begin to spin inside the tube like the turbine wheel of a jet
engine. This windmilling effect acted just like a windmilling prop on the
exhaust gas and definitely impeded gas flow. So can not permit the disc
to spin (the tips polished the inside of the tube where the spun)
Second because I donot weld, I did not secure the
tips of the blades of the disc to the sides of the tube. Well the shock
wave naturally causes those blades to flex and eventually break
off.
The SS disc were 2" in diam 1/8 thick and fit
really nice inside the 2 1/4" tubes. I cut slots in the outer part of
the SS disc and then used pliers to bend the tabs to an approx 45 deg
angle (see attached Jep).
So none of this was difficult to fabricate (tedious
perhaps but not difficult).
I gave up on it because without welding skills I could
not figure out away to secure the tips of the blades to the tube to give them
better support. Perhaps better than disc would have been cones but
couldn't find any {:>).
So since I couldn't see any way around my lack of
welding (and too cheap to hire someone), I went the hushpower II
route.
Just thought I would throw some fuel on your fire
{:>)
FWIW
Ed