Hi Paul,
I hope the Oshkosh experience was very good. The TTC project
is
very impressive.
I’m gradually working through my radiator and oil cooler
issues, and
also building an exhaust header / tangential muffler. I have
a
couple of questions on the latter.
Please see the attached, although very crude, drawing.
I am using the Racing Beat SS header, with short 2.5”x 1.75”
OD .065
304 SS tubes welded in place. These will slip into 0.65”
1.88” tubes
that will in turn be welded into a 6” 304 SS .065
cylinder/muffler.
On the front, a 90 degree 1.88” tube is used to reduce the
length of
the 6” tube and significant weight.
Due to space and other constraints, I need to bring the 3”
tailpipe
(also .065” 304 SS) out of the *rear* of the muffler and up.
This
gives me at least 3 options: 1. A straight 3” pipe welded to
the rear
of the muffler. 2. Squeeze the 3” tailpipe into a fish mouth
(your
previous drawings showed an area about 1/2 of that of the
tailpipe).
Or weld up a larger fish mouth. 3. Or, allow a short section
of the
3” tailpipe to remain inside of the muffler, which could be
closed
off and drilled with (e.g. 0.5”) holes to arrive at the same
exit
area as the fish mouth design. I am wondering if this might
be a
more conventional muffler design and possibly allow better
sound
reduction?
The prior concerns regarding the longevity of any metal living
“inside” the muffler have been noted. However, with a Renesis
engine
having exhaust ports coming through the iron housings, as well
as a
cooling tube, both giving lower exhaust temps, do you think
this is a
concern for .065" 304?
Thanks for your input,
Scott Gettings
You are on the leading edge Scott. Nothing like this has been
built
yet. The RX8 side port exhaust is a little cooler so it
should work
all right. If it burns through opposite the exhaust ports you
can
weld on doubler patches.
Paul Lamar
Scott, Suggest that you investigate 321 S/s as 304 is a very
low grade Stainless. Remember the exhaust temp will get up to 1800
degrees which is rather warm. Your design is similar to what I made
and is still alive, but I have not the cooling tube. Neil Unger
Nice work Neil.
Paul Lamar
Typically 309 & 310 are used for high heat applications, 309
is good for 2000F and 310 2100F.
Be sure to use the correct filler rod the material you are
working with or you will be wasting your time using these more
expensive grades.
I would not call 304 a low grade steel, they all have their
place in the appropriate application.
Andrew Campbell.
Paul, do you recommend having slip joints on the pipes just after
the SS flange like Scott has, or is it ok to put these further
downstream. Reason is ask is that I wanted to duct some cooling air
around that area in flight and my concern is when going from high
power straight to a power off, high rate of descent leading to
possible uneven temps around the exhaust due to cooling air
distribution.
I want to try and minimize the risk of possible cracking. With the
space I have to duct cooling air I have to duct it from front to
rear so the front (if sitting in the cockpit) exhaust header pipe
gets the coolest shot and the rear header pipe gets the air warmed
by the other 2 further in front.
Any issues you can see using thick wall stainless tubing bends
Alex Molteno
The thicker the wall the better. There is a weight draw back of
course,
.109 wall 304 and it hardly shows any problems at all. One can buy
304 SS hand rails
from
http://www.wagnercompanies.com/products-services/railing-systems-and-components/railing-components/elbows-and-wall-returns/
rfq@mailwagner.com
You can then use the exhaust plumbing for motor mounts :-) Joking of
course.
It is only the first 18 inches of a p-port or so and by that time it
has cooled. The slip joint
can go there. Scott has a problem in that it is a pusher so he has
way less
room in the cowl to work with. If you can avoid it keep the muffler
out of the cowl
and use a coax muffler.
Do you have an RX8 engine? Things are a lot easier and quieter as
the exhaust is a couple
hundred degrees F cooler with the side exhaust.
Paul Lamar
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