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 <mailto: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
OK thanks Paul, good to know for the parts source to use tubing
handrail. I've added a bit of extra weight already during the build so a
few extra lbs of exhaust weight will be OK for extra insurance against
cracking
Alex Molteno
Be careful what you get prices on, for the elbows. There are stamped
elbows and seamless. I would think seamless is what we want.
Steve Carlisle
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