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Mike, etal
Mid June, 1968, I was employed by the U S Army
Aviation Systems Cmd in St Louis as a Dept of Army Civilian Aeronautical
Engineer and assigned to the Fixed Wing Project Engineering Office. Shortly
thereafter, I was tasked with evaluating several Engineering Change Proposals on
the YO-3A aircraft. Early flight testing had uncovered some structural
weakness in the new retractable main landing gear installation in the wings
that were now repositioned as low wings, and other areas of the aircraft. This
may be common knowledge to most if not all of you but the eleven YO-3A
production all flew with Continental IO-360 210 hp engines and never with rotary
engines. There was a 12 V- belt reduction driving a 6 blade fixed pitch wooden
propeller, later replaced with 3 blade
constant speed wooden propellers. The earlier quiet development aircraft,
the QT-2, the two QT-2 Prize Crew aircraft that did Operational Evaluation in
Vietnam, and the Lockheed Q Star propeller eval aircraft all had Continental
O-200 100hp engines with reduction drives, high -mounted behind the
cockpit, with a long drive shaft and pylon on the nose supporting the
propeller end. The two QT-2 Prize Crew aircraft had a seat for the observer
behind the pilot. The Q Star had a conventional main landing gear similar to a
Cessna 180 and was the only one to also test the Curtiss-Wright FC2-60
Wankel rotary engine. The Info came from Google "YO-3A Aircraft" . The
header " Quiet Aircraft Association" was on the first page of Google. The first
page of QAA lists both test engines for the Q Star and a photo collage of all 4
aircraft is about mid -article. I gave up searching for any further data on the
Curtiss-Wright installation.
Dean Van Winkle Slo Build RV-9A
'89 -13B, RD-1B, EC2, EM2, Mistral Intake
----- Original Message -----
Sent: Friday, October 09, 2009 9:26
PM
Subject: [FlyRotary] Re: Your
muffler
George, I agree with you on getting the muffler
out of the cowl. But I know there are those that would like to keep it under
cowl, and of course the canard guys probably dont have a choice. For a canard
this could be a good way to go.
There's a youtube video from a guy restoring a
YO-3A up in the LA area. It's pretty dry but a minute in there is a shot of
the exhaust system unfaired. I'd like to know what if anything is in that
muffler at the front. Behind that muffler is what the guy refers to as a
"piccolo tube" which is also enclosed in the fairing. The fairing and the
fuselage side are lined with absorbant material held in place with a metal
screen.
Mike Wills
RV-4 N144MW
----- Original Message -----
Sent: Friday, October 09, 2009 2:12
PM
Subject: [FlyRotary] Re: Your
muffler
Thanks Mike,
For your kind comments, but I must emphasize
that this design is designed primarily for outside cowl use. I
understand that this, to some people, might give rise to concerns of extra
drag - but to my mind anything to get the heat out of the cowl.
For my own design I envisage the muffler
sitting within a half circle recess formed in the cowl, but there no
reason that it can't sit behind the cowl under the fuselage.
If your talking about the long under
fuselage design which forms part of the fuselage, I must admit I like that
design as well. The longer the better in my opinion, you could string a
number of light weight mufflers along a line, each feeing into the next
with cooling air mixing in, as well as cooling the OD. That would be
super quiet. I notice the best muffling ( to date) is done with more than
one muffler i.e. a primary and a secondary.
I'm not trying to convince anyone this is
the best design, merely putting it up for possible solution to the
problem. As you and others have said, off-the-shelf types
aren't lasting anywhere near long enough. Bill Jepson and I laboured over
this design for some time, before we came to the final design, I have been
unable to finish my single so haven't been able to test it yet - but it
sure looks good.
George ( down under)
OK George, my memory is now jogged having
seen your drawing. I liked the design when I saw it the first time but
discounted it for my application because I couldnt see a good way to
make any muffler with a tangential entry fit my airframe. This is the same
reason I passed on Al's proven muffler design.
I think the use of cooling airflow introduced
into the muffler makes a lot of sense and this is something your design
has in common with the YO-3A muffler I've been talking about. I believe
the YO-3A design would prove superior by virtue of the greatly increased
volume of the muffler and the use of absorptive materials.
Of course until someone builds one and tries
it who knows if it will hold up to the abusive exhaust output of a rotary.
But the YO-3A design does have the advantage of being flight proven in a
pretty tough environment - low altitude recon in
Vietnam.
Your muffler design (or Al's) is a
winner if the goal is to keep the muffler within the confines of the cowl.
My cowl is already too tight without a muffler in it.
Mike Wills
RV-4 N144MW
----- Original Message -----
Sent: Thursday, October 08, 2009
9:18 PM
Subject: [FlyRotary] Re: Your
muffler
Al,
Not tested yet, but have one almost
complete for the single.
The cones are there to stop the sound
waves having a direct line of sight out the rear end, the sound
waves will be going all over the place within the exhaust and I tried to
replicate that with the zig zaggy lines.
There is no restriction as the area around
the back to back cones, is equal to the area of the 2" exhaust
manifold area.
However I do take your point on swirl
restriction, but I don't see a problem as it will swirl out the end,
whereas sound waves travel in a straight line ( I
think). Bill did have me put in a
reflector plate opposite the incoming exhaust, but I don't know if this
will interrupt the swirl motion, I suspect it might. The reflector plate
is on the LHS of the parts count - photo attached.
George ( down under)
George;
Nice
design. Has anyone run one of these yet.
My concern
with the tangential muffler is something called ‘swirl flow choking’ –
discovered in connection with a similar attempt with gas turbine
exhaust. High circumferential velocity tends to keep the flow
from moving out the end, and consequent pressure buildup. I
don’t know whether it applies to the pulsed flow, but it might, and
your conical restriction toward the outlet could make it worse.
To avoid
that possibility in my tangential muffler I added internal vanes at a
45 degree angle opposite the ports, and extended the header pipes into
muffler to a squared end. Disrupts the circumferential flow and helps
direct the exhaust toward the exit.
Your
depiction of the idealized sounds waves going axially; ah-h, well;
maybe/maybe notJ.
Al
G
-----Original
Message-----
From:
Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
On Behalf Of George
Lendich
Sent:
Thursday, October 08, 2009 1:14 PM
To: Rotary motors in
aircraft
Subject:
[FlyRotary] Re: Your muffler
There you go
matey. All off the shelf SS cones and tube.
-----
Original Message -----
Sent:
Thursday, October 08, 2009 9:32 PM
Subject:
[FlyRotary] Your muffler
Do you have a photo or drawing
available of your muffler design..........I seem
to
remember
seeing some design info in the past but do not know where to find
it......
--
Kelly Troyer
"Dyke Delta"_13B
ROTARY Engine
"RWS"_RD1C/EC2/EM2
"Mistral"_Backplate/Oil
Manifold
-------------- Original message from
"George Lendich" <lendich@aanet.com.au>: --------------
> Ed,
> Cones are the GO.
>
>
Any bare edge will take a battering from the heat and shock waves.
Cones
> formed back to back eliminate any edges.
>
> There must be supporting structure for the cones, I've
used 1/4" solid
> round bar welded into the exhaust skin.
> George (down under)
--
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