----- Original Message -----

From: George Lendich

To: Rotary motors in aircraft

Sent: Tuesday, October 13, 2009 1:09 AM

Subject: [FlyRotary] Re: Your muffler

 

Dean,

Did you get the details of the muffler?

George ( down under)

 

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 -----

From: Mike Wills

To: Rotary motors in aircraft

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.

 

http://www.youtube.com/watch?v=rIhK8PWRMbI

 

Mike Wills

RV-4 N144MW

----- Original Message -----

From: George Lendich

To: Rotary motors in aircraft

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 -----

From: George Lendich

To: Rotary motors in aircraft

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

 

Kelly

There you go matey. All off the shelf SS cones and tube.

George ( down under)

----- Original Message -----

From: Kelly Troyer

To: Rotary motors in aircraft

Sent: Thursday, October 08, 2009 9:32 PM

Subject: [FlyRotary] Your muffler

 

  George,

   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......

 

 

Thanks,

--
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)

---

--
Homepage:  http://www.flyrotary.com/
Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/List.html