Neil,
We have experimented with other mufflers. We have one that is just slightly noisier but it makes 5 more HP. This is a "small port" engine. 1.5" diameter. We find the 185 hp WITH the quiet muffler to be satisfactory. 190 with a different muffler. We have housings with bigger ports which will make more than 200 easily but we are testing for efficiency. Good luck with your own effort.

Bill Jepson

On Oct 18, 2016 10:04 PM, "Neil Unger" <flyrotary@lancaironline.net> wrote:

Thanks Bill,  I would prefer you to spend the time anyway.  Thanks for intro, but have a new one myself which "fits" but I am not expecting much noise reduction.  Will know shortly.  Neil.

On 10/19/2016 8:23 AM, William Jepson wrote:

Neil,

Revisit the video. The muffler in the video is shown fairly obviously in one of the pans. That muffler was designed to fit in an RV-3! Pretty small space there. The slightly odd shape is to allow airflow around it and out. I have photos of the plane with the engine hung, but I promised my partner that these would not circulate until the plane is flying and proven. While I wanted to show some of what is going on we do not want to be one of many "smoke and mirrors" builders. This is intended to return a proven platform. I have perfect solidworks drawings of the muffler as well, but same situation.

Bill

On Tue, Oct 18, 2016 at 1:19 PM, Neil Unger <flyrotary@lancaironline.net> wrote:

Bill I get the basic idea, byut what size and volumes are we talking?  Will it fit under the aeroplane cowl??  That appears to be the problem.  Neil.

 

From: William Jepson

Sent: Tuesday, October 18, 2016 12:04 PM

To: Rotary motors in aircraft

Subject: [FlyRotary] Re: Just a bit of a update

 

Neil, 

Helmholtz resonators are used to either amplify or attenuate sounds. They describe it fairly well on Wicapedia. The idea is to use chambers that tune to the high frequency to kill the highs. The volumes are critical. The muffler is a bit clipped in the video, but the volume when the camera is looking over the RV-4 with dyno in the background is a good representation.

Bill

 

On Mon, Oct 17, 2016 at 4:38 PM, Neil Unger <flyrotary@lancaironline.net> wrote:

Bill, what are Helmholtz principles??  The muffler at 6000 rpm was so quiet it does not even sound like a rotary.  Do you have diagram of a description??  Allow that I am an idiot so all details needed.  Neil.

 

On 10/18/2016 10:34 AM, William Jepson wrote:

Neil,

The muffler in the video. It was designed using Helmholtz principles and it works very well at reducing the high frequencies from the rotary.

Bill

 

On Mon, Oct 17, 2016 at 4:18 PM, Neil Unger <flyrotary@lancaironline.net> wrote:

Bill,  Now you have got my interest,  What muffler and where??  Everything else on the Rotary can be handled,  Cooling, mounting, P porting etc, but mufflers have me beaten.  They are the next for me to investigate particularly how to keep small if possible,  The size in most cases affects how the engine mount can be constructed on that side.

Thanks in anticip[ation,  Neil. 

 

On 10/18/2016 9:58 AM, William Jepson wrote:

Charlie,

Pardon my haste in the original reply. The butterflies are very similar to the original, with the exception that we have devised a new way to make them that doesn't require drilling through the housings. Can't say more right now other than we do NOT use epoxy in the housings and NO sealing problems. Don't expect any. Also we DO NOT weld to the liner as sometimes pushed by others. I do not believe you can weld to the liner without catastrophic failure later. I believe you will either fail your apex seals or crack the weld due to crystallization of the steel. The muffler is a MAJOR win. It is quieter than a unmuffled Lyc, and successfully kills the annoying hi frequencies. It is more restrictive than some but only costs us a few HP. It also fits in an RV-3! I am experimenting with a larger version in hopes of repeating the success with a bit less restriction on cowls that aren't as tight as the RV-3

Bill

 

On Mon, Oct 17, 2016 at 3:15 PM, Charlie England <flyrotary@lancaironline.net> wrote:

Hi Bill,

 

Thanks for the link. I've been following it on the Homebuilt Airplanes forum; are you 'billsrv4' over there?

 

I've been trying to find a throttle mechanism in the video, but don't see one. Are they using the custom 'in the housing' butterflies, like the original Powersport engine?

 

Have you heard it run in person? If so, does the muffler work as well as it seems to in the video? (Hard to know how much the audio is clipped in level on a recording.)

 

Thanks,

 

Charlie

 

On Mon, Oct 17, 2016 at 4:52 PM, William Jepson <flyrotary@lancaironline.net> wrote:

Since it has been so quiet thought I would make some noise.

Try this package on for size.

 https://www.youtube.com/watch?v=EfreUJt-Fsk.

Think you will find it interesting.

Bill