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Subject: RE: [FlyRotary] Re: Cool Tube Muffler Sound Readings
Date: Thu, 12 Jan 2006 10:03:53 -0600
Message-ID: <87DBA06C9A5CB84B80439BA09D86E69E036103A7@MAIL01.austin.utexas.edu>
Thread-Topic: [FlyRotary] Re: Cool Tube Muffler Sound Readings
Thread-Index: AcYXiSYoLjNcuOrzR9GlGQgO/M0ZMQABdYcA
From: "Mark R Steitle" <mark.steitle@austin.utexas.edu>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>

Bob,
I would like to take some readings from a certified engine for
comparison.   I measured 104db at 3000 & 4000 rpm from my spiral flow
muffler.  My guess is the certified numbers would be very close to ours.
For what its worth, nobody that heard me running my engine felt the
noise levels were excessive.  But then they have yet to hear a ported
3-rotor running WOT at 7500 rpm either.   =20

Mark S.=20

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Bob White
Sent: Thursday, January 12, 2006 9:02 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Cool Tube Muffler Sound Readings

Hi Mark,

Yes it was.  Otherwise I would be buying a new engine right now because
of the WOT start I did last Saturday. :)  (dumb mistake)

Bob W.  (building checklists to minimize dumb mistakes)


On Thu, 12 Jan 2006 07:46:07 -0600
"Mark R Steitle" <mark.steitle@austin.utexas.edu> wrote:

> Bob,
> Was your prop installed when these readings were taken?
>=20
> Mark S. =20
>=20
> -----Original Message-----
> From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
On
> Behalf Of Bob White
> Sent: Wednesday, January 11, 2006 6:00 PM
> To: Rotary motors in aircraft
> Subject: [FlyRotary] Cool Tube Muffler Sound Readings
>=20
> Today I ran the engine to get the sound level readings.
>  =20
> Short review:
> This is the cool tube muffler built by Jerry Hey.  Each exhaust port
> has a short tube into a large round can.  The center of the can has a
> two inch tube down the center to permit cool air to aid in cooling the
> exhaust.  This tube is sealed from the actual exhaust gasses.  The
> exhaust exits the large tube thru a rectangular tube at the bottom of
> the large round can.  (photo attached)
>=20
> Here are the sound level readings with the engine running at 3000 RPM
>=20
> Location	A	C
> --------------	---	---
> Left Wing	98	105
> Right Wing	96	105
> Front (5 paces)	95	105
> Tail		91	103
> Pilot Seat	84	94
>=20
> The A weighting cuts out the low frequencies below 500 Hz.  I have no
> idea how these compare to the typical aircraft engine.  According to
> the instruction manual, the A weighting is used to determine area
noise
> levels, and C wighting is used to measure sound levels of musical
> instruments. =20
>=20
> I will get some higher rpm measurements after I get a little more time
> on the engine.
>=20
> Coolant temps seemed to stabilize at 200F and oil at 175F with the
> engine at 2500-3000 rpm tied down and no cowling installed.  I ran it
> for around 10 minutes in this mode.
>=20
> Bob W.
>=20


--=20
http://www.bob-white.com
N93BD - Rotary Powered BD-4 (first engine start 1/7/06)
Custom Cables for your rotary installation -
http://www.roblinphoto.com/shop/

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