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Subject: RE: [FlyRotary] Cool Tube Muffler Sound Readings
Date: Thu, 12 Jan 2006 07:46:07 -0600
Message-ID: <87DBA06C9A5CB84B80439BA09D86E69E03610294@MAIL01.austin.utexas.edu>
Thread-Topic: [FlyRotary] Cool Tube Muffler Sound Readings
Thread-Index: AcYXG/w4TPuaVzwMSsWi8o5/9PKBFAAYlDiQ
From: "Mark R Steitle" <mark.steitle@austin.utexas.edu>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>

Bob,
Was your prop installed when these readings were taken?

Mark S. =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

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)

Here are the sound level readings with the engine running at 3000 RPM

Location	A	C
--------------	---	---
Left Wing	98	105
Right Wing	96	105
Front (5 paces)	95	105
Tail		91	103
Pilot Seat	84	94

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

I will get some higher rpm measurements after I get a little more time
on the engine.

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.

Bob W.

--=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/