<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=Content-Type content="text/html; charset=iso-8859-1">
<META content="MSHTML 6.00.2800.1276" name=GENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY style="FONT-SIZE: 10pt; FONT-FAMILY: Arial; BACKGROUND-COLOR: #ffffff"
bgColor=#ffffff>
<DIV>Hi Earl,</DIV>
<DIV>Can you give us some idea of the frequencies where you measured the peak
amplitudes? I assume you saw some narrow band peaks where various things
went into resonance. I was talking to Jerry Budd and he figures the
resonant frequency of the modern light weight airframe is down around 1.5
Hz. There is probably a way to "ring" the airframe and measure the
resonances if you've still got the measuring equipment available.</DIV>
<DIV>Interesting stuff but it will probably all go away when we switch to
electrics.</DIV>
<DIV>Regards, Jim</DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=EHaury@aol.com href="mailto:EHaury@aol.com">EHaury@aol.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, February 19, 2004 4:50
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Tonight's Dumb Idea...</DIV>
<DIV><BR></DIV>
<DIV>When the suggestion that soft mounting provided more advantages than not
was proposed, most of us subscribed to the theory that power loss from
anything less than solid was unacceptable. I set up a test using a fuselage
that could be equipped with either a hard (cast aluminum) mount or soft (same
mount with radial Lord mounts and a Lord mounted nose ring). A miniature
accelerometer was mounted to the inside of the firewall by the lower mount
bolt and another to the mount at the same location. (Stud for solid, Lord
studs for soft.) The accelerometers were connected to a dual channel spectrum
analyzer to display amplitude g's as millivolts on a vertical scale vs.
frequency on the horizontal. Engine was a piped OS 61 with the MK prop of the
time. </DIV>
<DIV> </DIV>
<DIV>After gathering full throttle data several times, and reversing the
accelerometers to ensure similar output, the results dramatically told
the story. The solid mount produced a 600mv amplitude signal and the soft a
6mv signal. A 100 / 1 difference. BTW, no measurable difference in engine rpm.
Switched to soft mounts and never looked back!</DIV>
<DIV> </DIV>
<DIV>Earl</DIV></BLOCKQUOTE></BODY></HTML>