Ed I came up with an idea for tuning intake manifolds.
Hook your variable frequency  test oscillator to a small speaker on
one end of the manifold and a microphone hooked to your scope
on the other end. Vary the frequency slowly and watch the scope.

Paul Lamar

Ed Anderson wrote:

Hey, I like that idea.  When the resonant frequency of the system is
hit,
should see a major increase in amplitude of the signal!  I wonder if we
modulated the frequency with the equivalent of the engine rpm if that
might
reveal anything, say 200 Hertz for 6000 rpm, ooops, I guess that would
be
the resonant frequenty we would be looking for.

Great idea

Thanks, Paul

I discovered after getting back from the Mississippi flyin that my
rudder
had incurred damage.  The trailing edge was damaged with a crease at
one
place and actual metal rupture at another place.  I don't know the
cause,
but suspect it may have been accidentally struck by a golf cart based
on the
height of the damage and some white paint at one crease.  I need to
inspect
the hinges and bolts and determine what approach to repair.  I am
currently
thinking of placing an aluminum tube that would fit in the curve of the
trailing edge and give it structural integrity, its either that or
reskin
the rudder Ugh!  Composites do have their advantages {:>)

Ed.

A small speaker will also work as a mic. If you trigger the scope and
speaker
with a narrow pulse (click)  you can tell how long it takes to get to
the other end
of the pipe. Measure the speed of sound. If you point the speaker
at a wall some distance away you can determine the distance. (Sonar)

Tracy Saylor, Dave Anders and other Lycoming CS prop powered RV owners
are forever
replacing their rudders. Apparently they are 0h too thin. Consider
yourself lucky :)

BTW Van has an extrusion for the purpose of beefing up the trailing
edge of the rudder as I recall.

Paul Lamar

One other consideration is that the speed of sound (in the manifold)
fluctuates with
manifold pressure.

Chris C.
microcosman.com/aircraft

 
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