Ed,

OK, now I see.  One more question.  How are the disc assemblies held in
place?  Mark S.


-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Ed Anderson
Sent: Wednesday, January 19, 2005 11:58 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: turbine Exhaust??????? - No! not turbo related

Hi Mark,

Yes, sorry about that.  I've taken some photos of the modified discs -
but
basically they are made of 3" dia 1/8" SS 304 Discs.  I cut from the
perimeter in stopping 1/2" from the center.  This slices the disc into 8
equal area tabs.
The tabs are shaped like a truncated triangle.  I then twist each tab to
about a 45 deg angle from the plane of the disc - forming what looks
like a
8 bladed fan.

The FAW theory indicates that the shockwave pulse should see a (almost)
solid disc looking at it perpendicular to the plane of the discs
(provided
you don't bend the tabs more than 45 degs) this should reflect a
considerable amount of the energy of the wave back on the next incoming
wave
(and/or disc).  However, the exhaust gas molecules should be able to
still
find a path around the tabs.  If you look at the disc from the front (or
back) you see mostly metal - if you turn it 45 deg and view you see lots
of
open area created by the twisted tabs for the gas to flow through.

At least that is the Ed Anderson theory of how these discs should work.
I
first considered discs with holes - but  that would not preclude
propagation
of the energy of the pulse and would probably restrict gas flow
considerably.

It appears to work in that it does knock the noise level down
considerably
and (when not spinning) does not appear to be overly restrictive to the
exhaust gas flow.  The two discs per tube does not seem to adversely
affect
power and does knock  the sound from 125 dB to 104dB based on
measurements
using
the Radio Shack sound meter on setting C fast response.

Earnest's  suggestion that I reinstall all 4 (non-rotating) discs back
in
probably is a
good idea to see what kind of effect the additional discs would have.

I know flying back from Tracy's, I hit 6800 rpm in flight which is 200
higher than achieved with straight pipes and also hit 6000 rpm static on
take off - but, it was in cold dense air so much of that increase might
be
due to the denser air.

Photos

MVC-009F shows one of the discs shattered by the shock waves pounding.
Next
time I create a disc I will drill stress relief holes at the termination
of
the saw cut to relieve stress somewhat.

MVC-011F shows the discs from two views.  While there is some opening
the
shockwave would see, its fairly small compared to the opening the gas
sees
and I believe several discs reduces the  potential area for transmittal
of
the shock wave.  Also, the angle of the tab could be less than 45 deg
which
would reduce the open area the FAW sees even more - but, might impede
gas
flow more as well.

MVC-010F shows the violence that occurred in the exhaust system.  The
disc
has been shattered and the remnants stuffed into the perforated tube (I
initially used to maintain disc spacing).  Note the deformation of the
ends
of the perforated tube - evidence of tremendous heat and force.

Clearly any attempt to reduce the sound is a compromise with gas flow
and
this is just an experiment - but, which seems to have some merit.

But the violence of the rotary exhaust stream continues to impress me,
so
Treat the rotary exhaust with caution!

Ed