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From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-562509@logan.com>
Subject: Re: [FlyRotary] exhaust design question
Date: Fri, 10 Dec 2004 14:58:12 -0500
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Well, interestingly enough, while out fixing fuel leaks (wasn't an injector
after all) and getting the exhaust on, I noticed a Piper Arrow fixing to
take off.  So I grabbed my sound meter and took some reading.
25 ft from the tail of the Arrow at low rpm (idle)  the  meter read between
89 and 92 dB.  On take off roll, standing abeam the Arrow and  40 ft from
the center line I measure 107 db.  So it appears its as much the nature of
the Rotary "bark" as it is the sound level.

I now have my static rpm back and the sound level is down over the previous
muffler but not as much as when I had the 3 additional discs in the tubes.
But, will fly with this one as the sound is down by 3-4db not as good as the
8 db down previously but some improvement.

After going back to the drawing board and doing some calculations, its clear
that my objective of low back pressure and low noise level can not be met by
my 2" dia pipes.  It will require a 3" dia tube which then  requires reducer
cones (to match up to my 2" headers) etc, which starts to get expensive for
two 3" dia mufflers.

It appears one route would be to merge my two separate exhaust into one
header tube and use just one 3" dia tube. But then that would require
building a new header.  So just need to sit down and calculate the costs
both ways.

So sorry I can't offer any concrete suggestions on your 3 rotor, Kevin.

Good luck

Ed Anderson


----- Original Message -----
From: "kevin lane" <n3773@comcast.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Friday, December 10, 2004 12:27 PM
Subject: [FlyRotary] exhaust design question


> I am going to design my 20b exhaust, from plastic to start with.  when
> exhaust pipes join do they necessarily need to jump up in volume/dia.?
the
> exhaust is never flowing thru two at one time, correct?  my welder, Tom,
> with lots of race car experience, says that if I don't use a 3-to-1
> collector, and go to what he calls a log-type exhaust (with a plenum),
that
> the "log" should be of a larger diameter. the pics I see here for turbos
at
> least don't seem to follow that logic. the 3-1 design strikes me as
> difficult, heavy, and expensive. Tom says that the bellows are expensive,
> $120/ea, but wasn't sure how the log-type exhaust would handle the heat
> stress with it's inherently short runs.  The 3-1 works well for that
because
> of the extra flex in the design.
>     WWED? (what would Ed do?)  (if only straight pipes would be
acceptable!)
> Kevin Lane  Portland, OR
> e-mail-> n3773@comcast.net
> web-> http://home.comcast.net/~n3773
> (browse w/ internet explorer)
> ----- Original Message -----
> From: "Dale Rogers" <rogersda@cox.net>
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Sent: Friday, December 10, 2004 4:18 AM
> Subject: [FlyRotary] Re: In-line Oil Filter - reprise
>
>
> >
> >>
> >> From: Bulent Aliev <atlasyts@bellsouth.net>
> >> Date: 2004/12/10 Fri AM 06:51:08 EST
> >> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> >> Subject: [FlyRotary] Re: In-line Oil Filter - reprise
> >>
> >> Looks very good Dale. You can put one or two sensor holes or PSRU oil
> >> feed
> >> port too?
> >> Bulent
> >
> >   Yes.  In fact, that was my original intent - to make a
> > block with bosses for temp and pressure sensors.  This one
> > just got finished first.
> >
> >   I'm also working on another, larger, block that put the
> > oil filter hanging down at 30* from level, instead of the
> > current (nearly?) verticle.  It, too, will have bosses
> > drilled and tapped for sensors (or oil feed).
> >
> > Dale R.
> > COZY MkIV #1254
> >
> >
> >
> >>>  Homepage:  http://www.flyrotary.com/
> >>>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
>
>
> >>  Homepage:  http://www.flyrotary.com/
> >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
>