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From: <cardmarc@charter.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Counterweight for engine assy, 13Brewtt
Date: Wed, 5 Oct 2005 11:03:14 -0400
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Here's an even better one. I have a 93/94 engine. I have two counterweights I could use for this engine. They differ by 2 oz. (one has two holes drilled on the counterweight flange, the other 2, so it WAS balanced once for a particular engine assy). Which should I use, or do I need to get a dynamic balance of the assy after I clean up the rotors? Who does that-I saw a write up of balancing the assy.....? Is there an easy way I can determine which is best?
Marc Wiese
> 
> From: David Leonard <wdleonard@gmail.com>
> Date: 2005/10/04 Tue PM 07:21:08 EDT
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Subject: [FlyRotary] Telling rotors apart - Never trust Atkins!
> 
> On 9/28/05, Kelly Troyer <keltro@att.net> wrote:
> >
> >   Ed Anderson has a measurement to check the depth of the combustion
> > depression in the
> > face of the rotor to determine the compression ratio (the deeper one is
> > turbo).......
> >
>  How about it Ed, any info on this? Can it be used to tell the 9.4:1 86-88
> rotors from the 9.7:1 rotors?
> 
>  Bottom line check weight first then check the depth of the combustion
> > depression........I have
> > another way I use to determine what year my rotors are (all my engines are
> > NA 86 to 91).....The
> > combustion depression in the 86 to 88 is as cast in the rotor (slight
> > grainy surface finish).....The
> > 89-91 depression is machined and has straight machine marks.......
> >
>  That is really interesting. My old rotors are supposed to be 1991 T2 rotors
> but they have the cast appearance (However since I got them from Atkins I am
> not really sure they gave me what they sold me). The rotors that Earnest
> sent also have a cast appearance. But as I recall, the rotors in the engine
> I rebuilt had the milling marks... hmmm.. if that is true the balance in my
> current engine is all SNAFU. Are you sure that system is a valid way to do
> the measuring?
>  So I just got back from weighing my rotors - Sure enough, the ones Atkins
> sold me weighted in at 10.20 and 10.19 making them the 86-88 variety despite
> the fact that I paid for a '91 engine. Worse, I have no idea what
> counter-weights he decided to use. If it matched the rotors he sold me then
> I have been running an unbalanced engine for the last 150 hrs. (that
> explains part of why the wife won't fly in it)
>  Does anyone know what the correct weights of the counter weights should be
> for a given year group? Or perhaps some other way of telling them apart?
>  BTW Ernest, the rotors you sent also weigh in at 10.18.
>  Dave Leonard
> 
>  Check with Ed for his method to determine compression ratio as I do not
> > have it at hand......I
> > am attaching the rotor weight chart from "Mazdatrix" which will help (note
> > weight does not
> > include any seals or springs....just the bearing.........Hope this
> > helps........Any more questions
> > just ask !!
> >  --
> > Kelly Troyer
> > Dyke Delta/13B/RD1C/EC2
> >    *Engine* *Year* *Compression* *Weight (Grams)* *Weight (Pounds)* *12A *
> > *76-82* *9.4* *4603* *10.15* *12A * *83-85* *9.4* *4353* *9.60* *13B* *
> > 74-78* *9.2* *5253* *11.58* *13B* *84-85* *9.4* *5253* *11.58* *13B N/T* *
> > 86-88* *9.4* *4553* *10.04* *13B Turbo* *86-88* *8.5* *4553* *10.04* *13B
> > N/T* *89-92* *9.7* *4328* *9.54* *13B Turbo* *89-92* *9.0* *4328* *9.54* *13B
> > T/T* *93-95* *9.0* *4328* *9.54*
> >
> > *NOTE: Weights are approximate, and include rotor bearing, but do not
> > include any seals or springs. *
> >
> >
> >
> --
> Dave Leonard
> Turbo Rotary RV-6 N4VY
> http://members.aol.com/_ht_a/rotaryroster/index.html
> http://members.aol.com/_ht_a/vp4skydoc/index.html
> 
>