-------------- Original message from "Ed Anderson" <eanderson@carolina.rr.com>: --------------


> Certainly, I don't feel we can rule anything out at this point, Doug.
> Degree of Lubrication could certainly play a role, but I personally doubt
> that it is the root cause - could be wrong about that, of course. I believe
> it may have to do with the amount of play in the rotor housing apex seal
> slots. I suspect that if the seals were pressing against the rotor housing
> wall in the manner they were designed to - the rounded top tangential to the
> surface of the housing - there is minimal drag and friction. As the slots
> wear the seals become able to "flop" from one side to the other of the
> housing as its chamber undergoes the 4 cycles. When "flopped" the seal's
> rounded top is no longer in contact as designe d and the top edge
> (non-rounded part) of the seal may start to drag and cause unusual wear.
>
> If lubrication was sparse and this condition existed, I think it would
> contribute to accelerated wear and chatter marks. But, just a hypothesis.
>
> Ed
>
> Ed Anderson
> Rv-6A N494BW Rotary Powered
> Matthews, NC
> eanderson@carolina.rr.com...........
>
>
> ----- Original Message -----
> From: "Doug Mueller"
> To: "Rotary motors in aircraft"
> Sent: Thursday, March 16, 2006 12:30 AM
> Subject: [FlyRotary] Re: Motor teardown results
>
>
> > Hi Chuck and Ed could there be any relationship to the lack of lubrication
> > to
> > these housings? The Lubrication increase could dampen any resonant
> > frequency causing chatter? What would your opinion be on that idea?
> > Anyone?
> >>
> >> From: "Ed Anderson"
> >> Date: 2006/03/16 Thu AM 12:21:11 EST
> >> To: "Rotary motors in aircraft"
> >> Subject: [FlyRotary] Re: Motor teardown results
> >>
> >> MessageThe chatter marks are certainly apparent, Chuck. Whoa! 150
> > hours is certainly not much out of a brand new housing. It could be as
> > you
> > suggest that the two piece seal played a role. However, I have another
> > suggestion. Measure the apex seal slot at the top (across the gap) and
> > see
> > what the distance is. Do it both on the good rotor and the damaged one if
> > you can find an undamaged spot. If like my rotor, the slots are worn, I
> > believe they may contribute to the chatter and breaking of the apex seal.
> >>
> >> Here's the theory. As the slot "V"s there is less support for the seal
> >> near
> > its top, the bottom is still fairly well constrained. As a consequence,
> > the top
> > portion of the seal is more able to be swayed back and forth by
> > combustion
> > and friction forces. In other words, instead of just rubbing on the rotor
> > housing wall with the smooth top of the seal, the edge of the seal starts
> > to
> > drag along the wall. The seal (with less support at the top) acts like a
> > stiff
> > spring (up to a limit) and "vibrates" as it slides along the housing wall
> > leaving
> > the chatter marks. At some point the forces become too much and the seal
> > breaks.
> >>
> >> It might be interesting to determine the vibration frequency of a seal
> > ( given its dimensions and composition) and then m easure the average
> > distance between the peaks (or valleys) of the chatter. Then given the
> > resonant frequency of the seal determine at what rotor rpm it would leave
> > chatter marks of the measured distance. {:>). No, I don't have a clue
> > about
> > how to do this, but I'll bet some mechanical engineer could come up with
> > something.
> >>
> >> Just a theory, of course, but if your apex slot tops are within the
> > specifications called for by Mazda then that would discredit the theory.
> > If
> > they are worn then it might tend to give it support.
> >>
> >>
> >> When my seal broke it also caught the next seal down in is slot and
> > smeared the top of the slot such that it could not come back up.
> >>
> >> You and I are apparently the only ones (that I know of ) that seem to
> >> have
> > had this failure mode of an apex seal disintegrating for no apparent
> > reason.
> >>
> >> Thanks for sharing the photos and information.
> >>
> >> Are you going to try for Sun & Fun?
> >>
> >> Ed
> >>
> >>
> >> Ed Anderson
> >> Rv-6A N494BW Rotary Powered
> >> Matthews, NC
> >> eanderson@carolina.rr.com
> >>
> >> Ed
> >>
> >>
> >>
> >> ----- Original Message -----
> >> From: Chuck Dunlap
> >> To: Rotary motors in aircraft
> >> Sent: Wednesday, March 15, 2006 10:44 PM
> >> Subject: [FlyRotary] Motor teardown results
> >>
> >>
> >>
> >>
> >> I finally got time to get my failed 13b apart. The rear rotor was
> >> missing
> > one apex seal, the other 2 were intact but jammed due to the fragments of
> > the broken one. The rotor housing has the classic chatter marks all
> > around.
> > Doing a Google of "13B apex seal chatter" results in plenty of examples of
> > this failure mode. Apparently the chatter is from the natural resonant
> > frequency of the seal, it eventually fatigues the seal causing failure.
> >> The front rotor was in good shape, but the housing had the same chatter
> > marks, but not as severe as the rear rotor. The front rotor housing was
> > brand
> > new 150 hours ago when I rebuilt this motor after the Grand Canyon forced
> > landing. At that time the good rotor housing had slight chatter marks but
> > I
> > reused it. The front rotor was destroyed at that time due to foreign
> > object
> & gt; entering the rotor.
> >> Both rotors were missing the corner seal rubber plugs on the side with
> > the short apex seal segment. Perhaps the small segment vibrated more,
> > disintegrating the rubber seals?
> >> The first 260 hours of flying my rotary bird was with stock 3-piece
> >> seals,
> > and I never saw any chatter marks. The last 250 hours has been flown with
> > 2
> > piece seals and now I have chatter marks .
> >> I now have Tracy's 2 piece apex seals and I wonder how they will
> >> perform,
> > it appears that the heavier weight of the 2 piece seals puts the resonant
> > frequency in the cruising range of 6000RPM?
> >>
> >> Chuck Dunlap
> >> RV6 13B
> >>
> >>
> >>
> > -----------------------------------------------------------------
> > - ------------
> >>
> >>
> >> --
> >> Homepage: http://www.flyrotary.com/
> >> Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/
> >>
> >>
> >
> > Doug Mueller
> > RX-6 13BT
> > N900DM
> > Boulder City(61B),Nevada
> >
> >
> > --
> > Homepage: http://www.flyrotary.com/
> > Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/
> >
>
>
>
> --
> Homepage: http://www.flyrotary.com/
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