X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.103] (HELO ms-smtp-04-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 1036014 for flyrotary@lancaironline.net; Thu, 16 Mar 2006 08:37:21 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.103; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-025-165.carolina.res.rr.com [24.74.25.165]) by ms-smtp-04-eri0.southeast.rr.com (8.13.4/8.13.4) with SMTP id k2GDaXk4010278 for ; Thu, 16 Mar 2006 08:36:34 -0500 (EST) Message-ID: <001101c648fe$a8b67260$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Motor teardown results Date: Thu, 16 Mar 2006 08:36:40 -0500 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Virus-Scanned: Symantec AntiVirus Scan Engine 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 designed 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 measure 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 > 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/ >