X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.101] (HELO ms-smtp-02-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 1037239 for flyrotary@lancaironline.net; Fri, 17 Mar 2006 10:15:52 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.101; 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-02-eri0.southeast.rr.com (8.13.4/8.13.4) with SMTP id k2HFF5ex023690 for ; Fri, 17 Mar 2006 10:15:06 -0500 (EST) Message-ID: <002101c649d5$985707e0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Motor teardown results Date: Fri, 17 Mar 2006 10:15:15 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001E_01C649AB.AF409B80" 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 This is a multi-part message in MIME format. ------=_NextPart_000_001E_01C649AB.AF409B80 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MessageOk, Chuck. Thanks. I did not do that check on my rebuild and = it turns out my used rotors were out of specs. Don't know if there when = I put them in because I did not check - but they must have been close to = the limits because I only flew 160 hours before my apex seal failure. Ed ----- Original Message -----=20 From: Chuck Dunlap=20 To: Rotary motors in aircraft=20 Sent: Friday, March 17, 2006 12:14 AM Subject: [FlyRotary] Re: Motor teardown results I always measure the apex slot clearances as part of the = blueprinting process when I build a motor, I will check the good rotor = when I get a chance, to see if it has changed in 150 hours. A cursory = eyeball check looks OK. The destroyed rotor cannot be measured, the = remaining seals are jammed in the slot. Not sure about Sun-N-Fun yet Chuck=20 The 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. =20 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=20 Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com Ed ----- Original Message -----=20 From: Chuck Dunlap=20 To: Rotary motors in aircraft=20 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/ ------=_NextPart_000_001E_01C649AB.AF409B80 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
Ok, Chuck.   Thanks.  I did not = do that=20 check on my rebuild and it turns out my used rotors were out of=20 specs.  Don't know if there when I put them in because I did not = check -=20 but they must have been close to the limits because I only flew 160 = hours before=20 my apex seal failure.
 
Ed
----- Original Message -----
From:=20 Chuck = Dunlap=20
Sent: Friday, March 17, 2006 = 12:14=20 AM
Subject: [FlyRotary] Re: Motor = teardown=20 results

 
I  = always=20 measure the apex slot clearances as part of the blueprinting = process=20 when I build a motor, I will check the good rotor when I get a = chance, to=20 see if it has changed in 150 hours. A cursory eyeball check looks = OK. The=20 destroyed rotor cannot be measured, the remaining seals are = jammed in=20 the slot.
Not sure about Sun-N-Fun=20 yet
 
Chuck 
The chatter marks are certainly apparent, = Chuck. =20 Whoa!  150 hours is certainly not much out of a brand new=20 housing.  It could be as you suggest that the two piece seal = played a=20 role.  However, I have another suggestion.  Measure the = apex seal=20 slot at the top (across the gap) and see what the distance is. Do it = both on=20 the good rotor and the damaged one if you can find an=20 undamaged spot.    If like my rotor, the slots are = worn, I=20 believe they may contribute to the chatter and breaking of the apex=20 seal.
 
Here's the theory.   As the slot = "V"s there=20 is less support for the seal near its top, the bottom is still = fairly well=20 constrained.  As a consequence, the top portion of the seal is = more=20 able to be swayed  back and forth by combustion and = friction=20 forces.  In other words, instead of just rubbing on = the rotor=20 housing wall with the smooth top of the seal, the edge of the seal = starts to=20 drag along the wall.   The seal (with less support at the = top)=20 acts like a stiff spring (up to a limit) and "vibrates" as it slides = along=20 the housing wall leaving the chatter marks.  At some point the = forces=20 become too much and the seal breaks.  
 
It might be interesting to determine the = vibration=20 frequency of a seal ( given its dimensions and composition) and then = measure=20 the average distance between the peaks (or valleys) of the = chatter. =20 Then given the resonant frequency of the seal determine  at = what rotor=20 rpm it would leave chatter marks of the measured distance. = {:>). =20 No, I don't have a clue about how to do this, but I'll bet some = mechanical=20 engineer could come up with something.
 
Just a theory, of course, but if your = apex slot=20 tops are within the specifications called for by Mazda then that = would=20 discredit the theory.  If they are worn then it might tend to = give it=20 support.
 
 
When my seal broke it also caught the next = seal down=20 in is slot and smeared the top of the slot such that it could not = come back=20 up.
 
You and I are apparently the only ones (that = I know of=20 ) that seem to have had this failure mode of an apex seal = disintegrating for=20 no apparent reason.
 
Thanks for sharing the photos and=20 information.
 
Are you going to try for Sun & = Fun?
 
Ed
 
 
Ed Anderson
Rv-6A N494BW Rotary=20 Powered
Matthews, NC
eanderson@carolina.rr.com
 
Ed
 
 
 
----- Original Message ----- =
From:=20 Chuck=20 Dunlap
To: Rotary motors in = aircraft=20
Sent: Wednesday, March 15, = 2006 10:44=20 PM
Subject: [FlyRotary] Motor = teardown=20 results

 
 
I finally got=20 time to get my failed 13b apart. The rear rotor was missing one = apex seal,=20 the other 2 were intact but jammed due to the fragments of the = broken one.=20 The rotor housing has the classic chatter marks all around. Doing = a Google=20 of "13B apex seal chatter" results in plenty of examples of this = failure=20 mode. Apparently the chatter is from the natural resonant = frequency of the=20 seal, it eventually fatigues the seal causing = failure.
The front=20 rotor was in good shape, but the housing had the same chatter = marks, but=20 not as severe as the rear rotor. The front rotor housing was brand = new 150=20 hours ago when I rebuilt this motor after the Grand Canyon forced = landing.=20 At that time the good rotor housing had slight chatter marks but I = reused=20 it. The front rotor was destroyed at that time due to foreign = object=20 entering the rotor.
Both rotors=20 were missing the  corner seal rubber plugs on the side with = the short=20 apex seal segment. Perhaps the small segment vibrated more, = disintegrating=20 the rubber seals?
The first 260=20 hours of flying my rotary bird was with stock 3-piece seals, and I = never=20 saw any chatter marks. The last 250 hours has been flown with 2 = piece=20 seals and now I have chatter marks .
I now have=20 Tracy's 2 piece apex seals and I wonder how they will perform, it = appears=20 that the heavier weight of the 2 piece seals puts the resonant = frequency=20 in the cruising range of 6000RPM?
 
Chuck=20 Dunlap
RV6=20 13B

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