X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail27.syd.optusnet.com.au ([211.29.133.168] verified) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTPS id 1037554 for flyrotary@lancaironline.net; Fri, 17 Mar 2006 15:53:43 -0500 Received-SPF: none receiver=logan.com; client-ip=211.29.133.168; envelope-from=lendich@optusnet.com.au Received: from george (d220-236-141-101.dsl.nsw.optusnet.com.au [220.236.141.101]) by mail27.syd.optusnet.com.au (8.12.11/8.12.11) with SMTP id k2HKqqiF008024 for ; Sat, 18 Mar 2006 07:52:53 +1100 Message-ID: <001101c64a04$c573c0e0$658decdc@george> From: "george lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Motor teardown results Date: Sat, 18 Mar 2006 06:52:57 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000E_01C64A58.96AD38F0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 This is a multi-part message in MIME format. ------=_NextPart_000_000E_01C64A58.96AD38F0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MessageGentlemen - is there some sort of pattern here 150 hrs and 160 = hrs? George ( down under) Ok, 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_000E_01C64A58.96AD38F0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
Gentlemen - is there some sort of = pattern here 150=20 hrs and 160 hrs?
George ( down under)
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=20 before my apex seal failure.
 
Ed
----- Original Message -----
From:=20 Chuck=20 Dunlap
To: Rotary motors in = aircraft=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,=20 Chuck.  Whoa!  150 hours is certainly not much out of a = brand=20 new housing.  It could be as you suggest that the two piece = seal=20 played a role.  However, I have another suggestion.  = Measure the=20 apex seal slot at the top (across the gap) and see what the = distance is.=20 Do it both on 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=20 there is less support for the seal near its top, the bottom is = still=20 fairly well constrained.  As a consequence, the top portion = of the=20 seal is more able to be swayed  back and forth by = combustion and=20 friction forces.  In other words, instead of just rubbing on=20 the rotor housing wall with the smooth top of the seal, the = edge of=20 the seal starts to drag along the wall.   The seal (with = less=20 support at the top) acts like a stiff spring (up to a limit) and=20 "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=20 frequency of a seal ( given its dimensions and composition) and = then=20 measure the average distance between the peaks (or valleys) of the = chatter.  Then given the resonant frequency of the seal=20 determine  at what rotor rpm it would leave chatter marks of = the=20 measured distance. {:>).  No, I don't have a clue about = how to do=20 this, but I'll bet some mechanical engineer could come up with=20 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=20 back up.
 
You and I are apparently the only ones = (that I know=20 of ) that seem to have had this failure mode of an apex seal=20 disintegrating for 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=20 10:44 PM
Subject: [FlyRotary] = Motor teardown=20 results

 
 
I finally=20 got time to get my failed 13b apart. The rear rotor was missing = one apex=20 seal, the other 2 were intact but jammed due to the fragments of = the=20 broken one. The rotor housing has the classic chatter marks all = around.=20 Doing a Google of "13B apex seal chatter" results in plenty of = examples=20 of this failure mode. Apparently the chatter is from the natural = resonant frequency of the seal, it eventually fatigues the seal = causing=20 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=20 150 hours ago when I rebuilt this motor after the Grand Canyon = forced=20 landing. At that time the good rotor housing had slight chatter = marks=20 but I reused it. The front rotor was destroyed at that time due = to=20 foreign object entering the rotor.
Both rotors=20 were missing the  corner seal rubber plugs on the side with = the=20 short apex seal segment. Perhaps the small segment vibrated = more,=20 disintegrating the rubber seals?
The first=20 260 hours of flying my rotary bird was with stock 3-piece seals, = and I=20 never saw any chatter marks. The last 250 hours has been flown = with 2=20 piece 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=20 appears that the heavier weight of the 2 piece seals puts the = resonant=20 frequency in the cruising range of 6000RPM?
 
Chuck=20 Dunlap
RV6=20 13B

--
Homepage:  = http://www.flyrotary.com/
Archive and=20 UnSub:  =20 = http://mail.lancaironline.net/lists/flyrotary/
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