X-Virus-Scanned: clean according to Sophos on Logan.com X-PolluStop-Diagnostic: (direct reply)\eX-PolluStop-Score: 0.00\eX-PolluStop: Scanned with Niversoft PolluStop 2.1 RC1, http://www.niversoft.com/pollustop Return-Path: Received: from [65.54.168.118] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.3c4) with ESMTP id 869536 for flyrotary@lancaironline.net; Thu, 14 Apr 2005 22:32:14 -0400 Received-SPF: pass receiver=logan.com; client-ip=65.54.168.118; envelope-from=lors01@msn.com Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Thu, 14 Apr 2005 19:31:29 -0700 Message-ID: Received: from 65.54.98.151 by BAY3-DAV14.phx.gbl with DAV; Fri, 15 Apr 2005 02:31:28 +0000 X-Originating-IP: [65.54.98.151] X-Originating-Email: [lors01@msn.com] X-Sender: lors01@msn.com From: "Tracy Crook" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Rx-8 Rotors Date: Fri, 15 Apr 2005 22:33:28 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_02BA_01C5420B.2529D860" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 X-MimeOLE: Produced By MSN MimeOLE V9.10.0011.1703 Seal-Send-Time: Fri, 15 Apr 2005 22:33:28 -0400 X-OriginalArrivalTime: 15 Apr 2005 02:31:29.0131 (UTC) FILETIME=[3AA3D3B0:01C54163] This is a multi-part message in MIME format. ------=_NextPart_000_02BA_01C5420B.2529D860 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Here's my take (FWIW as usual). Ed's answer is essentially correct. = But there is another reason for the greater depth of the 2nd - 3rd gen = apex seals. The increased contact area in the groove is needed to = transfer heat from seal to rotor. So no milling down the RA seals to = fit RX-8 rotors in RX-7 engines. (but hell, it might work anyway). =20 Also, the center of mass of the rotor DOES rotate in a perfect circle. = No monkey motion is ever involved. =20 Another question was about why counter weights were required if the = rotors ballanced each other out. They are not in the same plane of = rotation which creates what is known as a "rocking couple". The = counterweights make another rocking couple (out of phase) to cancel out = that of the rotors. Tracy (still at SnF) Hi Doug, Some good thoughts and questions, of which I would like to know the = answers to as well. I believe the reason the experts are recommending = milling the RX-8 rotors for the older seals (when used in the older = rotor housings with peripheral exhausts) is that the RX-8 seal was not = designed to withstand the forces of crossing the exhaust port (in the = Peripheral wall) opening unsupported. Its rather skinny and long. = Mazdatrix reported the RX-8 seals warped as a consequence of the the hot = exhaust gas blowing over them and primarily the lack of wall support at = the exhaust opening(on the older housings). The combination of the = additional heat and lack of wall support appears to be more than the 8 = seal can take. However, I am in basic agreement with you why machine the rotor when = perhaps a new/modified seal is the answer. I want to check with Tracy = Crook since his seals are reportedly 800% stronger than stock apex seals = to see whether the seals could be machined down/created so that they fit = in the RX-8 rotor standard apex slot and still be strong enough - say = 300% stronger than stock {:>). Since they are not made of typical "gray = iron" alloy that the stock and most other seals are made and chill/case = hardened, they may be amenable to machining. Yes, having airports scattered around in just about every county and = sometimes three or more in a county, the geography is much kinder to = engine-out excursions here on the east coast. Fly High, Glide long! = Better yet, keep running on both rotors. Ed A ----- Original Message -----=20 From: Shearbond@aol.com=20 To: Rotary motors in aircraft=20 Sent: Thursday, April 14, 2005 10:10 AM Subject: [FlyRotary] Rx-8 Rotors So.....since the rotors weigh the same within measurement error, the = ability to rev to the 9,000s range vs. 7,000s range is not related to = the orbiting mass of the rotor. (Note: the motion is NOT truly = circular, it is an epicycloid path that the center of mass of the rotor = takes. That 10 lb. rotor flops around plenty (technical term) and 10 = lb. is lots heavier than an aluminum piston! It is apparent from an article on the "other" site, that the wall = thicknesses and casting detail are lots more refined on the RX8 rotors = than on earlier models...for more uniform and desirable heat transfer = and uniformity.....oil cooling the rotor, etc. The mass being basically the same, it becomes a high probability = that since centripetal force is F =3D (Mass x rotational velocity = squared)/radius of rotation, {F=3D(m x w^2)/r}, it must be the weight of = the seals themselves that are the critical element? The force at 8,500 = vx. 6,500 is (8.5/6.5) squared or 1.71 times greater. Might this be why = seal wear on the original seals goes up substantially at around 6,500 = rpm? Tell me....why would one increase the depth of the seal groove of an = RX8 rotor to allow a heavier seal???? On the RX8, 3.25mm/9.5mm =3D> = approx. 34% reduction in apex seal mass!! A lighter seal means a whole = lot less force of the seal against the housing at 8,500 rpm!! Anyone = want to go back to old seals and rev to 8,500 rpm? =20 Note: the seal force against the housing at 8,500 rpm on the RX8 is = still higher than the old seal at 6,500.... (.66 x 1.71 =3D 1.129). Not = much more, but there are probably even more very small details that we = are not at first glance able to know and understand? Seal = material/housing material compatability is probably one significant = factor?? (I used 9,000 vs. 7,000 and the numbers still come out about = 10% higher seal force on the RX8, even with the lighter seals.) =20 Having been an R&D engineer at FoMoCo, it is hard to explain to most = persons the creativity, detail, imagination, trial and testing and = testing and testing and testing and ...... which goes into making an = engine acceptable for production in quantities of XXX,XXX's and higher. = (One simply can't be wrong...it could bankrupt even the largest OEM.) = And....those Mazda engineers have done what many OEM's gave up on many = years ago. How? Through their persistence and incredible insight into = the issues. Before one gets the wire EDM out and starts going counter to what = Mazda no doubt spent many $$$$ (more than all of our annual incomes put = together??) on how to increase HP in an RX8, more information is needed = before we start mixing and matching just because the parts will fit. I = know we are experimenters here, but lives of some who may not understand = the "physics" limitations will ultimately be at stake. Above all: Just because something works for 100 miles in a sprint = race DOES NOT mean it will work while hummmming along for 5 hours at a = crack at 75-80% max. HP on a cross-country over and over and over = again....hopefully. So far, my Lyc is a piece of 30's era design and = materials...but it has run for 2,000 hours (350,000 miles) at 75-100% = without fail!! Most of us aren't as lucky as Ed and his "on airport" emergency = landings. Perhaps it is that his green carpet (Carolina's) is lots more = friendly than our granite peaks out here? Doug in Colorado ------=_NextPart_000_02BA_01C5420B.2529D860 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Here's my take (FWIW as usual).  Ed's answer is essentially=20 correct.  But there is another reason for the greater depth of the = 2nd -=20 3rd gen apex seals.  The increased contact area in the groove is = needed to=20 transfer heat from seal to rotor.  So no milling down the RA seals = to fit=20 RX-8 rotors in RX-7 engines.  (but hell, it might work = anyway). =20
 
Also, the center of mass of the rotor DOES rotate in a perfect=20 circle.  No monkey motion is ever involved. 
 
Another question was about why counter weights were required if the = rotors=20 ballanced each other out.  They are not in the same plane of = rotation which=20 creates what is known as a "rocking couple".  The counterweights = make=20 another rocking couple (out of phase) to cancel out that of the = rotors.
 
Tracy (still at SnF)
Hi Doug,
 
Some good thoughts and questions, of which I would like to know = the=20 answers to as well.  I believe the reason the experts are = recommending=20 milling the RX-8 rotors for the older seals (when used in the older = rotor=20 housings with peripheral exhausts) is that the RX-8 seal was not = designed to=20 withstand the forces of crossing the exhaust port (in the Peripheral = wall)=20 opening unsupported. Its rather skinny and long.  Mazdatrix = reported=20 the RX-8 seals warped as a consequence of the the hot exhaust gas = blowing over=20 them and primarily the lack of wall support at the exhaust opening(on = the=20 older housings).  The combination of the additional heat and lack = of wall=20 support appears to be more than the 8 seal can take.
 
However, I am in basic  agreement with you why machine the = rotor=20 when perhaps a new/modified seal is the answer.  I want to check = with=20 Tracy Crook since his seals are reportedly 800% stronger than stock = apex seals=20 to see whether the seals could be machined down/created so that they = fit in=20 the RX-8 rotor  standard apex slot and still be strong enough - = say 300%=20 stronger than stock {:>).  Since they are not made of typical = "gray=20 iron" alloy that the stock and most other seals are made and = chill/case=20 hardened, they may be amenable to machining.
 
Yes, having airports scattered around in just about every county = and=20 sometimes three or more in a county, the geography is much kinder to=20 engine-out excursions here on the east coast.  Fly High, Glide=20 long!  Better yet, keep running on both rotors.
 
Ed A
 
 
----- Original Message -----
From:=20 Shearbond@aol.com
To: Rotary motors in = aircraft=20
Sent: Thursday, April 14, = 2005 10:10=20 AM
Subject: [FlyRotary] Rx-8 = Rotors

So.....since the rotors weigh the same within measurement = error, the=20 ability to rev to the 9,000s range vs. 7,000s range is not related = to the=20 orbiting mass of the rotor.  (Note: the motion is NOT truly = circular,=20 it is an epicycloid path that the center of mass of the rotor = takes. =20 That 10 lb. rotor flops around plenty (technical term) and 10 lb. is = lots=20 heavier than an aluminum piston!
 
It is apparent from an article on the "other" site, that the = wall=20 thicknesses and casting detail are lots more refined on the RX8=20 rotors than on earlier models...for more uniform and desirable = heat=20 transfer and uniformity.....oil cooling the rotor, etc.
 
The mass being basically the same, it becomes a high = probability that=20 since centripetal force is F =3D (Mass x rotational velocity=20 squared)/radius of rotation, {F=3D(m x w^2)/r}, it must be = the=20 weight of the seals themselves that are the = critical=20 element?  The force at 8,500 vx. 6,500 is (8.5/6.5) squared or = 1.71=20 times greater.  Might this be why seal wear on the original = seals goes=20 up substantially at around 6,500 rpm?
 
Tell me....why would one increase the depth of the seal groove = of an=20 RX8 rotor to allow a heavier seal????  On the RX8, = 3.25mm/9.5mm=20 =3D> approx. 34% reduction in apex seal mass!!  A = lighter=20 seal means a whole lot less force of the seal against the = housing at=20 8,500 rpm!!  Anyone want to go back to old seals and rev to = 8,500=20 rpm? 
 
Note:  the seal force against the housing at 8,500 rpm on = the RX8=20 is still higher than the old seal at 6,500.... (.66 x 1.71 =3D = 1.129). =20 Not much more, but there are probably even more very small = details that=20 we are not at first glance able to know and understand?  Seal=20 material/housing material compatability is probably one significant=20 factor??  (I used 9,000 vs. 7,000 and the numbers still come = out about=20 10% higher seal force on the RX8, even with the lighter = seals.) 
 
Having been an R&D engineer at FoMoCo, it is hard to = explain to=20 most persons the creativity, detail, imagination, trial and testing = and=20 testing and testing and testing and ...... which goes into = making an=20 engine acceptable for production in quantities of XXX,XXX's and=20 higher.  (One simply can't be wrong...it could bankrupt even = the=20 largest OEM.)  And....those Mazda engineers have done what many = OEM's=20 gave up on many years ago.  How?  Through their = persistence and=20 incredible insight into the issues.
 
Before one gets the wire EDM out and starts going counter to = what Mazda=20 no doubt spent many $$$$ (more than all of our annual incomes = put=20 together??) on how to increase HP in an RX8, more information is = needed=20 before we start mixing and matching just because the parts will = fit.  I know we are experimenters here, but lives of some who = may not=20 understand the "physics" limitations will ultimately be at = stake.
 
Above all:  Just because something works for 100 miles in = a sprint=20 race DOES NOT mean it will work = while hummmming along=20 for 5 hours at a crack at 75-80% max. HP on a cross-country over and = over=20 and over again....hopefully.  So far, my Lyc is a piece of 30's = era=20 design and materials...but it has run for 2,000 hours (350,000=20 miles) at 75-100% without fail!!
 
Most of us aren't as lucky as Ed and his "on airport" emergency = landings.  Perhaps it is that his green carpet = (Carolina's) is=20 lots more friendly than our granite peaks out here?
 
Doug in = Colorado
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