Return-Path: Received: from taipan.wrtc.com ([69.26.24.11] verified) by logan.com (CommuniGate Pro SMTP 4.3c3) with ESMTP id 881165 for flyrotary@lancaironline.net; Sun, 17 Apr 2005 18:44:40 -0400 Received-SPF: none receiver=logan.com; client-ip=69.26.24.11; envelope-from=lhgcpg@westriv.com Received: from garceaus1wwhli (Bismarck-5300-a-161.westriv.com [69.26.30.163]) by taipan.wrtc.com (8.12.11/8.12.11) with SMTP id j3HMqtgx011904 for ; Sun, 17 Apr 2005 16:52:58 -0600 (MDT) Message-ID: <005401c5439e$eaa4cd90$a31e1a45@garceaus1wwhli> From: "Leonard Garceau" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Rx-8 Rotors Date: Sun, 17 Apr 2005 17:43:40 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_004B_01C54374.FE2322B0" 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 This is a multi-part message in MIME format. ------=_NextPart_000_004B_01C54374.FE2322B0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable How do I unsubscrib to Flyrotary? Leonard ----- Original Message -----=20 From: Tracy Crook=20 To: Rotary motors in aircraft=20 Sent: Friday, April 15, 2005 9:33 PM Subject: [FlyRotary] Re: Rx-8 Rotors 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_004B_01C54374.FE2322B0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
How do I unsubscrib to = Flyrotary?
 
Leonard
----- Original Message -----
From:=20 Tracy = Crook
Sent: Friday, April 15, 2005 = 9:33=20 PM
Subject: [FlyRotary] Re: Rx-8=20 Rotors

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=20 to transfer heat from seal to rotor.  So no milling down the RA = seals to=20 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=20 circle.  No monkey motion is ever involved. 
 
Another question was about why counter weights were required if = the=20 rotors ballanced each other out.  They are not in the same plane = of=20 rotation which creates what is known as a "rocking couple".  The=20 counterweights make another rocking couple (out of phase) to cancel = out that=20 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=20 reported the RX-8 seals warped as a consequence of the the hot = exhaust gas=20 blowing over them and primarily the lack of wall support at the = exhaust=20 opening(on the older housings).  The combination of the = additional heat=20 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=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=20 seals to see whether the seals could be machined down/created so = that they=20 fit in the RX-8 rotor  standard apex slot and still be strong = enough -=20 say 300% stronger than stock {:>).  Since they are not made = of=20 typical "gray iron" alloy that the stock and most other seals are = made and=20 chill/case 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 = 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=20 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=20 critical element?  The force at 8,500 vx. 6,500 is (8.5/6.5) = squared=20 or 1.71 times greater.  Might this be why seal wear on the = original=20 seals goes 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=20 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=20 small details that we are not at first glance able to know and=20 understand?  Seal material/housing material compatability is = probably=20 one significant factor??  (I used 9,000 vs. 7,000 and the = numbers=20 still come out about 10% higher seal force on the RX8, even with = the=20 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=20 Mazda no doubt spent many $$$$ (more than all of our annual = incomes=20 put together??) on how to increase HP in an RX8, more information = is=20 needed before we start mixing and matching just because the=20 parts will fit.  I know we are experimenters here, but = lives of=20 some who may not understand the "physics" limitations will = ultimately=20 be at stake.
 
Above all:  Just because something works for 100 miles = in a=20 sprint race DOES NOT mean it will work=20 while hummmming along for 5 hours at a crack at 75-80% max. = HP on a=20 cross-country over and over and over again....hopefully.  So = far, my=20 Lyc is a piece of 30's era design and materials...but it has run = for 2,000=20 hours (350,000 miles) at 75-100% without fail!!
 
Most of us aren't as lucky as Ed and his "on airport" = emergency=20 landings.  Perhaps it is that his green carpet = (Carolina's) is=20 lots more friendly than our granite peaks out here?
 
Doug in=20 Colorado
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