X-Virus-Scanned: clean according to Sophos on Logan.com X-PolluStop-Diagnostic: \eX-PolluStop-Score: 0.00\eX-PolluStop: Scanned with Niversoft PolluStop 2.1 RC1, http://www.niversoft.com/pollustop Return-Path: Received: from imo-m14.mx.aol.com ([64.12.138.204] verified) by logan.com (CommuniGate Pro SMTP 4.3c4) with ESMTP id 868600 for flyrotary@lancaironline.net; Thu, 14 Apr 2005 10:11:25 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.138.204; envelope-from=Shearbond@aol.com Received: from Shearbond@aol.com by imo-m14.mx.aol.com (mail_out_v38.7.) id q.19d.31b7cfc2 (18403) for ; Thu, 14 Apr 2005 10:10:32 -0400 (EDT) From: Shearbond@aol.com Message-ID: <19d.31b7cfc2.2f8fd3d8@aol.com> Date: Thu, 14 Apr 2005 10:10:32 EDT Subject: Rx-8 Rotors To: flyrotary@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1113487832" X-Mailer: 9.0 SE for Windows sub 5012 -------------------------------1113487832 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit 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 = (Mass x rotational velocity squared)/radius of rotation, {F=(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 => 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? 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 = 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.) 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 -------------------------------1113487832 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
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, i= t is=20 an epicycloid path that the center of mass of the rotor takes.  That 10= lb.=20 rotor flops around plenty (technical term) and 10 lb. is lots heavier than a= n=20 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 rotors = than=20 on earlier models...for more uniform and desirable heat transfer and=20 uniformity.....oil cooling the rotor, etc.
 
The mass being basically the same, it becomes a high probability that s= ince=20 centripetal force is F =3D (Mass x rotational velocity squared)/radius=20= of=20 rotation, {F=3D(m x w^2)/r}, it must be the weight of the=20 seals themselves that are the critical element? = ;=20 The force at 8,500 vx. 6,500 is (8.5/6.5) squared or 1.71 times greater.&nbs= p;=20 Might this be why seal wear on the original seals goes up substantially at=20 around 6,500 rpm?
 
Tell me....why would one increase the depth of the seal groove of an RX= 8=20 rotor to allow a heavier seal????  On the RX8, 3.25mm/9.5mm =3D>= ;=20 approx. 34% reduction in apex seal mass!!  A lighter seal mea= ns a=20 whole lot less force of the seal against the housing at 8,500 rpm!!  An= yone=20 want to go back to old seals and rev to 8,500 rpm? 
 
Note:  the seal force against the housing at 8,500 rpm on the RX8=20= is=20 still higher than the old seal at 6,500.... (.66 x 1.71 =3D 1.129).  No= t much=20 more, but there are probably even more very small details that we are n= ot=20 at first glance able to know and understand?  Seal material/housing=20 material compatability is probably one significant factor??  (I used 9,= 000=20 vs. 7,000 and the numbers still come out about 10% higher seal force on the=20= RX8,=20 even with the lighter seals.) 
 
Having been an R&D engineer at FoMoCo, it is hard to explain to mos= t=20 persons the creativity, detail, imagination, trial and testing and testing a= nd=20 testing and testing and ...... which goes into making an engine accepta= ble=20 for production in quantities of XXX,XXX's and higher.  (One simply can'= t be=20 wrong...it could bankrupt even the largest OEM.)  And....those Mazda=20 engineers have done what many OEM's gave up on many years ago.  How?&nb= sp;=20 Through their persistence and incredible insight into the issues.
 
Before one gets the wire EDM out and starts going counter to what Mazda= no=20 doubt spent many $$$$ (more than all of our annual incomes put together= ??)=20 on how to increase HP in an RX8, more information is needed before we start=20 mixing and matching just because the parts will fit.  I know we ar= e=20 experimenters here, but lives of some who may not understand the=20 "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=20 5 hours at a crack at 75-80% max. HP on a cross-country over and over and ov= er=20 again....hopefully.  So far, my Lyc is a piece of 30's era design and=20 materials...but it has run for 2,000 hours (350,000 miles) at 75-100%=20 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 lot= s=20 more friendly than our granite peaks out here?
 
Doug in Colorado
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