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 mail23.syd.optusnet.com.au ([211.29.133.164] verified) by logan.com (CommuniGate Pro SMTP 4.3c4) with ESMTPS id 869323 for flyrotary@lancaironline.net; Thu, 14 Apr 2005 18:35:17 -0400 Received-SPF: none receiver=logan.com; client-ip=211.29.133.164; envelope-from=lendich@optusnet.com.au Received: from george (d211-29-177-230.dsl.nsw.optusnet.com.au [211.29.177.230]) by mail23.syd.optusnet.com.au (8.12.11/8.12.11) with SMTP id j3EMYTEe003060 for ; Fri, 15 Apr 2005 08:34:30 +1000 Message-ID: <003901c54142$a36d6670$e6b11dd3@george> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Rx-8 Rotors Date: Fri, 15 Apr 2005 08:38:11 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0036_01C54196.74C710B0" 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_0036_01C54196.74C710B0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Doug, The seals, as pointed out by Richard Sohn don't come into the equation, = in regard to rotating mass. The shallower apex seals are because there is no hole the seal has to = jump over so a narrower seal will do. Those using RX7 housings need the = stronger seal otherwise they disappear out the exhaust - OK! George ( down under) 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_0036_01C54196.74C710B0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Doug,
The seals, as pointed out by Richard Sohn don't come into the = equation, in=20 regard to rotating mass.
 
The shallower apex seals are because there is no hole the seal has = to jump=20 over so a narrower seal will do. Those using RX7 housings need the = stronger seal=20 otherwise they disappear out the exhaust - OK!
George ( down under)
 
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, it=20 is an epicycloid path that the center of mass of the rotor = takes.  That=20 10 lb. rotor flops around plenty (technical term) and 10 lb. is lots = heavier=20 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=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 weight=20 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 times=20 greater.  Might this be why seal wear on the original seals goes = up=20 substantially at around 6,500 rpm?
 
Tell me....why would one increase the depth of the seal groove of = an RX8=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 means=20 a whole lot less force of the seal against the housing at 8,500 = rpm!! =20 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=20 still higher than the old seal at 6,500.... (.66 x 1.71 =3D = 1.129).  Not=20 much more, but there are probably even more very small details = that we=20 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 most=20 persons the creativity, detail, imagination, trial and testing and = testing and=20 testing and testing and ...... which goes into making an engine=20 acceptable for production in quantities of XXX,XXX's and higher.  = (One=20 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=20 ago.  How?  Through their persistence and incredible insight = into=20 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 = together??) on how to increase HP in an RX8, more information is = needed before=20 we start mixing and matching just because the parts will = fit.  I=20 know we are 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 5 hours at a crack at 75-80% max. HP on a cross-country over and = over and=20 over again....hopefully.  So far, my Lyc is a piece of 30's era = design=20 and 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 lots=20 more friendly than our granite peaks out here?
 
Doug in Colorado
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