X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from n6.bullet.re3.yahoo.com ([68.142.237.91] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with SMTP id 3577441 for flyrotary@lancaironline.net; Sat, 11 Apr 2009 08:43:03 -0400 Received-SPF: none receiver=logan.com; client-ip=68.142.237.91; envelope-from=casey.gary@yahoo.com Received: from [68.142.237.88] by n6.bullet.re3.yahoo.com with NNFMP; 11 Apr 2009 12:42:26 -0000 Received: from [66.196.97.156] by t4.bullet.re3.yahoo.com with NNFMP; 11 Apr 2009 12:42:26 -0000 Received: from [127.0.0.1] by omp209.mail.re3.yahoo.com with NNFMP; 11 Apr 2009 12:42:26 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 880558.96327.bm@omp209.mail.re3.yahoo.com Received: (qmail 10166 invoked by uid 60001); 11 Apr 2009 12:35:46 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1239453346; bh=RaFac/ILdNf0QfhHRH9BJ4zrlK4qwOrota+lgV/SFFc=; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:MIME-Version:Content-Type; b=oyDpXL4h4uOBEonanRHy+xqzggDsxvFgnH9bGyaibEla7LZFyG27s1SO+QBu4vM699fL+jsH2K4vK6Xbm8qm5czo19Cyz48qUjJztF/mHjq/yBKDEBOazkR8nZplbA+ZA8UK0j9KdbB64tvssUVob7wogID/+bx45uNMqYMU49E= DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:MIME-Version:Content-Type; b=WrMrBiGpt38vgDe8fcqbS7iSgXNfo8gOk8zUvJg7yA6T/0rdUIgVMKdFKHy1p69/wHU7npR32AL3j5UbAleFqz0c0J7kPbcmlerkUj+7QYlcK4iWsSRCzVei65aCsAd6yLz+eH4HNfKS4fmexu0pPcJKRCxPxZJ2wIbgefFKGcc=; Message-ID: <291398.48455.qm@web57505.mail.re1.yahoo.com> X-YMail-OSG: MW4fiygVM1m1cM0X874F_sXefa.nSSZ830yp8l.BcWg4EkTtP8Ss2bnfhXYEfrtjYm7zI9Bmfqd7TMXtF7RgwDYQDNsYbssKZIIRdLOdJ.6YPKoKid5qU1SY1u3J7IvJbeoE3W1f.xd20ApO4IAh79D4OCiEoNVJf_klNudJU5XfEjzd3mEj6EtUTjvdasZW.XAEaBp9NZ1F7hS3sBYnt.OzsEWnrM3r24tPpbNtaWt7zzdAbgE7vix6_kdFN7tNft9t1XhMPrUzp9iEy_lWH8xw Received: from [97.122.186.190] by web57505.mail.re1.yahoo.com via HTTP; Sat, 11 Apr 2009 05:35:46 PDT X-Mailer: YahooMailRC/1277.35 YahooMailWebService/0.7.289.1 Date: Sat, 11 Apr 2009 05:35:46 -0700 (PDT) From: Gary Casey Subject: Re: Rotary Engines To: flyrotary@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-2033284211-1239453346=:48455" --0-2033284211-1239453346=:48455 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Just to add a few more comments and answers to the several excellent commen= ts posted:=0A=0AHow many parts does it take to make a rotary rotate? Well,= "parts aren't parts" in this case. Mark was right in that there are maybe= 4 "major" components, but you have to define major. A piston engine certa= inly has far more major parts. Is a valve a "major" part? I think so. Is= a rotor corner button a major part? Not sure, but probably not. Is each = planet gear in the PSRU a major part? I say yes, and the PSRU is an integr= al part of the rotary engine. As someone correctly pointed out, it's not h= ow many parts, but the reliability of the total system that counts. Just l= ooking at the history of the rotary (which, from the implication of another= post) it's not that good, but I don't think it has anything to do with rel= iability of the concept. It's more to do with the experimental nature of t= he builds and installations. My original point, perhaps not well expressed= is that to say there are just 4 parts is an oversimplification. But let's= face it, to put in an engine that has had many thousands of identical predecessors = is less "experimental" than one that hasn't.=0A=0AAre we ES drivers more co= nservative? Probably so, since the ES is probably one of the experimentals= most similar to production aircraft, and not just because the Columbia (ca= n't force myself to say Cezzna :-) was a derivative. Therefore, it tends t= o attract conservative builders and owners. Not surprising then that almos= t all ES's have traditional powerplants, with the most excellent exception = of Mark. While there may be more, I know of only two off-airport landings = caused by engine failures in the ES in almost 20 years of experience. One = was caused by fuel starvation right after takeoff (fatal) and one was cause= d by a PSRU failure in an auto engine conversion. So our old-fashioned con= servative nature has served us pretty well.=0A=0AYes, I was assuming that t= he rotary had electronic fuel injection and ignition, but that by itself do= esn't change the inherent fuel efficiency of the engine. Direct injection = does have a potential to improve BSFC because the fuel charge can be strati= fied. It will probably decrease available power, though. I think the best= rotary will be 5% less efficient than the "best" piston engine(same refine= ments added to each). But I stated that as a simple disadvantage - as Mark= pointed out, it isn't that simple. The rotary already comes configured to= run on auto gas. The piston engine can also be so configured, but the com= pression ratio reduction would reduce its BSFC and maybe durability advanta= ge. The total operating cost is certainly significantly less if auto gas c= an always be used to refuel. I assumed in my assessment that it will only = be available 50% of the time. The real disadvantage, which I failed to sta= te, is that the extra fuel required for a given mission might be 5 or 10% higher and that negated the weight advanta= ge, if only for long-range flights.=0A=0AIs the engine less expensive? I d= id a thorough analysis of a direct-drive recip auto engine installation and= my conclusion was that if the auto engine were equivalent in reliability t= o the aircraft engine it would likely cost just as much. Is the same true = of the rotary? I'm not sure, but you have to consider the total cost, incl= uding engineering of all the parts in the system, not just the core engine.= I would love to do a rotary installation, but I don't think I could justi= fy it by cost reduction.=0A=0AIt wasn't mentioned in the posts, but some ha= ve claimed the rotary is "smoother" than a recip. I at first resisted that= notion. Sure, any rotary given sufficient counterbalancing, is perfectly = balanced. A 4-cylinder opposed recip is not - there is a significant secon= dary couple. The 6-cylinder opposed engine is perfectly balanced, but only= for PRIMARY and SECONDARY forces and couples - higher order forces have ne= ver really been analyzed, although they would be very small. And then cons= ider the forces within the engine that have to be resisted by that long, he= avy, but flexible crankshaft. So it isn't the mechanical balance that give= s the rotary an advantage. Let's take a look at the the torsional pulsatio= ns, comparing the 3-rotor against the 6-cylinder: A 6-cylinder engine has = 3 power impulses per rotation, as does the 3-rotor, so they are the same, r= ight? Wrong. They both incorporate 4 "stroke" cycles, meaning that there = separate and sequential intake, compression, power and exhaust events so that is the same for both= .. The power event, which is the source of the torque impulse, takes 1/2 of= a crank rotation for the recip. In the rotary the power event requires 1/= 4 of a ROTOR rotation, but the rotor rotates at 1/3 crank rotation - the re= sult is that the power impulse lasts 3/4 of a CRANK rotation, 50% longer th= an in a recip. Therefore, the torsional excitation delivered to the propel= ler, PSRU and to the airframe is significantly less than for a recip. And = if you analyze the actual forces imparted, they go down by the square of th= e rpm. The torsional vibration amplitude goes down by a factor of 4 just b= ecause the rpm of the rotary turns about twice as fast. If you've skipped = to the bottom of the paragraph, as you probably should have :-), yes the ro= tary is "smoother" - a LOT smoother. (my apologies to rotary purists, for s= implicity I used the word "crankshaft" for both engines)=0A=0ABut just beca= use you can burn auto gas should you? The biggest problems with auto gas i= n recip aircraft have nothing to do with the engine, but with the high vapo= r pressure of the fuel - it is more prone to vapor lock. The fuel systems = of certified aircraft are not particularly well designed with regard to vap= or lock. "Fortunately", rotary engines typically have no mechanical fuel p= ump and are forced to rely on electric pumps. Fortunately because the pump= s can be located at the very bottom of the aircraft and close to the fuel t= anks, making vapor lock much less likely. I would caution any builders to = consider vapor lock possibilities very seriously, much more so if you inten= d to run auto gas. when I was going to do this I planned to put one electr= ic pump in the wing root of each wing, feeding the engine directly(the chec= k valve in the non-running pump prevents back-feeding). Redundancy was by = a "crossfeed" line that could connect the tanks together.=0A=0AAnd thanks, Mark for - probably incorrectly - referring to = me as a "good engineer". I'll have to put that in my resume!=0A=0AHave a g= ood day,=0AGary=0A(do you allow us outsiders in your events? I'll park wel= l away :-)=0A=0A=0A=0A --0-2033284211-1239453346=:48455 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
Just to add a few more comments and= answers to the several excellent comments posted:

=
How many parts does it take to make a rotary rotate? = =A0Well, "parts aren't parts" in this case. =A0Mark was right in that there= are maybe 4 "major" components, but you have to define major. =A0A piston = engine certainly has far more major parts. =A0Is a valve a "major" part? = =A0I think so. =A0Is a rotor corner button a major part? =A0Not sure, but p= robably not. =A0Is each planet gear in the PSRU a major part? =A0I say yes,= and the PSRU is an integral part of the rotary engine. =A0As someone correctly pointed = out, it's not how many parts, but the reliability of the total system that = counts. =A0Just looking at the history of the rotary (which, from the impli= cation of another post) it's not that good, but I don't think it has anythi= ng to do with reliability of the concept. =A0It's more to do with the exper= imental nature of the builds and installations. =A0My original point, perha= ps not well expressed is that to say there are just 4 parts is an oversimpl= ification. =A0But let's face it, to put in an engine that has had many thou= sands of identical predecessors is less "experimental" than one that hasn't= ..

Are we ES drivers more conse= rvative? =A0Probably so, since the ES is probably one of the experimentals most similar to production aircraft, and not just because the Columbia (ca= n't force myself to say Cezzna :-) was a derivative. =A0Therefore, it tends= to attract conservative builders and owners. =A0Not surprising then that a= lmost all ES's have traditional powerplants, with the most excellent except= ion of Mark. =A0While there may be more, I know of only two off-airport lan= dings caused by engine failures in the ES in almost 20 years of experience.= =A0One was caused by fuel starvation right after takeoff (fatal) and one w= as caused by a PSRU failure in an auto engine conversion. =A0So our old-fas= hioned conservative nature has served us pretty well.
<= br>
Yes, I was assuming that the rotary had electronic = fuel injection and ignition, but that by itself doesn't change the inherent fuel efficiency of the engine. =A0Direct injection does have a potential t= o improve BSFC because the fuel charge can be stratified. =A0It will probab= ly decrease available power, though. =A0I think the best rotary will be 5% = less efficient than the "best" piston engine(same refinements added to each= ). =A0But I stated that as a simple disadvantage - as Mark pointed out, it = isn't that simple. =A0The rotary already comes configured to run on auto ga= s. =A0The piston engine can also be so configured, but the compression rati= o reduction would reduce its BSFC and maybe durability advantage. =A0The to= tal operating cost is certainly significantly less if auto gas can always b= e used to refuel. =A0I assumed in my assessment that it will only be availa= ble 50% of the time. =A0The real disadvantage, which I failed to state, is = that the extra fuel required for a given mission might be 5 or 10% higher a= nd that negated the weight advantage, if only for long-range flights.

Is the engine less e= xpensive? =A0I did a thorough analysis of a direct-drive recip auto engine = installation and my conclusion was that if the auto engine were equivalent = in reliability to the aircraft engine it would likely cost just as much. = =A0Is the same true of the rotary? =A0I'm not sure, but you have to conside= r the total cost, including engineering of all the parts in the system, not= just the core engine. =A0I would love to do a rotary installation, but I d= on't think I could justify it by cost reduction.

It wasn't mentioned in the posts, but some have claimed = the rotary is "smoother" than a recip. =A0I at first resisted that notion. =A0= Sure, any rotary given sufficient counterbalancing, is perfectly balanced. = =A0A 4-cylinder opposed recip is not - there is a significant secondary cou= ple. =A0The 6-cylinder opposed engine is perfectly balanced, but only for P= RIMARY and SECONDARY forces and couples - higher order forces have never re= ally been analyzed, although they would be very small. =A0And then consider= the forces within the engine that have to be resisted by that long, heavy,= but flexible crankshaft. =A0So it isn't the mechanical balance that gives = the rotary an advantage. =A0Let's take a look at the the torsional pulsatio= ns, comparing the 3-rotor against the 6-cylinder: =A0A 6-cylinder engine ha= s 3 power impulses per rotation, as does the 3-rotor, so they are the same,= right? =A0Wrong. =A0They both incorporate 4 "stroke" cycles, meaning that = there separate and sequential intake, compression, power and exhaust events= so that is the same for both. =A0The power event, which is the source of the = torque impulse,=A0takes 1/2 of a crank rotation for the recip. =A0In the ro= tary the power event requires 1/4 of a ROTOR rotation, but the rotor rotate= s at 1/3 crank rotation - the result is that the power impulse lasts 3/4 of= a CRANK rotation, 50% longer than in a recip. =A0Therefore, the torsional = excitation delivered to the propeller, PSRU and to the airframe is signific= antly less than for a recip. =A0And if you analyze the actual forces impart= ed, they go down by the square of the rpm. =A0The torsional vibration ampli= tude goes down by a factor of 4 just because the rpm of the rotary turns ab= out twice as fast. =A0If you've skipped to the bottom of the paragraph, as = you probably should have :-), yes the rotary is "smoother" - a LOT smoother= .. (my apologies to rotary purists, for simplicity I used the word "cranksha= ft" for both engines)

But just = because you can burn auto gas should you? =A0The biggest problems with auto= gas in recip aircraft have nothing to do with the engine, but with the hig= h vapor pressure of the fuel - it is more prone to vapor lock. =A0The fuel = systems of certified aircraft are not particularly well designed with regar= d to vapor lock. =A0"Fortunately", rotary engines typically have no mechani= cal fuel pump and are forced to rely on electric pumps. =A0Fortunately beca= use the pumps can be located at the very bottom of the aircraft and close t= o the fuel tanks, making vapor lock much less likely. =A0I would caution an= y builders to consider vapor lock possibilities very seriously, much more s= o if you intend to run auto gas. =A0when I was going to do this I planned t= o put one electric pump in the wing root of each wing, feeding the engine directly(the check valve in the non-running pump prevents back-feeding). = =A0Redundancy was by a "crossfeed" line that could connect the tanks togeth= er.

And thanks, Mark for - pro= bably incorrectly - referring to me as a "good engineer". =A0I'll have to p= ut that in my resume!

Have a g= ood day,
Gary
(do you allow us outs= iders in your events? =A0I'll park well away :-)

=

=0A=0A=0A=0A --0-2033284211-1239453346=:48455--