X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-ew0-f167.google.com ([209.85.219.167] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with ESMTP id 3577460 for flyrotary@lancaironline.net; Sat, 11 Apr 2009 09:36:18 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.219.167; envelope-from=msteitle@gmail.com Received: by ewy11 with SMTP id 11so2154571ewy.19 for ; Sat, 11 Apr 2009 06:35:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=alGsxyTRvLHLXXF0tWx6xYO+oJznxz0owo7JJXgIThY=; b=Gfi3uPJNOcSJrabLHCTIegNnaekHnJZbW2nGJe+7Mo/YZy/hNCR8FkuTL/2UfqlwdF XYobqrJUoyhWzc9A7CAJqhPKCTHFpBYsPhe874Dc24cyMtLGed40PuPYNncgzJxI99A5 Ru6xvebiHoW/73q/efdDm1OPFyNKr14YSNxeQ= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=VcgBWBSY6tFhes9ywaI3StOOE00Eh39cPyKgFwFRhK6U3/YTkbnw3q6u2ildWD0bwn HILHGkFOJa1IK2zIvNOgOcA43wcOLAjg0+kN18SmoKXAgwtWKluYT7FZLshFNBCcMlPf uOwJCqQ3ZWlk6cdRytarBuX28KctL2OzPfSu0= MIME-Version: 1.0 Received: by 10.210.133.2 with SMTP id g2mr458682ebd.82.1239456940180; Sat, 11 Apr 2009 06:35:40 -0700 (PDT) In-Reply-To: References: Date: Sat, 11 Apr 2009 08:35:40 -0500 Message-ID: <5cf132c0904110635s61f147cer3e9ddfe1505bebe6@mail.gmail.com> Subject: Re: [FlyRotary] Re: Rotary Engines From: Mark Steitle To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=0015174c1d94a245b90467478e37 --0015174c1d94a245b90467478e37 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Gary, Good post. I never had the vibration issue explained quite like you put it. I think I understand now why the roary is smoother than a 6-cyl a/c engine. On the parts count, I would like to point out that while each rotor has many little pieces, but then each rotor does the work of three pistons. So, that works out about equal. As I see it, there are three areas where the piston a/c engine typically fails. One is the exhaust vlaves. This type of failure is usually not catastrophic, unless the head of the valve separates from the stem. Another is the cylinder attach flange which cracks and the jug blows off the engine. (This was my experience). This could easily be a fatal (to the pilot) failure. Then there is the crankshaft. I am not familiar with what happens when you break a crankshaft in an a/c engine, but I do know what happens in a motorcycle when you break a crankshaft; the engine quits in short order. This too could be fatal. In your previous post, you barely touched on the significant differences in the "crankshafts" designs of the two engines. While I'm no engineer, it is very obvious to me by comparing the two designs why the piston engine crankshaft is prone to cracks, especially when bolted to a large spinning propeller. That may be a plus for running a psru, to isolate the prop from the crankshaft. (But that is just an assumption on my part.) But I do know that it is extremely rare for a rotary to break a crankshaft. To be fair, the rotary has failure modes too. Such as overheating due to a broken coolant hose, or a broken fanbelt. But at least the engine will continue running for a few minutes before it siezes. Then there is the apex seal failure. This is normally associated with detonation on turbo-charged engines. Being N/A, I doubt I will have to worry much about that. And then, like you pointed out, there is the psru. That may be the weakest link in most installations. But the RWS psru has many trouble-free hours by many different rotary-powered a/c. And the risk of failure can be mitigated by a good preflight inspection, and the use of a chip-detector. The planetary gearset is from the Ford turbo-diesel automatic trans and is well proven by millions of miles of heavy truck use. Electrical failure would be another catastrophic failure. That's why I run a dual system (two alternators, two batteries). Of course, this adds complexity and weight. Who knows, maybe someday there will be magnetos available for the rotary. Concerning the fly-in, yes, Anyone interested in rotary-powered aircraft are welcome. But please rsvp so we can plan accordingly. Mark S. On Sat, Apr 11, 2009 at 7:35 AM, Gary Casey wrote: > 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? 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 certainly 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 integral part > of the rotary engine. As someone correctly pointed out, it's not how many > parts, but the reliability of the total system that counts. Just looking 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 reliability of > the concept. It's more to do with the experimental nature of the 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.. > > Are we ES drivers more conservative? Probably so, since the ES is probably > one of the experimentals most similar to production aircraft, and not just > because the Columbia (can't force myself to say Cezzna :-) was a derivative. > Therefore, it tends to attract conservative builders and owners. Not > surprising then that almost 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 caused by a PSRU failure in an auto engine conversion. > So our old-fashioned conservative nature has served us pretty well. > > 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. Direct injection does have a potential to improve BSFC because > the fuel charge can be stratified. It will probably decrease available > power, though. I think the best rotary will be 5% less efficient than the > "best" piston engine(same refinements 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 compression ratio reduction would reduce its > BSFC and maybe durability advantage. The total operating cost is certainly > significantly less if auto gas can 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 state, is that the extra fuel required for a > given mission might be 5 or 10% higher and that negated the weight > advantage, if only for long-range flights. > > Is the engine less expensive? I 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. Is the same true of the rotary? I'm not sure, but you have > to consider the total cost, including 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 justify it by cost reduction. > > It wasn't mentioned in the posts, but some have 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 secondary couple. The > 6-cylinder opposed engine is perfectly balanced, but only for PRIMARY and > SECONDARY forces and couples - higher order forces have never really been > analyzed, although they would be very small. And then consider the forces > within the engine that have to be resisted by that long, heavy, but flexible > crankshaft. So it isn't the mechanical balance that gives the rotary an > advantage. Let's take a look at the the torsional pulsations, 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, right? 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 result is that the power impulse lasts 3/4 of a CRANK > rotation, 50% longer than in a recip. Therefore, the torsional excitation > delivered to the propeller, 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 the rpm. The torsional vibration amplitude goes down > by a factor of 4 just because 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 rotary is "smoother" - a LOT smoother.. (my > apologies to rotary purists, for simplicity I used the word "crankshaft" for > both engines) > > But just because you can burn auto gas should you? The biggest problems > with auto gas in recip aircraft have nothing to do with the engine, but with > the high vapor 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 vapor lock. "Fortunately", rotary engines typically have no > mechanical fuel pump and are forced to rely on electric pumps. Fortunately > because the pumps can be located at the very bottom of the aircraft and > close to the fuel tanks, making vapor lock much less likely. I would > caution any builders to consider vapor lock possibilities very seriously, > much more so if you intend to run auto gas. when I was going to do this I > planned to 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). Redundancy was by a "crossfeed" line that could connect the > tanks together. > > And thanks, Mark for - probably incorrectly - referring to me as a "good > engineer". I'll have to put that in my resume! > > Have a good day, > Gary > (do you allow us outsiders in your events? I'll park well away :-) > > > --0015174c1d94a245b90467478e37 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Gary,

Good post.=A0 I never had the vibration issue explained quite= like you put it.=A0 I think I understand now why the roary is smoother tha= n a 6-cyl a/c engine.=A0

On the parts count, I would like to point = out that while each rotor has many little pieces, but then each rotor does = the work of three pistons.=A0 So, that works out about equal.=A0

As I see it, there are three areas where the piston a/c engine typicall= y fails.=A0 One is the exhaust vlaves.=A0 This type of failure is usually n= ot catastrophic, unless the head of the valve separates from the stem.=A0 A= nother is the cylinder attach flange which cracks and the jug blows off the= engine.=A0 (This was my experience).=A0 This could easily be a fatal (to t= he pilot) failure.=A0 Then there is the crankshaft.=A0 I am not familiar wi= th what happens when you break a crankshaft in an a/c engine, but I do know= what happens in a motorcycle when you break a crankshaft; the engine quits= in short order.=A0 This too could be fatal.=A0 In your previous post, you = barely touched on the significant differences in the "crankshafts"= ; designs of the two engines.=A0 While I'm no engineer, it is very obvi= ous to me by comparing the two designs why the piston engine crankshaft is = prone to cracks, especially when bolted to a large spinning propeller.=A0 T= hat may be a plus for running a psru, to isolate the prop from the cranksha= ft.=A0 (But that is just an assumption on my part.) =A0 But I do know that = it is extremely rare for a rotary to break a crankshaft.

To be fair, the rotary has failure modes too.=A0 Such as overheating du= e to a broken coolant hose, or a broken fanbelt.=A0 But at least the engine= will continue running for a few minutes before it siezes.=A0 Then there is= the apex seal failure.=A0 This is normally associated with detonation on t= urbo-charged engines.=A0 Being N/A, I doubt I will have to worry much about= that.=A0 And then, like you pointed out, there is the psru.=A0 That may be= the weakest link in most installations.=A0 But the RWS psru has many troub= le-free hours by many different rotary-powered a/c.=A0 And the risk of fail= ure can be mitigated by a good preflight inspection, and the use of a chip-= detector.=A0 The planetary gearset is from the Ford turbo-diesel automatic = trans and is well proven by millions of miles of heavy truck use.=A0 Electr= ical failure would be another catastrophic failure.=A0 That's why I run= a dual system (two alternators, two batteries).=A0 Of course, this adds co= mplexity and weight.=A0 Who knows, maybe someday there will be magnetos ava= ilable for the rotary.=A0

Concerning the fly-in, yes, Anyone interested in rotary-powered aircraf= t are welcome.=A0 But please rsvp so we can plan accordingly.=A0

Ma= rk S.

On Sat, Apr 11, 2009 at 7:35 AM, Ga= ry Casey <case= y.gary@yahoo.com> wrote:
Just to add a few more comments and answer= s 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 maj= or parts. =A0Is a valve a "major" part? =A0I think so. =A0Is a ro= tor corner button a major part? =A0Not sure, but probably not. =A0Is each p= lanet 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 t= hat counts. =A0Just looking at the history of the rotary (which, from the i= mplication of another post) it's not that good, but I don't think i= t has anything to do with reliability of the concept. =A0It's more to d= o with the experimental nature of the builds and installations. =A0My origi= nal point, perhaps not well expressed is that to say there are just 4 parts= is an oversimplification. =A0But let's face it, to put in an engine th= at has had many thousands of identical predecessors is less "experimen= tal" than one that hasn't..

Are we ES= drivers more conservative? =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 t= ends to attract conservative builders and owners. =A0Not surprising then th= at almost all ES's have traditional powerplants, with the most excellen= t exception of Mark. =A0While there may be more, I know of only two off-air= port landings caused by engine failures in the ES in almost 20 years of exp= erience. =A0One was caused by fuel starvation right after takeoff (fatal) a= nd one was caused by a PSRU failure in an auto engine conversion. =A0So our= old-fashioned conservative nature has served us pretty well.

Yes, I wa= s 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 add= ed to each). =A0But I stated that as a simple disadvantage - as Mark pointe= d out, it isn't that simple. =A0The rotary already comes configured to = run on auto gas. =A0The piston engine can also be so configured, but the co= mpression ratio reduction would reduce its BSFC and maybe durability advant= age. =A0The total operating cost is certainly significantly less if auto ga= s can always be used to refuel. =A0I assumed in my assessment that it will = only be available 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 o= r 10% higher and that negated the weight advantage, if only for long-range flights.

Is the engine less expensive? =A0I did a thorough analysis of a direc= t-drive recip auto engine installation and my conclusion was that if the au= to engine were equivalent in reliability to the aircraft engine it would li= kely cost just as much. =A0Is the same true of the rotary? =A0I'm not s= ure, but you have to consider 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 don't think I could justify it by cost reduc= tion.

It wasn&#= 39;t mentioned in the posts, but some have claimed the rotary is "smoother" than a recip. =A0I at first resisted that n= otion. =A0Sure, any rotary given sufficient counterbalancing, is perfectly = balanced. =A0A 4-cylinder opposed recip is not - there is a significant sec= ondary couple. =A0The 6-cylinder opposed engine is perfectly balanced, but = only for PRIMARY and SECONDARY forces and couples - higher order forces hav= e never really been analyzed, although they would be very small. =A0And the= n consider the forces within the engine that have to be resisted by that lo= ng, heavy, but flexible crankshaft. =A0So it isn't the mechanical balan= ce that gives the rotary an advantage. =A0Let's take a look at the the = torsional pulsations, comparing the 3-rotor against the 6-cylinder: =A0A 6-= cylinder engine has 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, compressi= on, 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 "crankshaft" 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 mechanical fuel pump and are forced to rely on electric pumps. =A0Fortun= ately because the pumps can be located at the very bottom of the aircraft a= nd close to the fuel tanks, making vapor lock much less likely. =A0I would = caution any builders to consider vapor lock possibilities very seriously, m= uch more so if you intend to run auto gas. =A0when I was going to do this I= planned to put one electric pump in the wing root of each wing, feeding th= e engine directly(the check valve in the non-running pump prevents back-feeding). = =A0Redundancy was by a "crossfeed" line that could connect the ta= nks together.

And thanks, Mark for - probably incorrectly - referring to me as a "go= od engineer". =A0I'll have to put that in my resume!

Have a good day,<= /div>
Gary
(do you a= llow us outsiders in your events? =A0I'll park well away :-)
=


--0015174c1d94a245b90467478e37--