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Ken, I'm sorry I haven't convinced you it IS 3.9L. :) It just isn't a
3.9L piston engine.
Here's why. The displacement of one engine type isn't related to the
power produced in a different engine type. For example, by an analysis
similar to Ed's, a 1.3L 2 cycle engine has the same power production
ability and 'breathes' about like a 2.6L 4 cycle engine. But I don't
call it a 2.6L engine! Displacement is just the volume of the engine.
Both 2 and 4 cycle engines measures the volume by going thru one
complete engine cycle. The 2 stroke in one rev and the 4 stroke in two
revs. (This is key to my objection to Paul Lamar's recent statement
that the displacement of all engines are measured in one rev. This is
contrary to fact as opposed to opinion.) The rotary needs one rev of
the rotors and 3 revs of the output shaft to do a complete cycle. It
is my opinion that that proper way to measure the volume of the rotary
is to measure the volume displaced in one complete engine cycle.
Let me re-emphasize this: Every detail of Ed's analysis looks exactly
correct to me. The Mazda 13B produces power and breathes about the same
way a 4 cylinder 2.6L 4 cycle piston engine does, or about the same as a
2 cylinder 1.3L 2 cycle piston engine.
If you have a different opinion, that's quite all right with me. But I
won't change mine unless there is an error in my facts or asumptions,
which happens more often than I like.
I also think it sound better to think of the rotary as a 3.9L engine
turning 3000 rpm (rotor speed) rather than a 1.3L engine turning 9000
rpm (output shaft speed). It's too bad we can't easily couple the
propeller directly to the rotors and eliminate the PSRU. Now that
would be a setup.
Bob W.
On Mon, 17 Oct 2005 17:47:40 +0000
kenpowell@comcast.net wrote:
> ED, that is a really great explanation of the TIMING of the WORK that is being performed. This is the best comparison of oranges to orages that I have seen. And Monty and Bob ALMOST had me convinced that the rotary really was 3.9L.
>
> Ken Powell
> Bryant, Arkansas
> 501-847-4721
> C150 / RV-4 under construction
>
> -------------- Original message --------------
>
> Been there, done that {:>). If you are going to compare the power production of 13B rotary engine with a normal reciprocating engine, then the accepted standard for a power cycle (for a four stroke) is 720Deg crankshaft degrees of rotation. 720 degrees of a reciprocating engine has all cylinders firing be it a 4,6,8 or 12 cylinder engine.
>
> Clearly the 80 CID or 1.3 Liters comes from simplistic sum of the two 40 CID chambers per rotor. The 2.6 liters takes a bit more explaining.
>
> Where I believe the controversy comes in is that 720 degrees of a rotary leaves two faces of the 13B yet unfired. For all six faces to fire it takes 1080 degrees of crankshaft rotation. Each rotor face rotates 120 rotor degrees for a complete cycle- since the e shaft is geared 3:1 then 120 deg rotor rotation = 3*120 = 360Deg of E shaft rotation. Or another way to look at it is 360 deg of rotor rotation ( a complete rotor revolution) = 3*360 = 1080 deg of e shaft rotation.
>
> Now you can argue that the rotary has not finished its combustion cycle (all chambers firing) until all six faces have fire (1080 deg) - however, the accepted standard for a complete cycle of a reciprocating 4 stroke is 720 degs.
>
> So IF you are interested in comparing oranges and oranges, then its generally accepted you compare only 720 deg of the rotary's rotation to equal the 720 deg of a normal 4 stroke reciprocating engine.
>
> IF you do accept that - then that means 4 rotor faces have gone through their cycle in 720 deg of e shaft rotation. So at approx 40 CID per face we have 4 x 40 = 160 CID for the 720 deg cycle. And that turns out to be 2.62 liters of displacement.
>
> Its really no different than adding up the total displacement of all the cylinders in a reciprocating engine which do happen to complete a power stroke in that standard 720 deg. I think the fact that two faces or (80 CID of displacement) have not yet fire with the rotary is what bothers folks in this comparison.
>
> But if you are going to compare the power of the two different designs of engine you have to pick one or the other as the standard of comparison. And keep the parameters the same for both engines. For example:
>
> If you believe the cycle of the rotary is not complete until all six faces have fired then you have 6 x 40 = 240 CID in the 1080 degree rotary cycle.
>
> We could insist that the reciprocating engine be compared to the 1080 deg rotation of the rotary, but then you would have to increase the effective displacement of the reciprocating engine to include an additional 1/2 of its displacement since it will have gone through another 360 deg of rotation to match (720 + 360 = 1080) the rotary cycle of 1080deg. That way you again have oranges and oranges.
>
> But, in that case both we and the recip folks could boast about even more HP than we do now {:>)
>
> Since I am mainly interested in comparing a rotary with the reciprocating engines production of power, I adhere to the 720 deg standard for the comparison.
>
> Not taking any sides , but someone asked where the 2.6 liter figure came from and I hope I have answered that.
>
> Ed A
>
>
>
> ----- Original Message -----
> From: "Bob White" <bob@bob-white.com>
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Sent: Sunday, October 16, 2005 9:21 PM
> Subject: [FlyRotary] Re: flyrotary_Web_Archive Re: Banishment
>
>
> > Hi Dave,
> >
> > OK, one revolution of the e-shaft is 1/3 revolution of the rotors. So
> > each rotor has had one intake event. Each face has a calculated
> > displacement of about 650 cc. Two X 650 cc = 1.3L. If you can explain
> > why it's 2.6L, maybe I can send Paul an apology. Or are you just
> > trying to get my goat? :)
> >
> > I'm not trying to create a big discussion on the displacement of the
> > rotary, I just want to understand where that 2.6L per revolution number
> > is comming from. I haven't been able to see it. I think Paul gets it
> > from comparing to a piston engine, and I agree that the 13B compares
> > closest to a 2.6L 4 cycle 4 cylinder engine.
> >
> > Bob W.
> >
> >
> > On Sun, 16 Oct 2005 16:27:59 -0700
> > David Leonard <wdleonard@gmail.com> wrote:
> >
> >> Monty, Glad to have you and you know you will always be welcome here.
> >> However, you are wrong and 'he' is right about the displacement of the 13B.
> >> It is 2.6L or 159.6 cubic inches to be more exact.
> >> That is the volume of intake on one revolution of the e-shaft.
> >> But I think you knew that, you were just trying to get his goat. ;-)
> >>
> >> --
> >> Dave Leonard
> >> Turbo Rotary RV-6 N4VY
> >> http://members.aol.com/_ht_a/rotaryroster/index.html
> >> http://members.aol.com/_ht_a/vp4skydoc/index.html
> >>
> >> On 10/16/05, Monty Roberts <montyr2157@alltel.net> wrote:
> >> >
> >> > The doctrine of immaculate ingestion. Whereby molecules of air and fuel
> >> > magically migrate into a very small, very perfect engine,unsullied by the
> >> > mere laws of physics, thereby creating the salvation of the world through
> >> > massive power levels.
> >> > In the protestant tradition of placing the individual at the front of the
> >> > line rather than at the bottom of the church hierarchy, I will henceforth
> >> > place all replies at the TOP of each post.
> >> > Monty
> >> > Which doctrine was that Monty?
> >> >
> >> > Bob W.
> >> >
> >> >
> >>
> >
> >
> > --
> > http://www.bob-white.com
> > N93BD - Rotary Powered BD-4 (real soon)
> > Prewired EC2 Cables - http://www.roblinphoto.com/shop/
> >
> > --
> > Homepage: http://www.flyrotary.com/
> > Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/
> >
--
http://www.bob-white.com
N93BD - Rotary Powered BD-4 (real soon)
Prewired EC2 Cables - http://www.roblinphoto.com/shop/
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