X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail15.syd.optusnet.com.au ([211.29.132.196] verified) by logan.com (CommuniGate Pro SMTP 5.1.9) with ESMTPS id 2080821 for flyrotary@lancaironline.net; Sat, 02 Jun 2007 17:58:36 -0400 Received-SPF: none receiver=logan.com; client-ip=211.29.132.196; envelope-from=lendich@optusnet.com.au Received: from george (d220-237-205-137.dsl.nsw.optusnet.com.au [220.237.205.137]) by mail15.syd.optusnet.com.au (8.13.1/8.13.1) with SMTP id l52LvpNM031142 for ; Sun, 3 Jun 2007 07:57:52 +1000 Message-ID: <000c01c7a561$11eaf4d0$89cdeddc@george> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Lynn's Tuning Summation was: [FlyRotary] Re: PP Ve??? was Re: Intake CFM air flow Date: Sun, 3 Jun 2007 07:57:52 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0009_01C7A5B4.E2CED2D0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Antivirus: avast! (VPS 0657-0, 12/12/2006), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0009_01C7A5B4.E2CED2D0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ed, What sort of diameter/length did you settle on? George (down under) Great tuning summation! Lynn. While not a racer, my experience in experimenting with intake = manifolds on the rotary for aircraft use tracks with your comments. I = initially tried big, short tubes with my first intake and while it would = have probably given great HP at 8000+ rpm, the prop load prevented the = engine from ever getting to the magic land. When I went to smaller = diameter and longer tubes for the intake - performance at 6400 and below = improved considerably. About the only thing I might add a different perspective to is the rpm = regime for the HP tuning goal. Since I personally can't stand to see = the $$ flow at high cruise power settings , I seldom ever hit top HP in = flight for longer than a few minutes (just to see how it does). Most of the time I throttle back to 7.5-8.5 gph for economic cruise. = On the other hand, my personal priority is to accelerate rapidly on = take off and get a good initial climb rate to get my butt over and as = high above the trees as I can as quickly as I can. My (tongue in = cheek) viewpoint is that I don't care if you can hit 400 mph, if you = don't clear the trees, it doesn't matter {:>). So for my priorities, I concentrated on trying to achieve best power = at take off rpm - around 6000 rpm. The longer length and smaller = diameter tubes give the engine lots of oomph in that rpm regime. = Clearly if you wanted an all-out air racer you would more likely choose = shorter bigger tubes. =20 Thanks again for the great summation. Ed In a message dated 6/1/2007 8:20:04 P.M. Eastern Daylight Time, = daval@iprimus.com.au writes: Hi Lynn, since the Pport has a 'near lack of reversions' which are the = source of=20 "organ pipe" tuning theory; would you say that Pport engine is a = lot=20 less sensitive to "tuned length" than a side port engine? Or does the Pport overlap between exhaust and inlet also cause a=20 pulsation which enhances 'organ pipe' tuned length. I think this is what I wanted to ask :) As you can in see in pictures of the Le mans engine, great care was = taken to have the correct length of inlet tract for each RPM. The engine = was not used even close to its maximum RPM or HP. And it had 700 HP. = Having poor performance in the tuned area is not no performance, and = they went to great lengths to get as much as was possible.=20 Larger diameter tubes gets a poor peak tuned effect but flows better = from less drag. A smaller diameter tube gives a more profound tuned = effect but flows less outside of the tuned RPM because of drag. And = they had big tubes. But the Pport flows like a turbine and power is = limited by the strength of the pieces. The multi piece crank may have = been the limiting factor. They could have made a few changes and had 800 = HP with good reliability. But they wanted perfect reliability. The = Lemans cars are forced to have broad power bands because there is a low = RPM 1st gear corner and a 230 MPH straight, so they went for the wider = power band that all competitors must have.=20 In a fixed length situation, you can only tune for one RPM, and that = must be for cruise and still have enough mid range to get the prop and = plane into the cruise speed range. Up on the cam, or on the pipe. It is = not impossible to have a killer motor that will not pull hard enough to = get a dyno reading without going up to RPM (Minimum used for racing) = with no load on the dyno, because the lightest load cannot be pulled by = the engine. It might even be that you cruise at or near peak torque and = never get to peak HP. The other choice would be to cruise just above = peak HP.=20 I gear the car to pass through peak power well before the end of the = longest straight. So we are above best power RPM for much of the = distance. The driver could not get around that one. Once the drag is = equal to the available power the car goes no faster in any case.=20 It is the first car to its top speed that beats you to the other = end, and seldom the car with the highest top speed. Notice that = dragsters that are going for a top speed records use a taller gear than = the normal get there first gear (lower). =20 The highest HP is not the answer unless there is a variable prop = system to keep the engine near its best power. Not fun if it takes = constant attention on clime out to keep things going the right = direction. The other end of the scale is a broad power band that allows = clime with no thought of engine RPM and on a fixed pitch prop.=20 It is possible to stall a prop with a bit of extra power while = sitting still or while the plane is moving slowly in a takeoff attempt. = Most people never get to feel that one because at lower RPM there is not = enough power being produced. But the prop blade stalls the same as a = wing stalls. Angle of attack is the answer. The speed of the air passing = through the prop disc alters the effective angle of attack, on any prop = fixed or adjustable pitch. Of course it is more likely on a high pitched = fixed pitch prop. It is also counterintuitive to pull off a bit of = throttle to stop the stall on a take off roll.=20 So the tuning is not for the max HP but a broad band of power, = mostly to the south or lower than the maximum HP. A bit lower HP at the = bottom of the range is fine, and helps avoid the slipping prop (like = spinning the wheels) and as the speed comes up and more power can be = absorbed by the prop the RPM brings on more power.=20 So, straight tubes over curved tubes. Worse if fuel is injected = before the curve or with a carb at the very end. Longer tubes give a = broader band than shorter tubes. Smaller diameter tubes give a better = effect over a smaller range. A peaky cam effect. Long tubes work better = at lower RPM. Short tubes work better at higher RPM. Probably a tapered = tube of medium length would be fantastic, but difficult to manufacture. = No inter connection of the inlet tracts is used on Pport engines.=20 A smaller higher velocity port gives a wider band than a huge slower = flowing port.=20 A bigger port moves the peak power up the RPM band and is peaky. A = smaller port works over a wider range, and is less sensitive to tuned = length. I had a factory Pport housing and it had small "D" shaped ports = with the flat part on the bottom. So it opened quickly and closed = slowly. Later aftermarket Pports (Modified factory) had huge rectangular = ports you could stick your hands in. Those made the power between 9,000 = and 10,700. =20 Lynn E. Hanover -------------------------------------------------------------------------= --- See what's free at AOL.com. ------=_NextPart_000_0009_01C7A5B4.E2CED2D0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Ed,
What sort of diameter/length did you settle = on?
George (down under)
 Great tuning summation!  Lynn.
 
While not a racer, my experience in experimenting with intake = manifolds=20 on the rotary for aircraft use tracks with your comments.  I = initially=20 tried big, short tubes with my first intake and while it would have = probably=20 given great HP at 8000+ rpm, the prop load prevented the engine from = ever=20 getting to the magic land.  When I went to smaller diameter and = longer=20 tubes for the intake - performance at 6400 and below improved=20 considerably.
 
About the only thing I might add a different perspective to is = the rpm=20 regime for the HP tuning goal.  Since I personally can't = stand to=20 see the $$ flow at high cruise power settings , I seldom ever hit top = HP in=20 flight for longer than a few minutes (just to see how it does).
 
  Most of the time I throttle back to 7.5-8.5 gph = for economic=20 cruise.  On the other hand, my personal priority is to accelerate = rapidly=20 on take off and get a good initial climb rate to get my butt over and = as high=20 above the trees as I can as quickly as I can.  My  (tongue = in cheek)=20 viewpoint is that I don't care if you can hit 400 mph, if you don't = clear the=20 trees, it doesn't matter {:>).
 
So for my priorities, I concentrated on trying to achieve best = power at=20 take off rpm - around 6000 rpm.  The longer length and smaller = diameter=20 tubes give the engine lots of oomph in that rpm regime.  Clearly = if you=20 wanted an all-out air racer you would more likely choose shorter = bigger=20 tubes. 
 
 
Thanks again for the great summation.
 
Ed

In a message dated 6/1/2007 8:20:04 P.M. Eastern Daylight Time, = daval@iprimus.com.au = writes:
Hi=20 Lynn,
since the Pport has a 'near lack of reversions' which are = the=20 source of
"organ pipe" tuning theory; would you say that Pport = engine=20 is a lot
less sensitive to "tuned length" than a side port=20 engine?

Or does the Pport overlap between exhaust and inlet = also=20 cause a
pulsation which enhances 'organ pipe' tuned = length.

I=20 think this is what I wanted to ask = :)
As you can in see in pictures of the Le mans engine, great care = was=20 taken to have the correct length of inlet tract for each RPM. The = engine was=20 not used even close to its maximum RPM or HP. And it had 700 = HP. =20 Having poor performance in the tuned area is not  no = performance, and=20 they went to great lengths to get as much as was possible.
 
Larger diameter tubes gets a poor peak tuned effect but flows = better=20 from less drag. A smaller diameter tube gives a more profound tuned = effect=20 but flows less outside of the tuned RPM because of drag.  And = they had=20 big tubes. But the Pport flows like a turbine and power is limited = by the=20 strength of the pieces. The multi piece crank may have been the = limiting=20 factor. They could have made a few changes and had 800 HP with good=20 reliability. But they wanted perfect reliability. The Lemans = cars are=20 forced to have broad power bands because there is a low RPM 1st gear = corner=20 and a 230 MPH straight, so they went for the wider power = band that=20 all competitors must have.
 
In a fixed length situation, you can only tune for one RPM, and = that=20 must be for cruise and still have enough mid range to get the prop = and plane=20 into the cruise speed range. Up on the cam, or on the pipe. It is = not=20 impossible to have a killer motor that will not pull hard enough to = get a=20 dyno reading without going up to RPM (Minimum used for racing) with = no load=20 on the dyno, because the lightest load cannot be pulled by the = engine. It=20 might even be that you cruise at or near peak torque and never get = to peak=20 HP.  The other choice would be to cruise just above peak = HP.=20
 
I gear the car to pass through peak power well before the end = of the=20 longest straight.  So we are above best power RPM for much = of the=20 distance. The driver could not get around that one. Once the drag is = equal=20 to the available power the car goes no faster in any case.
 
It is the first car to its top speed that beats you to the = other end,=20 and seldom the car with the highest top speed. Notice that dragsters = that=20 are going for a top speed records use a taller gear than the normal = get=20 there first gear (lower).  
 
The highest HP is not the answer unless there is a variable = prop system=20 to keep the engine near its best power. Not fun if it takes constant = attention on clime out to keep things going the right direction. The = other=20 end of the scale is a broad power band that allows clime with no = thought of=20 engine RPM and on a fixed pitch prop.
 
It is possible to stall a prop with a bit of extra power while = sitting=20 still or while the plane is moving slowly in a takeoff = attempt. Most=20 people never get to feel that one because at lower RPM there is not = enough=20 power being produced. But the prop blade stalls the same as a wing = stalls.=20 Angle of attack is the answer. The speed of the air passing through = the prop=20 disc alters the effective angle of attack, on any prop fixed or = adjustable=20 pitch. Of course it is more likely on a high pitched fixed pitch = prop. It is=20 also counterintuitive to pull off a bit of throttle to stop the = stall on a=20 take off roll. 
 
So the tuning is not for the max HP but a broad band of power, = mostly=20 to the south or lower than the maximum HP. A bit lower HP at = the bottom=20 of the range is fine, and helps avoid the slipping prop (like = spinning the=20 wheels) and as the speed comes up and more power can be absorbed by = the prop=20 the RPM brings on more power.
 
So, straight tubes over curved tubes. Worse if fuel is injected = before=20 the curve or with a carb at the very end. Longer tubes give a = broader band=20 than shorter tubes. Smaller diameter tubes give a better effect = over a=20 smaller range. A peaky cam effect. Long tubes work better at lower = RPM.=20 Short tubes work better at higher RPM. Probably a tapered tube of = medium=20 length would be fantastic, but difficult to manufacture. No inter = connection=20 of the inlet tracts is used on Pport engines.
A smaller higher velocity port gives a wider band than a huge = slower=20 flowing port.
 
A bigger port moves the peak power up the RPM band and is = peaky. A=20 smaller port works over a wider range, and is less sensitive to = tuned=20 length. I had a factory Pport housing and it had small "D" shaped = ports with=20 the flat part on the bottom. So it opened quickly and closed = slowly.=20 Later aftermarket Pports (Modified factory) had huge rectangular = ports you=20 could stick your hands in. Those made the power between 9,000 and = 10,700.=20  
 
Lynn E. Hanover
 



See what's free at AOL.com. =
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