X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao103.cox.net ([68.230.241.43] verified) by logan.com (CommuniGate Pro SMTP 5.3.3) with ESMTP id 4155389 for flyrotary@lancaironline.net; Sun, 07 Mar 2010 12:18:32 -0500 Received-SPF: none receiver=logan.com; client-ip=68.230.241.43; envelope-from=rv-4mike@cox.net Received: from fed1rmimpo01.cox.net ([70.169.32.71]) by fed1rmmtao103.cox.net (InterMail vM.8.00.01.00 201-2244-105-20090324) with ESMTP id <20100307171756.XFAQ19579.fed1rmmtao103.cox.net@fed1rmimpo01.cox.net> for ; Sun, 7 Mar 2010 12:17:56 -0500 Received: from willsPC ([68.105.86.80]) by fed1rmimpo01.cox.net with bizsmtp id qHHw1d0061k005Q03HHwBq; Sun, 07 Mar 2010 12:17:56 -0500 X-VR-Score: -120.00 X-Authority-Analysis: v=1.1 cv=qY0/QvRffkjURHWZjC3q+nTs9PdPIIJxYa32KydkvE8= c=1 sm=1 a=4zM5C_qBEEoA:10 a=XruvlouZCDbGUgEaRUiNZQ==:17 a=ayC55rCoAAAA:8 a=arxwEM4EAAAA:8 a=QdXCYpuVAAAA:8 a=7g1VtSJxAAAA:8 a=ekHE3smAAAAA:20 a=UretUmmEAAAA:8 a=Ia-xEzejAAAA:8 a=kviXuzpPAAAA:8 a=nUuTZ29dAAAA:8 a=RvbBDXnpp8r3GTW-PFoA:9 a=kQSdGK05dITxYJloR4gA:7 a=tg0Lw4IYp0QsVII1KQsuPudl8jgA:4 a=wPNLvfGTeEIA:10 a=1vhyWl4Y8LcA:10 a=EzXvWhQp4_cA:10 a=4vB-4DCPJfMA:10 a=bNk5uJ301WpAsxZA:21 a=hz2qVE6oqFgBJAvB:21 a=t8wamvuBINOTA2MavrMA:9 a=zPZ6dHkr6sP-rDsdY18A:7 a=Tj8QvJQlJLDzV5ifiXc_Hq3lA1AA:4 a=iVkDmfvjeKcA:10 a=Auubunat5rPkzaaN:21 a=nwrIUAV9ZQsYYonV:21 a=XruvlouZCDbGUgEaRUiNZQ==:117 X-CM-Score: 0.00 Message-ID: From: "Mike Wills" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Performance 68x72 prop. [FlyRotary] Re: TB size, Travel and Power Date: Sun, 7 Mar 2010 09:17:54 -0800 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0081_01CABDD7.118DBB80" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8089.726 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8089.726 This is a multi-part message in MIME format. ------=_NextPart_000_0081_01CABDD7.118DBB80 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ed, Thanks a bunch for the offer. I will likely take you up on it at some = point in the not to distant future. My guess is that It would probably = be very close to fitting my spinner since Clark's props are very similar = to Margie Warnke's. The other potential gotcha is prop hub thickness. = Per the data I got with my Warnke it's a 68x80 but seems like all of = these wood prop manufacturers measure pitch differently so I don't know = if a meaningful comparison can be made. Can you tell me what sort of = performance you were getting with this prop? Static RPM? WOT RPM in = flight? On the MP gauge I'm going to need to go with an 2 1/4" due to panel = space. The reason I havent gotten to this yet has nothing to do with = cost. I need to revamp my panel (in addition to the intake manifold and = cowl - I may never be finished with this thing). My current panel has a = bunch of redundant steam gauges in the right side of the panel. My = vacuum gauge and EC-2 controls are mounted on a small console in front = of the stick. I want to eliminate some of the redundant steam gauges, = move the EC-2 controls up to the panel, and replace the vacuum gauge = with MP, also moved up to the panel. Its going to be quite a lot of work = so I've been stalling. In spite of the weather this weekend, Spring and soaring season are = approaching. My time is starting to get diverted to getting my sailplane = ready for the coming season. I need to retire. Mike Wills=20 From: Ed Anderson=20 Sent: Saturday, March 06, 2010 8:18 PM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Performance 68x72 prop. [FlyRotary] Re: TB size, = Travel and Power Actually, Mike, I do have a 68x72 Performance prop that I used for my = 2.17 gear box. Don't know if that's sufficiently different from yours = to make a difference or not. Let me know if interested - for the paltry = sum of shipping costs, just might be able to get it to you {:>). Don't = know if the blade profile will fit your spinner cut our or not - that's = about the only problem I could see. =20 Ed =20 Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://www.dmack.net/mazda/index.html http://www.flyrotary.com/ http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.rotaryaviation.com/Rotorhead%20Truth.htm -------------------------------------------------------------------------= ------- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On = Behalf Of Mike Wills Sent: Saturday, March 06, 2010 10:13 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: TB size, Travel and Power =20 Tracy, =20 Yes I have confirmed that I get full ambient pressure at 2/3 (roughly) = throttle near sea level. And yes I still have the POS vacuum gauge. I = know it needs replaced - just havent had the opportunity yet. =20 My point in bringing this up yet again was to emphasize the point Ed = made a couple of posts back - that this whole thing is a complex problem = with a lot of variables. And to not dive in and start whacking on the = prop until certain that is where the problem is. In my case I'm not sure = it is. Full ambient MP at the TB doesn't indicate how well the intake is = flowing and it is entirely possible to have full MP but a very poor = performing manifold. Guys in racing make lots of $ porting and flow = testing manifolds. =20 I need to make some changes to the intake anyway for other reasons so = I'm going to focus on that first. And once that's done, if I'm still = giving up some RPMs then I'll take a look at the prop. Unless of course = I can do it the easy way as Al suggested and borrow a prop. On that = note, are there any of you RV guys that have upgraded from the 2.17 gear = ratio to the 2.85 that have a "wrong way" prop you'd be willing to lend = for a test? =20 Meanwhile I havent been able to fly for the past 3 weeks due to this = crappy weather. Why's it always have to rain on the weekends? Its not = supposed to rain in SoCal at all. =20 Mike Wills =20 From: Tracy Crook=20 Sent: Saturday, March 06, 2010 7:06 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: TB size, Travel and Power =20 Mike, you are measuring the MP exactly where you should, You can't do it = properly anywhere else, at least not with a simple instrument. =20 But are you at last confirming that you DO have full ambient MP at 2/3 = throttle setting? That IS an important question if you want to know = the right answer to your question. BTW, ditch the vacuum gauge (if = that's what you are using) and get a proper MP gauge. =20 Tracy On Fri, Mar 5, 2010 at 9:30 PM, Mike Wills wrote: Ed, =20 I hear what your saying (and I get it). Here's the thing, and I admit I = may have a misunderstanding here. Your explanation applies if you are = measuring manifold pressure essentially at the rotor face. If you = measure MP closer to the TB as I do unfortunately, it is possible to see = ambient at full throttle but have restrictions in the intake tract that = would result in less than ambient at the rotor face. Conversely (and = again theory - I'm open to being shown wrong here), a properly designed = DIE manifold would show ambient MP measured at the TB and greater than = ambient measured at the rotor face. =20 I accept that by trimming the prop I can lighten the load and gain some = HP (though some here seem to think that HP will increase linearly with = RPM to infinity and I don't buy that either). But as you alluded to in = your previous, there's some potential for mistake in trimming any prop = until you are quite sure that you are not HP limited by something other = than load. And I'm not sure yet. Just a feeling based on the fact that = I'm using a cut down RX-7 TB that's maxed out about 1/3 short of fully = open. And honestly I still havent dug any deeper because the airplane is = flying well and has good performance. But sooner or later I'm going to = want to get more than the 5700RPM I'm currently getting - I want all the = performance that's there. =20 Mike Wills =20 From: Ed Anderson=20 Sent: Friday, March 05, 2010 6:36 PM To: Rotary motors in aircraft=20 Subject: [FlyRotary] TB size, Travel and Power =20 I am apparently not doing a very good job making the point about the = relationship between throttle body size, throttle travel and engine = power clear. So here is another try at it - using extreme examples and = no math. Let's assume your volumetric efficiency is 100% (no losses). =20 IF you put a =BD " dia TB on you engine. You could have it wide open = and your engine (under normal prop load) probably wouldn't turn 4000 = rpm. That is because even wide open, the =BD" dia TB restricts airflow = sufficiently - that the manifold air density never approaches the = ambient air density. Since we know that the engine power is directly = proportional to the density of air in the combustion chamber - and this = density is limited in this case to less than ambient, you engine is not = going to produce much power, certainly not full power. So this bit of = information tells us "Bigger Lithium Crystals, Scotty!!" - i.e try a = larger throttle body.=20 =20 Now if you keep enlarging the diameter of the TB you would find that at = fully open -your engine would be producing more power than it was, but = perhaps still not the maximum power it is capable of. This is because = the air density in the manifold has increase due to the less restrictive = flow, but is still below ambient. This is due to the better, but still = restrictive effect of the TB size on the air flow. Now if you continued = enlarging the TB size, you would reach a point where with the TB just = reaching fully open - your manifold air density is exactly ambient and = your engine is producing all the power it is going to. =20 Now if you enlarge the TB even further, you will simply find that you = can cause the manifold pressure (air density) to reach ambient without = opening the TB fully. Its simply large enough that all the air the = engine can use (ambient air density point) is met at partial throttle = opening. In fact , you can certainly continue to advance the throttle = thereby opening the throttle plate even more - but, you are not going to = increase the air density in the manifold and therefore you will not = produce any additional power for that additional throttle travel. =20 Bigger Throttle body's result in more power only up to the point the = airflow they permit causes manifold air density to reach ambient. = Beyond that point, the only thing they do is provide frustration - by = having all that throttle travel remaining which does nothing to produce = more power {:>). =20 Now if you can somehow lighten the load on your engine, then engine can = turn faster providing more "suction" on the manifold volume reducing the = air density below ambient, now opening your "oversize" TB a bit more = will produce more power because you are increasing the airflow again to = the point where the equilibrium point between ambient air density in the = manifold and rpm is again reached. Lighten the load further and you can = again increase engine power by opening your TB more. Etc, etc. =20 =20 Ah, ain't this hobby wonderful {:>)=20 =20 =20 Ed =20 Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://www.dmack.net/mazda/index.html http://www.flyrotary.com/ http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.rotaryaviation.com/Rotorhead%20Truth.htm =20 __________ Information from ESET NOD32 Antivirus, version of virus = signature database 3267 (20080714) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ------=_NextPart_000_0081_01CABDD7.118DBB80 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Ed,
 
Thanks a bunch for the offer. I will likely = take you up=20 on it at some point in the not to distant future. My guess is that It = would=20 probably be very close to fitting my spinner since Clark's props are = very=20 similar to Margie Warnke's. The other potential gotcha is prop hub=20 thickness. Per the data I got with my Warnke it=92s a 68x80 but = seems like=20 all of these wood prop manufacturers measure pitch differently so I = don=92t know=20 if a meaningful comparison can be made. Can you tell me what sort of = performance=20 you were getting with this prop? Static RPM? WOT RPM in = flight?
 
On the MP gauge I'm going to need to go with = an 2 1/4"=20 due to panel space. The reason I havent gotten to this yet has nothing = to do=20 with cost. I need to revamp my panel (in addition to the intake manifold = and=20 cowl - I may never be finished with this thing). My current panel has a = bunch of=20 redundant steam gauges in the right side of the panel. My vacuum gauge = and EC-2=20 controls are mounted on a small console in front of the stick. I want to = eliminate some of the redundant steam gauges, move the EC-2 controls up = to the=20 panel, and replace the vacuum gauge with MP, also moved up to the panel. = Its=20 going to be quite a lot of work so I've been stalling.
 
In spite of the weather this weekend, Spring = and soaring=20 season are approaching. My time is starting to get diverted to getting = my=20 sailplane ready for the coming season. I need to retire.
 
Mike Wills 

Sent: Saturday, March 06, 2010 8:18 PM
Subject: [FlyRotary] Performance 68x72 prop. [FlyRotary] Re: = TB=20 size, Travel and Power

Actually, = Mike, I do=20 have a 68x72 Performance prop that I used for my 2.17 gear box.  = Don=92t know=20 if that=92s sufficiently different from yours to make a difference or = not. =20 Let me know if interested =96 for the paltry sum of shipping costs, just = might be=20 able to get it to you {:>).  Don=92t know if the blade profile = will fit=20 your spinner cut our or not =96 that=92s about the only problem I could=20 see.

 

Ed

 

Ed=20 Anderson

Rv-6A N494BW=20 Rotary Powered

Matthews,=20 NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.r= otaryaviation.com/Rotorhead%20Truth.htm

From:=20 Rotary motors in aircraft=20 [mailto:flyrotary@lancaironline.net] On=20 Behalf Of Mike Wills
Sent: Saturday, March 06, 2010 = 10:13=20 PM
To: = Rotary motors in aircraft
Subject: [FlyRotary] Re: TB size, = Travel=20 and Power

 

Tracy,

 

Yes I have confirmed = that I get=20 full ambient pressure at 2/3 (roughly) throttle near sea level. And yes = I still=20 have the POS vacuum gauge. I know it needs replaced - just havent had = the=20 opportunity yet.

 

My point in bringing = this up yet=20 again was to emphasize the point Ed made a couple of posts back - that = this=20 whole thing is a complex problem with a lot of variables. And to not = dive in and=20 start whacking on the prop until certain that is where the problem is. = In my=20 case I'm not sure it is. Full ambient MP at the TB doesn=92t indicate = how well the=20 intake is flowing and it is entirely possible to have full MP but a very = poor=20 performing manifold. Guys in racing make lots of $ porting and flow = testing=20 manifolds.

 

I need to make some = changes to the=20 intake anyway for other reasons so I'm going to focus on that = first. And=20 once that's done, if I'm still giving up some RPMs then I'll take a look = at the=20 prop. Unless of course I can do it the easy way as Al suggested and = borrow a=20 prop. On that note, are there any of you RV guys that have upgraded = from=20 the 2.17 gear ratio to the 2.85 that have a "wrong way" prop you'd be = willing to=20 lend for a test?

 

Meanwhile I havent been = able to=20 fly for the past 3 weeks due to this crappy weather. Why's it always = have to=20 rain on the weekends? Its not supposed to rain in SoCal at=20 all.

 

Mike=20 Wills

 

From: Tracy=20 Crook

Sent: Saturday,=20 March 06, 2010 7:06 AM

To: Rotary motors in = aircraft=20

Subject:=20 [FlyRotary] Re: TB size, Travel and=20 Power

 

Mike,

   you are measuring the MP exactly = where you=20 should,   You can't do it properly anywhere else, at least not = with a=20 simple instrument.

 

But are you at last confirming that you DO = have full=20 ambient MP at 2/3 throttle setting?   That IS an important = question if=20 you want to know the right answer to your question.    = BTW, ditch=20 the vacuum gauge (if that's what you are using) and get a proper MP=20 gauge.

 

Tracy

On Fri, Mar 5, 2010 at 9:30 PM, Mike Wills = <rv-4mike@cox.net>=20 wrote:

Ed,

 

 I hear what your = saying (and=20 I get it). Here's the thing, and I admit I may have a = misunderstanding=20 here. Your explanation applies if you are measuring manifold = pressure=20 essentially at the rotor face. If you measure MP closer to the TB = as I do=20 unfortunately, it is possible to see ambient at full throttle but have=20 restrictions in the intake tract that would result in less than ambient = at the=20 rotor face. Conversely (and again theory - I'm open to being shown wrong = here),=20 a properly designed DIE manifold would show ambient MP measured at the = TB and=20 greater than ambient measured at the rotor=20 face.

 

I accept that by = trimming the prop=20 I can lighten the load and gain some HP (though some here seem to think = that HP=20 will increase linearly with RPM to infinity and I don=92t buy that = either). But as=20 you alluded to in your previous, there's some potential for mistake = in=20 trimming any prop until you are quite sure that you are not HP limited = by=20 something other than load. And I'm not sure yet. Just a feeling based on = the=20 fact that I'm using a cut down RX-7 TB that=92s maxed out about 1/3 = short of fully=20 open. And honestly I still havent dug any deeper because the airplane is = flying=20 well and has good performance. But sooner or later I'm going to = want to get=20 more than the 5700RPM I'm currently getting - I want all the performance = that=92s=20 there.

 

Mike=20 Wills

 

From: Ed = Anderson=20

Sent: Friday,=20 March 05, 2010 6:36 PM

To: Rotary = motors in=20 aircraft

Subject:=20 [FlyRotary] TB size, Travel and=20 Power

 

I am apparently not doing = a very=20 good job making the point about the relationship between throttle body = size,=20 throttle travel and engine power clear.  So here is another try at = it -=20 using extreme examples and no math.  Let=92s assume your volumetric = efficiency is 100% (no losses).

 

IF you put a =BD =94 dia = TB on you=20 engine.  You could have it wide open and your engine (under normal = prop=20 load) probably wouldn=92t turn 4000 rpm.  That is because even wide = open, the=20 =BD=94 dia TB restricts airflow sufficiently - that the manifold air = density never=20 approaches the ambient air density.  Since we know that the engine = power is=20 directly proportional to the density of air in the combustion chamber = =96 and this=20 density is limited in this case to less than ambient, you engine is not = going to=20 produce much power, certainly not full power.  So this bit of = information=20 tells us =93Bigger Lithium Crystals, Scotty!!=94 =96 i.e  try a = larger throttle=20 body.

 

Now if you keep enlarging = the=20 diameter of the TB you would find that at fully open -your engine would = be=20 producing more power than it was, but perhaps still not the maximum = power it is=20 capable of.  This is because the air density in the manifold has = increase=20 due to the less restrictive flow, but is still below ambient.  This = is due=20 to the better, but still restrictive effect of the TB size on the air=20 flow.  Now if you continued enlarging the TB size, you would reach = a point=20 where with the TB just reaching fully open - your manifold air density = is=20 exactly ambient and your engine is producing all the power it is going=20 to.

 

Now if you enlarge the TB = even=20 further, you will simply find that you can cause the manifold pressure = (air=20 density) to reach ambient without opening the TB fully.  Its simply = large=20 enough that all the air the engine can use (ambient air density point) =  is=20 met at partial throttle opening.  In fact , you can certainly = continue to=20 advance the throttle thereby opening the throttle plate even more =96 = but, you are=20 not going to increase the air density in the manifold and therefore you = will not=20 produce any additional power for that additional throttle=20 travel.

 

Bigger Throttle body=92s = result in=20 more power only up to the point the airflow they permit causes manifold = air=20 density to reach ambient.  Beyond that point, the only thing they = do is=20 provide frustration =96 by having all that throttle travel remaining = which does=20 nothing to produce more power {:>).

 

Now if you can somehow =  lighten=20 the load on your engine, then engine can turn faster providing more = =93suction=94 on=20 the manifold volume reducing the air density below ambient, now opening = your=20 =93oversize=94 TB a bit more will produce more power because you are = increasing the=20 airflow again to the point where the equilibrium point between ambient = air=20 density in the manifold and rpm is again reached.  Lighten the load = further=20 and you can again increase engine power by opening your TB more. Etc,=20 etc.

 

 

Ah, ain=92t this hobby = wonderful=20 {:>)

 

 

Ed

 

Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html<= o:p>

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.rotaryaviation.com/Rotorhead%20Truth.htm

 




__________ Information from ESET = NOD32=20 Antivirus, version of virus signature database 3267 (20080714)=20 __________

The message was checked by ESET NOD32 = Antivirus.

http://www.eset.com

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