X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail08.syd.optusnet.com.au ([211.29.132.189] verified) by logan.com (CommuniGate Pro SMTP 5.1.11) with ESMTPS id 2272752 for flyrotary@lancaironline.net; Sun, 19 Aug 2007 17:58:50 -0400 Received-SPF: none receiver=logan.com; client-ip=211.29.132.189; envelope-from=lendich@optusnet.com.au Received: from george (d58-105-68-189.dsl.nsw.optusnet.com.au [58.105.68.189]) by mail08.syd.optusnet.com.au (8.13.1/8.13.1) with SMTP id l7JLw66c023005 for ; Mon, 20 Aug 2007 07:58:07 +1000 Message-ID: <001701c7e2ac$07af4dd0$bd44693a@george> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Air/fuel flow Date: Mon, 20 Aug 2007 07:58:08 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0014_01C7E2FF.D884ACE0" 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_0014_01C7E2FF.D884ACE0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Thanks Richard! George ( down under) George, Mikuni is listing the 36mm for 50hp max. The 38 is all the same except = for 1mm more in the throat. Now, I have to make shure I do or do not have the float bowl issue. Richard Sohn N2071U ----- Original Message -----=20 From: George Lendich=20 To: Rotary motors in aircraft=20 Sent: Saturday, August 18, 2007 7:25 PM Subject: [FlyRotary] Re: Air/fuel flow Thanks Ed, I just thought I'd ask - just in case! If I find out I will let you and everyone else know! George George, nothing magic about 120 MPH (unless you're in free fall = {:>)). As you noted the airflow inside a carb can vary greatly. 176 = fps was just a wag that I felt comfortable with using as an example of = how to find the size opening IF you desired that air velocity at that = CFM flow rate.. Also even if you don't have a venture like in a carb, you will = still reach a choke velocity - it will just be at a bit higher rate of = flow. You can have you cake one of two ways, you can decide on what = velocity you want at a certain volume flow (CFM) and then size the = opening to get that velocity OR you can pick a carb with a specific = opening and see what velocity that gives you. As long as you are below = choke velocity you are probably OK. As you noted larger openings as on = race cars can result in less velocity, but since they are bigger, you = still get a lot air mass. Pros and Cons and compromise is the name of = the game. If I had the answers, I'd be a multimillionaire consultant to = NASCAR racing teams {:>)) Ed ----- Original Message -----=20 From: George Lendich=20 To: Rotary motors in aircraft=20 Sent: Friday, August 17, 2007 9:29 PM Subject: [FlyRotary] Re: Air/fuel flow Kelly, That's interesting - is Ed trying to tell me something? Just joking, I did know that but didn't relate the two. George ( down under) George, Not Ed and not great at math but from my skydiving days = the figure of 176 feet per sec (approx 120 mph) is called terminal = velocity for the average human body in a flat stable freefall = position........Just a bit of trivia......... -- Kelly Troyer=20 "Dyke Delta"_13B ROTARY Engine=20 "RWS"_RD1C/EC2/EM2=20 "Mistral"_Backplate/Oil Manifold=20 -------------- Original message from "George Lendich" = : --------------=20 Ed, I would like to clarify another point and that is = your velocity figure of 120 mph. I will explain:- I have studied carb sites for snippets of information = ( they don't give much away), however one did say that carb choke speeds = are usually 450' per second and racing cars 125' per second. I assume the racing car inlet speeds are lower because = the throttle is wide open with massive sized inlets, therefore lower = vacuum signal. Your calculations use 176' per second. Can you clarify = where you acquired that figure from as a higher figure would reduce the = inlet area calculations. The carb I am looking at is the Revmaster, they = currently only have 40mm carbs available due to slow demand of the = 42/44mm. One good thing is that the carb operates without a need of = venturi, however the vacuum signal must be weaker ( because of = this)coupled with a weaker signal because of the shape of the rotor = face.=20 At the very least the lack of venturi also eliminates = the choke potential. Some carbs have a 44mm inlet but are choked to 36mm = which would increase inlet speed (good), but as you say, may move into = the choke restriction area (bad). A weaker signal would also effect the idle mixture as = this is driven by vacuum rather than air flow, however I guess this can = be adjusted manually. Should be plenty of vacuum at idle with the slide = closed. I have asked Revmaster for air flow and velocity = figures, but these may be derived from piston engine type figures. If you or Lynn could comment on this it would be = greatly appreciated.=20 Also my research indicates that flow air/ fuel mix = richens at higher RPM and altitude. I can't remember why at higher RPM - = mind block, however for altitude it is because fuel flow is driven by = air flow and even though the density of the air is lower ( at altitude) = the flow remains the same - therefore richer mixture. Revmaster says = their needle design is self leaning ( to a degree) because of design. I = assume because the air density directly affects the suction to the rear = side of the flat ground needle, ( this provides the low pressure area = rather than the venturi) therefore with reduced density you have reduced = suction and reduced fuel and leaner mixture. However I will clarify that = when next we talk. I find this all very interesting! George ( down under) Well I'll be Ed, 2.4137sq" =3D (.877x.877xPi =3D 2.416), therefore .877 = Radius or 1.754 Dia or 44.55 mm for the carb opening. I'm working on the rest! George ( down under) For inlet, you take the CFM and you need one other = factor - what velocity do you want through your inlet? Lets say you = want a higher velocity of around 176 feet/sec (120 MPH) then we know = that Volume =3D Area * length. If were want 176 feet/sec velocity from = 176 CFM air flow then coverting CFM to cubic feet per second were have = 176Ft^3/min / 60 Second/Minute =3D 29.333 Ft^3/ Second ---------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG Free Edition.=20 Version: 7.5.484 / Virus Database: 269.12.0/959 - Release = Date: 17/08/2007 5:43 PM -------------------------------------------------------------------------= - No virus found in this incoming message. Checked by AVG Free Edition.=20 Version: 7.5.484 / Virus Database: 269.12.0/959 - Release Date: = 17/08/2007 5:43 PM -------------------------------------------------------------------------= --- No virus found in this incoming message. Checked by AVG Free Edition.=20 Version: 7.5.476 / Virus Database: 269.11.19/953 - Release Date: = 8/14/2007 5:19 PM -------------------------------------------------------------------------= ----- No virus found in this incoming message. Checked by AVG Free Edition.=20 Version: 7.5.484 / Virus Database: 269.12.0/960 - Release Date: = 18/08/2007 3:48 PM ------=_NextPart_000_0014_01C7E2FF.D884ACE0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Thanks Richard!
George ( down under)
George,
 
Mikuni is listing the 36mm for 50hp = max. The 38=20 is all the same except for 1mm more in the throat.
Now, I have to make shure I do or do = not have the=20 float bowl issue.
 
Richard Sohn
N2071U
----- Original Message -----
From:=20 George Lendich
To: Rotary motors in = aircraft=20
Sent: Saturday, August 18, = 2007 7:25=20 PM
Subject: [FlyRotary] Re: = Air/fuel=20 flow

 Thanks Ed,
I just thought I'd ask - just in=20 case!
If I find out I will let you and = everyone else=20 know!
George
George, nothing magic about 120 MPH = (unless you're=20 in free fall {:>)).  As you noted the airflow inside a = carb=20 can  vary greatly.  176 fps was just a wag that I felt=20 comfortable with using as an example of how to find the size = opening IF=20 you desired that air velocity at that CFM flow rate..
 
Also even if you don't have a venture like = in a=20 carb, you will still reach a choke velocity - it will just be at a = bit=20 higher rate of flow.
 
You can have you cake one of two ways, you = can=20 decide on what velocity you want at a certain volume flow (CFM) = and then=20 size the opening to get that velocity OR you can pick a carb with = a=20 specific opening and see what velocity that gives you.  As = long as=20 you are below choke velocity you are probably  OK.  As = you noted=20 larger openings as on race cars can result in less velocity, but = since=20 they are bigger, you still get a lot air mass.  Pros and Cons = and=20 compromise is the name of the game.  If I had the answers, = I'd be a=20 multimillionaire consultant to  NASCAR racing teams=20 {:>))
 
Ed
----- Original Message ----- =
From:=20 George Lendich =
To: Rotary motors in = aircraft=20
Sent: Friday, August 17, = 2007 9:29=20 PM
Subject: [FlyRotary] Re: = Air/fuel=20 flow

Kelly,
That's interesting - is Ed = trying to tell=20 me something?
Just joking, I did know that = but didn't=20 relate the two.
George ( down = under)
George,
    Not Ed and not great at math but from = my=20 skydiving days the figure
of 176 feet per sec (approx 120 mph) is called terminal = velocity=20 for the
average human body in a flat stable=20 freefall position........Just a bit of
trivia.........
--
Kelly Troyer =
"Dyke=20 Delta"_13B ROTARY Engine
"RWS"_RD1C/EC2/EM2=20
"Mistral"_Backplate/Oil Manifold =




--------------=20 Original message from "George Lendich"=20 <lendich@optusnet.com.au>: --------------

 
Ed,
 I would like to = clarify=20 another point and that is your velocity figure of 120=20 mph.
 
I will = explain:-
 
I have = studied carb sites=20 for snippets of information ( they don't give much = away),=20 however one did say that carb choke speeds  = are=20 usually 450' per second and racing cars 125' per=20 second.
 
I assume the racing = car inlet=20 speeds are lower because the throttle is wide open = with=20 massive sized inlets, therefore lower vacuum=20 signal.
 
Your calculations use = 176' per=20 second. Can you clarify where you acquired that figure = from as=20 a higher figure would reduce the inlet area=20 calculations.
 
The carb I am looking = at is the=20 Revmaster, they currently only have 40mm carbs = available due=20 to slow demand of the 42/44mm. One good thing is that = the carb=20 operates without a need of venturi, however = the=20 vacuum signal must be weaker ( because of this)coupled = with a=20 weaker signal because of the shape of the rotor face.=20
 
At the very least the = lack of=20 venturi also eliminates the choke potential. Some = carbs have a=20 44mm inlet but are choked to 36mm which would increase = inlet=20 speed (good), but as you say, may move into the choke=20 restriction area (bad).
 
A weaker signal would = also effect=20 the idle mixture as this is driven by vacuum rather = than air=20 flow, however I guess this can be adjusted manually. = Should be=20 plenty of vacuum at idle with the slide = closed.
 
I have asked = Revmaster for air=20 flow and velocity figures, but these may be derived = from=20 piston engine type figures.
 
If you or Lynn could = comment on=20 this it would be greatly appreciated.
 
Also my research = indicates that=20 flow air/ fuel mix richens at higher RPM and = altitude. I=20 can't remember why at higher RPM - mind block, however = for=20 altitude it is because fuel flow is driven = by air=20 flow and even though the density of the air is lower ( = at=20 altitude) the flow remains the same - therefore richer = mixture. Revmaster says their needle design is self = leaning (=20 to a degree) because of design. I assume because = the air=20 density directly affects the suction to the rear side = of the=20 flat ground needle, ( this provides the low pressure = area=20 rather than the venturi) therefore with reduced = density=20 you have reduced suction and reduced fuel and = leaner=20 mixture. However I will clarify that when next we=20 talk.
I find this all very=20 interesting!
George ( down = under)
 
 
 
Well I'll be = Ed,
2.4137sq" =3D = (.877x.877xPi =3D=20 2.416), therefore .877 Radius or 1.754 Dia or 44.55 mm = for the=20 carb opening.
I'm working on the=20 rest!
George ( down = under)
 
For inlet, you take the CFM = and you need=20 one other factor - what velocity do you want through = your=20 inlet?  Lets say you want a higher velocity of = around 176=20 feet/sec (120 MPH)  then we know that Volume =3D = Area *=20 length.  If were want 176 feet/sec velocity from = 176 CFM=20 air flow then coverting CFM to cubic feet per second = were have=20 176Ft^3/min / 60 Second/Minute =3D 29.333 Ft^3/=20 = Second

No virus found in this incoming message.
Checked by = AVG Free=20 Edition.
Version: 7.5.484 / Virus Database: 269.12.0/959 - = Release=20 Date: 17/08/2007 5:43 PM

No virus found in this incoming message.
Checked by AVG = Free=20 Edition.
Version: 7.5.484 / Virus Database: 269.12.0/959 - = Release=20 Date: 17/08/2007 5:43 PM

No virus found in this incoming message.
Checked by AVG = Free=20 Edition.
Version: 7.5.476 / Virus Database: 269.11.19/953 - = Release=20 Date: 8/14/2007 5:19 PM

No virus found in this incoming message.
Checked by AVG Free = Edition.
Version: 7.5.484 / Virus Database: 269.12.0/960 - Release = Date:=20 18/08/2007 3:48 PM
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