X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from access.aic-fl.com ([207.30.253.2] verified) by logan.com (CommuniGate Pro SMTP 5.1.11) with ESMTP id 2272023 for flyrotary@lancaironline.net; Sun, 19 Aug 2007 08:30:40 -0400 Received-SPF: softfail receiver=logan.com; client-ip=207.30.253.2; envelope-from=unicorn@gdsys.net Received: from main (gdsi-45.gdsys.net [207.30.255.45]) by access.aic-fl.com (Rockliffe SMTPRA 4.5.6) with SMTP id for ; Sun, 19 Aug 2007 07:26:18 -0500 Message-ID: <001e01c7e25c$ad798780$2dff1ecf@main> From: "Richard Sohn" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Air/fuel flow Date: Sun, 19 Aug 2007 07:29:23 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001B_01C7E232.AA786E90" 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 This is a multi-part message in MIME format. ------=_NextPart_000_001B_01C7E232.AA786E90 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable 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 ------=_NextPart_000_001B_01C7E232.AA786E90 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
George,
 
Mikuni is listing the 36mm for 50hp = max. The 38 is=20 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=20 Lendich
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 in=20 free fall {:>)).  As you noted the airflow inside a carb = can =20 vary greatly.  176 fps was just a wag that I felt comfortable = with=20 using as an example of how to find the size opening IF you desired = that air=20 velocity at that CFM flow rate..
 
Also even if you don't have a venture like = in a carb,=20 you will still reach a choke velocity - it will just be at a bit = higher rate=20 of flow.
 
You can have you cake one of two ways, you = can decide=20 on what velocity you want at a certain volume flow (CFM) and then = size the=20 opening to get that velocity OR you can pick a carb with a specific = opening=20 and see what velocity that gives you.  As long as you are below = choke=20 velocity you are probably  OK.  As you noted larger = openings as on=20 race cars can result in less velocity, but since they are bigger, = you still=20 get a lot air mass.  Pros and Cons and compromise is the name = of the=20 game.  If I had the answers, I'd be a multimillionaire = consultant=20 to  NASCAR racing teams {:>))
 
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 me=20 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 = 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 for=20 snippets of information ( they don't give much away), = however=20 one did say that carb choke speeds  are = usually 450'=20 per second and racing cars 125' per second.
 
I assume the racing car = inlet=20 speeds are lower because the throttle is wide open with = massive=20 sized inlets, therefore lower vacuum = signal.
 
Your calculations use = 176' per=20 second. Can you clarify where you acquired that figure = from as a=20 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 to=20 slow demand of the 42/44mm. One good thing is that the = carb=20 operates without a need of venturi, however = the vacuum=20 signal must be weaker ( because of this)coupled with a = weaker=20 signal because of the shape of the rotor face. =
 
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 flow=20 and velocity figures, but these may be derived from = piston=20 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 flow=20 and even though the density of the air is lower ( at = altitude)=20 the flow remains the same - therefore richer mixture. = Revmaster=20 says their needle design is self leaning ( to a degree) = because=20 of design. I assume because the air density = directly=20 affects the suction to the rear side of the flat ground = needle,=20 ( this provides the low pressure area rather than the=20 venturi) therefore with reduced density you have = reduced=20 suction and reduced fuel and leaner mixture. = However I will=20 clarify that when next we talk.
I find this all very=20 interesting!
George ( down = under)
 
 
 
Well I'll be = Ed,
2.4137sq" =3D = (.877x.877xPi =3D 2.416),=20 therefore .877 Radius or 1.754 Dia or 44.55 mm for the = carb=20 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 Date:=20 17/08/2007 5:43 PM

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