X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from EXHUB003-3.exch003intermedia.net ([207.5.74.110] verified) by logan.com (CommuniGate Pro SMTP 5.3c3) with ESMTPS id 3991778 for flyrotary@lancaironline.net; Thu, 26 Nov 2009 08:37:04 -0500 Received-SPF: none receiver=logan.com; client-ip=207.5.74.110; envelope-from=jwhaley@datacast.com Received: from EXVMBX003-5.exch003intermedia.net ([207.5.74.45]) by EXHUB003-3.exch003intermedia.net ([207.5.74.110]) with mapi; Thu, 26 Nov 2009 05:36:27 -0800 From: Jeff Whaley To: Rotary motors in aircraft Date: Thu, 26 Nov 2009 05:38:46 -0800 Subject: RE: [FlyRotary] Re: Vacuum System Regulation Basics Thread-Topic: [FlyRotary] Re: Vacuum System Regulation Basics Thread-Index: AcpuGyoVSaQcvIigTl6naoDrG6qUxAAe+yfQ Message-ID: References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: multipart/alternative; boundary="_000_C03ABB0A7362B84BB53D544B3C305E0E0153A41BD669EXVMBX0035e_" MIME-Version: 1.0 --_000_C03ABB0A7362B84BB53D544B3C305E0E0153A41BD669EXVMBX0035e_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Yes Ed, I put the restriction between the inlet and the suction gauge ... t= hinking this would reduce the venturi's ability to "suck" ... I knew from t= he results that the restriction was wrong, but now with your explanation I = understand why. Thanks. Jeff From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Beh= alf Of Ed Anderson Sent: Wednesday, November 25, 2009 5:03 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Vacuum System Regulation Basics As you know, there is no such thing as "suction" - it's just if one volume= has less pressure than another connecting volume then the one with the hig= h pressure pushes toward the one with the lower pressure. This might give = the impression that the one is "sucking", but its really the other (higher = pressure one ) pushing. So with your venture tube (Bernoulli effect) is creating an area of lower p= ressure in the venture tube. Since the pressure there is less than in your= hose, the air flows from you cabin through your vacuum gyros and vacuum ga= uge to the venture tube. Any restriction between your cabin and the ventur= e tube will reduce the air flow into the hose thereby reducing the amount o= f air in the hose and therefore the associated pressure. You didn't state where in the system you put the restriction, but if you pu= t between you cabin inlet and before your vacuum gauge, then in effect you = are restricting the flow of air from your cabin (higher pressure) into the = vacuum system. Therefore there is less air in that hose volume that there = was before and therefore less pressure and your gauge reads lower pressure = (more suction {:>). Well, at least that's the way it looks to me - but then I'm an electron guy= . 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 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 Beh= alf Of Jeff Whaley Sent: Wednesday, November 25, 2009 4:11 PM To: Rotary motors in aircraft Subject: [FlyRotary] Vacuum System Regulation Basics Can anyone explain the following: I have a 9" venturi on side of fuselage - connected with a 3/8" hose, the s= uction gauge reads 9". This is too much for gyros, so I put a restrictor i= n the line expecting to get less vacuum - instead it goes to >10". This wo= uld imply that if hose was larger, vacuum would be less. If I was to install a regulator should it go between venturi and gauges? or= after gauges between them and filter? I'm getting the feeling that a regulator is actually a "controlled leak" - = adjusted by a needle-valve? True or False? If True, it would make sense to put a controlled leak between venturi and g= auges, as any dust would get sucked out of cabin without passing through ga= uges. Jeff __________ Information from ESET NOD32 Antivirus, version of virus signatur= e database 3267 (20080714) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com --_000_C03ABB0A7362B84BB53D544B3C305E0E0153A41BD669EXVMBX0035e_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Yes Ed, I put the restri= ction between the inlet and the suction gauge … thinking this would reduce = the venturi’s ability to “suck” … I knew from the resul= ts that the restriction was wrong, but now with your explanation I understand why.  Thanks.

Jeff

 =

From: Rotary motors= in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed Anders= on
Sent: Wednesday, November 25, 2009 5:03 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Vacuum System Regulation Basics<= /span>

 

As you know,  there is no such thing as “suctionR= 21; – it’s just if one volume has less pressure than another connecting volume then the one with the high pressure pushes toward the one with the lower pressure.  This might give the impression that the one is “sucking”, but i= ts really the other (higher pressure one ) pushing.

 

So with your venture tube (Bernoulli effect) is creating an are= a of lower pressure in the venture tube.  Since the pressure there is less = than in your hose, the air flows from you cabin through your vacuum gyros and va= cuum gauge to the venture tube.  Any restriction between your cabin and the venture tube will reduce the air flow into the hose thereby reducing the am= ount of air in the hose and therefore the associated pressure.=

 

You didn’t state where in the system you put the restrict= ion, but if you put between you cabin inlet and before your vacuum gauge, then in ef= fect you are restricting the flow of air from your cabin (higher pressure) into = the vacuum system.  Therefore there is less air in that hose volume that t= here was before and therefore less pressure and your gauge reads lower pressure (more suction {:>). 

 

Well, at least that’s the way it looks to me – but = then I’m an electron guy.

 

Ed

 

 

From: Rotary motors= in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Jeff Whal= ey
Sent: Wednesday, November 25, 2009 4:11 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Vacuum System Regulation Basics

 

Can anyone explain the following:

I have a 9” venturi on side of fuselage – = connected with a 3/8” hose, the suction gauge reads 9”.  This is too much f= or gyros, so I put a restrictor in the line expecting to get less vacuum – instead i= t goes to >10”.  This would imply that if hose was larger, vacuum would= be less.

If I was to install a regulator should it go between v= enturi and gauges? or after gauges between them and filter?

I’m getting the feeling that a regulator is actu= ally a “controlled leak” – adjusted by a needle-valve? True or F= alse?

If True, it would make sense to put a controlled leak between venturi and gauges, as any dust would get sucked out of cabin witho= ut passing through gauges.

Jeff

 



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

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com

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