X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.123] verified) by logan.com (CommuniGate Pro SMTP 5.3c3) with ESMTP id 3991285 for flyrotary@lancaironline.net; Wed, 25 Nov 2009 17:03:30 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.123; envelope-from=eanderson@carolina.rr.com Received: from computername ([75.191.186.236]) by cdptpa-omta02.mail.rr.com with ESMTP id <20091125220253085.KEDF20286@cdptpa-omta02.mail.rr.com> for ; Wed, 25 Nov 2009 22:02:53 +0000 From: "Ed Anderson" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Vacuum System Regulation Basics Date: Wed, 25 Nov 2009 17:02:53 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000C_01CA6DF1.211D3A70" X-Mailer: Microsoft Office Outlook, Build 11.0.5510 Thread-Index: AcpuE38k8BFRLKF5SwmSfpw+NVMFjAAA1FGQ In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 Message-Id: <20091125220253085.KEDF20286@cdptpa-omta02.mail.rr.com> This is a multi-part message in MIME format. ------=_NextPart_000_000C_01CA6DF1.211D3A70 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit 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 high 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 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 vacuum 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 amount of air in the hose and therefore the associated pressure. You didn't state where in the system you put the restriction, but if you put 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 Behalf 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 suction gauge reads 9". This is too much for gyros, so I put a restrictor in the line expecting to get less vacuum - instead it 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 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 gauges, as any dust would get sucked out of cabin without passing through gauges. Jeff __________ 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_000C_01CA6DF1.211D3A70 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

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 high = 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 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 vacuum 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 amount of air in the hose and therefore the = associated pressure.

 

You didn’t state where in the = system you put the restriction, but if you put 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

 

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf 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 suction gauge reads 9”.  This is too much for = gyros, so I put a restrictor in the line expecting to get less vacuum – = instead it 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 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 = gauges, as any dust would get sucked out of cabin without passing through = gauges.

Jeff

 



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

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com

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