X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Wed, 22 Nov 2006 11:16:03 -0500 Message-ID: X-Original-Return-Path: Received: from mxo2.broadbandsupport.net ([209.55.3.82] verified) by logan.com (CommuniGate Pro SMTP 5.1.2) with ESMTP id 1593061 for lml@lancaironline.net; Wed, 22 Nov 2006 08:26:41 -0500 Received-SPF: none receiver=logan.com; client-ip=209.55.3.82; envelope-from=kloop@plantationcable.net Received: from George (host-12-163-6-172.plantationcable.net [12.163.6.172]) by mxo2.broadbandsupport.net (Postfix) with SMTP id B103E348FDB for ; Wed, 22 Nov 2006 08:26:03 -0500 (EST) X-Original-Message-ID: <004001c70e39$c1e36b20$ac06a30c@George> From: "George Shattuck" X-Original-To: "Lancair Mailing List" References: Subject: Re: [LML] Re: Electrical /Hydraulic system questionslancair235/320 X-Original-Date: Wed, 22 Nov 2006 08:26:02 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_003D_01C70E0F.D8C843D0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2869 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2962 X-broadbandsupport-MailScanner-Information: Please contact the ISP for more information X-broadbandsupport-MailScanner: Found to be clean X-broadbandsupport-MailScanner-From: kloop@plantationcable.net X-Spam-Status: No This is a multi-part message in MIME format. ------=_NextPart_000_003D_01C70E0F.D8C843D0 Content-Type: text/plain; charset="windows-1250" Content-Transfer-Encoding: quoted-printable Bob Belshe and all. The experience I have had with my 320 is exactly like yours. On jacks, = I have always made it a habit to push the gear up into the well to check = for fit and free fall. The dump valve is open for this. After every = flight and after engine shutdown, before I turn off the master switch, I = always open the dump valve and let the pump run for a couple seconds = then shut off the master, leaving the dump valve open.=20 George Shattuck N320GS, 1989 kit Danville, CA before moving to Georgia. From: Bob B.=20 To: lml@lancaironline.net=20 Sent: Wednesday, November 22, 2006 12:55 AM Subject: [LML] Re: Electrical /Hydraulic system = questionslancair235/320 : The fluid circuit is really a closed loop. The only options for = returning fluid to the reservoir are either through one of the pressure = relief valves or the low resistance back pressure circuit. Excess fluid = needs to return to the tank every time the rod volume displaces fluid = volume. When the rod volume is removed from the system, make up fluid = is pulled in from the tank through a one way check valve. During = retraction, the spool valve opens a low resistance path from the low = side to the reservoir, eliminating a large pressure build up in the low = circuit during retraction. - which also eliminate the possibility of = pressure build up due to thermal influence. One side effect of the correct spool valve orientation and a leak = free system is that you cannot manually push the gear up even with the = dump valve open unless the spool valve is moved into the retract = position. After opening the valve you still have a closed loop from = high to low that is now bypassing the pump. When you try to push the = gear up you get hydraulic lock. You are trying to add the rod volume to = a closed system and the only route back to the reservoir is through a = relief valve. By bumping the pump in the up direction, even with the = dump valve open, you can push the spool valve into the retract position = which opens up the low resistance path to the reservoir for the low side = circuit. If you are able to push the gear up at all without bumping the = pump, I would suspect the spool valve is backwards. Let us know what = observe in the low circuit during retraction. You can also try the = direction-reversal test during retraction. The response should be = instantaneous. good luck Chris, It would seem that there is no one answer for this problem. On my 235, with the plane on jacks; I can open the dump valve and easily push any of the gear up. = Spool valve is backward? When I do the direction reversal test the gear reverses instantly. = Spool valve is OK? When I put the gear up and then open the dump valve, all 3 drop = within 2-3 seconds. Years ago, I experienced a few instances of the gear not coming down = when the gear switch was put down. This situation was always relieved = by briefly opening the dump valve. It stopped happening, so I did not = change anything. Am I just lucky, or what? Bob Belshe Moraga, CA Lancair 235/320 =20 http://home.comcast.net/~rbelshe/=20 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.409 / Virus Database: 268.14.11/543 - Release Date: = 11/20/2006 ------=_NextPart_000_003D_01C70E0F.D8C843D0 Content-Type: text/html; charset="windows-1250" Content-Transfer-Encoding: quoted-printable
Bob Belshe and all.
 
The experience I have had with my 320 is exactly = like=20 yours.  On jacks, I have always made it a habit to push the = gear up=20 into the well to check for fit and free fall.  The dump valve is = open for=20 this.  After every flight and after engine shutdown, before I turn = off the=20 master switch, I always open the dump valve and let the pump run for a = couple=20 seconds then shut off the master, leaving the dump valve=20 open. 
 
George Shattuck
N320GS, 1989 kit
Danville, CA before moving to Georgia.
From:=20 Bob = B.=20
Sent: Wednesday, November 22, = 2006 12:55=20 AM
Subject: [LML] Re: Electrical = /Hydraulic=20 system questionslancair235/320

:
The fluid circuit is really a closed loop.  The only = options for=20 returning fluid to the reservoir are either through one of the = pressure=20 relief valves or the low resistance back pressure circuit.  = Excess=20 fluid needs to return to the tank every time the rod volume = displaces=20 fluid volume.  When the rod volume is removed from the = system, make=20 up fluid is pulled in from the tank through a one way check = valve. =20 During retraction, the spool valve opens a low resistance path = from the=20 low side to the reservoir, eliminating a large pressure build up = in the=20 low circuit during retraction. - which also eliminate the = possibility of=20 pressure build up due to thermal influence.
One side effect of the correct spool valve orientation and a = leak=20 free system is that you cannot manually push the gear up even with = the=20 dump valve open unless the spool valve is moved into the retract=20 position.  After opening the valve you still have a closed = loop from=20 high to low that is now bypassing the pump.  When you try to = push the=20 gear up you get hydraulic lock.  You are trying to add the = rod volume=20 to a closed system and the only route back to the reservoir = is=20 through a relief valve.  By bumping the pump in the up = direction,=20 even with the dump valve open, you can push the spool valve = into the=20 retract position which opens up the low resistance = path to the=20 reservoir for the low side circuit.  If you are able to push = the gear=20 up at all without bumping the pump, I would suspect the spool = valve is=20 backwards.  Let us know what observe in the low circuit = during=20 retraction.  You can also try the direction-reversal test = during=20 retraction.  The response should be instantaneous.
good luck
Chris,
 
 It would seem that there = is no one=20 answer for this problem.
 
On my 235, with the plane on=20 jacks;
 
I can open the dump valve and = easily=20 push any of the gear up.    Spool valve is=20 backward?
 
When I do the direction = reversal test=20 the gear reverses instantly.   Spool valve is = OK?
 
When I put the gear up and = then open the=20 dump valve, all 3 drop within 2-3 seconds.
 
Years ago, I experienced a few = instances=20 of the gear not coming down when the gear switch was put down.  = This=20 situation was always relieved by briefly opening the dump = valve.  It=20 stopped happening, so I did not change anything.
 
Am I just lucky, or = what?
 

Bob = Belshe
Moraga,=20 CA
Lancair 235/320  
http://home.comcast.net/~rbelshe/ =

 
 
 
 

--
No virus found in this outgoing = message.
Checked by=20 AVG Free Edition.
Version: 7.1.409 / Virus Database: 268.14.11/543 = -=20 Release Date: 11/20/2006

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