X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Wed, 22 Nov 2006 00:55:23 -0500 Message-ID: X-Original-Return-Path: Received: from rwcrmhc13.comcast.net ([204.127.192.83] verified) by logan.com (CommuniGate Pro SMTP 5.1.2) with ESMTP id 1591107 for lml@lancaironline.net; Tue, 21 Nov 2006 21:54:12 -0500 Received-SPF: none receiver=logan.com; client-ip=204.127.192.83; envelope-from=rbelshe@comcast.net Received: from desk (c-67-174-246-172.hsd1.ca.comcast.net[67.174.246.172]) by comcast.net (rwcrmhc13) with SMTP id <20061122025352m13004q6e8e>; Wed, 22 Nov 2006 02:53:52 +0000 From: "Bob B." X-Original-To: "'Lancair Mailing List'" Subject: RE: [LML] Re: Electrical /Hydraulic system questionslancair235/320 X-Original-Date: Tue, 21 Nov 2006 18:53:51 -0800 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_004E_01C70D9E.62DAD190" X-Mailer: Microsoft Office Outlook, Build 11.0.6353 Thread-Index: AccNzeoU964XafhWT2+eWi5Hhy8a5AAEiqQw In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2962 X-Original-Message-ID: This is a multi-part message in MIME format. ------=_NextPart_000_004E_01C70D9E.62DAD190 Content-Type: text/plain; charset="windows-1250" Content-Transfer-Encoding: 7bit : 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 HYPERLINK "http://home.comcast.net/~rbelshe/"http://home.comcast.net/~rbelshe/ -- 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_004E_01C70D9E.62DAD190 Content-Type: text/html; charset="windows-1250" Content-Transfer-Encoding: quoted-printable
:
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 fluid=20 volume.  When the rod volume is removed from the system, make = up fluid=20 is pulled in from the tank through a one way check valve.  = During=20 retraction, the spool valve opens a low resistance path from the low = side to=20 the reservoir, eliminating a large pressure build up in the low = circuit=20 during retraction. - which also eliminate the possibility of = pressure build=20 up due to thermal influence.
One side effect of the correct spool valve orientation and a = leak free=20 system is that you cannot manually push the gear up even with the = dump valve=20 open unless the spool valve is moved into the retract = position.  After=20 opening the valve you still have a closed loop from high to low that = is now=20 bypassing the pump.  When you try to push the gear up you get = hydraulic=20 lock.  You are trying to add the rod volume to a closed system = and the=20 only route back to the reservoir is through a relief = valve.  By=20 bumping the pump in the up direction, even with the dump valve=20 open, you can push the spool valve into the retract position = which=20 opens up the low resistance path to the reservoir for the = low side=20 circuit.  If you are able to push the gear up at all without = bumping=20 the pump, I would suspect the spool valve is backwards.  Let us = know=20 what observe in the low circuit during retraction.  You can = also try=20 the direction-reversal test during retraction.  The response = should be=20 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 push=20 any of the gear up.    Spool valve is = backward?
 
When I do the direction reversal = test the=20 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 AVG Free Edition.
Version: 7.1.409 / Virus Database: 268.14.11/543 - Release Date: = 11/20/2006

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