X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 08 Apr 2010 21:13:30 -0400 Message-ID: X-Original-Return-Path: Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122] verified) by logan.com (CommuniGate Pro SMTP 5.3.5) with ESMTP id 4214356 for lml@lancaironline.net; Thu, 08 Apr 2010 11:04:03 -0400 Received-SPF: none receiver=logan.com; client-ip=71.74.56.122; envelope-from=Wolfgang@MiCom.net X-Original-Return-Path: X-Authority-Analysis: v=1.1 cv=6F+LCzJuLsxGuJMJ5Tj2TUnLRzv3ZQG9k4OeZLOH/c4= c=1 sm=0 a=MHZY6FYWMEQOp7S43i2QIw==:17 a=SluSt9yLkyEvjg2o-2EA:9 a=zYVJLViUZaic-fil0MMA:7 a=TAHY-weyEytdfW_nqrFtvxZEsuwA:4 a=wPNLvfGTeEIA:10 a=b9NnZ3lsDJAaNysFi58A:9 a=dUyFrkyxGODYhjtG4-oA:7 a=fBgmH0lGYUl2dJOCVOsAnURYZdUA:4 a=MHZY6FYWMEQOp7S43i2QIw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 74.218.201.50 Received: from [74.218.201.50] ([74.218.201.50:1272] helo=Lobo) by hrndva-oedge04.mail.rr.com (envelope-from ) (ecelerity 2.2.2.39 r()) with ESMTP id 82/95-15516-140FDBB4; Thu, 08 Apr 2010 15:03:29 +0000 X-Original-Message-ID: <000e01cad72c$a24d7ac0$6401a8c0@Lobo> From: "Wolfgang" X-Original-To: Subject: FW: [LML] gear retract problems X-Original-Date: Thu, 8 Apr 2010 11:03:22 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000B_01CAD70B.1AEAAD80" 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_000B_01CAD70B.1AEAAD80 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Randy Snar in his just posted comments has hit the nail on the head. The = spool in the hydraulic pump does not always stay at the end point of = it's travel and when it doesn't, and since there is no accumulator in = the system, the fluid volume is trapped and heat will cause thermal = expansion opening the pressure switches. If you don't experience a large = temperature rise and the spool in your pump stays where it's supposed = to, you won't see the problem. So as Randy stated, if both switches = trip, nothing works except opening a fitting to relieve the pressure. = Installing a "dump" valve that vents both sides to the reservoir instead = of the standard of just equalizing between both sides will fix the = problem but still requires pilot intervention after the re-plumbing. But = how many people are ready to re-plumb their hydraulics to implement that = fix ? There is nothing in the pump except o-ring friction to keep the spool in = it's needed end position. Vibration can move it trapping the fluid = volumes. Activating the pump will force the spool back into it's end = position relieving the offending pressure and all is well with the = world. Problem is the pressure switch is open preventing the pump from = activating. Forcing the pump to activate when both switches are open = will do the trick. My electric module does exactly that . . . . = automatically . . . . without pilot intervention. It connects to both = pressure switches and forces the pump to activate in the direction = selected by the gear switch if both pressure switches are open. Wolfgang ------=_NextPart_000_000B_01CAD70B.1AEAAD80 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Randy Snar in his just posted comments = has hit the=20 nail on the head. The spool in the hydraulic pump does not always stay = at the=20 end point of it's travel and when it doesn't, and since there is no = accumulator=20 in the system, the fluid volume is trapped and heat will cause thermal = expansion=20 opening the pressure switches. If you don't experience a large = temperature rise=20 and the spool in your pump stays where it's supposed to, you won't see = the=20 problem. So as Randy stated, if both switches trip, nothing works except = opening=20 a fitting to relieve the pressure. Installing a "dump" valve that vents = both=20 sides to the reservoir instead of the standard of just equalizing = between both=20 sides will fix the problem but still requires pilot intervention = after the=20 re-plumbing. But how many people are = ready to=20 re-plumb their hydraulics to implement that fix ?
 
There is nothing in the pump except = o-ring friction=20 to keep the spool in it's needed end position. Vibration can move it = trapping=20 the fluid volumes. Activating the pump will force the spool back into = it's end=20 position relieving the offending pressure and all is well with the = world.=20 Problem is the pressure switch is open preventing the pump from = activating.=20 Forcing the pump to activate when both switches are open will do the = trick.=20 My electric module does exactly that . . . . automatically . . . . = without=20 pilot intervention. It connects to both pressure switches and forces the = pump to=20 activate in the direction selected by the gear switch if both pressure = switches=20 are open.
 
Wolfgang
 
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