X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 02 Apr 2013 22:05:33 -0400 Message-ID: X-Original-Return-Path: Received: from elasmtp-mealy.atl.sa.earthlink.net ([209.86.89.69] verified) by logan.com (CommuniGate Pro SMTP 6.0.4) with ESMTP id 6177169 for lml@lancaironline.net; Tue, 02 Apr 2013 21:34:05 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.69; envelope-from=cskelt@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=oyqe9Z/Wk6/eZMxx2DJD+Npbxnje07mAUtWcBdcw7sQh/ua7lBxw2I9GyTR1nmAL; h=Received:Message-ID:Reply-To:From:To:References:In-Reply-To:Subject:Date:MIME-Version:Content-Type:X-Priority:X-MSMail-Priority:Importance:X-Mailer:X-MimeOLE:X-ELNK-Trace:X-Originating-IP; Received: from [66.245.84.67] (helo=TheLittleHouse) by elasmtp-mealy.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1UNCZv-0002L7-NL for lml@lancaironline.net; Tue, 02 Apr 2013 21:33:32 -0400 X-Original-Message-ID: <5648D24C78FE4667B2E0A54149F40CE1@TheLittleHouse> Reply-To: "Christopher Skelt" From: "Christopher Skelt" X-Original-To: "Lancair_Mailing_List" References: In-Reply-To: Subject: Re: [LML] LNC2 Old Pump Hydraulics Grief X-Original-Date: Tue, 2 Apr 2013 20:33:11 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0052_01CE2FE1.4B551FA0" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 15.4.3555.308 X-MimeOLE: Produced By Microsoft MimeOLE V15.4.3555.308 X-ELNK-Trace: df7a2c4e012c7de094f5150ab1c16ac044d224e428e16b45d068df0dd4d08975c6e0db5cd8e1ca66350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 66.245.84.67 This is a multi-part message in MIME format. ------=_NextPart_000_0052_01CE2FE1.4B551FA0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Chris, The pump is 108AA19-AL-3VT with a date stamp 10/89 and presumably = predates the alphabet soup in your article. The spool is symmetrical. = The dip stick through hole is also the filler for the metal cylindrical = reservoir. Does the absence of a stand pipe mean the return is via the = low side PRV during retract? I=E2=80=99ll screw up the shut-off on the high side. The low side = pressure is building up over 1000 psi before the pump stops during = retraction. Can I also reduce the low side PRV operating pressure to = limit the low side pressure buildup? I see no reason why it should be = significantly more than the shutoff pressure on the low side pressure = switch.=20 Thank you for the reply=E2=80=94I wonder what folks did before the www. Regards, Chris.=20 From: Chris Zavatson=20 Sent: Monday, April 01, 2013 10:21 AM To: lml@lancaironline.net=20 Subject: Re: [LML] LNC2 Old Pump Hydraulics Grief Chris, The behavior you describe indicates the lack of a functioning back = pressure circuit. Does your pump part number have an "LB" in the = number? If instead it has an "LL", the pump pre-dates the LB back = pressure circuit. If it is an "LB" pump, your spool is in backwards and = just needs to be flipped around. Unfortunately, the photo hints at an older pump. I see only one TRV and = the dip-stick through hole is drilled out. Also, there is no stand pipe = for the return to reservoir. If it is indeed and older pump without a back pressure circuit (and they = are not retrofittable according to Parker), you'll need to raise the = operating pressure of the high side circuit to perhaps 1,500 psi. Right = now your net working pressure on the high side is reduced to: High side = settings minus low side PRV setting. -not enough to get the gear up = cleanly. The ball a spring you removed are for the thermal relief.=20 Chris Zavatson N91CZ 360std http://www.n91cz.net/ From: Christopher Skelt To: lml@lancaironline.net=20 Sent: Monday, April 1, 2013 4:08 AM Subject: [LML] LNC2 Old Pump Hydraulics Grief This is for the aficionados of old hydraulic pumps. Mine is from 1989 = and I=E2=80=99m having trouble with the retract cycle. Since my post = several months ago I have installed pressure gauges, rebuilt the nose = leg actuator, sequence valve and gear door actuator, and serviced the = pump with the kit from Lancair. Same problems, but at least the = pressure gauges help diagnose. On the retract cycle pressure builds up on the low side as well as the = high side and the pump stops until the low side pressure drops, the pump = restarts, raises the gear a bit further, stops, and so on. Once the = gear is up, the pressure on the low side drops off and high side = pressure is maintained. These are symptoms of a reversed spool valve, = but this pump=E2=80=99s is symmetrical with a single o-ring. Lowering is OK, and pressure is maintained in the down and locked = position, so apparently no internal leaks. =20 I guessed the return line was blocked, or the ball valve sticky. See = the attached photos. The spring is very stiff and takes about 15 lb to = close it about 0.1 inches. With a port diameter of less than 1/10 inch, = this translates into about 2000 psi to overcome that force. This = doesn=E2=80=99t look like it=E2=80=99s offering only 100 psi resistance = and it seems beefier than the example on Chris Zavatson=E2=80=99s = figure 14 on N91cz.com... Can anyone confirm that the spring looks = right or wrong=E2=80=94maybe Friday afternoon at the factory? And where = can I get a replacement return line spring and ball? =20 The photo of the pump shows the return valve location on the left. =20 Thanks in advance. Regards, Chris.=20 -- For archives and unsub = http://mail.lancaironline.net:81/lists/lml/List.html ------=_NextPart_000_0052_01CE2FE1.4B551FA0 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable
Chris,
The pump is 108AA19-AL-3VT with a date stamp 10/89 and presumably = predates=20 the alphabet soup in your article.  The spool is symmetrical.  = The dip=20 stick through hole is also the filler for the metal cylindrical = reservoir. =20 Does the absence of a stand pipe mean the return is via the low side PRV = during=20 retract?
 
I=E2=80=99ll screw up the shut-off on the high side.  The low = side pressure is=20 building up over 1000 psi before the pump stops during retraction.  = Can I=20 also reduce the low side PRV operating pressure to limit the low side = pressure=20 buildup?  I see no reason why it should be significantly more than = the=20 shutoff pressure on the low side pressure switch.
 
Thank you for the reply=E2=80=94I wonder what folks did before the = www.
 
Regards, Chris.
 
 
Sent: Monday, April 01, 2013 10:21 AM
Subject: Re: [LML] LNC2 Old Pump Hydraulics = Grief
 
Chris,
The behavior you describe indicates the lack of a functioning = back=20 pressure circuit.  Does your pump part number have an "LB" in the=20 number?  If instead it has an "LL", the pump pre-dates the LB back pressure circuit.  If it = is an "LB"=20 pump, your spool is in backwards and just needs to be flipped=20 around.
Unfortunately, the photo hints at an older pump.  I see = only one=20 TRV and the dip-stick through = hole is=20 drilled out.  Also, there is no stand pipe for the return to=20 reservoir.
If it is indeed and older pump without a back pressure = circuit (and=20 they are not retrofittable = according to=20 Parker),  you'll need to raise the operating pressure of the high = side=20 circuit to perhaps 1,500 psi.  Right now your net working pressure = on the=20 high side is reduced to: High side settings minus low side PRV setting.   -not enough to get the gear = up=20 cleanly.
The ball a spring you removed are for the thermal relief.=20
 
Chris Zavatson
N91CZ
360std
http://www.n91cz.net/
 
From: Christopher Skelt <cskelt@earthlink.net>
To: lml@lancaironline.net =
Sent: Monday, April 1, 2013 4:08=20 AM
Subject: [LML] = LNC2 Old Pump Hydraulics = Grief
 
This is for the aficionados of old hydraulic pumps.  Mine is = from 1989=20 and I=E2=80=99m having trouble with the retract cycle.  Since my = post several=20 months ago I have installed pressure gauges, rebuilt the nose leg actuator, sequence = valve and gear=20 door actuator, and serviced the pump with the kit from Lancair.  = Same=20 problems, but at least the pressure gauges help diagnose.
 
On the retract cycle pressure builds up on the low side as well as = the high=20 side and the pump stops until the low side pressure drops, the pump = restarts,=20 raises the gear a bit further, stops, and so on.  Once the gear is = up, the=20 pressure on the low side drops off and high side pressure is = maintained. =20 These are symptoms of a reversed spool valve, but this pump=E2=80=99s is = symmetrical=20 with a single o-ring.
 
Lowering is OK, and pressure is maintained in the down and locked = position,=20 so apparently no internal leaks. 
 
I guessed the return line was blocked, or the ball valve = sticky.  See=20 the attached photos.  The spring is very stiff and takes about 15 = lb to=20 close it about 0.1 inches.  With a port diameter of less than 1/10 = inch,=20 this translates into about 2000 psi to overcome that force.  This = doesn=E2=80=99t look like = it=E2=80=99s offering only 100 psi=20 resistance and it seems  beefier than the example on Chris = Zavatson=E2=80=99s=20 figure 14 on N91cz.com...  Can=20 anyone confirm that the spring looks right or wrong=E2=80=94maybe Friday = afternoon at=20 the factory?  And where can I get a replacement return line spring = and=20 ball? 
 
The photo of the pump shows the return valve location on the = left. =20
 
Thanks in advance.
 
Regards, Chris.
 
 
 
 
 
 
 

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