X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 15 Apr 2011 13:11:14 -0400 Message-ID: X-Original-Return-Path: Received: from hrndva-omtalb.mail.rr.com ([71.74.56.124] verified) by logan.com (CommuniGate Pro SMTP 5.4c3j) with ESMTP id 4946177 for lml@lancaironline.net; Thu, 14 Apr 2011 10:19:28 -0400 Received-SPF: none receiver=logan.com; client-ip=71.74.56.124; envelope-from=Wolfgang@MiCom.net X-Original-Return-Path: X-Authority-Analysis: v=1.1 cv=aqMe+0lCtaYvy4h0jyaoPGyq+DPF+P6rPG2xbekoY9Q= c=1 sm=0 a=ttCsPuSJ-FAA:10 a=MHZY6FYWMEQOp7S43i2QIw==:17 a=Ia-xEzejAAAA:8 a=5FIZSGrRAAAA:8 a=rTjvlri0AAAA:8 a=CjxXgO3LAAAA:8 a=AUIl_wRwNPlBKdBdD9UA:9 a=S43D-Da8kwjlLLG9NRQA:7 a=wPNLvfGTeEIA:10 a=wR8WdYEwGqoA:10 a=EzXvWhQp4_cA:10 a=Dr9Wx-Q63l4A:10 a=rC2wZJ5BpNYA:10 a=1EACODE83YPdM-iA2msA:9 a=3xS3TnLrpTGxVyNyE-cA:7 a=MHZY6FYWMEQOp7S43i2QIw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 74.218.201.50 Received: from [74.218.201.50] ([74.218.201.50:1506] helo=Lobo) by hrndva-oedge01.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id 77/4A-20102-C4207AD4; Thu, 14 Apr 2011 14:18:52 +0000 X-Original-Message-ID: <005c01cbfaae$dee675d0$6401a8c0@Lobo> From: "Wolfgang" X-Original-To: References: Subject: Re: [LML] Re: LNC2 Gear Hydraulics X-Original-Date: Thu, 14 Apr 2011 10:18:46 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0059_01CBFA8D.56F26510" 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_0059_01CBFA8D.56F26510 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable From a design point of view, I still have a big concern about relying on = the friction from an O-ring to keep the landing gear functioning = properly. Vibration levels can exceed 70 G's. I would be much happier = with a spring loaded ball detent or something similar. That's why I came up with the gear fix module. Wolfgang ----- Original Message -----=20 From: Chris Zavatson=20 To: lml@lancaironline.net=20 Sent: Wednesday, April 13, 2011 8:25 AM Subject: Re: [LML] Re: LNC2 Gear Hydraulics A symmetric back-pressure circuit and spool will eliminate the = possibility of installing the spool backwards as happened with pumps = manufactured in about the '96 through '98 time frame. The spool must = still remain in place after the pump shuts down to prevent both high and = low circuits from locking up simultaneously. Using o-ring 013-70 requires 30 g's to move the spool. Using o-ring 013-90 requires 70 g's to move the spool. This includes the return force generated by the poppet springs = (410462). =20 The difference between the two o-rings is durometer. I have been = using the softer one without any problems. The stiffer o-ring (intended = for pumps with back pressure circuits) should leave no doubt. The first = thing to do with a pump that has a history of locking up both sides is = to measure the return force for the spool and make sure it has an o-ring = installed. Chris Zavatson N91CZ 360std www.N91CZ.net -------------------------------------------------------------------------= ----- From: Wolfgang To: lml@lancaironline.net Sent: Mon, April 11, 2011 4:56:57 AM Subject: [LML] Re: LNC2 Gear Hydraulics When I first got into this problem with the hydraulic pumps last year, = I had a few conversations with the product manager of the Oildyne 108 = pump. There have been many changes in it's production life and one of = them was to make the spool symmetrical and have the relief circuit the = same both ways. Wolfgang -------------------------------------------------------------------------= ----- Wolfgang, Yes, I have considered this. The spool with O-ring is a very tight = fight. While I have not tried to measure the force to move it, I would = estimate something over 50 g's to move it (I'll measure this the next = time I have a pump opened up) Could it be that a pump somehow ended up = mounted such that it was subjected to some resonant frequency? Seems = like a remote possibilty given all the variables and the mass of the = pump. How about wear and tear? Perhaps sitting dry and idle for ten = years would do it. A missing O-ring or a spool that doesn't utilize an = O-ring would allow the spool to move very easily. Parker does make = spools that don't even have O-rings. Did these end up getting installed = by chance? Based on reports from the LML, the behavior seems to be rather binary. = On the one hand we have planes with over 1000 hours and more than ten = years of service that have never once had the spool move off the poppet. = On the other hand, we have planes with circuits that lock up right out = of the box (put into service). This leads me to believe there is a difference in configuration. The = easiest way to verify this is to simply open up a pump that is known to = lock up hi and low circuits simultaneously. While I have opened up several pumps (primarily to flip around spool = valves), I have not yet worked on one that had this lock up issue. I am = optimistic the difference will be quite obvious upon inspection. =20 Chris Zavatson N91CZ 360std www.N91CZ.net Sent from my iPad On Apr 7, 2011, at 11:53 AM, "Wolfgang" wrote: Chris, have you considered what effect airframe vibration has on the = position of the spool in the pump and the problem in general ? Wolfgang -------------------------------------------------------------------------= --- From: Chris =20 Sender: =20 Subject: Re: [LML] Re: LNC2 Gear Hydraulics=20 Date: Wed, 06 Apr 2011 07:38:35 -0400=20 To: lml@lancaironline.net=20 =20 =20 I would like to extend the offer to the whole group. I think = the entire community would benefit from understanding why some pumps are = allowing the system to lock up. If anyone has a pump that exhibits this = behavior and could part with it for a week, I am willing to check it out = on the test stand and examine the internal configuration. Chris Zavatson N91CZ 360std www.N91CZ.net=20 ------=_NextPart_000_0059_01CBFA8D.56F26510 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
From a design point of view, I still = have a big=20 concern about relying on the friction from an O-ring to keep the landing = gear=20 functioning properly. Vibration levels can exceed 70 G's. I would be = much=20 happier with a spring loaded ball detent or something = similar.
 
That's why I came up with the gear=20 fix module.
 
Wolfgang
 
----- Original Message -----
From:=20 Chris=20 Zavatson
Sent: Wednesday, April 13, 2011 = 8:25=20 AM
Subject: Re: [LML] Re: LNC2 = Gear=20 Hydraulics

A symmetric back-pressure circuit and spool will eliminate the=20 possibility of installing the spool backwards as happened with pumps=20 manufactured in about the '96 through '98 time frame.  The spool = must=20 still remain in place after the pump shuts down to prevent both high = and low=20 circuits from locking up simultaneously.
Using o-ring 013-70 requires 30 g's to move the spool.
Using o-ring 013-90 requires 70 g's to move the = spool.
This=20 includes the return force generated by the poppet springs = (410462). =20
The difference between the two o-rings is durometer.  I have = been=20 using the softer one without any problems.  The stiffer o-ring = (intended=20 for pumps with back pressure circuits) should leave no doubt.  = The first=20 thing to do with a pump that has a history of locking up both sides is = to=20 measure the return force for the spool and make sure it has an o-ring=20 installed.
 
Chris Zavatson
N91CZ
360std

From: Wolfgang=20 <Wolfgang@MiCom.net>
To: = lml@lancaironline.net
Sent: Mon, April 11, 2011 = 4:56:57=20 AM
Subject: [LML] = Re: LNC2=20 Gear Hydraulics

When I first got into this problem = with the=20 hydraulic pumps last year, I had a few conversations with the product = manager=20 of the Oildyne 108 pump. There have been many changes in it's = production life=20 and one of them was to make the spool symmetrical and have the relief = circuit=20 the same both ways.
 
Wolfgang
Wolfgang,
Yes, I have considered this.  The spool with O-ring is a = very tight=20 fight.  While I have not tried to measure the force to move it, I = would=20 estimate something over 50 g's to move it (I'll measure this the next = time I=20 have a pump opened up)  Could it be that a pump somehow ended up = mounted=20 such that it was subjected to some resonant frequency?  Seems = like a=20 remote possibilty given all the variables and the mass of the pump. =  =20  How about wear and tear?  Perhaps=20 sitting dry and idle for ten years would do it.  A missing O-ring = or a=20 spool that doesn't utilize an O-ring would allow the spool to move = very=20 easily.  Parker does make spools that don't even have O-rings. =  Did=20 these end up getting installed by chance?

Based on reports from the LML, the = behavior=20 seems to be rather binary.  On the one hand we have planes with = over 1000=20 hours and more than ten years of service that have never once had the = spool=20 move off the poppet.  On the other hand, we have planes with = circuits=20 that lock up right out of the box (put into service).
This leads me to believe there is = a=20 difference in configuration.  The easiest way to verify this is = to simply=20 open up a pump that is known to lock up hi and low circuits=20 simultaneously.

While I have opened up several pumps (primarily to flip around = spool=20 valves), I have not yet worked on one that had this lock up issue. =  I am=20 optimistic the difference will be quite obvious upon inspection. =  

Chris Zavatson
N91CZ
360std


Sent from my iPad

On Apr 7, 2011, at 11:53 AM, "Wolfgang" <Wolfgang@MiCom.net>=20 wrote:

Chris, have you considered what = effect airframe=20 vibration has on the position of the spool in the pump and the = problem in=20 general ?
 
Wolfgang
From: Chris <chris_zavatson@yahoo.com<= /A>>
Sender: <marv@lancaironline.net&= gt;
Subject: Re: [LML] Re: LNC2 Gear=20 Hydraulics
Date: Wed, 06 Apr 2011 07:38:35=20 -0400
To: lml@lancaironline.net
I would like to extend the offer to the whole group. =  I=20 think the entire community would benefit from understanding = why some=20 pumps are allowing the system to lock up.  If anyone has = a pump=20 that exhibits this behavior and could part with it for a week, = I am=20 willing to check it out on the test stand and examine the = internal=20 configuration.

Chris Zavatson
N91CZ
360std
www.N91CZ.net
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