X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 16 Apr 2011 20:24:29 -0400 Message-ID: X-Original-Return-Path: Received: from mail-iy0-f180.google.com ([209.85.210.180] verified) by logan.com (CommuniGate Pro SMTP 5.4c3j) with ESMTPS id 4947866 for lml@lancaironline.net; Fri, 15 Apr 2011 23:09:48 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.210.180; envelope-from=vonjet@gmail.com Received: by iyf40 with SMTP id 40so15499965iyf.25 for ; Fri, 15 Apr 2011 20:09:12 -0700 (PDT) DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=eJOIFfVp2RREnIVy4N230vLNMmulSieO49c/hQm4mGwZAxtXfMAu7vmpRjPqzjqbes EdrGIeR+WuweT/YeG1EXSQ3Bxah87ynVI7Zmq8f9+f89QSjGbvXaCqptgqXSzASSQrxY yzkBtR5jFJBucmAu5ZSDJdlXXQggERAIn992Q= MIME-Version: 1.0 Received: by 10.231.74.2 with SMTP id s2mr2172844ibj.8.1302923352577; Fri, 15 Apr 2011 20:09:12 -0700 (PDT) Received: by 10.231.178.38 with HTTP; Fri, 15 Apr 2011 20:09:12 -0700 (PDT) In-Reply-To: References: X-Original-Date: Fri, 15 Apr 2011 20:09:12 -0700 X-Original-Message-ID: Subject: Re: [LML] Re: LNC2 Gear Hydraulics From: Bryan Wullner X-Original-To: Lancair Mailing List Content-Type: multipart/alternative; boundary=000e0cd6b2de99961d04a1007b1d --000e0cd6b2de99961d04a1007b1d Content-Type: text/plain; charset=ISO-8859-1 Wolfgang, What is your gear fix module? Bryan On Fri, Apr 15, 2011 at 10:11 AM, Wolfgang wrote: > 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 ----- > *From:* Chris Zavatson > *To:* lml@lancaironline.net > *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). > 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. > > Chris Zavatson > N91CZ > 360std > www.N91CZ.net > > > Sent from my iPad > > On Apr 7, 2011, at 11:53 AM, "Wolfgang" < > Wolfgang@MiCom.net> 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 < > chris_zavatson@yahoo.com> Sender: < > marv@lancaironline.net> Subject: Re: [LML] Re: LNC2 Gear Hydraulics Date: Wed, > 06 Apr 2011 07:38:35 -0400 To: > lml@lancaironline.net > 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 > > --000e0cd6b2de99961d04a1007b1d Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Wolfgang,
What is your gear fix module?
Bryan

On Fri, Apr 15, 2011 at 10:11 AM, Wolfgang <Wolfgang@micom.net> wrote:
From a design point of view, I still h= ave a big=20 concern about relying on the friction from an O-ring to keep the landing ge= ar=20 functioning properly. Vibration levels can exceed 70 G's. I would be mu= ch=20 happier with a spring loaded ball detent or something similar.
=A0
That's why I came up with the gear= =20 fix=A0module.
=A0
Wolfgang
=A0
----- Original Message -----
Sent: Wednesday, April 13, 2011 8:2= 5=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.=A0 The spoo= l 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=A0013-70 requires 30 g's to move the spool.
Using o-ring=A0013-90 requires 70 g's to move the spool.
This= =20 includes the return force generated by the poppet springs (410462).=A0=20
The difference between the two o-rings is durometer.=A0 I have been= =20 using the softer one without any problems.=A0 The stiffer o-ring (intende= d=20 for pumps with back pressure circuits) should leave no doubt.=A0 The firs= t=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.
=A0
Chris Zavatson
N91CZ
360std
From: Wolfgang=20 <Wolfgang@MiCom.net>
To: lml@lanc= aironline.net
Sent: M= on, April 11, 2011 4:56:57=20 AM
Subject: [LML] Re: L= NC2=20 Gear Hydraulics

=20
When I first got into this problem w= ith the=20 hydraulic pumps last year, I had a few conversations with the product man= ager=20 of the Oildyne 108 pump. There have been many changes in it's product= ion life=20 and one of them was to make the spool symmetrical and have the relief cir= cuit=20 the same both ways.
=A0
Wolfgang
Wolfgang,
Yes, I have considered this. =A0The spool with O-ring is a very tigh= t=20 fight. =A0While 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) =A0Could it be that a pump somehow ended up mounte= d=20 such that it was subjected to some resonant frequency? =A0Seems like a=20 remote possibilty given all the variables and the mass of the pump. =A0= =20 =A0How about wear and tear?=A0=A0Perhaps=20 sitting dry and idle for ten years would do it. =A0A missing O-ring or a= =20 spool that doesn't utilize an O-ring would allow the spool to move ve= ry=20 easily. =A0Parker does make spools that don't even have O-rings. =A0D= id=20 these end up getting installed by chance?

Based on reports from the LML, the behavior=20 seems to be rather binary. =A0On the one hand we have planes with over 10= 00=20 hours and more than ten years of service that have never once had the spo= ol=20 move off the poppet. =A0On 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. =A0The easiest way to verify this is to simp= ly=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. =A0I a= m=20 optimistic the difference will be quite obvious upon inspection. =A0

Chris Zavatson
N91CZ
360std


Sent from my iPad

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

Chris, have you considered what ef= fect airframe=20 vibration has on the position of the spool in the pump and the problem = in=20 general ?
=A0
Wolfgang
=
From: Chris <chris_zavatson@yahoo.= com>
Sender: <marv@lancaironline.net><= /td>
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. =A0I=20 think the entire community would benefit from understanding why s= ome=20 pumps are allowing the system to lock up. =A0If 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 interna= l=20 configuration.

Chris Zavatson
N91CZ
360std
=

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