Sender: <marv@lancaironline.net>
To: lml
Date: Mon, 27 Nov 2006 22:34:29 -0500
Message-ID: <redirect-1614591@logan.com>
Received-SPF: none
 receiver=logan.com; client-ip=206.190.49.115; envelope-from=randylsnarr@yahoo.com
DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws;
  s=s1024; d=yahoo.com;
  h=Message-ID:Received:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding;
  b=wOinkR3bnXllfoaeN9dTjhgprA1OEq95Wc7LVWbl+oVIjgudHSQtJcGiANSAuMCR320KiLVOpVErmBcuSlImUqx7Fnj+cFLIJsbdcF7M7HOJBZ+K+9Vn9ipo9EsR9OhD0mQJitVgGmn1Qm33Zlc7SVQSrED6nqpCCemvtwj9B6c=  ;
From: randy snarr <randylsnarr@yahoo.com>
Subject: Re: [LML] Re: Electrical /Hydraulic system questionslancair235/320
In-Reply-To: <list-1610104@logan.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit

Chris,
My system does not appear to be allowing pressure on
the low side to dump pressure to the pump with the
gear retracted. Is that a spool valve issue or could
it be a clog in the low pressure relief?

Thoughts?

Randy.

--- Christopher Zavatson
<Christopher.Zavatson@baesystems.com> wrote:

> Randy, Lorn, Scott, et al,
> One of the issues raised was the trapping of
> pressure in the down side
> circuit with the gear in the up position.  In the
> current pump
> configurations (?? at least back to 1995, probably
> much longer),  the
> back pressure circuit opens up a low resistance path
> back to the
> reservoir.  Without it, the low side can rise to the
> setting of the
> relief valve during retraction, leaks from the high
> side, thermal
> expansion, etc.  Again, we appear to have some older
> configurations that
> may behave differently, however, trapping pressure
> on the low side up to
> its operating operating is exactly what the back
> pressure circuit is
> supposed to prevent (assumes the spool valve is in
> the correct
> orientation, of course).
>  
> The following link is to a video of an intentional
> leak from the high
> to low sides, with the system pressurized in the up
> direction.  I used a
> leaking dump valve (removed from my plane several
> years ago) as my leak
> source.  To accelerate the leak for purposes of
> taping, I just barely
> cracked the valve.  You'll see the movement in the
> high side pressure
> gauge as the pressure rises and falls.  Pressure
> never builds in the low
> side.  All fluid is returned to the reservoir.
> http://www.N91CZ.com/Hydraulics/Pump_Cycling_1.WMV
>  
>  
> This second video is sort of a follow on the one
> above.  I used a
> shutoff valve to isolate the low side of the test
> subject - the faulty
> dump valve - from the return side of the pump.  In
> that way I can charge
> the high side, then open the test valve and  let the
> pressure start to
> build on the low side of the test valve.  I continue
> this cycle until I
> have about 1000 psi on each side of the faulty dump
> valve.  Now I
> reconnect the return line to the pump.  The low side
> immediately dumps
> back to the reservoir.  No pressure is maintained in
> the low side
> circuit.
>  
>
http://www.N91CZ.com/Hydraulics/Pump_Cycling_Closed_Exit.WMV
>  
> Chris
>  
>  
>  
>  
>  
>  
> Chris Zavatson
> N91CZ
> 360std.
> www.N91CZ.com
>  
> 


____________________________________________________________________________________
Yahoo! Music Unlimited
Access over 1 million songs.
http://music.yahoo.com/unlimited