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To: lml@lancaironline.net
Date: Thu, 01 Nov 2007 07:51:36 -0400
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From: "Bob B." <rbelshe@comcast.net>
References: <list-2442349@logan.com>
Subject: RE: [LML] LNC2 Hyd Chirp Alternative Mousetrap
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Larry,
It is a bi-directional system, so where would you put the accumulator?   In
one direction it would be working against you. 

In 815 hours, I have had one main gear actuator shaft seal fail.  Never have
rebuilt any of the others.  I get a pump chirp only every 30 minutes or so,
and I do not know why my system works so well.  I would like to drain it and
put in fresh fluid but I'm afraid that might do more harm than good.

Bob Belshe
Moraga, CA
Lancair 235/320  
http://home.comcast.net/~rbelshe/ 


-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of
lhenney@charter.net
Guys,

I've got 750 hrs on my 360 and rebuild a cylinder (1 of 6) or more every
annual.  I was thinking this pump chirp discussion through and am
considering installing an accumulator.  

My reasoning is as follows.  I believe that the total of 6 cylinders have a
combined leak affect that is not reducable to zero.  Rebuild all 6
cylinders, replace the valve and two cylinders.  You name it, there is still
some minor amount of fluid always getting around those O rings.  We mask
this reality based on the following.

When we first fill our hyd systems there is air in them.  Try as I did to
purge the system,  I think that some air remains initially.  This air is
acting as an internal accumulator.  As up hyd pressure reaches 1200psi, the
air volume is compressing.  As the slow leak through one or more seals
drains fluid and resultant pressure, the air expands maintaining system
pressure.  Thus, when we first rebuild a cylinder and add a little air to
the system, we fly along fat dumb and happy that we've "solved" the problem
when in reality we just recharged our accumulator (air in system).

However, over the course of many gear cycles, air tends to work it's way
back to the resevoir resulting in less accumulator affect (and less air
friction and damage to the seals).  This reveals itself as more frequent
pump chirps.  The operator therefore assumes he has "developed a leak" when
in reality the system total leak has not changed.