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Message-Id: <p04330100b7397f87a90f@[128.102.191.43]>
Date: Tue, 29 May 2001 10:00:02 -0700
To: lancair.list@olsusa.com
From: "Mike S. Reinath" <mreinath@mail.arc.nasa.gov>
Subject: Re: Lancair LNC2 and Legacy Hydraulic System Problems
Cc: sky2high@hotmail.com
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Reply-To: lancair.list@olsusa.com

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Scott,
I had problems with my hydraulic system cycling also when I tried it 
out for the first time. I installed pressure gauges in both the up 
and down circuits, so I had a much easier time solving the problem. 
My system cycled about every 30 seconds in the up position. Now it 
will sit for at least 2 hours before it cycles.

To find the leaks, I removed one cylinder at a time and observed the 
rate of pressure decay on the gauge over time. I had leaks in two of 
the main cylinders (they were new). I used the Swagelok valve that 
has been discussed on the list for my dump valve. I found that this 
valve was leaking a little, so I tightened the packing as described 
in the instructions that came with the valve. That got rid of another 
leak, but my system would still not hold more than 1030 psi -- it 
would leak down to this value fairly quickly and then stabilize. I 
suspected there was a problem with the pump, so I called Oildyne. I 
found out that there is a pressure relief valve inside the pump for 
both the high and low pressures. Mine was set to 1030 psi (high 
pressure), which is too close to the set point. I re-adjusted mine to 
about 1200 psi, and with the other fixes, allows the system to hold 
pressure for hours. Also, I find that the pump overshoots the set 
point pressure of the pressure switch. This effectively gives you the 
dead band you are looking for. If you call Oildyne, they will fax you 
a sketch describing how to adjust the pressure relief valves. I 
suspect yours may be set too low if you have found all the other leaks.
Mike Reinath

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