Message-ID: <001501c12fdc$7adf9c30$372f6bc6@COLORADO>
From: "David Lowry" <dave@edt.com>
To: <lancair.list@olsusa.com>
Subject: Hydraulics
Date: Tue, 28 Aug 2001 09:14:14 -0700
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List,

I set up my hydraulic pump in a bench test configuration. I plumbed the 
high pressure and low pressure to the dump switch and the dump into the
return. I have a pressure guage on the high pressure side and a "component
under test" position on the high pressure side. It is really Rube Goldberg.

Here are the results:
 1) The high pressure side is unstable with just a tube or a hose under
test. It plays a catchy tune but I had to add a cylnder on a stub to
stop the oscillation.
 2) Initially, without the pressure guage, the high side stayed above the
switch point for hours. Adding the pressure guage it dropped out in 30
minutes or so due to leaks in the additional 5 joints.
 3) It really takes a very small leak, about a drop in 24 hours at 1000psi
to get this 30 minute cycle rate.
 4) The Lancair pressure switch seems to be accurate, turning on 900psi
and off at 1050 or so. The high end overshoots to 1200psi  sometimes probably
because of the small size of the system.
 5) The leaks seem to be at joints between the steel flex hose fitting to
the aluminum nipple. These are the Lancair supplied, home-built, flex hoses.
How far should I go in tightening these? Other suggestions?
 6) My flare fittings work well. I wanted to test this before I tested
all 50 or so in the completed system at once.
 7) The one new cylinder I tested does not leak.

 I have built a number of hydraulic pipes and am getting better at it
(I have 2 now that have only been made once). Some things that worked for me.
 Fit: I have been using 12 guage solid (house wire) to make a model of the
tube I need to make. Saves throwing one peice away, although the first
bad one is also a good model.
 Quick 90 degree bends: On the Legacy the tubes in the wheel well need
to make an immediate 90 degree bend to avoid interference
with the wheel.
If you bend first and then flare it doesn't work . If you flare first and
then bend (with the tool), it is better but still not good. What worked
for me was to flare first, bend with the tool to 80 degrees, put a 
union on the joint (for leverage) and bend the remaining 10 degrees by hand 
on the flare side.

 See you in Redmond Saturday. I will be the guy buying more tubing :).

 David Lowry
 dave@edt.com


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