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If it takes that much force to move the spindle against the O-rings then
those springs must be pretty darn strong. I find that dificult to accept.
Still, that port with the added spring, I believe it's a return port for
excess hydraulic fluid that can be used with a three port dump valve.
. . . but why the spring if it's plugged anyway ?
If the ultimate answer is to remove the "extra" springs, then let's
demonstrate that by testing a pump with the springs under pressure, heat, AND
simulated engine vibration. Short of that, this failure mode remains a
question.
Wolfgang
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Wolfgang,
The ball and spring go in the port labeled "Cavity "E"
Back-Pressure". This is the pipe plug that sits in between the two
output ports.
You might consider securing
the dump valve with a secondary locking feature. It too relies on
friction alone to stay in position. Seriously, given the force it
takes to move the spool, if mine were not staying put, I would want
to know why.
From previous measurements:
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.
The 013-90 is specified for pumps with back pressure circuits
such as we have.
Chris
Zavatson
N91CZ
360std
From: Wolfgang
<Wolfgang@MiCom.net>
To:
lml@lancaironline.net
Sent: Monday, February 6,
2012 9:24 AM
Subject: [LML] Fw: [LML] Re: 320/360
Hydraulic Pressure Switch
I see the centering springs but what about the added spring, eyelet
and ball ? Where does that fit into the schematic ?
I still don't like the idea of friction being the only thing keeping
spindle at it's end point. Sure, removing the springs will help but a
positive system to pressure the spindle back into it's required position
automatically as needed still seems prudent.
Wolfgang
----- Original Message -----
Sent: Sunday, February 05, 2012 8:34 AM
Subject: Re: [LML] Re: 320/360 Hydraulic Pressure
Switch
Several folks have been asking privately about the spool centering
springs mentioned below. This link contains both schematics and
photos showing how to revert a new pump back to the
original 320/360 functionality.
http://www.n91cz.com/Hydraulics/Pump-Unlock.pdf
Chris Zavatson
N91CZ
360std
From: Chris Zavatson
<chris_zavatson@yahoo.com>
To:
lml@lancaironline.net
Sent: Wednesday, February 1,
2012 12:46 PM
Subject: [LML] Re: 320/360 Hydraulic
Pressure Switch
Lorn,
Had the temperature been 90 or 100 degrees your pressure would have
been even higher. In some of my hydraulics videos, you will see
the 2,000 psi gauge pegged on occasion during thermal heating tests.
http://www.n91cz.com/Hydraulics/Lancair_Hydraulics.htm
Your predicament of having to crack a hydraulic line is exactly
what can happen if the spool centers after pump shut down. I find
that a completely unacceptable design. Imagine taking off into IMC
and the gear won't come up. I had the opportunity to test out a pump
in this configuration last summer. Just as you experienced, I was
able to reproduce a complete lock up.
http://www.n91cz.com/Hydraulics/NewPumpLockUp_0001.wmv - hi
res
http://www.n91cz.com/Hydraulics/NewPumpLockUp_0002.wmv - low
res
After discussions with Lancair and Parker, I reverted the
configuration back to the original
320/360 config and all is good now. Only one side can ever be
pressurized at a time. Unfortunately due to employee turn-over, no
one currently at Parker or Lancair knows why the centering springs were
added. After reviewing the 320/360 system both agreed that a system
lock up is possible using replacement pumps currently sold
(108AMS32-CZZ-3V-14-08-Y). Parker sent me parts to revert three
pumps back to the original configuration.
The TRVs in our pumps are the lowest available -fixed setting of
2,500 psi. This may be too high to protect some of our
components. I have run them up to 2,000 psi. In
flight, I have seen 1,800 psi, descending from 18k into the southwest
deserts.
Chris Zavatson
N91CZ
360std
From: Lorn H
Olsen <lorn@dynacomm.us>
To:
lml@lancaironline.net
Sent: Wednesday, February 1,
2012 6:33 AM
Subject: [LML] Re: 320/360 Hydraulic
Pressure Switch
Again, My Oildyne internal
pressure switch came (set by Oildyne) at 1,500 PSI. How do I know? I
parked my plane on the ramp at Newport News, Va in the evening. The
temperature was 40°F. 3 days later, when I was going to take off. The
temperature was 80°F. I looked at my pressure gauges. Both the up and down
were at 1,500 PSI. I had to crack a nut in a hydraulic line to release the
pressure. The gear would not go up or down, at this pressure. The
emergency dump valve would not release, at this pressure. The pump would
not run at all, at this pressure. Now, I have Wolfgang's high
pressure adapter in the system. It runs the pump whenever the pressure is
high on both the up and the down side. There is no speculation
here. Just the facts, mam. -- Lorn H. 'Feathers' Olsen, MAA,
ASMEL, ASES, Comm, Inst DynaComm, Corp., 248-345-0500, mailto: lorn@dynacomm.usLNC2, FB90/92,
O-320-D1F, 1,800 hrs, N31161, Y47, SE
Michigan |
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