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Interesting . . . indeed.
So, since there seems to be no published standard
on the required pump details from Oildyne and more importantly from Lancair, one
is left to chance to have the right components in their pump to assure proper
and reliable operation as needed for a Lancair. The only way to validate a pump
is to take it apart and verify the spring situation and durometer of the O-rings
after the fact.
Shameless plug . . . or install my add-on safety
module which doesn't care about springs or durometer but simply makes the pump
operate like it's supposed to.
Wolfgang
----- Original Message -----
Sent: Saturday, February 11, 2012 8:50 PM
Subject: Re: [LML] Re: 320/360 Hydraulic Pressure Switch
Indeed, the springs are very strong. You can sort of see that in
the photos. The wire diameter is quite hefty.
Using a brand
new 013-70 O-ring (for applications where the spool does not need to stay
put), the spring generates 4x the force required to move the spool.
If your spool is not staying
in position:
1. Check for and, if
found, remove return springs (for pumps purchased new or repaired by Oildyne
since ~2003)
2. Make sure the spool has an
O-ring (two for symmetric spools)
3. Make sure the spool
has the 90 durometer O-ring
Chris Zavatson
N91CZ
360std
From: Wolfgang
<Wolfgang@MiCom.net>
To:
lml@lancaironline.net
Sent:
Friday, February 10, 2012 7:26 AM
Subject: [LML] Re: 320/360 Hydraulic
Pressure Switch
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, InstDynaComm, Corp., 248-345-0500, mailto:lorn@dynacomm.usLNC2, FB90/92,
O-320-D1F, 1,800 hrs, N31161, Y47, SE
Michigan |
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