REFLECTOR: Oildyne Retract Pump Spool Valve

Fri Jul 8 18:52:04 CDT 2005

There is an adjusting screw located on top of the switch, between the wiring 
terminals.  Screw in (turn right) to raise the pressure.  I understand not 
all of the switches have this adjustment - some supplied by Velocity have 
fixed set points.

Re the snapping into position, there is no other valving that sequences the 
operation.  I think it is just a matter of when the mains get all the way 
up, then the nose gear gets ll of the flow and pressure.  However, someone 
mentioned that there was port in the nose gear cylinder that may be getting 
covered and perhaps causing the problem - but I can't find that note.  You 
would think that the nose gear would retract first since it is the lighter 
of the two (nose and mains).  But mine is like yours, nose moves first, gets 
about mid position, then the mains go up, then finally the nose finishes 
last, and then the doors close.

By the way, my nose gear doors do not slam shut like many of the other V's. 
My sequence valve is actuated by the reinforcing web welded next to the nose 
gear pivot.

I found the following note from Dave Black:

Oscar,

> I am a new Velocity owner, and after replacing the hy hoses I
> did the gear test and hear a slamming noise, apparently in
> the front doors. Is, I believe the problem that you are
> discusing. Can you please, tell me in which area you recomend
> the valve be installed? I have a top loader, rg. Perhaps the
> early hases replacement was due to this problem?.

I have a top-loader as well.

>From listening to dozens of owners describing the nose door slamming 
>problem,
I've come to the conclusion the nose doors (and specifically the sequence
valve) have never worked as Velocity intended. One would expect the nose 
doors
to close as soon as the nose gear retracts and the button on the sequence
valve is pushed. But they NEVER do. The doors jiggle a little bit when the
nose gear first retracts, but don't close until the main gear is fully up. 
I'm
guessing that the designer of the retraction system observed that the nose
doors did not operate as expected, but decided it worked well enough that 
they
never diagnosed the problem.

My investigation showed that under hydraulic pressure the sequence valve
requires a great deal of force to activate. It's not easy to push that 
button
when the sequence valve is pressurized. So if the button is mounted where 
it's
easy to get to (as in plans) the nose gear mechanism simply does not have
enough force or torque to push the button. The inertia of the gear coming up
activates the button momentarily, which causes the nose doors to jiggle but
not close. Only after the mains are fully up does the hydraulic pressure go
high enough to provide the torque needed to activate the sequence valve and
close the doors. Trouble is, by then the hydraulic pressure is so high the
doors slam with authority.

Try this: With the plane on jacks, retract the gear. Note that the nose gear
comes up first, followed by that little jiggle of the nose door. Next the
mains come up. Finally the nose doors slam. This is the way the nose doors
work in all the RG Velocities. It's not the way they were intended to work,
but they do work.

Now, try this test: Open the nose hatch and repeat the retraction. But this
time, when the nose gear reaches its upper limit, grab it manually and pull 
it
up the last half inch or so. You will notice that the nose doors close
immediately, without slamming, and before the mains retract. That's because
you have provided that extra force needed to actuate the sequence valve when
it is supposed to be activated.

Most owners don't mind that their nose doors close late and slam. Most of
those who do mind install flow restrictors in the hydraulic line to the nose
gear actuator. Adjusted properly, the restrictor stops the slamming, but 
still
does nothing to get the door to close in the correct sequence.

Initially I moved my sequence valve to a point only 2 inches in front of the
rearmost nose gear pivot in the keel. It worked perfectly. The doors closed
gently as soon as the nose gear was up. But that location presented
maintenance issues -- I could hardly get to it.

So I came up with a better way. I mounted the sequence valve in the
comparatively accessible forward part of the keel, just to the left of the
factory's location. BUT, instead of having the nose gear mechanism push the
sequence valve directly, I installed a lever to multiply the force applied 
to
the button. The sequence valve is mounted to the side of the keel. A gate
hinge (with long arm) is mounted right above the sequence valve. The button 
is
pushed by the hinge when the far end of the hinge arm is pushed down by the
nose gear mechanism. The long arm of the hinge provides about a 10:1 
leverage
advantage. Thus the button gets pushed at the proper time, and the nose 
doors
close very smoothly.

I will get you a picture of this little mod the next time I'm at the hangar.
The mod takes a bit more effort than installing a flow restrictor, but it
actually fixes the problem rather than just putting a Band-Aid on it.

Dave Black
ShortWing RG

----- Original Message ----- 
From: "Chuck Jensen" <cjensen at dts9000.com>
To: "Ron Brown" <romott at adelphia.net>
Sent: Friday, July 08, 2005 5:57 PM
Subject: RE: REFLECTOR: Oildyne Retract Pump Spool Valve

Where I'm lost is what influences the sequence.  I assume the nose comes up 
because that's the least resistance, then the mains are snatched and stored. 
Then (and this is a question) the pressure builds up and the nose gear jumps 
up into its final position, triggering the doors to close.

When I saw the failure to erect to the final position on the ground, it 
seemed like the nose gear came up to about 90% of its normal resting 
position waiting for the mains to stow.  Then nothing happened.  Is there 
some switch or something that gets triggered after the mains are stored that 
causes the nose gear to 'jump' into final position.  That final movement is 
really a quick, positive movement--not slow like pressure if finally 
building enough to push it into position.  Then again, maybe its just when 
the nose spring is going over center that it seems to go into the final up 
position with authority.

If it would finish closing after a few seconds, I wouldn't mind, but all the 
way from PDK outside Atlanta today, I had the red light and I could tell by 
the noise and air infiltration that the doors were definitely ajar.  Is 
there an adjustment on the high pressure switch?

Baffling,
Chuck

-----Original Message-----
From: Ron Brown [mailto:romott at adelphia.net]
Sent: Friday, July 08, 2005 5:33 PM
To: Chuck Jensen; reflector at tvbf.org
Subject: Fw: REFLECTOR: Oildyne Retract Pump Spool Valve

This may be the problem with your nose gear not wanting to complete the
cycle.  I have seen the same thing on my plane on occasion.  The pump stops
running because the high pressure switch has opened, but the gear is not all
the way up.  Then after a few seconds or more, it may finally finish the job
of retracting the nose.

I have not disassembled my pump yet because most of the time mine works fine
as is.  But it may be something to investigate.

----- Original Message ----- 
From: "Ron Brown" <romott at adelphia.net>
To: <reflector at tvbf.org>
Sent: Monday, June 20, 2005 7:33 PM
Subject: REFLECTOR: Oildyne Retract Pump Spool Valve

>
> My hangar mate has a Lancair 320 RG which has exactly (or very nearly) the
> same hydraulic pump that we have in our Velocity RG's.  I have observed
> similar operation as Mike describes below in his note that I copied from
> the
> Lancair "Reflector".  Any body else notice this hesitation at the final
> stage of retract, like the nose gear doors don't quit shut all the way,
> the
> pump has already shut off, then it runs again and the doors finally close.
> The hydraulic lock that occurs after flying for a couple of hours where
> the
> reset button has to be pressed to relieve the down side pressure so the
> pump
> will run is also similar to the descriptions below.  Scott B., have you
> all
> heard anything about this???
>
>
> Mark,
>
> The operation of the system may seem to be almost completely normal
> with the spool valve reversed. Without gauges, the only symptom may
> be a slightly weak retraction at the top of the cycle, and you can
> overcome that problem by raising the high-side pressure switch
> setting. That was the way I had my system set up initially with the
> spool-valve problem. There is one other symptom, but it doesn't
> normally come up under normal operation. The gear won't come down
> immediately after a retraction or during a retraction near the top of
> the cycle (this is because the low-side pressure has increased during
> the retraction and the low-side pressure switch is open as the
> pressure bleeds off). If the spool valve is in correctly, you will be
> able to lower the gear at any point during the up cycle without the
> system hesitating. I say it doesn't come up under normal operation
> because once you raise the gear, you normally don't lower if for a
> while, and the pressure has time to bleed off. Therefore, it is
> possible to have a reversed spool valve and not really have any
> significant symptoms, if you don't have pressure gauges.
>
> If you are seeing pressure in the low side during the retraction
> cycle (increasing a little from the down setting all the way up),
> then I would check the spool valve.
>
> Mike Reinath
> LNC2 at 460 hrs TT
> San Jose, CA (RHV)
>
> After looking at the picture, it appears that the pump could use either
> side
> as the high pressure one, as long as one knew which way the "O" ring
> pointed. Is it possible the "reversed spool valve" was the design
> intention
> of the manufacturer? Could we (builders) or Lancair just be putting the
> pressure valves in the wrong ports? If I had your picture prior to putting
> the hydraulic system together I think I would have opened the pump up,
> ascertained which way the spool valve pointed and put the pressure
> switches
> in accordingly.
>
> Thanks again for taking the mystery out of an unknown!
>
> Mark
>
> We do in fact use the pump in a non-standard configuration with the work
> being done during cylinder retraction instead of extension. Therefore,
> when viewing the generic pump schematic from Oildyne, high and low side
> are backwards.
> My original pump was assembled correctly. Some time after '95 the build
> instructions from Lancair got mixed up and every pump was being
> assembled with a reversed spool valve. Every pump I have worked on
> since then was backwards including the spare I bought for a hydraulics
> test bench. I'm sure there are quite a few out there still needing to
> be fixed.
> Chris Zavatson
> N91CZ
> 360 std
>
>
> Below is a communication thread between Parker and myself about the
> hydraulic pump on the 360.
> I thought it would be helpful for those of you that have not yet
> experienced
> the joys of trouble shooting the hydraulic pump issues on your 360, to
> post
> this sad story. Even with the help of Randy, Scott, Lorn and Gerard, I was
> unable to remove the shuttle valves to get to the spool valve.
> So................... I decided to apply some pressure......bad idea! The
> pressure needs to be applied in the proper place and to make a long story
> short...... I damaged the manifold. In my own defense, Parker Hannifin was
> initially unclear on where to apply this pressure. I do have to commend
> their customer service which was very responsive but I still had a broken
> pump. At this point, the remainder of the damaged pump, (after a very
> detailed explanation by an Oildyne service guy) was performed (it took
> five
> minutes) and guess what, the spool valve was reversed.
>   Oildyne found me a replacement manifold, which comes complete with
> internal pieces (spool valve, etc.) in Orlando, so after spending some
> money
> I was back in business. As I was looking at the new manifold, it occurred
> to
> me that Oildyne probably learned their lesson years ago about the correct
> orientation of the spool valve. They probably received thousands of
> complaints from the field over the years about the improper assembly issue
> which did not comply with the engineering drawings and brought this to the
> attention of their people. I decide to check and low and behold the spool
> valve was installed reversed!!! I check the drawing again to make sure my
> eyes weren't fooling me. AGGGGGGGGGGGGGG..........HH. (This is why I
> haven't
> bought and American car in fifteen years.)
>   I reversed the spool valve, transferred the motor and the rest of my
> good
> pump pieces to the new manifold and reinstalled the assembly. The system
> worked perfectly. The gauges read the correct pressures, the high and low
> were not fighting each other and even the hydraulic gear door cylinders
> started operating without starts and stops of before. I now have a big
> smile
> on my face but my stomach churns thinking about the time I wasted working
> on
> this system that had a simple problem. Another lesson learned and now I am
> a
> hydraulic pump "expert". Someday, maybe this plane will fly.
>
> ONE MORE SAD BUILDER STORY!
>
> MARK QUINN
>
> Christian,
>   Attached below is a drawing showing the orientation of the spool valve.
> The
> down side referred to in the e-mail below is to the right. You need to
> pull
> out both end plug retainers and the poppet assemblies also. Then with a
> small
> diameter punch inserted through the poppet seat from the left hand side
> (High
> pressure) strike the punch with a small hammer. Not much contact is
> needed.
> This will push the spool valve against the poppet seat on the right hand
> side
> (Low Pressure) and cause it to come out. Continue to push the spool valve
> until it comes out and note on which end of the spool the o-ring is
> installed.
> THE O-RING SHOULD BE TOWARD THE LEFT END OF THE SPOOL VALVE. If it is not,
> flip the spool valve over and reinsert it toward the high pressure side
> and
> reassemble the manifold. Once you see it you will understand the above
> instructions. Let me know if you have any questions. O-rings in my unit
> did
> not need to be replaced.
>
> MARK QUINN
> DAYTONA BEACH, FLORIDA
>
>

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