Fw: REFLECTOR: Oildyne Retract Pump Spool Valve

Ron Brown romott at adelphia.net
Fri Jul 8 16:33:26 CDT 2005


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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