REFLECTOR: HYDRAULIC PUMP

[Ron Brown]

Tom, 

I had the same problem as you are describing.  This happened during the first hours of flight testing. The pump would turn on and off every few seconds while on the ground.  Moving the dump valve open to close would improve/change the symptoms.  

I replaced the valve about 200 hours ago and no more problems.  Try changing it first before you get into the cylinders and hydraulic pump.  I used the valve a lot during construction and testing - typically using the pump to move the gear around, then cracking the valve to get gear in the exact position.  I think this led to damage to the valve internals.

Ronnie
  ----- Original Message ----- 
  From: Tom Martino 
  To: reflector at tvbf.org 
  Sent: Sunday, July 16, 2006 4:14 PM
  Subject: REFLECTOR: HYDRAULIC PUMP


   
  BACKGROUND:  This query comes as a result of my hydraulic pump turning on and off quickly when gear was retracted.  A gear retraction test revealed that the system is not holding pressure. 

  QUESTION:  Can anyone tell me the actual Manufacturer, model and part number for our Hydraulic Pumps? (I realize I can get them from Velocity, but I am curious about some other things and would like to contact the manufacturer.)

  Also . I am told there are "rebuild" kits for them.  I know the rebuild kit includes "o" rings . but they are for keeping the fluid from leaking to the outside world.  

  My pump (and plumbing) had absolutely NO LEAKS - anywhere.

  The only conclusion I could make is that the pressure was "bleeding off" from the high side to the low side and the only parts in the pump that maintain internal pressure are the "spring loaded metal-seated cone check-valves" (one on each side).

  Do the rebuild kits include new springs and cones?

  Also . has anyone ever had the "dump valve" leak internally from high to low side?  Without showing any wear or exterior leaking?  A local hydraulic shop tells me they hardly ever see those simple quarter-turn vales go bad.

  Any help on any of this would be great!

  Tom



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