X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Thu, 23 Nov 2006 10:49:06 -0500 Message-ID: X-Original-Return-Path: Received: from vms046pub.verizon.net ([206.46.252.46] verified) by logan.com (CommuniGate Pro SMTP 5.1.2) with ESMTP id 1596983 for lml@lancaironline.net; Thu, 23 Nov 2006 10:40:02 -0500 Received: from HOMEFAMILY1 ([71.105.183.148]) by vms046.mailsrvcs.net (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) with ESMTPA id <0J960020BWUAUHAC@vms046.mailsrvcs.net> for lml@lancaironline.net; Thu, 23 Nov 2006 09:39:48 -0600 (CST) X-Original-Date: Thu, 23 Nov 2006 07:39:47 -0800 From: "Steve Rosenzweig" Subject: Re: [LML] Re: Electrical /Hydraulic system questionslancair235/320 X-Original-To: "Lancair Mailing List" X-Original-Message-id: <000d01c70f15$9bc2c030$6401a8c0@HOMEFAMILY1> MIME-version: 1.0 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2962 X-Mailer: Microsoft Outlook Express 6.00.2900.2869 Content-type: multipart/alternative; boundary="----=_NextPart_000_000A_01C70ED2.8D474E10" X-Priority: 3 X-MSMail-priority: Normal References: This is a multi-part message in MIME format. ------=_NextPart_000_000A_01C70ED2.8D474E10 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable About the pressure building in flight, I have a seperate light that = illuminates anytime the pump is running. Sometimes it cycles on during = flight to repressurize. Do you know if your pumps are doing that? Steve Rosenzweig LNC360 ----- Original Message -----=20 From: randy snarr=20 To: lml=20 Sent: Thursday, November 23, 2006 6:27 AM Subject: [LML] Re: Electrical /Hydraulic system = questionslancair235/320 Bob, You describe the exact same thing as I am experiencing. I have pressure gauges on the high and low side. In my case, both the = high an low sides sometimes creep up in pressure during flight. Just = today I noticed everying normal after takeoff 1300 high and 0 on the = low. After 20 mins or so the high was 1700 or so and the low was 400. = Gear came down normally. If the low side reaches 600 psi the gear will = not come down without cycling the dump valve. I theorize that the down = side pressure switch shuts off the pump because of this pressure. Ironically, The first time this happened was when I flew to the last = labor day fly in at Redmond. It has happened several times since. I also = noticed one day when I pulled the airplane out of the cool hangar and = parked it out in the warm sun for an hour. When I got in the low side = was very high and the high side was not far behind it. It alarmed me = enough that I opened the dump valve and equalized the 2 sides. Don't = remember what the pressures were. They equalized at something above 0. = Maybe around 6-700 psi. It seems like increased heat increases pressure = in the entire system. I am going to check the dipstic(not the pilot) and = make sure it is not tight. I believe mine is. To answer your question about what the down side pressure is during = retraction, it is running around 200 psi. The upside is 0 when the gear = is being lowered. Thanks for the input... Randy,. "Bob B." wrote: : The fluid circuit is really a closed loop. The only options for = returning fluid to the reservoir are either through one of the pressure = relief valves or the low resistance back pressure circuit. Excess fluid = needs to return to the tank every time the rod volume displaces fluid = volume. When the rod volume is removed from the system, make up fluid = is pulled in from the tank through a one way check valve. During = retraction, the spool valve opens a low resistance path from the low = side to the reservoir, eliminating a large pressure build up in the low = circuit during retraction. - which also eliminate the possibility of = pressure build up due to thermal influence. One side effect of the correct spool valve orientation and a = leak free system is that you cannot manually push the gear up even with = the dump valve open unless the spool valve is moved into the retract = position. After opening the valve you still have a closed loop from = high to low that is now bypassing the pump. When you try to push the = gear up you get hydraulic lock. You are trying to add the rod volume to = a closed system and the only route back to the reservoir is through a = relief valve. By bumping the pump in the up direction, even with the = dump valve open, you can push the spool valve into the retract position = which opens up the low resistance path to the reservoir for the low side = circuit. If you are able to push the gear up at all without bumping the = pump, I would suspect the spool valve is backwards. Let us know what = observe in the low circuit during retraction. You can also try the = direction-reversal test during retraction. The response should be = instantaneous. good luck Chris, It would seem that there is no one answer for this problem. On my 235, with the plane on jacks; I can open the dump valve and easily push any of the gear up. = Spool valve is backward? When I do the direction reversal test the gear reverses instantly. = Spool valve is OK? When I put the gear up and then open the dump valve, all 3 drop = within 2-3 seconds. Years ago, I experienced a few instances of the gear not coming = down when the gear switch was put down. This situation was always = relieved by briefly opening the dump valve. It stopped happening, so I = did not change anything. Am I just lucky, or what? Bob Belshe Moraga, CA Lancair 235/320 =20 http://home.comcast.net/~rbelshe/=20 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.409 / Virus Database: 268.14.11/543 - Release Date: = 11/20/2006 -------------------------------------------------------------------------= ----- Everyone is raving about the all-new Yahoo! Mail beta. ------=_NextPart_000_000A_01C70ED2.8D474E10 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
About the pressure building in flight, = I have a=20 seperate light that illuminates anytime the pump is running.  = Sometimes it=20 cycles on during flight to repressurize.  Do you know if your pumps = are=20 doing that?
 
Steve Rosenzweig
LNC360
----- Original Message -----
From:=20 randy=20 snarr
To: lml
Sent: Thursday, November 23, = 2006 6:27=20 AM
Subject: [LML] Re: Electrical = /Hydraulic=20 system questionslancair235/320

Bob,
You describe the exact same thing as I am=20 experiencing.
I have pressure gauges on the high and low side. In = my case,=20 both the high an low sides sometimes creep up in pressure during = flight. Just=20 today I noticed everying normal after takeoff 1300 high and 0 on the = low.=20 After 20 mins or so the high was 1700 or so and the low was 400. Gear = came=20 down normally. If the low side reaches 600 psi the gear will not come = down=20 without cycling the dump valve. I theorize that the down side pressure = switch=20 shuts off the pump because of this pressure.
Ironically, The first = time=20 this happened was when I flew to the last labor day fly in at Redmond. = It has=20 happened several times since. I also noticed one day when I pulled the = airplane out of the cool hangar and parked it out in the warm sun for = an hour.=20 When I got in the low side was very high and the high side was not far = behind=20 it. It alarmed me enough that I opened the dump valve and equalized = the 2=20 sides. Don't remember what the pressures were. They equalized at = something=20 above 0. Maybe around 6-700 psi. It seems like increased heat = increases=20 pressure in the entire system. I am going to check the dipstic(not the = pilot)=20 and make sure it is not tight. I believe mine is.

To answer = your=20 question about what the down side pressure is during retraction, it is = running=20 around 200 psi. The upside is 0 when the gear is being = lowered.

Thanks=20 for the input...

Randy,.

"Bob B."=20 <rbelshe@comcast.net> wrote:
:
The fluid circuit is really a closed loop.  The only = options=20 for returning fluid to the reservoir are either through one of = the=20 pressure relief valves or the low resistance back pressure=20 circuit.  Excess fluid needs to return to the tank every = time the=20 rod volume displaces fluid volume.  When the rod volume is = removed=20 from the system, make up fluid is pulled in from the tank = through a one=20 way check valve.  During retraction, the spool valve opens = a low=20 resistance path from the low side to the reservoir, eliminating = a large=20 pressure build up in the low circuit during retraction. - which = also=20 eliminate the possibility of pressure build up due to thermal=20 influence.
One side effect of the correct spool valve orientation and = a leak=20 free system is that you cannot manually push the gear up even = with the=20 dump valve open unless the spool valve is moved into the retract = position.  After opening the valve you still have a closed = loop=20 from high to low that is now bypassing the pump.  When you = try to=20 push the gear up you get hydraulic lock.  You are trying to = add the=20 rod volume to a closed system and the only route back to = the=20 reservoir is through a relief valve.  By bumping the pump = in the up=20 direction, even with the dump valve open, you can push the = spool=20 valve into the retract position which opens up the = low resistance=20 path to the reservoir for the low side circuit.  If = you are=20 able to push the gear up at all without bumping the pump, I = would=20 suspect the spool valve is backwards.  Let us know what = observe in=20 the low circuit during retraction.  You can also try the=20 direction-reversal test during retraction.  The response = should be=20 instantaneous.
good luck
Chris,
 
 It would seem that there is no one answer for = this=20 problem.
 
On=20 my 235, with the plane on jacks;
 
I=20 can open the dump valve and easily push any of the gear=20 up.    Spool valve is = backward?
 
When=20 I do the direction reversal test the gear reverses = instantly.  =20 Spool valve is OK?
 
When=20 I put the gear up and then open the dump valve, all 3 drop within = 2-3=20 seconds.
 
Years ago, I experienced a few instances of the gear = not coming=20 down when the gear switch was put down.  This situation was = always=20 relieved by briefly opening the dump valve.  It stopped = happening, so=20 I did not change anything.
 
Am I=20 just lucky, or what?
 
Bob Belshe
Moraga, CA
Lancair=20 235/320  
http://home.comcast.net/~rbelshe/=20
 
 
 
 

--
No virus found in this outgoing = message.
Checked=20 by AVG Free Edition.
Version: 7.1.409 / Virus Database: = 268.14.11/543 -=20 Release Date: 11/20/2006

Everyone is raving about the=20 all-new Yahoo! Mail beta. ------=_NextPart_000_000A_01C70ED2.8D474E10--