Return-Path: Sender: (Marvin Kaye) To: lml@lancaironline.net Date: Tue, 21 Oct 2003 17:18:46 -0400 Message-ID: X-Original-Return-Path: Received: from imo-d04.mx.aol.com ([205.188.157.36] verified) by logan.com (CommuniGate Pro SMTP 4.1.5) with ESMTP id 2645543 for lml@lancaironline.net; Tue, 21 Oct 2003 14:17:13 -0400 Received: from Sky2high@aol.com by imo-d04.mx.aol.com (mail_out_v36_r1.1.) id q.bd.38439cc0 (16781) for ; Tue, 21 Oct 2003 14:16:41 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: X-Original-Date: Tue, 21 Oct 2003 14:16:41 EDT Subject: Re: [LML] Re: Gear pump pressure switches X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1066760201" X-Mailer: 9.0 for Windows sub 1100 -------------------------------1066760201 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 10/21/2003 11:02:17 AM Central Daylight Time, Christopher.Zavatson@udlp.com writes: Does anyone know why the up and down pressure switches have different set points? Is it something to do with applying less force to the stops in the up position?>> 1. The down pressure could be less but 500 psi is adequate to hold the doors open against any air loads and keep the over center links locked. After all, the emergency extension requires no hydraulic pressure at all (doors spring loaded, nose extended and locked by gas strut and mains locked by rat-trap springs) except for a small push to help the rat-trap springs lock the main overcenter links. 2. 500-600 psi will retract the gear and close the doors (in a non-leaking system) but it will not be a crisp result. If you watch the system carefully on the up cycle, after the mains are almost tucked away, the doors may move a bit (mains tap on the door valves) before the nose overcenter can be uncocked (hi pressure spike, lo volume needed) and then withdrawn at the 500 psi level since it is hard to maintain a high pressure while moving so much fluid. Finally, the gear is almost tucked away and the doors close. At this point the pressure must rise to 1000-1200 psi to hold everything tight (remember there is no up-lock) against sucking airloads on the doors and g-loads on the gear. There is little leverage left on the mains at full up. The pressure is always applied between the actuator thru-plate/rod-seal and the piston on up cycles, and the back plate and piston on the down cycles. Note that there are pressure relief valves in the pump which should be set 300-400 psi higher than the pressure switches. I believe these are factory set to around 1000 and 1500 psi, down and up respectively. Scott Krueger Sky2high@aol.com II-P N92EX IO320 Aurora, IL (KARR) -------------------------------1066760201 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

In a message dated 10/21/2003 11:02:17 AM Central Daylight Time, Christ= opher.Zavatson@udlp.com writes:

Does anyone know why the up and down pressure=20= switches have
different
set points? Is it something to do with applyin= g less force to the
stops
in the up position?>>

1. The down pressure could be less but 500 psi is adequate to hold the=20= doors open against any air loads and keep the over center links locked. = ; After all, the emergency extension requires no hydraulic pressure at all (= doors spring loaded, nose extended and locked by gas strut and mains locked=20= by rat-trap springs) except for a small push to help the rat-trap springs lo= ck the main overcenter links.

2. 500-600 psi will retract the gear and close the doors (in a non-leak= ing system) but it will not be a crisp result. If you watch the system= carefully on the up cycle, after the mains are almost tucked away,&nbs= p;the doors may move a bit (mains tap on the door valves) before t= he nose overcenter can be uncocked (hi pressure spike, lo volume needed)&nbs= p;and then withdrawn at the 500 psi level since it is hard to maintain a hig= h pressure while moving so much fluid. Finally, the gear is=20= almost tucked away and the doors close. At this point the pressure mus= t rise to 1000-1200 psi to hold everything tight (remember there is no up-lo= ck) against sucking airloads on the doors and g-loads on the gear. The= re is little leverage left on the mains at full up.

The pressure is always applied between the actuator thru-plate/rod= -seal and the piston on up cycles, and the back plate and piston on the= down cycles. Note that there are pressure relief valves in the pump w= hich should be set 300-400 psi higher than the pressure switches. I be= lieve these are factory set to around 1000 and 1500 psi, down and up re= spectively.

Scott Krueger
Sky2high@aol.com
II-P N92EX IO320 Aurora, IL (KARR)

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