X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 08 Nov 2007 09:07:48 -0500 Message-ID: X-Original-Return-Path: Received: from imo-m26.mx.aol.com ([64.12.137.7] verified) by logan.com (CommuniGate Pro SMTP 5.2c1) with ESMTP id 2460671 for lml@lancaironline.net; Wed, 07 Nov 2007 19:15:06 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.7; envelope-from=Sky2high@aol.com Received: from Sky2high@aol.com by imo-m26.mx.aol.com (mail_out_v38_r9.3.) id q.d22.10795d51 (48600) for ; Wed, 7 Nov 2007 19:14:23 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: X-Original-Date: Wed, 7 Nov 2007 19:14:23 EST Subject: Re: [LML] Re: LNC2 Hyd Chirp Tim/ Joe/ Brent Question X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1194480863" X-Mailer: AOL 9.0 VR sub 5006 X-Spam-Flag: NO -------------------------------1194480863 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Brent, Yes. I'll see if I can find that ring (probably near my big ball of string) and take another picture. It was smooth and tapered to a small diameter at its thinnest point. It was either damaged at pump build or the ring originally had a material fault. I chased so many internal leak situations until I couldn't fix them completely (eventually replaced both the pump and the dump valve). Also, the pump must have been assembled with a air-driven lug-nut wrench because it took an extension on my "normal" wrenches to break the end nuts free. Your comment on the symmetric shuttle makes sense and explains why the very small reservoir on the older pumps was adequate. The problem with completely flushing the gear actuators would be the extra work to remove the retraction stops so that the piston reaches the physical end of the cylinder and all of the fluid on that side is expelled. When I rebuilt main actuators I was surprised to see blackened fluid at the retraction end along with visible residue from o-ring deterioration/wear (your use of "silt" was a very good description). Of course that wear could have come from other contamination causing the wear in the first place. I don't know about how others did it but I was so very careful to keep everything clean as it was assembled and built. But, this was not done in a white room and I did occasionally have eye irritation. Maybe since I did so many rebuilds and replaces (including the pump) I eventually "flushed" the system. Since I was such a mushroom (kept in the dark, etc.) when I was a lonely garage-located slow-builder back in the early 90's, I could only do things that then were reasonable to me - thus repeating so many problems already solved by others earlier in the century. Alas, where was the internet when I needed it? Scott In a message dated 11/7/2007 2:12:34 P.M. Central Standard Time, brent@regandesigns.com writes: Tough to tell from the picture but, because the seat is static it is unlikely that the O-ring is "worn". It does look like the O-ring was "bitten" during installation. Part of the O-ring was sheared off when the seat was pushed past the step in the bore. This can be avoided by inspecting the bore for burrs (and removing them), using an assembly lubricant (like Vaseline) and carefully assembling the parts. I am assuming that the other difference with the symmetrical shuttle is an absence of a central vent port. Without the port the system would be slow to self bleed any air in the circuit. The pumps are valved such that there is no circulation through the reservoir. You could loop the system with a line and remove the reservoir without affecting flow. Reservoir flow only occurs with tidal flow due to cylinder rod volume, fluid / air compression and system bulk modulus. This "recirculating" design means that any system contamination is trapped in the circuit without much chance to get into the reservoir. Changing the fluid does nothing to remove contamination, moisture or debris from the circuit. Hydraulic maintenance should therefore involve flushing the system by disconnecting lines, exercising the cylinders and running the pump. Internal port to port leaks are most commonly caused by contamination in the system. Metal chips, moisture, sanding dust, dirt etc. all spell death for the system. If contamination gets to the pump it turns the pump into a contamination generator. A tight, leak free system will only stay that way if it is very clean. I used to instruct the technicians that were assembling the servo hydraulic tele-manipulators that I designed that the system would tolerate contamination as well as their eyes do. We had 3 micron filters in the supply line and even with that the servo valves would "silt up" during fixed flow tests. ************************************** See what's new at http://www.aol.com -------------------------------1194480863 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
Brent,
 
Yes.  I'll see if I can find that ring (probably near my big ball=20= of=20 string) and take another picture.  It was smooth and tapered to a small= =20 diameter at its thinnest point.  It was either damaged at pump build or= the=20 ring originally had a material fault.  I chased so many=20 internal leak situations until I couldn't fix them completely=20 (eventually replaced both the pump and the dump valve).  Also, the pump= =20 must have been assembled with a air-driven lug-nut wrench because it took an= =20 extension on my "normal" wrenches to break the end nuts free.
 
Your comment on the symmetric shuttle makes sense and explains why = ;the=20 very small reservoir on the older pumps was adequate.
 
The problem with completely flushing the gear actuators would be t= he=20 extra work to remove the retraction stops so that the piston reaches the=20 physical end of the cylinder and all of the fluid on that side is=20 expelled.  When I rebuilt main actuators I was surprised to see blacken= ed=20 fluid at the retraction end along with visible residue from o-ring=20 deterioration/wear (your use of "silt" was a very good=20 description). Of course that wear could have come from other contaminat= ion=20 causing the wear in the first place.  I don't know about how others did= it=20 but I was so very careful to keep everything clean as it was assembled and=20 built.  But, this was not done in a white room and I did occasionally h= ave=20 eye irritation.  Maybe since I did so many rebuilds and replaces (inclu= ding=20 the pump) I eventually "flushed" the system. 
 
Since I was such a mushroom (kept in the dark, etc.) when I was a lonel= y=20 garage-located slow-builder back in the early 90's, I could only do things t= hat=20 then were reasonable to me - thus repeating so many problems already solved=20= by=20 others earlier in the century.  Alas, where was the internet when I nee= ded=20 it? 
 
Scott
 
 
In a message dated 11/7/2007 2:12:34 P.M. Central Standard Time,=20 brent@regandesigns.com writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Tough to=20 tell from the picture but, because the seat is static it is unlikely that=20= the=20 O-ring is "worn". It does look like the O-ring was "bitten" during=20 installation. Part of the O-ring was sheared off when the seat was pushed=20= past=20 the step in the bore. This can be avoided by inspecting the bore for burrs= =20 (and removing them), using an assembly lubricant (like Vaseline) and caref= ully=20 assembling the parts.

I am assuming that the other difference with=20= the=20 symmetrical shuttle is an absence of a central vent port. Without the port= the=20 system would be slow to self bleed any air in the circuit. The pumps are=20 valved such that there is no circulation through the reservoir. You could=20= loop=20 the system with a line and remove the reservoir without affecting flow.=20 Reservoir flow only occurs with tidal flow due to cylinder rod volume, flu= id /=20 air compression and system bulk modulus.

This "recirculating" desig= n=20 means that any system contamination is trapped in the circuit without much= =20 chance to get into the reservoir. Changing the fluid does nothing to remov= e=20 contamination, moisture or debris from the circuit. Hydraulic maintenance=20 should therefore involve flushing the system by disconnecting lines,=20 exercising the cylinders and running the pump.

Internal port to po= rt=20 leaks are most commonly caused by contamination in the system. Metal chips= ,=20 moisture, sanding dust, dirt etc. all spell death for the system. If=20 contamination gets to the pump it turns the pump into a contamination=20 generator. A tight, leak free system will only stay that way if it is very= =20 clean. I used to instruct the technicians that were assembling the servo=20 hydraulic tele-manipulators that I designed that the system would tolerate= =20 contamination as well as their eyes do. We had 3 micron filters in the sup= ply=20 line and even with that the servo valves would "silt up" during fixed flow= =20 tests.
 



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