X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 04 Nov 2007 21:28:20 -0500 Message-ID: X-Original-Return-Path: Received: from colossus.formysite.com ([64.58.34.10] verified) by logan.com (CommuniGate Pro SMTP 5.2c1) with ESMTPS id 2454477 for lml@lancaironline.net; Sat, 03 Nov 2007 22:31:57 -0400 Received-SPF: none receiver=logan.com; client-ip=64.58.34.10; envelope-from=genemartin@enid.com Received: from gene (mobile-166-217-209-087.mycingular.net [166.217.209.87]) by colossus.formysite.com (8.12.8/8.12.8) with SMTP id lA42V76V012864 for ; Sat, 3 Nov 2007 21:31:11 -0500 X-Original-Message-ID: <003401c81e8a$c5cb3c10$57d1d9a6@gene> From: "genemartin" X-Original-To: "Lancair Mailing List" References: Subject: Re: [LML] Re: FW: [LML] LNC2 Hyd Chirp Alternative Mousetrap X-Original-Date: Sat, 3 Nov 2007 21:31:12 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0031_01C81E60.DB4A6A40" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 This is a multi-part message in MIME format. ------=_NextPart_000_0031_01C81E60.DB4A6A40 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I have such a secret override switch...top secret unmarked don't ask = don't tell. Gene ----- Original Message -----=20 From: Sky2high@aol.com=20 To: lml@lancaironline.net=20 Sent: Saturday, November 03, 2007 9:06 AM Subject: [LML] Re: FW: [LML] LNC2 Hyd Chirp Alternative Mousetrap In a message dated 11/2/2007 10:48:32 A.M. Central Daylight Time, = LHenney@charter.net writes: Air is good if your breathing and bad if leaking into your brain. = OK, I'll go out and rebuild one this am and report back. Oh, but wait, = I guess the rebuild of the leaker will have an affect on our test.=20 Larry, I love spirited discussions leading to one's spirit sipping spirits = during contemplation of the metaphysical. I thought more about all the = problems reported over the years and the possible effect of air. Let's = see if we can work thru this by picking the system apart. But first, I = said you should only introduce air into the system as a test of your = theory, not rebuild a cylinder. =20 Air in cylinders=20 4 of the six cylinders, those associated with the main gears and = doors, can be eliminated because they are oriented horizontally with all = ports pointed upward so the air will not remain in those actuators. =20 The nose gear door cylinder, vertically oriented cannot hold much air = in the bottom after extension because the air would have to fit in a = donut cylinder volume 5/32 high with the inside 1/2" diameter and the = outside 5/8 diameter - a volume of .017 cubic inches. This space is = inside of the extension piston stop that allows fluid to be passed in = and out of the cylinder. Upon retraction, even though the piston does = not tightly reach the top, the fluid exit is at the top and air would be = expelled. The .017 ci of air could be trapped at the piston that is = pushed in by the hi pressure retraction activity and the bubble could = rise to the bottom of the piston. The nose gear cylinder is somewhat vertically oriented and the = cylinder cannot hold any air in the bottom beyond the piston at full = extension since it is stopped tightly against the forward bulkhead (if = properly rigged). However, retraction is limited by the external stop = and the fluid exit is at the aft lower side of the cylinder. I forgot = to check how vertically oriented the cylinder gets on retraction, but = let's say the whole remaining space can retain air. That is a cylinder = approximately 3/4" high with a diameter of 9/8" for a volume of about = .75 cubic inches. Of course, at retraction this pocket would not be = under pressure since it is the other side of the piston that is under = pressure. So, it is on extension that some of this pocket could be = compressed although it would seem that some of the air would come out at = each retraction. =20 Air in lines There also are short pieces of Easton flexible line that feeds into = 1/4" hard Al lines. Let's discuss how much volume these lines can hold. = For the Easton line (I could not find a sample), assume it has an = interior cross section of 1/4". That is 20.37 inches of tube per 1 = cubic inch of fluid volume. The 1/4" hard lines have a wall thickness = of .035, thus the interior diameter is .18" or 39.3 inches of tube per = cubic inch of volume. Door actuators move about .9 ci of fluid in when extended and .7 ci in = when retracted. The nose gear cylinder (I forgot to measure the length, = say 4.5" of movement) moves about 4.5 ci of fluid in when extended and 4 = ci in when retracted. Since the opening of doors requires fluid passage thru sequence = valves, those lines might not be completely cleared because of the hard = line length may hold more fluid than is transferred to and from the = actuator. One could consider a small bubble remaining in those lines. = The retraction side moves more fluid thru shorter lines so it is less = likely that air is trapped in those lines. The large actuators move = much more fluid and it is hard to believe any air remaining in those = lines. Air Elsewhere The dump valve body can't hold air once it has been opened. Perhaps = the teed vertical lines leading to the pressure switches retain air. Gas Laws For those that suspect that heated trapped air raises the system = pressure quite a bit should note that when the volume is held constant, = the pressure increases as the temperature ratio, in Kelvin, increases. = A rise from 50F to 80F is 299K/283K or approximately a 5% increase - = Hardly accounting for a rise of several hundred psi. I await an = engineer to evaluate effects of the differing expansion factors for = aluminum, Easton lines, cylinders and the fluid itself. On the converse, if the air is compressed (so far this looks like a = problem that is possible solely on the down side at the nose gear = actuator), I would finally have to agree that more volume of fluid under = pressure from the air would have to pass through the system leak to = activate the pressure switch than that from incompressible fluid on its = own. Maybe. That these air pockets may work themselves out so that the = chirp rate increases is interesting. So I can see where an accumulator could delay pump activation. No = problem as long as other parts of the system are working properly. It = is hard to see where any air bubbles could influence the up side of the = system other than those trapped in the sequence valve circuits. ---- As to some of the other contentions................. You said: "You're an electrics guy. Does that little chirp every 20 = seconds not bother you just a little? You know, arcing and corrosion in = the relays, airborne fire, alternator shorting, etc?" You are correct, the wiring is correct. Thus, arcing and corrosion = are not a problem - intermittent relays are operating intermittently . = Airborne fire and alternator shorting are not a problem from the pump = blips for the small percentage of block time that the gear is down, nor = is anything else associated with the hydro-electric gear system. = However, "etc." does indeed bother me, although it is not related to = this situation. One of the risks you may add is that the accumulator on the high = pressure side may lock up the low pressure side if you have a failure = like that sometimes described by other Lancairites and not yet fully = understood. This is the case where opening the dump valve does not = resolve the peculiarly built system pressure present on both sides and = that trips both pressure switches. There may be an electrical solution = - perhaps bring duplicate wires from the pressure switches forward to = secret over ride switches operable by the captain. Forced activation of = the pump may free the lockup if it is the case of a stuck shuttle valve. = Of course the captain's hearing has to be good enough to perform an = "undo" if the pump is straining as the captain becomes the acting = pressure switch. Good Luck, Scott Krueger AKA Grayhawk Lancair N92EX IO320 SB 89/96 Aurora, IL (KARR) Darwinian culling phrase: Watch This! -------------------------------------------------------------------------= ----- See what's new at AOL.com and Make AOL Your Homepage. ------=_NextPart_000_0031_01C81E60.DB4A6A40 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
I have such a secret override switch...top secret unmarked don't = ask don't=20 tell.
Gene
----- Original Message -----
From:=20 Sky2high@aol.com=20
Sent: Saturday, November 03, = 2007 9:06=20 AM
Subject: [LML] Re: FW: [LML] = LNC2 Hyd=20 Chirp Alternative Mousetrap

In a message dated 11/2/2007 10:48:32 A.M. Central Daylight Time, = LHenney@charter.net = writes:
Air is good if your breathing = and bad if=20 leaking into your brain.  OK, I'll go out and rebuild one this = am and=20 report back.  Oh, but wait, I guess the rebuild of the leaker = will have=20 an affect on our test. 
Larry,
 
I love spirited discussions leading to one's spirit sipping = spirits=20 during contemplation of the metaphysical.  I thought more = about all=20 the problems reported over the years and the possible effect of=20 air.  Let's see if we can work thru this by picking the system=20 apart.  But first, I said you should only introduce air into the = system=20 as a test of your theory, not rebuild a cylinder.  
 
Air in cylinders
 
4 of the six cylinders, those associated with the main gears and = doors,=20 can be eliminated because they are oriented horizontally with all = ports=20 pointed upward so the air will not remain in those actuators.  =
 
The nose gear door cylinder, vertically oriented cannot hold much = air in=20 the bottom after extension because the air would have to fit in a = donut=20 cylinder volume 5/32 high with the inside 1/2" diameter and the = outside=20 5/8 diameter - a volume of .017 cubic inches.  This space is = inside of=20 the extension piston stop that allows fluid to be passed in and out of = the=20 cylinder.  Upon retraction, even though the piston does not = tightly reach=20 the top, the fluid exit is at the top and air would be expelled.  = The=20 .017 ci of air could be trapped at the piston that is pushed in by the = hi=20 pressure retraction activity and the bubble could rise to the bottom = of the=20 piston.
 
The nose gear cylinder is somewhat vertically oriented and the = cylinder=20 cannot hold any air in the bottom beyond the piston at full = extension=20 since it is stopped tightly against the forward bulkhead (if properly=20 rigged).  However, retraction is limited by the external stop and = the=20 fluid exit is at the aft lower side of the cylinder.  I forgot to = check=20 how vertically oriented the cylinder gets on retraction, but let's say = the=20 whole remaining space can retain air.  That is a cylinder=20 approximately 3/4" high with a diameter of 9/8" for a volume of about = .75=20 cubic inches.  Of course, at retraction this pocket would not be = under=20 pressure since it is the other side of the piston that is under=20 pressure.  So, it is on extension that some of this pocket could = be=20 compressed although it would seem that some of the air would come out = at each=20 retraction. 
 
Air in lines
 
There also are short pieces of Easton flexible line that = feeds into=20 1/4" hard Al lines. Let's discuss how much volume these = lines can=20 hold.  For the Easton line (I could not find a sample), assume it = has an=20 interior cross section of 1/4".   That is 20.37 inches = of tube=20 per 1 cubic inch of fluid volume.  The 1/4" hard lines have a = wall=20 thickness of .035, thus the interior diameter is .18" or 39.3 inches = of tube=20 per cubic inch of volume.
 
Door actuators move about .9 ci of fluid in when extended and .7 = ci in=20 when retracted.  The nose gear cylinder (I forgot to measure the = length,=20 say 4.5" of movement) moves about 4.5 ci of fluid in when = extended and 4=20 ci in when retracted.
 
Since the opening of doors requires fluid passage thru sequence = valves,=20 those lines might not be completely cleared because of the hard line = length=20 may hold more fluid than is transferred to and from the = actuator.  One=20 could consider a small bubble remaining in those = lines. =20 The retraction side moves more fluid thru shorter lines so it is less = likely=20 that air is trapped in those lines.  The large actuators = move much=20 more fluid and it is hard to believe any air remaining in those = lines.
 
Air Elsewhere
 
The dump valve body can't hold air once it has been = opened. =20 Perhaps the teed vertical lines leading to the pressure switches = retain=20 air.
 
Gas Laws
 
For those that suspect that heated trapped air raises the system = pressure=20 quite a bit should note that when the volume is held constant, the = pressure=20 increases as the temperature ratio, in Kelvin, increases.  A = rise=20 from 50F to 80F is 299K/283K or approximately a 5% increase - Hardly=20 accounting for a rise of several hundred psi.  I await an = engineer to=20 evaluate effects of the differing expansion factors for aluminum, = Easton=20 lines, cylinders and the fluid itself.
 
On the converse, if the air is compressed (so far this looks like = a=20 problem that is possible solely on the down side at the nose = gear=20 actuator), I would finally have to agree that more volume of fluid = under=20 pressure from the air would have to pass through the = system=20 leak to activate the pressure switch than that from incompressible = fluid on=20 its own. Maybe.  That these air pockets may work themselves = out so=20 that the chirp rate increases is interesting.
 
So I can see where an accumulator could delay pump = activation.  No=20 problem as long as other parts of the system are working = properly.  It is=20 hard to see where any air bubbles could influence the up side of the = system=20 other than those trapped in the sequence valve circuits.
 
----
 
As to some of the other contentions.................
 
You said: "You're an electrics guy.  Does that little chirp = every 20=20 seconds not bother you just a little?  You know, arcing and = corrosion in=20 the relays, airborne fire, alternator shorting, etc?"
 
You are correct, the wiring is correct.  Thus, arcing and = corrosion=20 are not a problem - intermittent relays are operating = intermittently=20 .  Airborne fire and alternator shorting are not a problem from = the pump=20 blips for the small percentage of block time that the gear = is down,=20 nor is anything else associated with the hydro-electric gear=20 system.  However, "etc." does indeed bother me, although it is = not=20 related to this situation.
 
One of the risks you may add is that the accumulator on the high = pressure=20 side may lock up the low pressure side if you have a failure like that = sometimes described by other Lancairites and not yet fully = understood. =20 This is the case where opening the dump valve does not resolve the = peculiarly=20 built system pressure present on both sides and that trips = both=20 pressure switches.  There may be an electrical solution -=20 perhaps bring duplicate wires from the pressure switches forward = to=20 secret over ride switches operable by the captain.  Forced = activation of=20 the pump may free the lockup if it is the case of a stuck shuttle = valve.  Of course the captain's hearing has to be good = enough=20 to perform an "undo" if the pump is straining as the = captain becomes the=20 acting pressure switch.
 
Good Luck,
 
Scott=20 Krueger AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL=20 (KARR)

Darwinian culling phrase: Watch=20 This!



See what's new at AOL.com=20 and Make AOL Your=20 Homepage.
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