X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 27 Jan 2012 13:40:37 -0500 Message-ID: X-Original-Return-Path: Received: from qmta11.emeryville.ca.mail.comcast.net ([76.96.27.211] verified) by logan.com (CommuniGate Pro SMTP 5.4.3) with ESMTP id 5367176 for lml@lancaironline.net; Fri, 27 Jan 2012 12:29:58 -0500 Received-SPF: pass receiver=logan.com; client-ip=76.96.27.211; envelope-from=n16dx@comcast.net Received: from omta11.emeryville.ca.mail.comcast.net ([76.96.30.36]) by qmta11.emeryville.ca.mail.comcast.net with comcast id ShBR1i0040mlR8UABhVPzh; Fri, 27 Jan 2012 17:29:23 +0000 Received: from JohnPC ([98.247.186.0]) by omta11.emeryville.ca.mail.comcast.net with comcast id ShVM1i01000wjd68XhVNeX; Fri, 27 Jan 2012 17:29:22 +0000 X-Original-Message-ID: <6590F31846EF4E75B5ED1E1CC9AA5E54@JohnPC> From: "John Richardson" X-Original-To: "Lancair Mailing List" References: In-Reply-To: Subject: Re: [LML] Re: Canopy seal pump X-Original-Date: Fri, 27 Jan 2012 09:29:26 -0800 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0463_01CCDCD6.29749500" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6002.18197 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6002.18463 This is a multi-part message in MIME format. ------=_NextPart_000_0463_01CCDCD6.29749500 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Nice job with the Legacy canopy seal pump / pressure switch Leighton. I = changed mine too. Like you, I found the factory supplied pressure = switch was set at around 20 psi....way too high for the Legacy canopy. = I reset it to around 4 psi but then found it was not stable in flight. = The pump would oscillate on and off rapidly plus it would change = pressure dependent on temperature in the location where it's mounted. = When set that low, the pressure switch seems to not have enough dead = band (hysteresis) so it continuously cycles on and off. I ended up = discarding the factory pressure switch and designed a new circuit using = an inexpensive silicon differential pressure sensor from Freescale = Semiconductor along with a comparator circuit to provide about a 30% = dead band around 4 psi. =20 I had fun with the circuit but the important point here is that the = factory pressure switch is 1) set way too high and 2) seem to not work = well when reset lower (may be unique to my switch on a sample of one). = Perhaps some of you have seen the Lancair Legacy brochure with Carl = Lewis' N14CL in flight (Josh Burngardt flying) with the moon in the = background. If you look closely at the canopy, it seems to be pushed up = in the front showing a gap. I think this gap may be caused by 20 psi in = the canopy seal. Just a guess but high pressure in the seal may stress = the Legacy canopy latch / hinge mechanism. =20 John Richardson Legacy N16DX ----- Original Message -----=20 From: marv@lancair.net=20 To: lml@lancaironline.net=20 Sent: Friday, January 27, 2012 4:59 AM Subject: [LML] Re: Canopy seal pump Posted for "Leighton Mangels" : All the seal pump pressure switches I've seen come set at 20psi, = which is way=20 too high. I reset them on the bench to about 6 psi which is more than = adequate. We use a small 3- way solenoid valve in lieu of the brass = toggle=20 dump valve. If the pump switch is turned off the seal then = automatically=20 deflates. If the master is turned off it deflates. On the Legacys we = put a=20 small micro switch at the bottom of the inside canopy latch lever so = that if=20 the canopy is unlatched the seal automatically deflates. In other = words, if=20 the power is turned off to the pump the seal deflates. That way = there's no way=20 to open or close the canopy with the seal inflated. And it eliminates = the=20 toggle valve from the panel, or wherever you choose to put it. I'll = attach a=20 pic of the pump assembly with all the components I use. The part with = the=20 yellow top is the solenoid valve. =20 =20 Leighton Mangels leighton@teleport.com 503-647-5779 -------------------------------------------------------------------------= ----- -- For archives and unsub = http://mail.lancaironline.net:81/lists/lml/List.html ------=_NextPart_000_0463_01CCDCD6.29749500 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Nice job with the Legacy canopy seal = pump /=20 pressure switch Leighton.  I changed mine too.  Like you, I = found the=20 factory supplied pressure switch was set at around 20 psi....way = too high=20 for the Legacy canopy.  I reset it to around 4 psi but then found = it was=20 not stable in flight.  The pump would oscillate on and off = rapidly=20 plus it would change pressure dependent on temperature in the location = where=20 it's mounted.  When set that low, the pressure switch seems=20 to not have enough dead band (hysteresis) so it continuously cycles = on and=20 off.  I ended up discarding the factory pressure switch and = designed a new=20 circuit using an inexpensive silicon differential pressure sensor from = Freescale=20 Semiconductor along with a comparator circuit to provide about a 30% = dead band=20 around 4 psi. 
 
I had fun with the circuit but the = important point=20 here is that the factory pressure switch is 1) set way too high and 2) = seem to=20 not work well when reset lower (may be unique to my switch on a sample = of=20 one).  Perhaps some of you have seen the Lancair Legacy brochure = with Carl=20 Lewis' N14CL in flight (Josh Burngardt flying) with the moon in the=20 background.  If you look closely at the canopy, it seems to be = pushed up in=20 the front showing a gap.  I think this gap may be caused by 20 psi = in the=20 canopy seal.  Just a guess but high pressure in the seal may stress = the=20 Legacy canopy latch / hinge mechanism. 
 
John Richardson
Legacy N16DX
 
----- Original Message -----
From:=20 marv@lancair.net=20
Sent: Friday, January 27, 2012 = 4:59=20 AM
Subject: [LML] Re: Canopy seal = pump


Posted for "Leighton Mangels" <leighton@teleport.com>:
<= BR> All=20 the seal pump pressure switches I've seen come set at 20psi, which is = way=20
too high.  I reset them on the bench to about 6 psi = which is=20 more than
adequate.  We use a small 3- way solenoid = valve in=20 lieu of the brass toggle
dump valve.  If the pump switch = is=20 turned off the seal then automatically
deflates.  If the = master=20 is turned off it deflates. On the Legacys we put a
small micro = switch at=20 the bottom of the inside canopy latch lever so that if
the canopy = is=20 unlatched the seal automatically deflates.  In other words, = if=20
the power is turned off to the pump the seal deflates. That way = there's no=20 way
to open or close the canopy with the seal = inflated.  And it=20 eliminates the
toggle valve from the panel, or wherever you choose = to put=20 it.  I'll attach a
pic of the pump assembly with all the = components I use.  The part with the
yellow top is the = solenoid=20 valve.  
 
 Leighton=20 Mangels
 leighton@teleport.com
 503-647-5779

--
For archives and unsub=20 = http://mail.lancaironline.net:81/lists/lml/List.html
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