X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 05 Nov 2009 21:21:06 -0500 Message-ID: X-Original-Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.121] verified) by logan.com (CommuniGate Pro SMTP 5.2.17) with ESMTP id 3931721 for lml@lancaironline.net; Thu, 05 Nov 2009 09:38:37 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.121; envelope-from=super_chipmunk@roadrunner.com Received: from Laptop ([74.75.176.139]) by cdptpa-omta04.mail.rr.com with SMTP id <20091105143800705.XHE2725@cdptpa-omta04.mail.rr.com> for ; Thu, 5 Nov 2009 14:38:00 +0000 X-Original-Message-ID: <5179761757A74F0B914B96AE9FECA9EC@Laptop> From: "Bill Wade" X-Original-To: "Lancair Mailing List" References: In-Reply-To: Subject: Re: [LML] Re: L-IVP Battery Cooling X-Original-Date: Thu, 5 Nov 2009 09:38:31 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_025B_01CA5DFB.BC9F4750" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6002.18005 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6002.18005 This is a multi-part message in MIME format. ------=_NextPart_000_025B_01CA5DFB.BC9F4750 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Re: L-IVP Battery CoolingHi Colin- Your earlier post indicated that you were not going to = protect against starter loads so that leaves the rest of the electrical = system. I may be missing something but I don't understand how a fuse between = the cable and the power buss(es) would provide protection. Given the = variable nature of the loads, particularly the inrush current each time = the hydraulic pump starts up or a landing light is turned on, how would = you size it? It would have to be sufficient to handle every device = operating at once plus some additional capacity to prevent the fuse = blowing inadvertantly. I generally operate with a number of circuits turned off. For example, = I don't use cockpit, nav and landing lights during the day. (The landing = lights are retracted except at low speed). I don't use pitot heat VFR. = Under those conditions would there be enough additional sustained = current from a given short, particularly one of the small gauge wires = that are most numerous, to cause the fuse to blow? I agree that an = electrical fire is something to be avoided. I think the liberal use of = heat shrink and careful mechanical installation are a good defense. I = cover the shanks of battery and other uninsulated terminal lugs with = heat shrink to reduce exposure. Incidentally, the stuck PTT switch I experienced was due to the switch = terminals getting pushed together and shorting out. The avionics shop = hadn't put heat shrink on each terminal, just over the whole assembly. I = covered each one on the replacement. It seems to me that the odds of a = loose wire shorting against the cables would be enhanced by the ANL fuse = and holder. It would require two extra terminal lugs, also the holder's = terminal posts and the exposed areas of the fuse itself are vulnerable. = A solid cable would have continuous insulation. Speaking of Nuckolls, a quick glance at his diagrams shows no fuses on = any battery leads. One difficulty I thought of with remote battery installation is with a = pressurized model. Those cables would have to penetrate the firewall and = I'm not sure what a good method might be for sealing them. That would be = one advantage of the firewall mounted battery. -Bill Wade ----- Original Message -----=20 From: Colyn Case at earthlink=20 To: lml@lancaironline.net=20 Sent: Wednesday, November 04, 2009 5:39 PM Subject: [LML] Re: L-IVP Battery Cooling The Bob Nuckolls wisdom on this is that some voltage drop is okay for = a starting system. I'm only repeating that not endorsing it. (Caveat, if you have a full feathering prop and would like to air = restart after feathering, it takes 20-30 seconds of vigorous cranking under nasty cold conditions to get it out of feather. = Voltage, and cold cranking amps helpful here) That doesn't worry me nearly so much as high current unprotected wires = in the cockpit, at least when not in starting mode. ------=_NextPart_000_025B_01CA5DFB.BC9F4750 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Re: L-IVP Battery Cooling
Hi Colin-
          =  =20 Your earlier post indicated that you were not going to protect against = starter=20 loads so that leaves the rest of the electrical system.
 
  I may be missing something = but I don't=20 understand how a fuse between the cable and the power buss(es) = would=20 provide protection. Given the variable nature of the loads, particularly = the=20 inrush current each time the hydraulic pump starts up or a landing = light is=20 turned on, how would you size it? It would have to be sufficient to = handle=20 every device operating at once plus some additional capacity to = prevent the=20 fuse blowing inadvertantly.
 
  I generally operate with a = number of=20 circuits turned off. For example, I don't use cockpit, nav and = landing=20 lights during the day. (The landing lights are retracted except at = low=20 speed). I don't use pitot heat VFR. Under those conditions would there = be enough=20 additional sustained current from a given short, particularly one=20 of the small gauge wires that are most numerous, to cause the fuse = to blow?=20 I agree that an electrical fire is something to be avoided. I think the = liberal=20 use of heat shrink and careful mechanical installation are a good = defense. I=20 cover the shanks of battery and other uninsulated terminal lugs with = heat shrink=20 to reduce exposure.
 
  Incidentally, the stuck PTT = switch I=20 experienced was due to the switch terminals getting pushed together = and=20 shorting out. The avionics shop hadn't put heat shrink on each terminal, = just=20 over the whole assembly. I covered each one on the=20 replacement. It seems to me that the odds of a loose wire shorting = against=20 the cables would be enhanced by the ANL fuse and holder. It=20 would require two extra terminal lugs, also the holder's = terminal=20 posts and the exposed areas of the fuse itself are vulnerable. A solid = cable=20 would have continuous insulation.
 
 Speaking of Nuckolls, a quick = glance at his=20 diagrams shows no fuses on any battery leads.
 
  One difficulty I thought of with = remote=20 battery installation is with a pressurized model. Those cables = would have=20 to penetrate the firewall and I'm not sure what a good method might be = for=20 sealing them. That would be one advantage of the firewall mounted = battery. =20 -Bill Wade
 
 
 ----- Original Message -----
From:=20 Colyn=20 Case at earthlink
Sent: Wednesday, November 04, = 2009 5:39=20 PM
Subject: [LML] Re: L-IVP = Battery=20 Cooling

The Bob Nuckolls wisdom on this is = that some=20 voltage drop is okay for a starting system.
I'm only repeating that not endorsing = it.
(Caveat, if you have a full = feathering prop and=20 would like to air restart after feathering, it takes 20-30 seconds of=20 vigorous
cranking under nasty cold conditions = to get it=20 out of feather.   Voltage, and cold cranking amps helpful=20 here)
 
That doesn't worry me nearly so much = as high=20 current unprotected wires in the cockpit, at least when not in = starting=20 mode.
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