X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imr-da04.mx.aol.com ([205.188.105.146] verified) by logan.com (CommuniGate Pro SMTP 6.0c3) with ESMTP id 5929823 for flyrotary@lancaironline.net; Sat, 08 Dec 2012 17:27:18 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.188.105.146; envelope-from=Lehanover@aol.com Received: from mtaomg-ma04.r1000.mx.aol.com (mtaomg-ma04.r1000.mx.aol.com [172.29.41.11]) by imr-da04.mx.aol.com (Outbound Mail Relay) with ESMTP id 863311C000197 for ; Sat, 8 Dec 2012 17:26:43 -0500 (EST) Received: from core-moe002c.r1000.mail.aol.com (core-moe002.r1000.mail.aol.com [172.29.188.69]) by mtaomg-ma04.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 57071E000082 for ; Sat, 8 Dec 2012 17:26:43 -0500 (EST) From: Lehanover@aol.com Full-name: Lehanover Message-ID: Date: Sat, 8 Dec 2012 17:26:42 -0500 (EST) Subject: Re: [FlyRotary] Re: Aeroquip hose To: flyrotary@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_f43b.51be16fd.3df518a2_boundary" X-Mailer: AOL 9.7 sub 55 X-Originating-IP: [173.88.28.139] x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1355005603; bh=aM5SRK8jfMY9dFcLkIIpzMbMqakjRu4zECOAN+ObEPI=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=TlZZAYPUbmklsY3I+RMPZkjyeCqamVo1JjdLY0VSdYJkHsuW19yf/cslH8P4EoKSX 8vVJdF4PMKnIE3wV4wzqocPNdL3S3FYWLOR8MkzcqUE8tH+6RKk4xgOvrg3gs0hKJ2 hH4QVyAwoG8V32nMgxxPK7i8URjaiqPTQaR/BsqY= X-AOL-SCOLL-SCORE: 0:2:391492256:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d290b50c3bea31aba --part1_f43b.51be16fd.3df518a2_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit On the other hand, I have seen many fuel lines and oil lines ending up being ground straps as well. The Aeroquip stainless braid will work for this for years in some cases, and for a few seconds in others. The failure mode involves open braid that is under a crossing braid, so it cannot be seen. If you have evidence of conduction like a black oxide on the braid where it is easy to see, there may be some parted strands against the hose liner. Build a new hose. It will eventually puncture the liner and produce a leak. Grounding is a great big deal. Starters can draw over 100 amps. A high amperage strap from the battery to a starter mounting bolt is a good start. Many other hoses will be included in this same circuit. Anything from a bulkhead fitting on the fire wall will be at ground potential. So you have a number of parallel paths. Solve for resistors in parallel. The battery ground strap has to have the very lowest resistance of all of those paths, lest excessive sharing begin. So clean shiny contact surfaces, protected from corrosion. Lynn E. Hanover In a message dated 12/8/2012 4:53:09 P.M. Eastern Standard Time, SBoese@uwyo.edu writes: Bill, From your description, your ground architecture sounds very similar to mine. I have the forest of tabs bolted to the firewall with a brass bolt. On the cabin side, the battery ground is connected to this bolt. Everything else grounds to the forest of tabs. On the engine side of the firewall, the engine ground is connected from the front (in the car) cover to that brass bolt. My arrangement has not had any electrical problems that I am aware of. I also have a stainless wire braid covered fuel line from the firewall bulkhead fitting to the fuel rail on the engine. I have seen no damage to it. The fact that your wire braid on the fuel line has been burnt suggests that it might have intermittently served as the engine ground at one time or another. The braid must not have conducted a large current for very long or it would been destroyed completely. I can't think of a worse place to have an uncontrolled resistance heater than on that fuel line. Verifying the integrity of the ground from the engine to the airframe and from the battery to the airframe certainly seems like a worthwhile endeavor. Depending on the details of the alternator installation, an intermittent connection inside the battery also might be a possibility although this would not explain the damage to the fuel line braid. FWIW Steve Boese RV6A, 1986 13B NA, RD1A, EC2 --part1_f43b.51be16fd.3df518a2_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
On the other hand, I have seen many fuel lines and oil lines ending up= =20 being ground straps as well. The Aeroquip stainless braid will work for thi= s for=20 years in some cases, and for a few seconds in others. The failure mode invo= lves=20 open braid that is under a crossing braid, so it cannot be seen. If you hav= e=20 evidence of conduction like a black oxide on the braid where it is easy to = see,=20 there may be some parted strands against the hose liner. Build a new hose. = It=20 will eventually puncture the liner and produce a leak.
 
Grounding is a great big deal. Starters can draw over 100 amps. A high= =20 amperage strap from the battery to a starter mounting bolt is a good start.= Many=20 other hoses will be included in this same circuit. Anything from a bulkhead= =20 fitting on the fire wall will be at ground potential. So you have a number = of=20 parallel paths.
Solve for resistors in parallel.
The battery ground strap has to have the very lowest resistance of all= of=20 those paths, lest excessive sharing begin. So clean shiny contact surfaces,= =20 protected from corrosion.
 
Lynn E. Hanover
 
In a message dated 12/8/2012 4:53:09 P.M. Eastern Standard Time,=20 SBoese@uwyo.edu writes:
=

Bill,

 

From your description, your ground architecture sounds very simil= ar to=20 mine.  I have the forest of tabs bolted to the firewall with a = brass=20 bolt.  On the cabin side, the battery ground is connected to this=20 bolt.  Everything else grounds to the forest of tabs.  On the e= ngine=20 side of the firewall, the engine ground is connected from the front = (in=20 the car) cover to that brass bolt.  My arrangement has not= had=20 any electrical problems that I am aware of.

 

I also have a stainless wire braid covered fuel line from the firewall= =20 bulkhead fitting to the fuel rail on the engine.  I have seen no dam= age=20 to it.  The fact that your wire braid on the fuel line has been burn= t=20 suggests that it might have intermittently served as the engine grou= nd at=20 one time or another.  The braid must not have conducted a large curr= ent=20 for very long or it would been destroyed completely.  I can't think = of a=20 worse place to have an uncontrolled resistance heater than on that fuel= =20 line.  Verifying the integrity of the ground from the engine to the= =20 airframe and from the battery to the airframe certainly seems like=20 a worthwhile endeavor.

 

Depending on the details of the alternator installation, an intermitte= nt=20 connection inside the battery also might be a possibility although this w= ould=20 not explain the damage to the fuel line braid.

 

FWIW

 

Steve Boese
RV6= A,=20 1986 13B NA, RD1A,=20 EC2

        

 

 

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