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dave.gribble(at)mchsi.com
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 Posted: Mon Aug 31, 2009 5:06 pm Post subject: Why Brass Bolt for ground terminal? |
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I'm building a firewall ground terminal system consisting of faston tabs soldered to sheets of brass stock. I'll sandwich these around the RV firewall (thin stainless steel) and use a big bolt on one side to attach the battery and engine ground straps to.
I see that the B&C version of this calls for a brass bolt - what is the reason for this, and also what size of bolt to use? I assume it is a dissimilar metals corrosion problem... I have designed for a few smaller #8 bolts to hold the brass sheets together.. do these have to be brass too?
Thanks for any info,
Dave Gribble
Cedar Rapids IA
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nuckolls.bob(at)aeroelect
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| Posted: Mon Aug 31, 2009 6:25 pm Post subject: Why Brass Bolt for ground terminal? |
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At 08:00 PM 8/31/2009, you wrote:
| Quote: |
I'm building a firewall ground terminal system consisting of faston
tabs soldered to sheets of brass stock. I'll sandwich these around
the RV firewall (thin stainless steel) and use a big bolt on one
side to attach the battery and engine ground straps to.
I see that the B&C version of this calls for a brass bolt - what is
the reason for this, and also what size of bolt to use? I assume it
is a dissimilar metals corrosion problem... I have designed for a
few smaller #8 bolts to hold the brass sheets together.. do these
have to be brass too?
|
If the Big bolt is long (like through a composite
firewall) the brass bolt is preferred for electrical
conductivity. But for a thin firewall, regular AN
hardware is fine. The #8 hardware is mechanical only,
plain vanilla AN hardware there too.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
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icubob(at)gmail.com
Guest
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| Posted: Tue Sep 01, 2009 3:33 am Post subject: Why Brass Bolt for ground terminal? |
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the brass bolt will carry the current thru the firewall to the ''forest of tabs'' you will mount on it on the cabin side of the firewall.
bob noffs
On Mon, Aug 31, 2009 at 9:23 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
[quote]--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>
At 08:00 PM 8/31/2009, you wrote:
| Quote: | --> AeroElectric-List message posted by: dave.gribble(at)mchsi.com (dave.gribble(at)mchsi.com)
I'm building a firewall ground terminal system consisting of faston tabs soldered to sheets of brass stock. I'll sandwich these around the RV firewall (thin stainless steel) and use a big bolt on one side to attach the battery and engine ground straps to.
I see that the B&C version of this calls for a brass bolt - what is the reason for this, and also what size of bolt to use? I assume it is a dissimilar metals corrosion problem... I have designed for a few smaller #8 bolts to hold the brass sheets together.. do these have to be brass too?
|
If the Big bolt is long (like through a composite
firewall) the brass bolt is preferred for electrical
conductivity. But for a thin firewall, regular AN
hardware is fine. The #8 hardware is mechanical only,
plain vanilla AN hardware there too.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
s such as List Un/Subscription,
www.matronics.com/Navigator?AeroElectric-List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
ronics.com/" target="_blank">http://forums.matronics.com
Matt Dralle, List Admin.
=====
[b]
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dave.gribble(at)mchsi.com
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| Posted: Tue Sep 01, 2009 6:43 am Post subject: Why Brass Bolt for ground terminal? |
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Hi Glenn - I built the ground block because I like building things! I enjoy the challenge, and also learning new skills (never sweat soldered brass before)....Sort of the same reason I'm building my plane instead of buying one 
I'm sure the B&C parts are nice, but $50 is about $49 more than I spent and I can save that money and put it towards my EFIS. Besides, B&C has already got enough ca$h from me this month!
-------------- Original message ----------------------
From: <longg(at)pjm.com>
| Quote: |
Bob,
Wow, I really appreciate your craftsmanship effort, but why would you
build one of these? B & C sells them relatively cheaply and they are
perfect for the job. Drill a hole, add the appropriate number of washers
and move on.
Glenn
From: owner-aeroelectric-list-server(at)matronics.com
[mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of bob
noffs
Sent: Tuesday, September 01, 2009 7:28 AM
To: aeroelectric-list(at)matronics.com
Subject: [Probable SPAM] Re: Why Brass Bolt for
ground terminal?
the brass bolt will carry the current thru the firewall to the ''forest
of tabs'' you will mount on it on the cabin side of the firewall.
bob noffs
On Mon, Aug 31, 2009 at 9:23 PM, Robert L. Nuckolls, III
<nuckolls.bob(at)aeroelectric.com> wrote:
<nuckolls.bob(at)aeroelectric.com>
At 08:00 PM 8/31/2009, you wrote:
I'm building a firewall ground terminal system consisting of faston tabs
soldered to sheets of brass stock. I'll sandwich these around the RV
firewall (thin stainless steel) and use a big bolt on one side to attach
the battery and engine ground straps to.
I see that the B&C version of this calls for a brass bolt - what is the
reason for this, and also what size of bolt to use? I assume it is a
dissimilar metals corrosion problem... I have designed for a few smaller
#8 bolts to hold the brass sheets together.. do these have to be brass
too?
If the Big bolt is long (like through a composite
firewall) the brass bolt is preferred for electrical
conductivity. But for a thin firewall, regular AN
hardware is fine. The #8 hardware is mechanical only,
plain vanilla AN hardware there too.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
s such as List Un/Subscription,
www.matronics.com/Navigator?AeroElectric-List"
target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
ronics.com/" target="_blank">http://forums.matronics.com
Matt Dralle, List Admin.
=====
|
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Eric M. Jones
Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts
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| Posted: Wed Sep 02, 2009 5:42 am Post subject: Re: Why Brass Bolt for ground terminal? |
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Since you want ground termination on both sides of the firewall, you can do approximately the following:
Take a 2X long copper strap, fold it in the middle and insert it through a slot in the firewall (or around the edge). Then drill a battery ground bolt hole through both layers and the firewall too. The bolt hole is better if it is closer to the fold, but this is a fine detail.
Teamwork: " A lot of people doing exactly what I say."
(Marketing exec., Citrix Corp.)
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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net |
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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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| Posted: Thu Sep 03, 2009 4:49 am Post subject: Why Brass Bolt for ground terminal? |
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9/03/2009
Hello Eric, Your proposal (see below) is not entirely clear to me.
So you fold the copper strap only 90 degrees in the middle? Then you insert
one leg of the angle through the slot in the firewall and place that leg
along the stainless steel firewall and drill through both? Then place the
battery ground bolt through that hole to connect the lug on the battery
ground wire to the copper strip and the firewall? Then use the copper strap
leg that is at 90 degrees to the firewall to connect things for grounding on
the other side of the firewall through a previously drilled hole in the
copper strap?
Sounds good, but don't expect that the stainless steel of the firewall will
provide a good reliable ground in other locations because of a non
conducting film that tends to build up on the surface of the stainless
steel.
'OC' Says: "The best investment we can make is the effort to gather and
understand knowledge."
================================
Time: 06:44:26 AM PST US
Subject: Re: Why Brass Bolt for ground terminal?
From: "Eric M. Jones" <emjones(at)charter.net>
Since you want ground termination on both sides of the firewall, you can do
approximately
the following:
Take a 2X long copper strap, fold it in the middle and insert it through a
slot
in the firewall (or around the edge). Then drill a battery ground bolt hole
through
both layers and the firewall too. The bolt hole is better if it is closer
to the fold, but this is a fine detail.
Teamwork: " A lot of people doing exactly what I say."
(Marketing exec., Citrix Corp.)
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Thu Sep 03, 2009 5:17 am Post subject: Why Brass Bolt for ground terminal? |
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| Quote: |
Sounds good, but don't expect that the stainless steel of the
firewall will provide a good reliable ground in other locations
because of a non conducting film that tends to build up on the
surface of the stainless steel.
|
In the best of all ELECTRICAL worlds, we don't worry about
high quality electrical bonding to the firewall. The goal
of optimum ground system is to avoid using the firewall sheet
(or engine mounts) for any electrical purpose.
The diagrams suggested in Z-15 go toward those goals and
suggest that for metal airplanes, it's no REALLY big deal
to ground strobes, nav lights, and a few odd accessories
locally.
What Eric is suggesting is a 'lamination' of the firewall
sheet between the folds of a copper strap that is fastened
to the firewall with one fat bolt for battery and crankcase
grounds . . . and spreading the other grounds out over the
outside surface of the U-shaped copper strap by what ever
means is most attractive. If everything grounded to this
construct, then it wouldn't matter if the copper were well
bonded to the stainless.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
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