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Ground Block On Firewall

 
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jmoreau2(at)cox.net
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PostPosted: Thu Aug 03, 2006 6:50 am    Post subject: Ground Block On Firewall Reply with quote

I wish to install one of the multi tab type ground blocks to the stainless steel firewall on my RV8-A. This will have a block of tabs on both sides of the firewall.
Do I need to anything special to the stainless steel to prepare the surface?
Since I will be grounding many items in the aircraft to these gounds, I want to insure that this is a really good ground.
Also is it necessary to have the mounting bolt go into one of the aluminum angles behind the firewall or is it enought just to have the bolt go through the stainless?
Any help or comments are most welcome.
Jeff


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dennis.glaeser(at)eds.com
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PostPosted: Thu Aug 03, 2006 9:46 am    Post subject: Ground Block on Firewall Reply with quote

The firewall is just a place to hang the ground block. It doesn't
participate electrically in any significant matter - that's why
everything is connected to the ground block. Since you will have ground
blocks on both sides of the firewall, you need to be sure they are
connected well electrically - like with a nice brass bolt (available
from the Aviation/Plumbing aisle at Lowes or Home Depot). B&C has a
grounding block kit you can either get, or emulate.

I don't think it is necessary to mount it to one of the angles, but if
it is convenient, it wouldn't hurt. I haven't mounted mine yet, but if
it feels flimsy just mounted to the firewall, I'll put in a backing
plate (probably .040 aluminum).

Dennis Glaeser
RV7A - Finishing Kit

------------------------------------------------------------------------
-------------------

Subject: Ground Block On Firewall
From: jmoreau2(at)cox.net

I wish to install one of the multi tab type ground blocks to the
stainless steel
firewall on my RV8-A. This will have a block of tabs on both sides of
the firewall.
Do I need to anything special to the stainless steel to prepare the
surface?
Since I will be grounding many items in the aircraft to these gounds, I
want to
insure that this is a really good ground.
Also is it necessary to have the mounting bolt go into one of the
aluminum angles
behind the firewall or is it enought just to have the bolt go through
the stainless?
Any help or comments are most welcome.
Jeff


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bicyclop(at)pacbell.net
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PostPosted: Thu Aug 03, 2006 11:35 am    Post subject: Ground Block on Firewall Reply with quote

But what about stuff that's grounded locally on the wing such as pitot
heat, landing lights, etc.? That stuff's ground has to make it's way to
the forest of tabs on the firewall and back to the battery through the
stainless firewall. If the firewall is as poor a conductor as has been
recently said, doesn't that raise the possibility of ground loops as the
pitot heat, lights, etc. try to return and wind up finding an easier
route such as through the chassis of a radio?

Pax,

Ed Holyoke

<dennis.glaeser(at)eds.com>

The firewall is just a place to hang the ground block. It doesn't
participate electrically in any significant matter - that's why
everything is connected to the ground block. Since you will have ground
blocks on both sides of the firewall, you need to be sure they are
connected well electrically - like with a nice brass bolt (available
from the Aviation/Plumbing aisle at Lowes or Home Depot). B&C has a
grounding block kit you can either get, or emulate.

I don't think it is necessary to mount it to one of the angles, but if
it is convenient, it wouldn't hurt. I haven't mounted mine yet, but if
it feels flimsy just mounted to the firewall, I'll put in a backing
plate (probably .040 aluminum).

Dennis Glaeser
RV7A - Finishing Kit

------------------------------------------------------------------------
-------------------

Subject: Ground Block On Firewall
From: jmoreau2(at)cox.net

I wish to install one of the multi tab type ground blocks to the
stainless steel
firewall on my RV8-A. This will have a block of tabs on both sides of
the firewall.
Do I need to anything special to the stainless steel to prepare the
surface?
Since I will be grounding many items in the aircraft to these gounds, I
want to
insure that this is a really good ground.
Also is it necessary to have the mounting bolt go into one of the
aluminum angles
behind the firewall or is it enought just to have the bolt go through
the stainless?
Any help or comments are most welcome.
Jeff


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N6030X(at)DaveMorris.com
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PostPosted: Thu Aug 03, 2006 12:21 pm    Post subject: Ground Block on Firewall Reply with quote

Don't just leave the FOT on each side of the firewall trying to find
their grounds through the firewall metal somehow. Hook up a big fat
ground wire directly from the bolt to the battery. The bolt a ground
wire from the wing to the battery (or FOT) as well.

Dave Morris

At 02:29 PM 8/3/2006, you wrote:
Quote:


But what about stuff that's grounded locally on the wing such as pitot
heat, landing lights, etc.? That stuff's ground has to make it's way to
the forest of tabs on the firewall and back to the battery through the
stainless firewall. If the firewall is as poor a conductor as has been
recently said, doesn't that raise the possibility of ground loops as the
pitot heat, lights, etc. try to return and wind up finding an easier
route such as through the chassis of a radio?

Pax,

Ed Holyoke

<dennis.glaeser(at)eds.com>

The firewall is just a place to hang the ground block. It doesn't
participate electrically in any significant matter - that's why
everything is connected to the ground block. Since you will have ground
blocks on both sides of the firewall, you need to be sure they are
connected well electrically - like with a nice brass bolt (available
from the Aviation/Plumbing aisle at Lowes or Home Depot). B&C has a
grounding block kit you can either get, or emulate.

I don't think it is necessary to mount it to one of the angles, but if
it is convenient, it wouldn't hurt. I haven't mounted mine yet, but if
it feels flimsy just mounted to the firewall, I'll put in a backing
plate (probably .040 aluminum).

Dennis Glaeser
RV7A - Finishing Kit

------------------------------------------------------------------------
-------------------

Subject: Ground Block On Firewall
From: jmoreau2(at)cox.net

I wish to install one of the multi tab type ground blocks to the
stainless steel
firewall on my RV8-A. This will have a block of tabs on both sides of
the firewall.
Do I need to anything special to the stainless steel to prepare the
surface?
Since I will be grounding many items in the aircraft to these gounds, I
want to
insure that this is a really good ground.
Also is it necessary to have the mounting bolt go into one of the
aluminum angles
behind the firewall or is it enought just to have the bolt go through
the stainless?
Any help or comments are most welcome.
Jeff



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brian



Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

PostPosted: Thu Aug 03, 2006 12:28 pm    Post subject: Ground Block on Firewall Reply with quote

On Aug 3, 2006, at 3:29 PM, Ed Holyoke wrote:

Quote:

<bicyclop(at)pacbell.net>

But what about stuff that's grounded locally on the wing such as pitot
heat, landing lights, etc.? That stuff's ground has to make it's
way to
the forest of tabs on the firewall and back to the battery through the
stainless firewall. If the firewall is as poor a conductor as has been
recently said, doesn't that raise the possibility of ground loops
as the
pitot heat, lights, etc. try to return and wind up finding an easier
route such as through the chassis of a radio?

The firewall is not a poor conductor. A big slab of stainless steel,
while less conductive than an equivalent copper plate, is still a
very good conductor.

As for ground loops, we really don't have ground loops, just multiple
paths. The current from your pitot heat and landing light is going to
return to the battery negative through the airframe to the firewall.
This is not going to be a problem.

The real advantage of the single-point ground is to reduce the number
of multiple path returns, especially for more sensitive equipment
like avionics.

What you propose, grounding your pitot heat, positions lights, and
landing light(s) to the airframe will work just fine and will not
cause any problems.

Brian Lloyd 361 Catterline Way
brian-yak AT lloyd DOT com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
— Antoine de Saint-Exupéry


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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery
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nuckollsr(at)cox.net
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PostPosted: Thu Aug 03, 2006 6:37 pm    Post subject: Ground Block On Firewall Reply with quote

At 10:47 AM 8/3/2006 -0400, you wrote:

Quote:


I wish to install one of the multi tab type ground blocks to the stainless
steel firewall on my RV8-A. This will have a block of tabs on both sides
of the firewall.
Do I need to anything special to the stainless steel to prepare the surface?
Since I will be grounding many items in the aircraft to these gounds, I
want to insure that this is a really good ground.
Also is it necessary to have the mounting bolt go into one of the aluminum
angles behind the firewall or is it enought just to have the bolt go
through the stainless?
Any help or comments are most welcome.

The whole purpose of the ground block is to take the firewall sheet
out of the equation irrespective of what ever material it is made
of. When you use the single point ground block that is THE ground.
The airplane (if it happens to be metal) becomes grounded to it,
not the other way around. If the airplane happens to be plastic,
then obviously, the airplane doesn't get 'grounded'.

So your concerns about the ground-block to airplane interface
are not well founded. If your airframe local grounds are limited
to the items oft suggested (wing mounted lights, pitot heaters,
strobe supplies) then simply bolting a clean ground block to stainless
firewall with hardware supplied is quite sufficient. I'd torque
the fasteners to max rated for the materials and call it good.

Even if you remote mount the battery with local grounding

(See:
http://aeroelectric.com/articles/Battery_Grounds/Battery_Grounds.html )

the technique described above is quite sufficient. The key words
are "clean" and "pressure."

The "fat" bolt and nuts are 5/16" brass (typically 1/2 yield strength of
steel so 50 in-lb torque) . The smaller holes in the ground
blocks should be bolted to the firewall with 10-32 steel screws
and metal lock nuts (25 in-lb + "drag torque"). See section 7
of AC43-13.

If the parts go together clean, then sustained pressure will keep
the contact areas clean for the lifetime of the airplane.

Bob . . .


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nuckollsr(at)cox.net
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PostPosted: Thu Aug 03, 2006 6:37 pm    Post subject: Ground Block on Firewall Reply with quote

At 12:29 PM 8/3/2006 -0700, you wrote:

Quote:


But what about stuff that's grounded locally on the wing such as pitot
heat, landing lights, etc.? That stuff's ground has to make it's way to
the forest of tabs on the firewall and back to the battery through the
stainless firewall. If the firewall is as poor a conductor as has been
recently said,

it's not necessarily a "poor" conductor, just harder to achieve
and sustain good electrical connection . . . clean and pressure.

Quote:
doesn't that raise the possibility of ground loops as the
pitot heat, lights, etc. try to return and wind up finding an easier
route such as through the chassis of a radio?

not if you get clean and apply pressure . . . and since all radios
and other potential victims for noise are NOT grounded to the airframe
but to grounding features described in Figure Z15, then ground
loop possibilities are eliminated no mater what else is going on
in the system.

Bob . . .


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