Through Firewall Gound Terminal
Posted: Wed Feb 21, 2024 12:34 pm
by BobDz
Today’s “invention”:
Through the firewall ground terminal complete with cockpit ground bus bar.
The plywood in the picture is the firewall.
When I get closer to needing/ using it, I will drill and tap several holes for 8-32 hardware.
The fun part was using my new “scotchbrite” belts on my 1x42 bench top belt sander. VERY happy with them.
Re: Through Firewall Gound Terminal
Posted: Wed Feb 21, 2024 3:46 pm
by Bryan Cotton
Looks good! I’d recommend using lock nuts on the outsides.
Re: Through Firewall Gound Terminal
Posted: Wed Feb 21, 2024 4:03 pm
by BobDz
Bryan Cotton wrote:Looks good! I’d recommend using lock nuts on the outsides.
I have internal star lock washers on there. Off to the hardware store soon to complete this little project.
Re: Through Firewall Gound Terminal
Posted: Wed Feb 21, 2024 5:17 pm
by BobDz
Drilled and tapped! Added ring terminals to verify my spacing and thought process. Nine ground connections shown. Can easily be 18 by putting the ring terminal back to back. AC 43.13-1B 11-98(f) allows 36.
Very neat. Very clean.
Success!!
Re: Through Firewall Gound Terminal
Posted: Thu Feb 22, 2024 6:07 pm
by lakespookie
If you double up i would change the approach direction so the top comes in over the top and the bottom comes in from the bottom that will make it a little cleaner with double stacking.
Re: Through Firewall Gound Terminal
Posted: Thu Feb 22, 2024 6:43 pm
by BobDz
lakespookie wrote:If you double up i would change the approach direction so the top comes in over the top and the bottom comes in from the bottom that will make it a little cleaner with double stacking.
Good idea!
I’ve actually come up with multiple solutions if I need to double up. In reality, at least for my plane, they won’t be needed.
Re: Through Firewall Gound Terminal
Posted: Thu Feb 22, 2024 10:02 pm
by Skippydiesel
I apologise in advance for being “picky” -
First - Great idea! Probably don’t need such a heavy bolt.
Why not use brass/copper through bolt & nuts, for least electrical resistance, minimised potential for electrolysis and I agree with Brian, use a lock nut for best anti vibration security.
Re: Through Firewall Gound Terminal
Posted: Thu Feb 22, 2024 10:47 pm
by Bryan Cotton
I had a piece of copper I was going to use, and that stuff is heavy! Aluminum has been good enough for me. Threads in aluminum can be sketchy so I use a nut on the back side.
Re: Through Firewall Gound Terminal
Posted: Thu Feb 22, 2024 10:59 pm
by BobDz
Skippydiesel wrote:I apologise in advance for being “picky” -
First - Great idea! Probably don’t need such a heavy bolt.
Why not use brass/copper through bolt & nuts, for least electrical resistance, minimised potential for electrolysis and I agree with Brian, use a lock nut for best anti vibration security.
Not “picky” at all. I always appreciate a second set of eyes. That’s why i posted this. Otherwise I would have tunnel vision.
This is my first iteration and basically used what I had on hand. I used brass because (1) I had it, and (2) most all of the commercial bus bars I have seen are brass. In hindsight (always 20/20), the 3/8" stud IS too big. I could easily use 5/16". And I do have tons of 5/16" threaded rod. And it can, and will be, much shorter.
And I do agree with Bryan that it should be a lock nut, and it will be.
Re: Through Firewall Gound Terminal
Posted: Thu Feb 22, 2024 11:02 pm
by BobDz
Bryan Cotton wrote:I had a piece of copper I was going to use, and that stuff is heavy! Aluminum has been good enough for me. Threads in aluminum can be sketchy so I use a nut on the back side.
I could easily use aluminum, and probably should. Afterall, if I used the airframe as ground it would obviously be aluminum.
Appreciate the comments. Helps to refine my project. And prevents tunnel vision.
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 12:12 am
by daleandee
BobDz wrote:
Bryan Cotton wrote:I had a piece of copper I was going to use, and that stuff is heavy! Aluminum has been good enough for me. Threads in aluminum can be sketchy so I use a nut on the back side.
I could easily use aluminum, and probably should. Afterall, if I used the airframe as ground it would obviously be aluminum.
Appreciate the comments. Helps to refine my project. And prevents tunnel vision.
Nicely done and the more you develope it the better it gets.
FWIW I bought a grounding block from B&C Specialities (forrest of tabs) with 24 connections on it and found out that I needed more than that. Of course I have an electrically dependent airplane but I never imagined I’d need that many connections …
Dale
3.0 Corvair/Tailwheel
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 9:33 am
by BobDz
daleandee wrote:
BobDz wrote:
Bryan Cotton wrote:I had a piece of copper I was going to use, and that stuff is heavy! Aluminum has been good enough for me. Threads in aluminum can be sketchy so I use a nut on the back side.
I could easily use aluminum, and probably should. Afterall, if I used the airframe as ground it would obviously be aluminum.
Appreciate the comments. Helps to refine my project. And prevents tunnel vision.
Nicely done and the more you develope it the better it gets.
FWIW I bought a grounding block from B&C Specialities (forrest of tabs) with 24 connections on it and found out that I needed more than that. Of course I have an electrically dependent airplane but I never imagined I’d need that many connections …
Dale
3.0 Corvair/Tailwheel
Thanks Dale!
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 9:48 am
by Friesen5
I did something similar almost 20 years ago. It’s providing a solid ground for my Sonex. I took a photo of it yesterday, so I’ll try to attach it.
Mervin Friesen
Sonex 122
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 10:02 am
by BobDz
Friesen5 wrote:I did something similar almost 20 years ago. It’s providing a solid ground for my Sonex. I took a photo of it yesterday, so I’ll try to attach it.
Mervin Friesen
Sonex 122
That definitely is the lightest solution I have seen!
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 10:04 am
by BobDz
The things I learn in the rabbit hole.
Looks like my next iteration should be a brass stud with an aluminum bar.
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 10:37 am
by Bryan Cotton
Looks good Mervin!
Like Dale, I find that too many ends up being not enough. Two lugs per screw is really just a serving suggestion.
3/8 is massive. I wouldn’t go bigger than #10, but I would support both ends with that design. Or mount it in the middle possibly.
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 10:45 am
by BobDz
Bryan Cotton wrote:Looks good Mervin!
Like Dale, I find that too many ends up being not enough. Two lugs per screw is really just a serving suggestion.
3/8 is massive. I wouldn’t go bigger than #10, but I would support both ends with that design. Or mount it in the middle possibly.
I originally used 3/8" because on the engine side of the firewall there will be two 2/0 cables attached and I have 2/0 x 3/8" lugs. I also have 2/0 × 5/16" lugs. So I will downsize to 5/16.
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 10:54 am
by BobDz
But that brass angle does look tempting.
OR…
I will soon have a few scraps of 1/8 ×1 aluminum angle!!
This rabbit hole is getting deeper…
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 11:00 am
by Bryan Cotton
As bad as steel looks on that list, consider that resistance/conductivity is also a function of cross section area and length. The length is very small, and the cross section area is large. It really won’t matter what you select.
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 11:04 am
by Bryan Cotton
BobDz wrote:I originally used 3/8" because on the engine side of the firewall there will be two 2/0 cables attached and I have 2/0 x 3/8" lugs. I also have 2/0 × 5/16" lugs. So I will downsize to 5/16.
2/0 is massive! The Aerovee manual specifies 6ga minimum and I think I used 4ga.
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 11:07 am
by BobDz
Bryan Cotton wrote:As bad as steel looks on that list, consider that resistance/conductivity is also a function of cross section area and length. The length is very small, and the cross section area is large. It really won’t matter what you select.
Very true. I am way over thinking this!
Right now I’m thinking of 5/16 brass threaded rod (toilet flange bolt) with a 4" piece of 1/8 × 1 aluminum angle (scrap from longeron). Using the angle will offer many, probably too many, possible terminal locations. Should be the neatest and coolest iteration yet.
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 11:17 am
by BobDz
“If you’re going to make it, make it beautiful!” Bob Emser
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 12:31 pm
by BobDz
For illustration purposes, my original brass bus bar with 18 terminals neatly installed
Add a locknut to the backside, and you get 18 more.
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 2:50 pm
by BobDz
My “final” answer (?)
I will have the correct lock washers for the final install.
13 holes will accommodate a maximum of 52 terminals.
1/16 ×1" angle is much lighter. The 5/16 brass stud will accept the 2/0 cable(s) on the engine side.
Time for lunch!
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 3:37 pm
by BobDz
And no, the irony of doing a distraction project that required drilling and deburring because I didn’t feel like working on the plane doing drilling and deburring, is not lost on me…
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 9:05 pm
by Skippydiesel
On my last aircraft (composite airframe) I installed a length of aluminium angle (from faulty memory 25 x 25 x 2mm) behind the instrument panel, from one side of the fuselage to the other.
I pop riveted a top/bottom row of male spade connectors (with a dab of electrolytic grease) ie two connectors per rivet, at strategic points, corresponding to instruments in the panel.
Both ends of the angle were securely connected into the aircrafts earth/ground (-) return ring circuit (including external anti static fuel terminal).
The aluminium angle earth buss facilitated short cable runs from each instrument and provided an excellent low resistance earth return.
It also acted as a handy support for the cable loom & other loose “stuff” behind the panel.
Some may frown on the use of spade connectors however I have always found they work well, when correctly installed. They are a low weight, much less fiddly solution, compared with a screw/nut fixing (I always drop either the nut and or washers, into the depths of the aircraft, taking much time consuming/frustrated searching to find).
Re: Through Firewall Gound Terminal
Posted: Fri Feb 23, 2024 9:17 pm
by BobDz
Skippydiesel
I certainly see the use of having the angle completely across. Lots of uses for that. And you would probably have the shortest ground wires.