Frame grounding points

[chevynut]

I need to put two grounding studs/pads on my frame and want to make them as electrically conductive as possible, so I've been trying to figure out the best way to do it. My battery is behind my passenger wheelwell, and I have a #1 positive cable running up to the starter through a kill switch. From the battery I have a fairly short #1 ground cable that I need to attach to the frame. I will also have a #1 cable from the engine block to the frame in front, so the frame is my negative conductor. Then there are two other body grounds, a 6 gauge wire going from the battery to the body, and another ground from the engine block or frame ground stud to the body.

I could simply weld a steel bolt to the frame and attach the cable to it, but that seems crude and potentially resistive not to mention the corrosion issues. Carbon steel isn't that great of a conductor, and stainess steel is much worse than carbon steel.

I've been thinking about making a short brass cylinder, drilling and tapping a 5/16" or 3/8" hole in the center, then brazing or hard silver soldering it to the frame to get a good electrical connection. To protect it from getting painted, I would simply put tape on top of it.

What have you guys done with your battery relocations to accommodate the ground connections?

[OLKY55]

I can't take credit for the idea, as I believe it came from RickL. I welded a 3/4npt half coupling to the frame, and screwed a brass pipe plug in it. The pipe plug has a square head, which I tapped for a 3/8-16 and attached my cables to that. I did the same thing up front by the engine.

[chevynut]

Thanks for the idea olky55. So what makes that approach better than just welding an internally threaded steel cylinder to the frame? Is it the connection between the cable and the brass?

I thought about using silicon bronze to attach the cylinder, but the electrical conductivity is about the same as carbon steel. It would be nice to get a full wetting of the underside, that's why I thought silver solder would be a good choice.

[OLKY55]

You don't have to worry so much about the brass corroding where the lug attaches. You don't have to worry about soldering dissimilar metals. Also, I like that that the plug can be replaced, if necessary.

I think RickL suggested it, and I had previously done the same for offshore oilfield equipment. I had used a steel boss for grounds, but there was always a problem with saltwater corrosion. The brass plug with a little grease sealing the connection solved that problem offshore.

[Rick_L]

That indeed is something I've been suggesting on these forums for a while. The reason for the brass is it won't corrode and you don't have to paint it. The pipe thread's interference helps make a good connection there.

I expanded on a technique from my work years ago where we used to provide a ground lug using a brass bolt brazed to a truck frame. Only problem there was that brazing required flux and if you didn't clean that well your paint wouldn't stick to the steel. But it was easy to make a good connection to the brass stud. To me welding the coupling to the frame and using pipe thread just seems a bit cleaner.

[OLKY55]

This is the only picture I could find of mine. You can just see the coupling.

may235.jpg

[NickP]

With your TIG tallent, these might work pretty well. 1/4" NPT Weld Bung.

[chevynut]

Thanks for the great idea Rick and Olky55. Olky55, that looks like your radiator drain bung, not your ground!

I went to HD to get some couplings and brass fittings, and I decided that 3/4" pipe was much bigger than what's needed. I ended up getting two 1/2 x 1/8" brass reducer bushings and after messing with the black iron pipe on my lathe, I decided to just make my own frame bushings out of mild steel tubing. It's not as brittle and actually has a little better conductivity, but I'm not sure that matters much.

I tapped the frame bushings to 1/2 NPT and tapped the brass reducer bushings to 3/8-24. I would have liked to go 3/8-16 but the 1/8" pipe thread was a little too big, and worked well with the fine threads.

Here's my pieces:

20150319_001.jpg 20150319_002.jpg

And here's how they fit together. The 1/2" reducer bushing is just about the same size as the cable lug.

20150319_003.jpg

Now I need to drill some holes in the frame, weld the bushings in, and put a plug in them for painting. Should make for a nice, clean installation.

[NickP]

For me, your attachments don't seem to be working.

[OLKY55]

LOL. Okay, here's a better pic.

20150319_190848.jpg

[chevynut]

Got them welded in....thanks again for the great idea guys. The brass fitting will sit lower in the bung when I assemble the car.

20150320_003.jpg20150320_007.jpg

[WagonCrazy]

I think ill do this same frame grounding strategy on mine too. thumbs up for the pics.

[tgolfguy80@yahoo.com]

Hello I’m flattered to be joining I know I will be learning a great deal from you folks and hopefully I can throw in some helpful things for someone I have a 56 nomad that I’ve owned forever 30 years and Mr Ernie jitter god rest his sole helped me a great deal on it yrs ago