3 Point Seat Belt Installation Questions

cj8oh8

Basic User
City
Kailua
State
HI
#1
I have read through a ton of posts about converting from 2 point seat belts to 3 point seat belts and I have a couple of questions for everyone. I have an idea of what I think I want to do, but I want some expert opinions on whether or not it is safe and good way to go.

I am thinking about getting these

http://shop.poisonspyder.com/Machined-Steel-Seatbelt-Bungs-p/14-19-031.htm

and cutting the wider end off. Then drilling a hole through the front of the roll bar in the proper location, sliding these modified tubes in and welding a ring around the front. Because of the slanted roll bar in the back I cant access to weld the back, is a weld around just the front enough?

Thoughts?
 

walkerhoundvm

Just trying to stay upright
LIFETIME
CJ-8.com Member
City
Cave Creek
State
AZ
#2
Dunno, but aloha and welcome to the forum! I grew up near Kahaluu :)

You're not gonna get off that easy without posting pictures, you know ;)
 

pav1

Legacy Registered User
City
Acton
State
ON
#3
I was wondering the best way as well.

Can a nut and large washer be fished up from the bottom of the rollbar?
 

Bad Karma

Captain Sarcasm
LIFETIME
CJ-8.com Member
City
Garden Hill, Ontario, Cana
State
da
#4
TMR has those as well. Made and sold in Ontario, save getting screwed with border fees.
 

Spieg

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Aurora
State
CO
#5
Those look like they would work well. A friend used a couple of large coupling nuts from the hardware store for about $2 each.
 

Randyzzz

Blown Budget
LIFETIME
CJ-8.com Member
SOA Member
City
Redmond
State
OR
#6
It really needs to be welded on both sides of the tube- a longer piece that goes all the way through. The factory roll bar isn't that thick.

Get a piece of DOM and tap the threads, and weld that in.
 

Spieg

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Aurora
State
CO
#8
The back side of the tube where the insert would go is right in the down tube area isn't it?
Yes, the mount is directly across from the support tube. Would be tricky to weld both ends. Not sure if it would be possible to fish a nut up from the bottom of the tube. As I said earlier, a friend of mine welded a coupling nut in from the front of the bar, and it worked fine (very sturdy).
I also ran into this at BTF... a variety of sizes and thread patterns (and a few $ cheaper);
http://www.bluetorchfab.com/Product/1316/BTF-Seatbelt-Bung.aspx
 

gr8dain

Scrambler Junkie
LIFETIME
CJ-8.com Member
SOA Member
City
Ashburn
State
VA
#9
There is a very good write up here on this forum where a plate was fished up through a trap door cut into the bar and welded back closed. You should be able to find it. I took pics of measurements for the original poster. I am on my phone or I would try to find the thread for you and post the link. Sorry.
 

hefavitzen

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Rock Hill
State
SC
#11
I am gathering parts for getting 3-points installed currently. I found a local shop that specializes in Porsche racing cars including roll cage installations. They are going to drill a hole straight through the entire bar, put in the appropriate tubing straight through and have the front part actually sticking out a bit to support the seat belt bolt since it has to stick out a ways to get past the hard top. They will leave the back side open or will weld it up, depending on my need to screw anything into that point, such as for a fire extinguisher.

that gives me a mount point that is welded at both ends. Since this thing will hopefully save me if one day turns horribly wrong, I'm hoping this is the way to go. I asked them to photograph this install since I probably won't be there for it, which they are happily going to do.

They figure it will take 3 hours and they are $90 an hour labor. Not as bad as I thought.

I was walking through the shop feeling dirt poor and slobbering all over these incredible cars in various states of repair, refurbishment or upfitment when I spied a set of Dana 60 axles. Those certainly were out of place! I asked about them and the owner took me to the next room where his M-715 was also getting a work over!

Anyway, you might want to consider finding a shop that can add welds to both ends of the mount point.
 

Randyzzz

Blown Budget
LIFETIME
CJ-8.com Member
SOA Member
City
Redmond
State
OR
#12
I am gathering parts for getting 3-points installed currently. I found a local shop that specializes in Porsche racing cars including roll cage installations. They are going to drill a hole straight through the entire bar, put in the appropriate tubing straight through and have the front part actually sticking out a bit to support the seat belt bolt since it has to stick out a ways to get past the hard top. They will leave the back side open or will weld it up, depending on my need to screw anything into that point, such as for a fire extinguisher.

that gives me a mount point that is welded at both ends. Since this thing will hopefully save me if one day turns horribly wrong, I'm hoping this is the way to go. I asked them to photograph this install since I probably won't be there for it, which they are happily going to do.

They figure it will take 3 hours and they are $90 an hour labor. Not as bad as I thought.

I was walking through the shop feeling dirt poor and slobbering all over these incredible cars in various states of repair, refurbishment or upfitment when I spied a set of Dana 60 axles. Those certainly were out of place! I asked about them and the owner took me to the next room where his M-715 was also getting a work over!

Anyway, you might want to consider finding a shop that can add welds to both ends of the mount point.
This is how it should be done. The stock bar is thin, I think .095 wall if that, and I have heard it varies in thickness. You can't trust 1 linear inch of weld to hold the forces transferred in a collision- Look at this illustration-



Go to the extra expense of boring completely through the roll bar, and inserting a long piece of threaded thickwall DOM. After all, it's your life you're saving...not a place to go cheap.

The illustration came from here- interesting read. https://thescienceclassroom.wikispaces.com/Seat+Belts
 
Last edited:

BattleJeep

Basic User
City
Honolulu
State
HI
#13
I have an 85 with the stock 3 point. I'm over the Pali from you in the downtown area. Shoot me up if you want to take a look at what the factory did.
 

jims chop shop

Scrambler Junkie
LIFETIME
CJ-8.com Member
SOA Member
City
stafford
State
va
#14
What Hardware should be used to mount the rollbar to the floor, if not using the factory torx bolts, are grade 8 sufficient !!??
 
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