3 point seat belt install

[68Broncoz]

Has anyone installed these poison spyder machined seat belt Bungs? They required drilling a 3/4 inch hole thru the roll bar and welding in place. They are about 1 7/8" long.

Tom's bronco 3 point install comes with a 3/4" bolt to drill thru the roll bar.

https://www.morris4x4center.com/poi...tent=dynamic_&utm_campaign=dynamicretargeting

Debating which way to go.

Chris

 

[pcf_mark]

There is zero chance I would ever drill a hole in a roll bar and install this. Zero. The NHRA would disqualify a car if that was done to the roll bar.

Just do this instead:

https://www.summitracing.com/parts/...MIlL6q2_bm6AIVUj0MCh3DbwgfEAQYASABEgIcGfD_BwE

No damage to the roll bar and the bolts are in double shear - significantly stronger.

 

[Steve83]

Since an eb isn't a HR, and will never be raced, drilling the cage is fine. But I just weld in common nuts.

(phone app link)


(phone app link)

 

[spap]

I used bungs that you just drill one hole and have it welded does not go all the way through. If you hit something so hard in a bronco that the seatbelt bung is going to make the roll bar crack your going to the ER anyways

 

[cs_88]

I used the Poison Spyder bungs on my cage and wouldn’t hesitate to use them again.
They are very nice heavy duty bungs and are a great size for my 1 3/4” cage.
They are 7/16” fine thread which worked perfectly with my humvee belts hardware.
I also mounted two of them at the front of the cage to support the windshield.

 

[pcf_mark]

It's your safety. There was a member on here who posted pics of his roll bar folding from a simple roll over. It did not go on the roof just the side but it must have had enough energy to get partially onto the roof / side and it just bent the roll bar. Your rig weighs over 4000 lbs plus it is moving so all that energy concentrated on a small point can cause a failure. I never get the "it is not a hot rod" I am simply citing an industry accepted safety standard. 60 years of safety evolution in non-stock vehicles.

 

[Steve83]

There are MANY industries, each with its own set of safety standards. Why not choose neurosurgery standards? Or cabinetry standards? Or poodle grooming standards? They each have more than 60 years of safety evolution.

Because none of them are relevant to early Broncos, just like NHRA standards.

There was a member on here who posted pics of his roll bar folding from a simple roll over.

Did it fold at a drilled & welded seat-belt bung? Did it ONLY fold there? Was it an actual roll bar that met NHRA standards before the bungs were drilled in, or was it just a cosmetic bar that would have folded no matter what? How about posting a link to that thread, or just embedding those pics in this thread?

 

[spap]

Both valid points, and it is how far the owner wants to go. The fact that a 3 point seat belt is going in compared to a lap belt is a huge improvement. Definitely would use a welded in bung before drilling a hole for a bolt to go through the roll bar.

I bought both of my daughters cars based on safety ratings,

 

[Remos69]

I used a split collar tube clamp and then drilled and welded a heim bung. Held onto place with 6 Allen bolts. Everything from Amazon.

 

[Skinnyr1]

I installed the welded bungs. Someone makes clamp on type too if you don't want to drill it. No matter what, it is an improvement over stock. 3 point belts, 6 point cage.

If I ever roll it over, I expect it to be a total loss. My goal isn't to roll it, I left it stock height.

Personally, I'm not worried about the bungs pulling out. I think the bigger concern for these rigs is what the roll cage is attached to. Rusty sheetmetal and what not.

 

[langester]

I machined out my own bungs for the lower seat belt mounts in the cage drilled through the tube and welded on both sides. I used collars similar to Remos69 for the upper mounts, that way if I change seats I can change the height of the upper belt mount.

 

[wrenchjockey]

Chris,
I did the same setup. I used these bungs and welded them in

https://www.summitracing.com/parts/aaf-all18552

Then I used these shouldered seat belt anchor bolts and the worked and fit perfect!


https://www.summitracing.com/parts/oer-sb193

 

[mattyq17]

My BIL made these up for the seatbelt mounts.

 

[pcf_mark]

Geez Steve83 you have 100 more years and builds than me and came in pretty hot. Any professionally engineered and vetted seat belt installation should be considered as solid information when making a decision. Weakening a roll bar is logically wrong to me but I only drive my crap box on the street. Welding on tabs seems so easy to me.

The site is great because people share experience. I have no idea if I can ever find those pics but the bar bent right at belt anchor bolt for the upper bracket. I'll never forget it because he had an empty car seat in the back seat.

 

[Steve83]

It's called a discussion forum for a reason - I'm discussing the topic. No, we're not all professional engineers, and very few things we do to these trucks are professionally engineered. But that's not what we're discussing, so don't get dramatic.

How exactly do you think welding in a nut weakens the tube? Yes, there's a hole, but it gets filled with a nut or bung that's between 3 & 6 times as thick as the tube wall that was removed. Then that gets filled with an even-harder bolt that's 10-15 times as long as the tube was thick. So the bolt will never compress or allow the nut/bung to compress, and the nut/bung isn't likely to stretch. So where's this weakening you're discussing?

If you think the weld causes some weakness, then your welded tabs do the same.

Yes, I like discussion forums, too, for the same reason. And I'm looking forward to seeing those pics, if you find them.

 

[68Broncoz]

All thanks for everyone's comments and really didn't mean to start a controversial discussion.

I do appreciate everyone's input it helps me make the right decision for my Bronco and how it will it be used.

Thanks

Chris

 

[pcf_mark]

My last thought on this (no I did not find the pics). Would you drill a hole through your driveshaft, insert a bolt or bung, re-weld it and then drive it super hard? Do some hole shots? Climb some rocks? Probably not because you understand how the force is distributed through the skin of the driveshaft. The energy is going to concentrate at the change in the wall of the tube. The roll cage tube is the same. When you pierce it - regardless of how well you weld it or what you put in the hole - you have created a difference in the section width. The tube is fundamentally weaker here. The real problem is this change to the tube is using along the length where it is the weakest. Not at a junction where several tubes intersect.

Welding something to the outside caused significantly less impact because the vast majority of the tube is not impacted.

 

[Steve83]

Would you drill a hole through your driveshaft, insert a bolt or bung, re-weld it and then drive it super hard? ... Probably not because you understand how the force is distributed through the skin of the driveshaft.

You're right: I understand how the oscillating torque on a paper-thin driveshaft skin that has to remain balanced at 7,000RPM is entirely different from the compression & bending applied to a thick cage tube wall. Your comparison is like apples & eggs.

Welding something to the outside caused...

...exactly the same change in section thickness as the bolt in the bung.

And no, it doesn't make the tube weaker there; it makes it stronger, OF COURSE, because there's so much more material. What you're confusing it with is a stress riser, which occurs at a SUDDEN & substantial change in the section. But a welded bung & bolt don't create a stress riser because the change is neither sudden nor substantial. But even if it did, that's still not a weakness because it still doesn't make the tube weaker. It would make that area of the tube stronger, which would make it flex less (given the same loading), meaning the point of the sudden change would have to flex more, and over time, that causes work-hardening, and stress fractures, leading to failure. But only from cyclic loads at or near the structure's capacity, which doesn't happen to a cage.

 

[charlie6976]

My last thought on this (no I did not find the pics). Would you drill a hole through your driveshaft, insert a bolt or bung, re-weld it and then drive it super hard? Do some hole shots? Climb some rocks? Probably not because you understand how the force is distributed through the skin of the driveshaft. The energy is going to concentrate at the change in the wall of the tube. The roll cage tube is the same. When you pierce it - regardless of how well you weld it or what you put in the hole - you have created a difference in the section width. The tube is fundamentally weaker here. The real problem is this change to the tube is using along the length where it is the weakest. Not at a junction where several tubes intersect.

Welding something to the outside caused significantly less impact because the vast majority of the tube is not impacted.

But, has this single seat belt hole in the roll bar compromised the intended use of the roll bar in the eb? Not race intended. Drill the hole if that is what works for you. Example: https://s3.amazonaws.com/cdn.wildhorses4x4.com/downloads/WH/3627 07-24-18.pdf