As some of you may be aware I recently purchased the BMW cart from Robbie after the challenge. I would like to reinstall a set of factory BMW seats in the cart in lieu of the racing seats that were in it at the challenge. I would like to also install the factory 3 point belts for use when I drive it around the beach. The b pillar is obviously not in the car anymore so securing the belt to the factory upper mount is not an option.
My question is would it be better to simply weld a nut to the roll bar or to use a through bolt with an inner sleeve? I imagine the sleeve option would be the stongest but figured I would get the hives opinion.
Sonic
UberDork
11/4/22 12:22 p.m.
In the past I have welded a sturdy metal plate to the cage in more than one side and through bolted the harness mount with a hole in the plate.
Can you cut the chunk of b pillar that the seatbelt bolts to and weld that to the roll bar?
In reply to Robbie (Forum Supporter) :
That may be a bit cumbersome. I am pretty sure the seat belt is height adjustable in the factory application. I will pull the b pillar apart tomorrow in the yard when I go to buy the seat belts and see if that is feasible. I figured a simple nut would be cleaner.
I think the nut would probably be fine, but just not a ton of surface area for the weld, and sometimes welding a nut screws up the threads.
If the nut won't work and you have to fab a bracket, the stock b pillar cut to size is a bracket made for you already. And yeah, the height adjustment is probably complication you don't need.
Sonic said:
In the past I have welded a sturdy metal plate to the cage in more than one side and through bolted the harness mount with a hole in the plate.
Yep this is a great way to do it, it's stronger than stock and you don't need to worry about potentially weakening tubes by drilling them.
Tom1200
UberDork
11/4/22 12:58 p.m.
Through hole with sleeve is what I would do. Although a plate welded to the cage would probably work as well.
I hate the idea of drilling a hole in roll cage tubing here is a rough sketch of what I would do
Two plates one on each side of a tube to anti crush a bolt going through welded attached to the roll cage
In reply to Apexcarver :
That makes sense. I was worried about the hole in the cage weakening the integrity. The two plates with a sleeve makes more sense.
Easy button:
Full Pipe Clamp Clamshell for 1.25" Pipe (bmisupply.com)
Weld it for even more beefiness. I use these to hang battens at the theater. Rated for something crazy like 5000 lbs
Mr_Asa
UltimaDork
11/4/22 2:12 p.m.
Curtis73 (Forum Supporter) said:
Easy button:
Full Pipe Clamp Clamshell for 1.25" Pipe (bmisupply.com)
Weld it for even more beefiness. I use these to hang battens at the theater. Rated for something crazy like 5000 lbs
So there is not a lot of information given on that page, but I don't think I would do this
Generally, lifting equipment/hangers are designed for a load that goes straight up or straight down, not at any sort of angle. Installing a seat belt anchor to something designed to fit into that world feels iffy.
Check out the note/disclaimer on the bottom of the page for McMaster part 3013T45 (first one i pulled up on their site.) Thats what I'm concerned with
https://www.mcmaster.com/3013T45/
3014T45 has a similar warning, but that one has the shoulders that 3013T45 lacks and the note mentions.
Lifting/restraining loads is serious bizness.
Mr_Asa said:
Curtis73 (Forum Supporter) said:
Easy button:
Full Pipe Clamp Clamshell for 1.25" Pipe (bmisupply.com)
Weld it for even more beefiness. I use these to hang battens at the theater. Rated for something crazy like 5000 lbs
So there is not a lot of information given on that page, but I don't think I would do this
Generally, lifting equipment/hangers are designed for a load that goes straight up or straight down, not at any sort of angle. Installing a seat belt anchor to something designed to fit into that world feels iffy.
Check out the note/disclaimer on the bottom of the page for McMaster part 3013T45 (first one i pulled up on their site.) Thats what I'm concerned with
https://www.mcmaster.com/3013T45/
3014T45 has a similar warning, but that one has the shoulders that 3013T45 lacks and the note mentions.
Lifting/restraining loads is serious bizness.
Good point. Remind me not to ride in it. 
Curtis73 (Forum Supporter) said:
Easy button:
Full Pipe Clamp Clamshell for 1.25" Pipe (bmisupply.com)
Weld it for even more beefiness. I use these to hang battens at the theater. Rated for something crazy like 5000 lbs
That is equivalent of a 25g deceleration for a 200lb figure, assuming that there are no leverage effects (straight pull vs. a pull with a very shallow angle that will multiply the load on the bracket)
Seems pretty close to the edge for me...
Agreed. Obviously with the car in question, having a safety factor of 2 on all equipment is the OP's imporante issue numerous uno.
True, but he was talking about attaching 3-point belts for cruising, not a race harness. Also, rated for lifting comes with a factor of 3-5. A wire rope rated for 2000 lbs pull is often rated for 600 lbs lifting. I think there is a generous safety factor involved. If you have a break strength of 9000 lbs, you don't have a working load greater than 3000. That 5000-lb clamshell (if that's what it's actually rated) might have a break strength of 15,000 lbs.
... but I do agree... that's likely rated at a linear pull, not angular.
Mr_Asa
UltimaDork
11/4/22 10:40 p.m.
In reply to Curtis73 (Forum Supporter) :
That linear pull is also likely tested under a gentle lead-in that won't immediately damage the lifting eye. Not really something that happens in an accident.
Pete. (l33t FS) said:
Curtis73 (Forum Supporter) said:
Easy button:
Full Pipe Clamp Clamshell for 1.25" Pipe (bmisupply.com)
Weld it for even more beefiness. I use these to hang battens at the theater. Rated for something crazy like 5000 lbs
That is equivalent of a 25g deceleration for a 200lb figure, assuming that there are no leverage effects (straight pull vs. a pull with a very shallow angle that will multiply the load on the bracket)
Seems pretty close to the edge for me...
But what about the lap belt? Won't the 200lb be split into roughly 1/3?
I would be weary of attaching the belts to the cage if the seats are not attached to the cage as well.
You can end up with the seat moving and the cage doesn't and the belt being useless or worse.
buzzboy
SuperDork
11/5/22 10:27 a.m.
In reply to wvumtnbkr :
That's pretty standard for racecars though, no? Most I've seen the seat is mounted to the floor and some of the belts are mounted to the cage.
buzzboy said:
In reply to wvumtnbkr :
That's pretty standard for racecars though, no? Most I've seen the seat is mounted to the floor and some of the belts are mounted to the cage.
Some people do that, for sure. I have part of the cage attached to the seat mounts.
It becomes more important when the cage is mounted to sheet metal and not to multiplane rigid areas of the car. If this cage is tied into the sills and each mounting plate covers horizontal and vertical planes, it's probably fine!
