fatbillybob

I have a hardware question for you guys. When mounting say a lap belt to your floor or rollcage many of the floor anchors or lapbelt chassis tab or clavis link brackets are welded. Then you clip-in or bolt-in your lap belt anchors to the anchor/clavis/tabs. Why don’t fabricators save weight and possible failure points by just welding a chassis tab the same thickness as a lap belt “clip-in anchor” and mill a 2” x 1/4” slot in it for the belt to go through? It just seems so much cleaner. What am I missing?

For the ultra technical a bolt in lapbelt anchor box stitched is better than a bolt-in or clip-in harness anchor retained by a anti-slip clip with typical wrap. But 90% of harness are sold with anti-slip clips because the makers do not know the ultimate belt lengths needed. So the only time I can see bolting a “bolt-in” lapbelt anchor to a clavis link bracket is if you have a box stitched “bolt-in” anchor and known lap belt lengths. Any comments?

RedlineMan

Hey;

Part 1 - I think the answer to part 1 is Heat Treated Steel. If I understand what you are saying, any fabricated mount tab that you sought to snap a spring clip belt end too directly would not be heat treated steel like a eye bolt or even a grade 8.8> bolt. Since you would have to place the end of the hole where the clip rides very close to the outside edge of the plate (and therefore very thin) to allow it to pivot freely, I would think this would offer more of a failure mode than more parts and pieces. Non heat treated steel is not particularly impervious to abrasion is such situations. Nope, wouldn't go there.

Part 2 - Yes, stitched terminus belt ends are the best, but as you note they are rather limiting. For what it is worth, you should try to avoid at all costs using open belts with 3-bar slide adjusters for lap belts. If you have ever seen test footage of how these items act when a force is applied, it will scare you to death... or should. They SLIDE until they bottom out against the the end plate/clip. For that reason, "if you must" use 3-bar slides on your lap belts, you want as little "open loop" of belt between the slider and the endplate/clip as you can possibly get.

Also, you should ALWAYS triple loop your belt through any 3-bar slider to lock it better and help pevent belt slip.

fatbillybob

Perhaps you are correct but I do not know if these pieces are heat treated. However, my thought was not to weld an existing off the shelf bolt-in anchor by its thin metal but to make from similar 3/16" plate about twice the size but with slot milled for the belt. Then the mass of metal will overcome the lack of heat treat I would think.


[/QUOTE] Since you would have to place the end of the hole where the clip rides very close to the outside edge of the plate (and therefore very thin) to allow it to pivot freely[/QUOTE]

You brought up another technical issue that of free pivoting. Assuming you angle my proposed weled brackt in the right position free pivot to take stress off the belt to prevent cutting under pressure if there is such a think would be largely eliminated unless the violence of a crash alters the terminal position of said belt alot. If free pivoting of a bolt in anchor is mandatory then the clavis double shear bracket is the only way to mount a belt anchor to put all things in your advantage.

[/QUOTE]- Yes, stitched terminus belt ends are the best, but as you note they are rather limiting. For what it is worth, you should try to avoid at all costs using open belts with 3-bar slide adjusters for lap belts. If you have ever seen test footage of how these items act when a force is applied, it will scare you to death... or should. They SLIDE until they bottom out against the the end plate/clip..[/QUOTE]

Wow! I know they had a longer lock-up time but I did not know they slipped to that extreme. 90% of guys are using these in ametuer racing. Do you know if once you set-up your car belt lengths if you can have anyone "after the sale" box stitch in bolt-in anchors? Can that be a do it yourself action? It looks low tech but if done wrong you die. It looks like anyone with a sewing machine and proper thread could do it .

Thanks for your replys

RedlineMan

Re: 3-bar slides;

Yes, they will slip until the slack is gone. The ones pictured below would actually slide until all the slack is gone and the loop finally cinches tight around the belt bar.



I guess I really don't understand what you are trying to work out re: belt termination points. I'd need to see a drawing to understand it.

Cory M

I see a couple of problems with what you're proposing (assuming I understand it right). One is the fact that your belts couldn't pivot at the base which could cause them to bunch up and rub in the corners of your mount. When fabric rubs on metal, the fabric always loses. Second is that a simple plate with a slot cut in it will be pretty sharp unless you really go the extra mile deburring it, ever notice how all of the factory belt ends have smooth radiused edges. The factory parts are also chrome plated to prevent corrosion. You can lookup the tensile strength but I don't think the lack of heat treat would be an issue. As to your question of why fabricators aren't doing it now- simple, it's more work than just bolting on off the shelf parts. I would also imagine that they would assume a big liability risk by manufacturing their own seatbelt parts, which I'm sure would void the belt manufacturers warranty. In this case I just don't think the pro's outweigh the cons. I agree with your statement about stitched belts but that could be a pain if multiple people drive the car and need some added adjustment, especially with instructor ride-alongs.

fatbillybob

Cory...I agree with you about free pivot. It "could" be an issue that is largely ignored. I wonder how many G's a bunched up belt could take. I have never seen anyone use a steel spacer in the bolt-in belt terminus that allowed free rotation in the tyipcal single shear bolt down often seen. So this problem is already happening but we are not seeing torn belts to my knowledge. As to radiusing the milled peice I agree again and that is an absoulte must do. John...basically more stuff means more stuff to go wrong just like the unknowing who haev too big loops in their 3 bar sliders. So my proposal was to make basically a large 2 3/4" x 2" bolt-in seatbelt anchor that was welded rather than bolted. As you pointed out in an earlier post the current bolt-in's haev thin metal at the bolt hole and not suitable for just welding this small surface area in my opinion either hence my design of a larger weld-in seat belt anchor. I just thought is would be easier, cleaner, with less failure to just weld in. Does anyone know if someone will "W" box stitch anchors on to your harness after they have been purchased? Is it as easy as having the local seamstress sew in a "W" box with appropriotly thick thread?

RedlineMan

Re: Stitching;

I'm sure that any upholstery shop could sew it, but there is a bit more that goes into that stitching than just the sewing. My Simpson belts have sewn in ends. I believe the Schroth Hybrids are as well. There must be others.

As for the belt attachment, I'm still not sure what you are talking about. Are you talking about welding these in place?

fatbillybob

John,

Yes welding in place. Imagine the bolt-in anchor as pictured but flat plate about 25% wider ( for beefier strength) and the triangular part as a rectangle , I.E. more metal and larger surface area to weld. Making the plate larger eliminates potential heat treat issues with size vs. strength. By doing this you would eliminate a welded chassis tab or clavis bracket to hold the anchor in your picture , no nut, no bolt, no lock washer, and no washer and maybe no safety wire on your bolt (I always drill mine). Less parts = less parts to maintain and no bolts to ever come loose, less weight it all adds up. It is clean and neat but then you must use the 3 bar slider that 90% of people use and the webing may saw on the mounting plate besause the welded mounting plate will not rotate and freely move.

fatbillybob

Sidebar:
Notice that the sparco kit in your picture also probably does not freely move when bolted. There is no steel sleeve that the anchor rotates around with bolt inside and the bolt has no grip area. This is not intended for proper shear. Also, since the plate is not set-up to rotate webing can bunch up. That's being really technical and it likely does not matter. That is why I think I can make a larger welded mount as I propose. You see often times I just see that sparco anchor bolted to metal 18G floors with a backside washer. Proper mounting IMO is with a double sheer clavis bracket welded to a 0.80 plate welded to the floor or actually the cage and the sparco plate bolted with a proper drilled bolt having the proper grip length (the non-threaded part) that is the width of the clavis bracket all neatly safety wired. Now we are getting picky.

RedlineMan

OK, gotcha;

ARE YOU NUTS? You REALLY SHOULD have free rotation of your mount plate. When you move forward in a crash, the belt angles change and you need the mount to pivot forward and distribute load evenly on the mount plate and belt material. Any bunching of material risks a shear point of the material.

You are over thinking this. Just build your double shear clevis mount properly and be done with it. They are pretty foolproof if done right.



Alternately, if your chassis does not have them or they are positioned wrong for your needs, just build a single shear vertical (nut welded on a large plate) and weld it to the side sills.

gbaker

Go John!

I'm surprised the photo doesn't show a short bushing (slightly longer than the plate thickness) used inside the mounting hole specifically to allow the anchor to rotate. These are standard with the Hooker Harnesses we use for crash testing.

You'll see this whole harness mounting thing change in a couple of years.

Alan C.

There are lots of alloys out there that will more than make up for a lighter gauge. I wouldn't get to hung up on heat treated steel until the grade is defined. PH grades have much higher strength levels than your typical 1010's and 1020's. A 17-7 PH treated to condition R100 would have a T.S. of 175 ksi and a Y.S. of 115 ksi and still have an elongation of 9%.

I do like John's double shear example. I've seen cars with the tabs bolted in with no chance of aligning with the load.

fatbillybob

LMAO! John you crack me up. Yes I agree 100%. My last post last pargrapgh talked about the ideal double shear clavis mount as you pictured.

I do tend to overthink...too much time on my hands.

I say no way on the single sheer. as Alan C. says you end up with no plate movement without a steel spacer like I tlaked about earlier and GBaker commented about your sparco kit picture.

GBaker...how do you see all this mounting stuff changing in the coming years?

gbaker

FBB,

I love your posts! Perfect for working late on a Friday night. (Family out of town.)

Uh, well, I won't answer your question directly (I can but I won't), but will pose the question: What is the ideal location for mounting harness anchors?

Once that question is answered, the issue of anchor mechanics is secondary--and greatly simplified.

Have a good weekend.

Bill Verburg

Is there any preference for attachment place, upper or lower bar being the choices?