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Lap Belt Anchor Point...

4K views 21 replies 10 participants last post by  ogre 
#1 ·
Hi All,

Prolly the wrong forum to ask. Over the years I've gotten accustomed to using 3-point belts, which were not an option in '63 cars. Take a look at this pic of the "B" pillar on my Rambler American and tell me if there's enough structure here to support the upper anchor point. I'm thinking I'd be better off with just a lap belt. If something were to happen, it seems like the entire pillar would cave in under the stress...

Russ
 

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#2 ·
anchor point, no. what you'd need to do is design a bracket that you can weld in there that will have a spread out anchor.
a T shape that is welded to the metal above the door and down half way on the b-pillar, made out of 1/4 plate would work.
adding seat/shoulder belts to a not belt car is shake of the dice; the car is not designed for it, but you want to add belts for safety.

same goes for floor mounts of your belts. a bolt with a fender washer would pull through the floor in a mild wreck.
i used 1/4x3x6 plates welded under the floor to anchor my seats, since my belts attach to my seats
there is no good place to mount a shoulder belt in a big window 55-59 chevy truck
and from experience i do not want a shoulder belt holding me up in a roll over as the roof on these trucks is weak weak weak. :D
 
#4 ·
same goes for floor mounts of your belts. a bolt with a fender washer would pull through the floor in a mild wreck.
Not necessarily, depends on the size of the washer and the force of the hit. Some belt systems come from the aftermarket with a washer that is, I'm trying to remember, I think 3/16" thick and 3" in diameter (7 square inches of area). We used to allow these mountings in anything that would go 10's or slower (135 MPH).

i used 1/4x3x6 plates welded under the floor to anchor my seats, since my belts attach to my seats
My hero. :thumbup:
 
#3 ·
I think you would be better off installing a simple hoop roll bar and attaching it to that instead of the b-pillar.

Otherwise you are going to have to add gussets to reinforce the area around where it attaches to. This distributes the load over a wider area making it less likely to tear when force is applied to it. Make sure it is thick enough. At the very minimum 3/16". Every seat belt anchor point I have seen that goes through sheet metal has a backer which distributes the load over a wide area like I mentioned.

Look at your S10 and make it similar to that.
 
#5 ·
No thanks on the rollbar, don't relish the idea of my nekkid brain bucket bouncing off that... Guess I'll stick with the lap belts, I can easily anchor them directly to the 2" x 4" rear subframe.

Thanks!

Russ
 
#6 ·
Seat belt anchors

Russ,
You didn't say if you had picked out what you were using for seats, but you could go after some seats with an integral shoulder belt system built into the seat. I know that some GM trucks, and even some of the bigger cars, and converts had the shoulder belts as part of the seat. Can't say for sure what other makes also did this, but I know there were a few. Just my $.02 worth.
Rick
 
#8 ·
Russ,
You didn't say if you had picked out what you were using for seats, but you could go after some seats with an integral shoulder belt system built into the seat. I know that some GM trucks, and even some of the bigger cars, and converts had the shoulder belts as part of the seat. Can't say for sure what other makes also did this, but I know there were a few. Just my $.02 worth.
Rick
I've already got the seats. They're from a Mitsu Mirage and have the lap belt attachment point on the tunnel side, but nothing else. It'll feel kinda strange to have only a lap belt, but I'd rather have that than have the shoulder point tear out and the whole thing become useless during an accident...

Russ
 
#7 ·
I'm sure there's a table of forces involved, a body's ability to withstand the point-load..... etc.

If you are in such a serious crash that the mounts welded to a metal pillar tear loose, you probably didn't survive for a variety of other reasons. Remember, it's your body pulling on the belt, the belt pulling on the mount and the welds/bolts/whatever ripping loose that you are worried about here.

Once your attachments are stronger than the forces that can be survive-ably applied by flesh and bone I figure you can stop welding.
 
#9 ·
I would still engineer them as best as you and install the shoulder belts. I did that on my car, a 37 Pontiac coupe. My thinking is that they will help for sure in less severe accidents, and even if they pull out in a major accident; I would think that they would absorb some of the force before reaching their limit. I'll take any improvement I can get to keep my face off the steering wheel and dashboard.
 
#11 ·
My thoughts (and they may be totally wrong) are that once the shoulder anchor pulls out in a retractable system, should that ever happen, the lap belt becomes a useless piece of cloth...

your throwing you hat in on this? easy peasy to do if you want a shoulder belt
if this is too much work, drilling the holes in the floor to mount your seat will kill you :D
Well, considering I got the car in pieces and proceeded to remove the flooring from the firewall to the trunk, I don't think anchoring a belt in the floor will be much of a problem. ;) The floors are built, just not installed yet. I really have no idea what trim goes on the "B" pillar (if any), and if I manage to kludge up some kind of anchor point, whatever trim does go there will likely no longer work. Oh, and did I mention the outer body is fully painted? Any welding in that pillar would likely result in serious damage to the paint. There are only 2 other peeps I know with 61 - 63 Rambler Americans, and one of those hasn't answered my last few e-mails. So, I'm pretty much in uncharted territory here...

Russ
 
#12 ·
Look at it this way -- even if a washer does pull through the floor, it took a lot of force to do that. So the seat belt would still hold you back/slow you down significantly. It would take one hell of a lot of force to pull even a standard 3/8" washer (about 1" diameter) through a steel floor, especially if there is some kind of reinforcement near the anchor point. I would use something more like a 3" square plate (1/8" cold rolled steel would be enough if at least spot welded at the corners) for a seat belt anchor under a sheet metal floor, less if through a seat mount reinforcement.

The structure around the roof of the Rambler will easily support the car if it's rolled. Put in a 1/4" plate and anchor the shoulder harness to it. If you hit something going over 100 mph you might pull it out, but as I stated earlier -- it will take considerable force, and whatever force it takes will at least slow your body down. That's why the most effective armor has spaces between layers -- first layer takes most of the hit, second layer has little force to deal with. I guess I'm saying any seat belt anchor is better than none. Unless you have a head on collision with another vehicle moving over 50 (your 50 mph + theirs = 100 mph into a wall), you're safe though. Reasonably safe in 90% of collisions is better than none!
 
#13 ·
3/16 ss rivets.

3/16 stainless steel pop rivets were an approved substitute for spot welds when I was an engineer at Ford. You need a good hand tool to set them. The cast aluminum tool works. just a hard squeeze. I have an old surplus air powered tool. The gripper teeth have to be cleaned after using a lot of aluminum rivets.
 
#14 ·
Bumping this back up!

I decided to make "B" pillar mounts from some scrap-bin 3/8" x 1 1/2" bar stock after seeing the sheetmetal supports Juliano's offers on their site. Used my plasma cutter to remove about 2" of that pinchweld, then cut a slot just under it so the plate will slide down inside that triangle looking part of the pillar. The tapped hole will be roughly centered inside the three trim holes and being 7/16-20, has 7 fully engaged threads.

Now for the $64 question! What setting do I use on my MIG to weld 19 ga sheetmetal to 3/8" plate without making a mess? The outer side of the pillar is finish-painted and got hot-to-touch just from the plasma cuts...

Russ
 
#18 ·
I'm pretty fair with similar sized material, but don't have a lot of experience with thickness differences of this magnitude. Should my welder be set for the 19ga, 3/8", or (I ASSume) somewhere in between?

Never do that!!
Never attach your seat belt anchor to the frame. The frame can move seperately from the body in a solid hit. Frame stays there, body moves forward, cuts you in half right across the waist.
Anchor it to the body instead.
Sorry, this is a unibody car with the new "frame" welded into the original rockers at the rear and both sides. Even up front now that I consider it...

Russ
 
#19 ·
You have to set the welder just a little hotter than you would to weld the 16 gauge. Start the weld on the thicker material, and keep most of the heat directed at the thicker material, as the 16 gauge will melt back quicker. By keeping the heat mostly on the thicker material (point the nozzle toward the thicker material) you will get it a bit hotter than the 16 gauge. You need it a little hotter to get penetration. It's tougher to weld thin to thick, but not too bad.

When you need to reinforce a thin section like this it's best to put the thick material behind the thin, not cut the thin out. Then it won't matter so much that you don't get much penetration in the thicker material. Can't always do that though.
 
#20 ·
Hey Frank, long time no hear!

I made my slug so it fits behind the pillar and snugs up against the inside. I'm planning on three rosette plugs on the face, two beads along the top side edges, and one across the top into what's left of the pinchweld I removed for clearance. Should be good on that, just need to get off the couch and do it!

Russ
 
#21 ·
Only ended up being a 4 hr job from start to finish, here are some pix. I kept the two original trim holes by drilling the slug and countersinking the rear face for trim clips. Welds look cr@ppy as usual, but they just need to hold the slug in place as the shape of the pillar will prevent it from going anywhere. The plasma cutter put more heat into the exterior panels than the welder. Thank God for the after-air purge, it made cooling the paint easier. All ground and seam-sealed now, just trying to decide on my interior color before buying belts...

Russ
 

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