Seatbelt/harness dilemma. Will 4 point crush my spine?

[INTMD8]

The car I'm building is a pillarless hardtop 4 door so adding seat belts is a bit of trouble. I experimented with having the shoulder strap mounting point at the roof but the angle is too severe no matter how far forward or back I have it on the roof line and the belt cuts into my neck.

So, my other option, which I would prefer is to retrofit 3 point belts directly into the original seats. These are from the 3rd row seat of an Escalade and they exit the top of the seat the same as I have them set up-






Now, I can make this happen but my only problem with this is it puts all the load on the seat itself. I can reinforce the seat frame and the floor pan of the car no problem, what I'm concerned about is will the original ball bearing seat tracks take the force of a crash or just blow apart? I don't see much of a way to make them stronger.

Last option is to run a 4 point harness. The car is not getting a roll cage, not really a good way to do it without ruining the functionality of the interior. These instructions show mounting them to the floor but most are saying that will end up crushing your spine in an accident. My question is, if the harness is draped over the top of the seat it would be going over my shoulder at the same (rather shallow) angle over my shoulders so in order for it to crush my spine it would also have to crush the entire seat frame.

http://wescoperformance.stores.yahoo...seat-belt.html
http://wescoperformance.stores.yahoo.net/am4point.html

I think with the way this car is built I would be dead in a high speed crash unless it had a full cage anyway, so should I just look at the belt/harness as a way of keeping me in the seat and not a 100% solution in a crash? I don't think any of these options would be good at 80+mph but if it was lower speeds, say 30-40mph would I not be better off not smashing the steering wheel? Btw, no plans on racing this car, it will spend 99% of it's time on the street.



Any input appreciated.

[kawaden]

do you know anyone who can make seat belts? make a 3 point with a drop link off the roof so the belt is closer to your sholder.

[chuckd71]

Are you set on using that bench? I just bought some BMW E46 convertible seats with the belt built in; Sebrings, CTS-V coupes and a couple other cars have them as well. There is no 100% solution in a crash, and your "I'd be dead anyway" logic is faulty and just a way of rationalizing your potential acceptance of a less than truly acceptable option.
The belts as pictured are not safe because they run straight down. Yes they will destroy your back even without crushing the seat, because should you hit something the seat itself is strong enough not to slam forward but you are not, and as distance between your back and the seat increases so will the tension wanting to snap your spine in half.
The seat belt as pictured looks like a good way to ensure that you damage at least some part of your spine if and when you hit something.

[morrisclassic]

We agree with Chuck that the set up you picture will result in injury to yourself in the event of an accident.

Our seat belts have a soft lanyard or drop down on them and a standard GM mounting bracket.
Look at our web page www.morrisclassicconcepts.com
Billy

[69cutlassrkt]

BTW most crashes happen around 40mph, I just took defensive driving for a speeding ticket. I have the morris belts they work well and are easy to install. There is a thread somewhere about their seatbelts.

[morrisclassic]

Kyle,

Thank you for purchasing our seat belts and the compliment.
The thread is in the General Tech and Safety section.

Billy

[dontlifttoshift]

Back to the original post. The way the harness you linked to is mounted is not safe period. When the shoulder straps go straight down (side view) there is nothing to keep your shoulders in place. Most harnesses need to be mounted at a minimum 45 degree angle downward from your shoulders. With the essentially making a 180 degree turn over the top of your shoulders you will still slide forward. I would skip the "harness" idea. It will never look right and the safety would be marginal at best.

The simple solution seems to be upgrade the seat tracks to something late model that was engineered for for integral seat belts but you are dealing with a bench seat with two passengers strapped to it. It's pretty hard to find a late model with a bench seat with integral seat belts. Not only do the seat tracks have to be up to the task, so does any recline mechansim.

I wish I had an easy answer here. I still think your best bet is to use DTS seats and dress them up to look as oem as possible.

[INTMD8]

The simple solution seems to be upgrade the seat tracks to something late model that was engineered for for integral seat belts but you are dealing with a bench seat with two passengers strapped to it. It's pretty hard to find a late model with a bench seat with integral seat belts. Not only do the seat tracks have to be up to the task, so does any recline mechansim.

This is what I'm leaning towards doing. I think some early 90's trucks may have had a bench seat with integrated belts, I will check into it.

As for the belt geometry how it's pictured on the original seat, I believe it should be fine as it's copying the setup identically from the 3rd row seat I took them from.

Such as this-




When I considered mounting the shoulder harness to the roof, I was planning on having seperate regulators/buckles for the shoulder belt and lap belt so I could pull the shoulder belt up and clip it into a buckle on the roof. (so out of sight when not in use) I don't want belts to be permanently hanging from the roof.

[dontlifttoshift]

We did a 41 caddy many years ago and I searched high and low for a bench with seat belts to no avail. Our problem was that we needed the seat back to lean forward for access to the back.....you don't have that problem. Base model, I mean el strippo work trucks, had a bench with seat belts.

Third row seats aren't uber comfortable

[INTMD8]

I would never use the 3rd row seat in the front, just posted the picture to illustrate that I have the seat belt arrangement exactly the same as a factory vehicle, using the same belts.

If I have to use the tracks from a single newer seat on the original bench I'm thinking it would still be stronger than the original tracks.

The original tracks could just slightly separate and pull around the ball bearings. Maybe I could weld a clamshell type piece over it for more support but still would not know how strong it is-



Here is the track from a TBSS. Not a great pic but each half of the rail is doubled over so it appears like it would take much more stress-




Thanks for all of the input thus far. You couldn't imagine how much time I have spent trying to decide which way to go with this.

[INTMD8]

This is what I ended up doing. (copying the escalade 3rd row seat belt arrangement as pictured above^}

I measured the distance on the Escalade seat from the seat bottom to the bezel and made pieces to mount these at the same height on the Brougham seat. Feels like it will be comfortable and the angle on the belt is minimal. (should be fine as it exactly duplicates the geometry of the stock cadillac seat).

Seat frame will be strengthened. Where the rearmost seat mounting holes are in the floor I'm going to add a body mount there to the frame.

Now I need to take the seat back frame and modify the structure to go around the seat belt assemblies. Over this will be a shaped piece of high density foam that will take place of the original springs. I'll have the plastic seat belt bezels duplicated in aluminum and chrome plated.