3 point seat belts in a '31 Chrysler sedan

Forgive me for making this such a long post but the subject is about your safety. Following is a description of installing 3 point retractable seat belts in a '31 Chrysler model 70 Royal sedan.

As a note, any use of these suggestions is the responsibility of each owner or seatbelt installer.

I installed lap belts in my Chrysler weeks after buying it in 2013 but was concerned every time I drove it. Lap belts alone may keep you in the seat but your upper body will hinge at the waist and your head will hit the steering wheel, the dash or the windshield in a head-on. On a side hit, your head will likely hit the side window, B pillar, or you will be thrown against the opposite side of the car.

My objective was to install 3 point retractable belts with the shoulder belt extending back through the space between the rear seat back and cushion with the retractable mechanism attached to a reinforced mounting in the floor behind the rear seat. A floor angle bracket will be needed which is available from any seat belt supplier. I had to bend a 90 degree bracket slightly to get the correct angle for the retractor. One of my requirements was that the belt going to the back needed to be detachable so it could be hidden under the rear seat for shows while the front belt could be tucked out of sight under the front seat. An added advantage allows the tail belt to be disconnected for passenger access to the rear and reconnected once they are seated.

Not finding a suitable belt anywhere on the internet, I turned to the racing belt people where I found a 3 point harness from Corbeau. The belt is really a two belt harness with a single tail belt to the retractor. The tail is detachable directly behind the driver's head where the two shoulder belts join the tail.

There may be questions about the angle of the tail belt coming from the shoulder to the rear seat cushion. Corbeau's website and others show the tail belt installed this way. They also show the anchoring point not directly behind the driver but attached to the outboard factory seat belt mounting behind the rear seat at the side of the car. This would be the C pillar in a modern car. I talked to Corbeau about my planned installation and was advised the angle would be fine so long as it did not exceed 45 degrees from the horizontal. Installing the retractor at the floor directly behind the front seat would be taboo as that will cause shoulder and spine injury in a crash. Mine ended up at about 26 degrees which is ok.

These belts are listed by the makers as not suitable for street use and they cite, likely for legal reasons, that this harness will keep you rigid in the seat. They are meant to be used with roll bars or cages and helmets. In the event of a rollover, they feel stock 3 point belts will allow the occupant to duck down and not be crushed by a collapsing roof where the harness will keep your head upright an in place. My own personal opinion is that I would rather my body be held firmly in place and not free to move. Also, in a rollover, I think gravity and the downward force of the rollover would make it impossible to duck anyway.

There are no airbags, collapsible steering columns padded dashes or other safety features in our cars. Therefore, I would rather be held firmly in place in an accident but still have the freedom with the retractor to move comfortably while driving and not be plastered to the seat back for the duration of my ride. The Corbeau retractor is made so it can be set in a locked position if the driver wishes. These are decisions you will have to make for yourself.

It is important to understand that no seat belt arrangement is absolutely safe and mine isn't either. This fact has been pointed out on this and other forums by some who apparently don't have any belts at all in their cars for this reason. Common sense should tell us that lap belts are better than nothing and that lap belts with shoulder restraints are better than lap belts alone.

Glen

Interesting to say the least. But should keep the driver out of the steering wheel.

Last time I made a setup like this I got an adjustable shoulder piece from a sedan of some sort and welded that adjustable bracket to the B pillar. Since the car was so tall in comparison I had to raise the mount behind the seat a few inches.

Interesting to say the least. But should keep the driver out of the steering wheel.

Last time I made a setup like this I got an adjustable shoulder piece from a sedan of some sort and welded that adjustable bracket to the B pillar. Since the car was so tall in comparison I had to raise the mount behind the seat a few inches.

Jack,

Your comment reminds me I should have mentioned the obvious. In older cars like the '31, the B pillars are usually made from wood with metal body cladding. I don't think there is any way these pillars could be beefed up enough to safely attach the usual modern seat belt pivot bracket and therefore, should not be considered as possible mounting points for any belts.

Welding in a suitable bracket on a later all steel B pillar as you apparently have done would be a much stronger installation.

Glen

Good work Glen. Thanks for sharing this.

Dwight

A very well written and executed plan of installing shoulder belts in an antique car. It's a design I, for one, have never seen, and does make a lot of sense.

How well is the rear retractor anchored to the floor? Is it just through sheet metal or does it go to a frame crossbrace? Large washer underneath? Same with lap belt?

If I did this to a car, I'd also reinforce the mounting of the front seat to the floor. I'm working on a high end 1940 car now, and the only thing holding the seat in place are four quarter-inch bolts, which, in certain collisions, could easily fail.

Your statement is very well made that no system is perfect, but in some cases your solution may be advantageous, and it does make you feel more comfortable. Thanks for sharing!

A very well written and executed plan of installing shoulder belts in an antique car. It's a design I, for one, have never seen, and does make a lot of sense.

How well is the rear retractor anchored to the floor? Is it just through sheet metal or does it go to a frame crossbrace? Large washer underneath? Same with lap belt?

If I did this to a car, I'd also reinforce the mounting of the front seat to the floor. I'm working on a high end 1940 car now, and the only thing holding the seat in place are four quarter-inch bolts, which, in certain collisions, could easily fail.

Your statement is very well made that no system is perfect, but in some cases your solution may be advantageous, and it does make you feel more comfortable. Thanks for sharing!

Luckily, the Chrysler has a rear support member directly under where the retractor is installed so the bolt is held by both the floor and the support member. I also used a heavier 1/2" bolt. Large washers are used at the anchor points. The front mounts also attach to a support member.

In the Chrysler as is common with many older cars, the seat bottoms are just set down into a wooden frame with nothing to anchor them in place. This was a concern when designing my system but I feel the harness will hold my body in place even though the bottom seat cushion may dislodge and slide forward in an accident. My front adjustable seat rails like yours also have four 1/4" bolts holding each rail to the floor. The rails are light guage metal and I agree with you that they will not hold in a bad accident. I have not devised a way to beef up these rather flimsy rails but feel with the belts anchored to reinforced mountings front and rear, my body will stay put even if the seat rails tear out and the whole seat and frame slide forward under me.

The front seat back poses a similar problem in that it has a wooden frame which will likely tear out in a bad accident. Again, with the driver held firmly in place by the lap and shoulder belts mounted through the floor, the seat back may want to move forward but can't because of my body strapped against it. Hopefully, the heavy cushion will absorb the shock.

Another problem with our cars is that they do not have seat back head rests to absorb the shock of head movement in an accident.

Once again, no system is totally safe, especially in these older cars. If I can keep my head from hitting the steering wheel or windshield and my body away from being impaled on the steering column, I might be relatively protected in a minor accident. If I get hit by a semi, no safety equipment I could devise would save me.

For those who read this thread, please think seriously about installing belts in your vehicles but don't think for a moment you will be totally safe. Folks still die in modern cars with a multitude of safety equipment. Be careful and drive defensibly but enjoy driving your vintage vehicle.

Glen

Interesting to say the least. But should keep the driver out of the steering wheel.

Last time I made a setup like this I got an adjustable shoulder piece from a sedan of some sort and welded that adjustable bracket to the B pillar. Since the car was so tall in comparison I had to raise the mount behind the seat a few inches.

It was a 31 DG8. The pillar is steel.

The one thing I didn't take a picture of.

Glen, your last paragraph is excellent and the truth. One must drive an older car conservatively and defensively, but there are still no guarantees of safety....

Quote: The rails are light guage metal and I agree with you that they will not hold in a bad accident. I have not devised a way to beef up these rather flimsy rails but feel with the belts anchored to reinforced mountings front and rear

I have been concerned about the flimsy way the front seat is attached to the floor also (If I push hard enough I can pop the seat out of the frame!). I have decided to replace the track with a modern universal bracket bolted to the car frame just like the seat belts.

Something like this:

http://www.summitracing.com/parts/sum-g1151/overview/

Quote: The rails are light guage metal and I agree with you that they will not hold in a bad accident. I have not devised a way to beef up these rather flimsy rails but feel with the belts anchored to reinforced mountings front and rear

I have been concerned about the flimsy way the front seat is attached to the floor also (If I push hard enough I can pop the seat out of the frame!). I have decided to replace the track with a modern universal bracket bolted to the car frame just like the seat belts.

Something like this:

http://www.summitracing.com/parts/sum-g1151/overview/

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Dwight,

You may have a good solution for the flimsy original seat rails and I'll be crawling under my "31 to see how I can reinforce the mounting points. It's hard to see from your Avatar but is that also a '31 Chrysler? .....can't make out the configuration of the grille. If so, what model? If you are doing this project soon, I would appreciate a photo or two of the process when you get finished.

Glen

Glen,

No, not a Chrysler. It's a 1930 Buick Model 47. I expected to have the seats in three years ago. And three years ago I stopped making predictions about when I would get things done! The installation will be straightforward though. The seat has a sturdy wood frame on the bottom. I will bolt on the one part of the bracket. There are two steel supports under the seat. I will bolt the other piece to those.

Dwight

Glen,

No, not a Chrysler. It's a 1930 Buick Model 47. I expected to have the seats in three years ago. And three years ago I stopped making predictions about when I would get things done! The installation will be straightforward though. The seat has a sturdy wood frame on the bottom. I will bolt on the one part of the bracket. There are two steel supports under the seat. I will bolt the other piece to those.

Dwight

Dwight,

I came close to buying a '30 Buick before opting for the Chrysler....it was a nice car. Looks like you are well on your way to a fine restoration. I admire your patience.........I have enough on my plate with constant tinkering on our Model A and the Chrysler. Good luck!

Glen