Seats and Seatbelts: What to Bolt them to?

I'm about to put belts in my '38 Chrysler. I've read back through the old posts, and looked at some mfg web sites. Some say to bolt the belts to the frame because they can pull through the floor (even with proper mounting hardware), and some -including Juliano's- that say bolting to the floor is the way to do it.

As I looked under the car I found that the seat itself (oem install) is only bolted to the floor.

Does it make any sense to attach the belts to the frame if the seat is bolted to the floor?

Should I make an adapter that would let me bolt the seat to the frame?

Do I just bolt the belts to the floor ala Juliano's and leave the seat as-is?

What Juliano's suggests: http://www.julianos.com/how2_62Galaxy.html

 

I would think bolting the seatbelts to the frame would be the strongest, as for the seat, it weighs a lot less than a person. If you were in an accident the belt would hold you and the seat in.

 

If all you have is the floor, DO use the anchor plates. Washers don't hack it.

 

The Frame

 

NEVER EVER EVER EVER bolt seat belts to your seats...depending on what you feel safe with, I've always used two large diameter thick fender washers, or made plates of my own from 14 or 16 gauge sheetmetal, above and below the stock floor...prepped the areas and welded them into place...or you could get the seatbelt mounting kits, it's your choice...and it really depends on the quality of the sheetmetal in your floors, if there's any holes or rot it's best to take care of those areas first...

 

Are the body mounts/floor structure in good enough condition that the body would stay attached to the frame in the event of a bad crash?

I'd attach the belts to what your seat is attached to (reinforce the floor if needed).

It would suck to have the body come lose and only be attached by the seatbelt that is around you.

If it is going to separate, I'd much rather be attached to the part I'm riding in.



.

 

I was told to not bolt them to the frame. In the case of an accident, they need some 'give' so to avoid real serious injury. I have mine securley bolted through the floor (wood) with big, thick washers on either side.

 

If it is a serious wreck or your in a roadster you probably aint gonna live either way. SO you may as well get ejected. I am installing a seatbelt for two reasons. To protect my son or daughter and to be able to drag at the hamb drags and the Day of the Drags. I welded some 2" by 1" thick wall tubing to the body cross braces to hold the seatbelts. Always remember whatever you do you are only as strong as the weakest link.

 

The floor was replaced, so it is solid- maybe 16 or 18 gauge I think. The seatbelts ( from Speedway) Came with extremely thick, giant washers for the mounting.

 

In my opinion it really depends on how the car is built.. I think as a rule of thumb you'll want to mount it to where the seat is attached... You'd only attach it to the frame if the floor was integrated or very firmly attached to the frame (kinda like a pan on a VW).

 

Good timing ! I am just fitting seatbelts on my '38 Ford coupe, so was reading up on this last night.

Here in NZ, we have a Hot Rod 'code of construction' developed between the NZ Hot Rod association and the Government, and it has a section on seatbelt mounts. It is acceptable here to mount seatbelts through an original metal floor, providing a suitable reinforcement is added beneath the floor.

For an 18 gauge floor, the reinforcement they recommend is 3 inches square x 1/8 steel with a 7/8 diameter x 1/2 inch threaded boss welded to it to accept the seat belt bolt. For a 20 gauge floor, it should be 4 inches square.

This reinforcement plate should have radiused edges on the side that faces the floor (to avoid it pulling through the floor in a crash) and should be plug welded or skip welded to the floor pan.

This assumes it is an original style floor with swages for reinforcement. If it is a flat floor, they recommend L shaped stiffening braces be welded to the floor as well.


On the '38 Fords, the seat is mounted straight to the floor with the bolts going through a reinforcing channel for additional strength. I am going to leave these as is, and mount the belts to reinforced mounts welded into the B-pillar with the centre mounts through the floor with reinforcing plates as above.

 

I think you'd want to stay with the seats/body instead of the frame during a wild ride

 

I vote sturdy plates on the floor to prevent pull-through. If something would cause the frame and body to shift in relation to each other you could come loose...or you could get squeezed!

 

or cut in half!

 

NEVER bolt seat belts to the frame! If the body shifts in a severe collision the seatbelt will not move with you in the seat, and could feasibly cut you in half. Seats and seatbelts should be bolted to the floor pans with sturdy bolts, in my opionion a minimum of 3/8" grade 5, and use nylock nuts to prevent things from vibrating loose. Seat belts should be held in with very large, thick washers to disperse load.

 

As posted before bolting seatbelts to the frame is a bad setup. No one wants to think about getting in an accident or getting hurt but safety needs to be a first thought here. I originally had my belts mounted to a frame point because I figured it would be strong but later realized that if I was broad sided the belt would cut me or my family into. I have since moved all the belt mounts to one of the sub floor cross rails under the floor skin that I buiilt when I channeled my sedan.

 

I used Juliano's seat belt mounting plates which are heavyduty and mount to the floor.

 

The OEM's, who must pass strict government safety tests regularly, routinely attach the safetly belts to the seat frames.

 

My thought is that if it's good enough for Juliano's, it's good enough for me

 

you're talking the difference between apples and rusty vintage sheetmetal...vintage cars are built WAY differently than today's standards, and if you take a look at almost all pre-2000 vehicles the seat belts are mounted to the floors...now I haven't seen any modern vehicles with seat belts mounted to the seat mounts, but I'm assuming that they were engineered for that specific application and shouldn't be duplicated by any of us...we are not OEM manufacturers, and our vehicles don't meet any of those government safety requirements as far as floor and support structure are concerned...so I say this as confidently as I did before, NEVER EVER EVER mount your seatbelts to your seat mounts...if you want to do that then go ahead, thin out the herd and we'll go to your estate auction and have coffee and buy your leftover cars and parts...

 

it's only my opinion; not based on any engineering study or calculations that i can quote; BUT i think there's a lot of really good logic in this answer...

 

I know when I had mine inspected in PA the isnpector said to the floor.

Bill

 

They also have crash testing facilities, and computers, and are able to design safety from the whiteboard up.

I've seen many wrecks, and serious ones have the frames and floors in very different places. Bolt them to the floor. Don't cut your ass off!

 

No, I'm not really. I use a seat from a Chrysler mini van and it has very sturdy seat belt mounting points right on the seat frame. The seat itself is mounted securely to the floor. In the event of an accident the seatbelt, the seat and my ass are all going to stay in relatively the same place.

As others have mentioned, if the seatbelts were mounted to the frame they could slice me in half if the frame and body decided to part company.

 

Juliano's is on the right track but I would fit an anchour plate top and bottom. The top plate would have a spacer built on it so the belt is free of the floor and the belt can swivel. That is how I did them in my 55.

 

If there are no factory holes for seatbelts I unbolt the seat and slip them under there and retorque the shit outta them... but that's just me.

I've drilled new holes too, and made sure to washer both sides of floorpan with bigassed flat washers and quality bolts.

 

Me too on the Chrysler mini van seat although the outer belts will go through the floor and into a threaded weld bung - with a large inside the frame area to prevent pull-through if the weld failed - of the frame.
The car also has seat belt threaded weld bungs in a crossmember dedicated to seat belts and roll bar laterals.

The seat proper mounts to the 'hat' channels that form the A roadster body's body sub-frame.


I note as well that NHRA requires seat belts and harnesses attached to frame or crossmember.


This particular discussion - argument? - has been around a couple of times.
With people being on both sides of the floor or frame equation.

I think either method will suffice in a survivable wreck.

And if the wreck is bad enough, it's a moot point....

 

NHRA also has rules to determine how the roll bars are done. I do a lot of seat frame repair. I can tell you a large number of the newer seats have seat belt mount points, and those seat frames are nothing special! Many trucks and vans have a 1/4" x 1 1/2" bar that runs across the bottom of the seat, where the seat bolts to the seat track, that the belts are attached to. Look inside any conversion van. As long as the seat is secured to a good floor, I see no reason why you can not mount the seat belt to the seat frame. You just need to be sure the belt is in a straight pull, should it need to save your ass.

Personnally, I've seen enough wrecks where the floors have been so distorted that the belts had to loosen up. Any time I've ever heard of seat belts getting loose more injury was caused. Give me a good seat frame with the seat belts mounted to it and secure the seat to a good floor with good bolts and the proper bracing. I'll take my chances that way.

Reality is, I suspect even installed wrong, any seat belt has to be lots better then no seat belts... Gene

 

I note that the Julianos article shows a Galaxie with lap belts only.
If you're putting in seatbelts, install Lap/Sash not just Lap.
A friend of mine was involved in a major crash back in high school, she was sitting in the middle of the back seat with a lap belt.
Everyone else in the car had lap/sash belts.
They all walked away with minor injuries, my friend is in a wheelchair for the rest of her life. The impact folded her up over the lap belt and snapped her spine.

 

I have 3-point belts up front in my Ford. They work great and I had a good B pillar to attach the upper restraint to. I had to substitute another grade-8 bolt and make up a bushing, the supplied bolts were too short with my garnish molding.