Mounting seats and belts to a wood floor?

First off, I'm working with a 1935 Pontiac Coupe, obviously. It's pretty much the same as 35-36 Chevys, Buicks, etc, with the wood framing of the body. I am mounting seats with integrated belts and trying to figure out the mounting setup. I have seen both sides of the argument that you have to mount the seats and belts to the body of the car since the body moves at a different rate than the frame. However, with a wood framed body such as mine, how would that work? I'm not too keen on mounting the seats to the wood floors, especially since the belts are mounted to the seats.

I've read a lot of different suggestions, and the one I like the most is running a piece of square tube or c-channel across underneath the floor to take the strain, however, if that's mounted to the frame, what happens when the body of the car gets pushed back and the frame keeps moving in a head-on collision? Since the steering column is mounted to both (more substantially to the frame though) which way would that move?

What is the best, and safest, way to mount these? Tearing out ALL the wood is not an option right now.

 

I wouldn't use seat belts in a wood framed car. In a roll over the body can come off of the frame, so you do not want the belts fastened to the frame. Just go without belts is the safest way in my opinion.

 

mount to frame. split the back of my head on the package tray. i was in the front seat with a 3" lap belt. seat and belt ripped out of the floor. long story, like i said go to the foundation or risk the lives in the car.

 

Were you rear ended? Did you have headrests?

No seat belts is not an option for me. The body bolts to the frame in the front and rear through steel. It's just the mounts inside the cabin that are through wood.

 

I heard on here in another thread I believe that if you mount seatbelts to the frame and the body comes off thats how people can get cut in half..

 

I've never heard of people being cut in half, but this is what I'm worried about. Maybe the night crew can shed a little light...

 

street racing a newer mustang, we were in the right lane. was over 100 mph when up ahead a car came out onto the street in our lane, slammed on the brakes then threw the the hurst quarter stick into low, the car veered left then when the tranny went down the gears it spun us around (180 degrees) went up the center divide, the front fender on the passenger side slammed the tree which then slung shot us backwards into the next tree in line and that stopped us. the tree was at the back window. no back seat in the car. the back of the car looked like a u. i was the passenger. im lucky to be here. the spot is popular in san fran for street racing, my dad ran it in 69/70 with his mustang. ive never seen a car come off the body mounts in all the years in collision repair so this whole body separating from the frame may not apply to all. still have the blood ridden shirt from that night which was in april of 95. id still go to the frame

 

oh and i was still in the racing bucket laying in the back where the back seat used to be. the seat and i went flying backwards

 

wow got my attention I thought mounting seatbelts was pretty straight forward. would like to know more about it also.

 

The seats were not mounted to the floor, they were mounted to a fairly hefty crossmember going from sill to sill, with the floorboards butting up to the crossmember/s, which is plenty strong to mount seat belts to. I'm of the opinion that since you are using seats with the belts mounted to them that you might need to augment the present wood crossmember/s or slave in some square steel tubing on the front/back edge of the current crossmember/s.

No! do not mount the seat belts to the frame, mount them to the body crossmember/s, or body sills.

 

i dont think i'd ride in a car where the body could come off the frame, lol


with or without belts, sounds like you aint gonna fare to well



skull

 

Are you talking about the original seats? They were mounted to a piece of wood that runs the length of the cabin, which is bolted to the frame with body bolts. I don't know if that's the sill, I thought the sill was the rocker panel. Whatever it is, that's what they were mounted to. However, there were also no seatbelts involved and the only thing restraining you into the car was the windshield. There was no stress on the seat bolts in an accident. The crossmembers aren't very hefty (maybe 1x4) and had nothing mounted to them besides the steel floorpans, which are just screwed to the wood pieces. I don't really trust them to be able to hold 5000 lbs or even a fraction of that...

I'm getting the same answers that I've seen in all the other threads- that everybody has their own opinions on what is safe. Is there any definitive guidance from any of the race agencies or anything like that?

 

I dont think you can compare a new unibody mustang here. I dont think your mustang had a wood floor.
Mount to a steel floor member and never the frame of the car. If you mount to a wood floor you are only fooling yourself. The seatbelts of course.

 

Yes, on each side, running front to rear along the top of the frame, that's what the car mfgrs called the sills. Also from side to side, under the seat there should be a crossmember, about the size of a 2x8 tying the side sills together. If it's absent, it seems to me that with the donor seats with seat belts attached to them you will need one, possibly two, crossmembers to support the weight. If I were doing it I would go with steel, because new oak will cost more.

 

I'd weld a heavy strap or "C" beam from rocker to rocker underneath the body *NOT TO THE FRAME* and attatch the belts to that.

 

A Mustang doesn't even have a seperate frame to come off, it's unibody, wtf?

In your Pontiac just add some steel crossmembers for the seats and belts to bolt to that are securely welded to the body. Then if through some freak accident the body does come off, you're still attached to the body and not to the frame. Take a look under some late model cars to get an idea what the factory, crash-tested cars like to have for attachments. Hell, you could put an entire steel floor in it if you wanted, the floors in those cars are pretty flat, it wouldn't be that hard to fabricate.

 

What Mustangs are you guys even talking about?

I'm thinking the c-channel might be a good idea, however, if it's not welded to the frame, it will still be contained within the frame. From under the car, there is the c-channel frame, then the sills. There's no other place to mount the crossmember on the body!

Thanks for the lesson on sills, I've been wondering what the heck to call them! I checked again, and the crossmember is only 1.25" by 4". Maybe you're comparing with a sedan? I don't know if they had a bigger crossmember! I agree that I need new crossmembers, but how would they be mounted? The original crossmembers are dovetailed (or whatever) and screwed into the sills. Everything ties into the sills, basically, and I don't know if I trust them to withstand that much force, even with a 2x2 square tube running across them...

 

Arent you paying attention. The story the guy gave when he crashed his mustang. Some people.Hahahaha.

 

The floor is entirely flat, actually! But, I don't like the idea of intermingling the wood with new steel, that's the main reason I am putting off an entirely new floor. I wouldn't be able to do the doors and upper body and they would have to come into contact with the new sills that would have to be fabricated. Not to mention having to take the body off to replace the sills... I plan on replacing some of the wood with steel, but they still will have to tie into the wood sills...

 

Yea, I just went back and reread everything and saw it there! Weird.

 

Here's the floor, you can't see it very well but the two pieces of steel floorpan are screwed to that 1x4 all the way across.

 

Thats because when a car is in a bad enough wreck for the body to come off, it doesn't go to the shop. It goes to the scrapyard. and when they come off, they dont completely seperate, but if the body moves even a foot or two from the frame that's enough for the seatbelt to do some serious damage... Ask a cop. It happens. Glad you syrvived, sounds like a terrible wreck.

 

Yes, car bodies DO come off frames in bad accidents.

I saw one just a few months ago, late 60's full sized Olds hit a steel telephone pole at highway speed... It was not pretty.

Think about it, the body weighs anywhere from 1000 to 2500 lbs, and it's held on with anywhere from 6 to 10 bolts. Add a little rust into the equasion, and 50 to 75 G's of instant shock in a serious accident and ........ Yikes!

 

No car manufacturer would use a 1x4 as a rigid member to tie the sills together and mount the seats on.

Where I've outlined in yellow, it appears the heavy crossmember normally present in all Fisher Bodies is absent. It would have been attached to the sills with a mortise and tenon joint in line with the two intermediate bolts that mount the sills to the frame. If mounted there now, the heavy crossmember would interefere with that floor shifter, so I'm guessing that somebody has modified your floor, removed the crossmember, in the past. It would also be usual in a Fisher body to have another crossmember a couple of feet further back as further side to side support for the sills and vertical support for the floor/seat mounts.

Whatever the case??, It will be necessary to install two heavy duty wood crossmembers or two steel crossmembers, sill to sill, as a minimum, NOT attached to the frame, to mount your seats to.

 

I don't want to call you a liar, I've read many of your posts and respect your knowledge. However, that is just not the case here with this Fisher body. Look at the pictures that I just took. The crossmember that was cut out was at the front of the seat and was cut out by me. However, it was nowhere near 2x8, that's why I cut it out- I couldn't believe that it was structural and that it was just a place for the front floors to mount to. There is one piece that is completely gone, and that was maybe 2" wide. The remaining chunk is 4" wide. It's only 3/4" thick too. And it's not mortise and tenon with the sill- they were mortised with each other, but not the sill. They were just screwed into the lip on the sill. I have no reason to believe that these floors have been modified in any other way... When I got the car it was still all original.

As you said, whatever the case, I need to mount something on the underside to reinforce the floors. How would I mount them if I can't mount to the frame? As you can see in the one picture, the sills are mounted to the frame. And the seat mounts go almost to the rocker panels so they will be out on the sill as well. I could mount the tube/c-channel to the floor at points throughout the floor and not to the frame, but it will still have to sit inside of the frame rail. That would allow fore-aft movement with the body but not vertical in case of the absolute worst case.

I'm really not trying to be combative, and I really respect your knowledge and want to keep working to figure out how to do this. I just want to point out that my body is not the same as your experience...

 

Use common sence on this. When your car was made its top speed was close to normal freeway speeds. Crash saftey wasent a concern. What ever you mount seatbelts to, the seat should mount to the same peice.
29nash is directing you to weld in a new peice and call it a day. It doesnt matter what your car came with, its what your going to add to make it better. I think.

 

my fault,...we were NOT in a mustang

 

the other car was a stang.

 

Top speeds of normal freeway speeds? I'd say the top speed was about 45! I don't know, but that's my guess.

I'd love to just weld in a new piece, but I can't. That's my frustration! There's nothing to weld to besides the frame of the car. The rest is wood and that's on the edge of the frame. If it were safe to just weld to the frame, I would have been done a long time ago! Maybe my situation is just too complex to try to explain over the forum...

 

i'm understanding the separating of the body a little better now,...hell just throw some bolts through that floor and call it good. i guess if you want safety then i suggest a volvo. i gotta put a belt in the 54 as soon as it gets out of the shop. need it to pass tech. good luck and thanks to those who found my error.