Mounting Seats in a Glass Body??

[seadog]

I'm just about ready to mount seats in my five-window project.  Question for those of you here who have built glass cars...What's the best way to mount the seat frame to the floorboard.  Is it sufficient to simply thru-bolt the frames with a healthy backing plate/washer to spread the load or do the seats need to be tied in to the chassis to be strong and safe?  
Thanks.
-Tom

[Dirk35]

It is my understanding that you do NOT want the seats mounted to the Frame, only to the body. Also the same for seat-belt fasteners.... mount then to the body.

That way, if your in an accident, the body can seperate from the frame and you will stay snugly fastened in to the body as it goes on its way. Where if you were to mount the seats to the frame, and the seat belts to the frame, when the cab seperates from the frame in an accident, itll squish you with the body panels as the seats try to stay with the frame.

I know thats how modern day vehicles are also made if you think about their seat mountings and seat-belt mountings.

[alchevy]

I second that!!!!!!!!!!

Does the manufacturer of the glass car have any info on how to mount seat belts? Looks like they could tell you where they put in some support pieces for mounting the seat belts. Different glass cars use several different kinds of structural materials inside the car such as steel, wood, etc.

[Ohio Blue Tip]

My plan for the 34, not yet executed, is to mount 3/16 steel plates approximately 6 inches square under the glass floor and bolt seat mounts and seat belts through the floor and the plate.  I will seat the plates in fiberglass bonding agent to insure even load on the glass floor.  That's my plan unless some one has a better one.

[EMSjunkie]

On my '34 Street Beast, I put a piece of 1/4" X 2" flat steel on the underside, it ran the length between the bolt holes, plus
a 3" overhang on each side. inside, I mounted the seat on a piece
of 1/4" X 2" riser, about 3" tall on the front holes, and used 2" square
tubing for rear risers. (I'm short, couldn't see over the dash)



Vance

[Beck]

It sound like I may have screwed up again. When putting my '32 together I welded tabs on the frame to mount the seat and the seat belts to. The mounting bolts go through the seat bracket, then the body, then the frame. I did the same for the seat belt mounts. OOPS!
Beck

[32coupe]

Here in OZ, the body that I have came with a steel floor and bracing to the rest of the body. It had seat belt mount built into the floor and door pillars, and all I had to do to mount the seats was to put 1/8 plates 3" x 3" under the floor.

Sound like you guys have it a bit harder over there

[revhed]

With a plywood floor glassed into the body New Zealand laws mean we have to anchor through to the frame for seats and seat belt mounts also steel framing and side intrusion bars are now mandotory in fibreglass cars

[rumrumm]

Juliano's sells seat belt anchors--I have them in my '32. They are 1/8 inch steel about 2 1/2 inches by 4 1/2 inches and have a nut welded to the bottom side. If you do not want to build them, you can order them.

[nzsimon]

You cannot mount seatbelts to a fibreglass floor the stresses in even a small accident will be the equivelent of several tonnes of force and will tear them straight out no matter how big the washer is

[PeterR]

You cannot mount seatbelts to a fibreglass floor the stresses in even a small accident will be the equivelent of several tonnes of force and will tear them straight out no matter how big the washer is

It can be done, just a matter of careful engineering.  

Many people do not realise the high speed PT boats (the type JFK served in) with huge Allison engines and pedestal mount deck guns were made of plywood.  The entire Mosquito bomber was balsa/ply sandwich and neither experienced problems with armament, engine, or seat mountings.

And if you look at a fibreglass boat, the pedestal seats which take more pounding than any car seat are mounted on a fibreglass floor.

The magnitude of the applied forces is not the problem; it is the material stress that is the killer. The essence of it all is to keep the stress levels in the base material within appropriate levels, and this is not peculiar to ply or 'glass.   If you examine the suspension mountings on an aluminium mono bodied open wheeler, the pivot may be a HT 3/8" bolt, but the cast or fabricated mount distributes the load into the skin over an area the size of your hand using 20~25 1/8" rivets.

[paul2748]

I did the same as EMSJunkie.  This spreads the load over a very wide area.  Make a sandwich, putting the flat stock on top and bottom of the floor.  You could even add an extra bolt in the middle

[slocrow]

Are grade 8 bolts strong enough or should something else be used?? Tks, Frank

[EMSjunkie]

Are grade 8 bolts strong enough or should something else be used?? Tks, Frank

I use grade 8 for everything.
they held my seat in my sprint car during 6 end over end
flips.  


Vance