Making floor and mounting body when theres a roll cage

[boseefus402]

I have a 28-29 1 piece roadster shell, kind of an altered dragster thing but a little heavier.

I want to put in a roll bar, a front hoop right behind the firewall, and a few downbars, nothing NHRA legal which is impossible to do without it looking like garbage, just a little safety.

What do you do for a floor and body reinforcements then? The cage basically kills the plywood floor being glassed in. My only thought was to reinforce it with 1" steel square tubing, fiberglass that to the body, and then bolt the body to the frame with some steel connector plates. After its bolted on, weld or sheet metal screw on a sheet metal floor.

Any other ideas? If i stick with the square tubing, can you structurally bond steel to glass? What do you use? Just rough up both then go at it with matt and resin? It's not like wood where it will just soak in and bond.

 

[bentbaggerlen]

Build the floor as part of the chassis, and then bolt the body to the floor? Something like a VW pan.

 

[Wild Mango]

Getting glass (epoxy) to bond to steel is a mission. Rough the steel up with a grinder immediately before you glass it, and glass it all round so the steel is captive works OK, but try as you might unless the ends are totally sealed, ultimately rust will creep into the interface.
For something to bolt through, I glass in plywood blocks and use fender washers to spread the load.

 

[boseefus402]

You might have something with the VW pan idea. The idea is coming together in my head a little better now. So make the cage, then make the floor structure and bolt that to the frame. Then steel out the body then make tabs on the body steel to bolt it to the floor structure.

I'm going with no interior in the car. I saw a T bucket with rhino lining on the inside over all the enforcements and the floor and I thought it looked as good or better than just sheet metal panels for a dragster.

Rather than encasing the steel tubing to the body in fiberglass, is there a structural bonding agent that works well enough instead?

 

[jbisme]

Getting glass (epoxy) to bond to steel is a mission. Rough the steel up with a grinder immediately before you glass it, and glass it all round so the steel is captive works OK, but try as you might unless the ends are totally sealed, ultimately rust will creep into the interface.

Or... try this with the epoxy. Drill hundreds of holes with a #30 drill bit in your steel. Liberally smear the epoxy on your steel and lay the glass. The epoxy will fill these holes and make a bead on the backside. When the epoxy hardens, it becomes like little rivets.

I don't know about long term hold-up as in beyond 10 years, because the coefficient of expansion is different between steel and fiberglass. But I've had some auto body panels rust through and have done this technique with success.

 

[Youngster]

If you're building this as a street car, I would glass 3/4" plywood floor in the body and build the cage as a bolt in piece. I would suggest at least a 6 point mounting if not an 8 point. Weld plates on the frame to bolt the cage to and they could double as body mounts. If you run seatbelts, these could also funtion as body mounts.

As for body stiffing, look at using plain old pine ribs in the body. The different expansion rates of the fiberglass and the metal will cause problems down the road as will the mentioned rust factor. The wood will actually be easier to shape to the body. if you glass it in completely, it will last longer that you will own the car.

Ron

 

[boseefus402]

If you're building this as a street car, I would glass 3/4" plywood floor in the body and build the cage as a bolt in piece. I would suggest at least a 6 point mounting if not an 8 point. Weld plates on the frame to bolt the cage to and they could double as body mounts. If you run seatbelts, these could also funtion as body mounts.

As for body stiffing, look at using plain old pine ribs in the body. The different expansion rates of the fiberglass and the metal will cause problems down the road as will the mentioned rust factor. The wood will actually be easier to shape to the body. if you glass it in completely, it will last longer that you will own the car.

Ron

Id actually prefer to put in a plywood floor and wood ribs because I think it would be alto easier and faster, but how would you do a roll cage then, even bolt in. Its a 28-29 roadster body so I dont think I could snake the cage under the cowl and under the deck in the back. You could put the cage in first then set the body over it all but then Id have these huge slots where the hoops and bars have to pass through.

 

[oldtman]

Since this is not going to be aproved design mabe do a bolt together cage. The one I put into my old 5.0 Capri had the rear braces with the telescoping joint. pinned with grade 8 bolts. I had the frame stiffner kit with a ladder each side under the floor and the main tube inside bolted thru the floor to the brackets underneath ....not as good as a full welded one but a guy in town rolled his 4 X 4 and the shinny box mounted bar kept the cab intact.

 

[Youngster]

Set your body up on the frame, build your cage, install the ribs in the body, glass the flor in from the bottom, install the body and finish glassing the floor from the top side.

Ron

 

[boseefus402]

Set your body up on the frame, build your cage, install the ribs in the body, glass the flor in from the bottom, install the body and finish glassing the floor from the top side.

Ron

I guess I could do it this way, but then I could never get the body back off again. Not that I really want to be putting the body on and off, but its a lot easier to paint the chassis and body as separate items. The plywood floor and wood body stiffeners really do seem alot easier though. Im not shooting any of it down, still thinking. Thanks so far!

 

[boseefus402]

Ooo! This guy's blog helps me out if anyone else has the same problem....

Possums Ratty-T: October 2009

If I do it that way, make the side struts out of wood and do a plywood floor, and then for the front substructure, must make that standalone bolt in and not really crash rated, just out of 1" square tubing to bolt my cowl steering box and pedals to. Then the roll bar be also bolt in and not tied into the front structure.

Not the best solution, but not the worst.