Cage Floor Mount and plates:Weld/Sandwich?

[67RT]

I still haven't put together my TBP family cage, but am wondering about the different ways I have seen them fabbed/bolted to the floor pans.
People I know with race cars have the roll cage feet welded with a 6x6x1/8" plate to the floor pan and that has passed cert for an 8.5 second car. That may be overkill with our application, but it passed cert so must be safe.
However, if we bolt the cage to the floor, it seems like many here recommend a larger "sandwiched" plate underneath to prevent bolts pulling thru and/or pinching the floor pan.
I recently saw a very high end Bronco around town that was built by one of our members shop here (a rare sight in DC metro). It had no sandwich plate underneath the floor pan on the three cage attachment points (two rear/one mid) that I looked at. Just bolts and if there were washers, they were not noticeable. It was surprising to me as this thing was SUPER NICE with really nice metal work, paint, cage, lighting, steps sliding out with the door opening, Fittech, new everything, etc..
I guess it would take a lateral force to pull the bolts out thru the floor and maybe some think the primary worry is punching down thru the floor? I would not be comfortable with that, however. Thoughts?

 

[Apogee]

Yeah, that's pretty poor practice. Nothing worse than a solid looking cage that inspires more confidence than it should. I would prefer to use an offset sandwich plate arrangement with frame tie-ins myself and/or spreader bars between the B/C-pillars, but to each his own. My EB currently has a 4-point installed by a previous owner with the biggest booger welds I've ever seen...it's near the top of my list to replace.

A lot of the sanctioned drag racing cage specs you see, or any racing for that matter (NASA, SCCA, etc) that tends to use street cars, are mostly for unibody applications, so there is no real frame to tie into in most instances. The minimum plate sizes as determined by gauge thickness and other factors serve to keep the tubs attached to the unibody, and works well in those applications, but don't universally apply to all applications IMHO.

 

[blubuckaroo]

For my application, I've decided not to do a frame tie-in. However, I wouldn't install any roll bar without using under body sandwich pads. They're easy to fabricate and the weight is negligible.
Flat washers or even fender washers isn't enough.

 

[67RT]

I agree with the unibody statement as there really isn't anything else to tie into.
I was pretty shocked when I looked under and saw that. I alerted the caretaker of the truck and I think they are going to add the plates..

 

[Steve83]

The reason race cars & boats have a cockpit cage that separates easily from the vehicle is: the chassis weight is THE danger to the occupant. Letting it rip free during a catastrophic wreck is MUCH safer than keeping all that weight, fuel, & battery acid close to the human.

Forget tying the cage to the frame - concentrate on making the CHAIRS & belts stay attached to the cage, and let the rest break away.