thats basically what im doing with mine...

 

Should work fine. Roll cages in uni body or sub frames cars use flat plates sandwiched between the body and they are NHRA legal. Should be fine to use plate on teh bottom side and run the rest to the frame.

 

The difference between a unibody and a pickup is the pickup's frame flexes far more than a unibody does. If you're set on the frame mounting the way you're describing, I would suggest using bushings at the frame - similar to aftermarket engine mounts, or suspension links. Using rubber, or a soft poly bushing will allow most of the amount of flex it'll need, to keep from ripping your floors apart

 

On 2004-09-14 11:45, davids78bronco wrote:
The difference between a unibody and a pickup is the pickup's frame flexes far more than a unibody does. If you're set on the frame mounting the way you're describing, I would suggest using bushings at the frame - similar to aftermarket engine mounts, or suspension links. Using rubber, or a soft poly bushing will allow most of the amount of flex it'll need, to keep from ripping your floors apart

I believe he wants it frame mounted to provide more roll over protetion than prevent flex. The poly body bushings wont help keep the frame attached to the body in a roll over. Attaching the bar to the frame kills 2 birds with 1 stone

 

i kinda wanna do both, stiffen the frame and make the roll bar functional... and like i said im not trying to be cheap but i already have most of the work done by having the factory roll bar, just seemed like the simplist way to do it would be just make seperate peices that bolt to the bottom mounts of the roll bar and then to the frame....

i also need it to be "removable" so i dont have to hack it to peices when i take the body off....

ideas and critism welcome....

 

On 2004-09-14 11:45, davids78bronco wrote:
The difference between a unibody and a pickup is the pickup's frame flexes far more than a unibody does. If you're set on the frame mounting the way you're describing, I would suggest using bushings at the frame - similar to aftermarket engine mounts, or suspension links. Using rubber, or a soft poly bushing will allow most of the amount of flex it'll need, to keep from ripping your floors apart

I agree with this, however there are issues.

Agreeing:

Make the plates that bolt up under the body to match the existing ones on top of the body and then drop a brace down to the frame and attach it via a bushing to a mount on the frame.

Stiffen up the frame and provide a solid mount for thebar.

Disagreeing:

Now, how will the body react in a serious roll? What if the body rips of the body mounts/frame? Will the body hold up only sandwiched between the plates or will is separate and beat the crap out of you as it is now loose an you are bolted to it via teh seats/belts and the roll bar/cage is there mounted to the frame not moving?

If the cage/bar was bolted to the body only with plates on top and bottom and those plates are tied together to minimze the chance of ripping the body the cage/bar will stick with you if the body separates from the frame and you'll be safer. But it does not stiffen up the frame enough, nor does it provide as good of protection ina hard roll but the body doesnt separate.

There was a good post on Pirate about this. Some guys fell 100 feet down a hill at Tellico or someplace and only lived (and walked away) becuase the body separated from the frame and the cage held up as it was bolted to the body only.

 

yea there was a previous post about roll cages where i mentioned that....

my idea of a roll cage for optimum saftey, the seats mounted to the cage, the cage incasing the driver but not solidly attached to the frame. except on somthing like a full tube chassis where the frame IS the cage.

but im not trying to build a roll cage, i dont roll down moutains i just drive slow trails... basicly i just want the roll bar to be able to support the roof if the truck where to tip over on a steep bank so the roof doesnt cave in... right now i dont think it would do that, the roof would just push the roll bar through the floor and probably totally cluster @#*@ the body and wack me on the head....

if the 4 mounts attached to the frame, and it "fell over" technically it should only dent the roof and the bar would support the truck, and i could just winch it back on its feet...

not looking to make something to survive tumbling down a moutain, just something to save my truck in the event of a slow speed tip...

 

i just dont feel like it would be a good idea if there is any frame flex at all, b/c i think wonce you start mounting it hard like that i think it will buckel your floor if the frame twists at all. but i dont no how your frame moves so basically that is something you have to know.

i like the idea like said above of using some kind of ploy bushing like a body busing that would enable it to move around a little but it would not move enough that it would still not work.

know this is all written strange but i cant think of a better way to word it

 

Quick drawing in autocad, but this is what I was talking about, as well as most others -

[img=500x259]http://www.supermotors.org/getfile.php?id=119503&toggle=fullsize&f=.jpg[/img]

I might even consider this, for the 4-point cage. Even Boss' auggestion, about the self-mounted cage, referenced from POR, is a good idea

 

Bad idea IMO.

Keep the 'cage away from the frame or you will fatigue it, possibly causing it to fail when you need it most.

 

wtf are you talking about tim... the way that cad drawing is very close to how lots of people tie their cages into the frame and the ones that i know have unfortunatly tested their cage out walked away in good shape with the exception of bruises and what not. although most people put the bushing up by the plate that bolts to the floor rather than the frame.... having a cage that isnt tied into the frame wouldnt hold up as well in a roll over depite what you may think. ive seen first hand the horror that can happen in a roll over where the cage is just mounted to the floor rather than being tied into the frame.

if you dont tie it into the frame you might as well get you a chrome light bar (be it a 2,4,or 6 point version).... it will work about the same when it comes to a roll over.

 

here is just one example of what happens to a roll cage that is just bolted to the floor and not tied into the frame after a mild roll over.

[img=500x375]http://classicbroncos.com/forums/attachment.php?attachmentid=6582[/img]

 

yea... see thats what i dont want....

right now thats all my roll bar would do, bust through the floor pans and be completely and utterly useless even in the slightest roll over

its like trying to jack your truck up by the floor pans.... sheetmetal isnt exactly load bearing :bigthumb:

 

why not like this?

the section at the frame side would be hard mounted with bolts or welded what ever you wanted to do, and the roll bar side would be attached with a body bushing just as if you were attaching the body to the frame, that way you would be able to still have a little bit of frame flex but in a roll over the bar would still be attached by way of the bolt that you would run through the new mount.

sorry i used the other pic to make mine :silly:

 

at this point it would seem easier to just cut the floor out where the flanges bolt to it so it doesnt touch the body at all.... :roll:

 

that is also a possibility, you could always just get some kind of huge rubber gromit and run the cage through that.

 

On 2004-09-16 12:48, okiebronco wrote:
here is just one example of what happens to a roll cage that is just bolted to the floor and not tied into the frame after a mild roll over.

[img=500x375]http://classicbroncos.com/forums/attachment.php?attachmentid=6582[/img]

I all comes down to the size and number of attaching points, as well as cage design. My cage uses 7 mounting plates, each one is 30 square inches.

The three plates under the 'B' hoop and 'V' brace are bolted through a heavily reinforced part of the body where the body mounts are on my truck. The two rear mounts are through the tailpan (again a reinforced area) Only the two front plates are through sheet metal only, but they are next to the front body mounts.

There is no way in hell my cage will go through the floor. Seats and belts are all mounted to the cage as well.

I figure the cage firms up the body and helps keep the frame from over-flexing, without creating stress risers in the frame itself.

i have to find some place to host a few pic's.

Rene

 

http://www.villagephotos.com/pubbrowse.asp?selected=1010035&foldername=Photos

Rene

 

On 2004-09-16 15:00, SalvagExpert wrote:
at this point it would seem easier to just cut the floor out where the flanges bolt to it so it doesnt touch the body at all.... :roll:

That the best IMHOP.
When you use a bushing as in the pic's the bolt becomes the weakest point.I would not want to count on a few 9/16" bolts to hold up my truck

 

your thinking too small, use like a 1 inch bolt