Roll Cage Connected to Frame

[buckintone]

put as close to a 45 degree gusset rom the frame to the cage, put a flat 1/4" polyurethane bushing, possessing the same hardness derometer as the polyurethane body mounts you're (probably, or should be)using now, sandwiching the floor pan between the gusset and the cage mount. Make your gusset frame mount 3 sided over the top, outside and bottom of frame rail (3)attachment points to ward off a shear failure from occurring in the event of a roll over. The added benefit of this is chassis rigidity, which is highly desirable in any vehicle. I even ran a bar over and through my engine compartment to tie my shock hoops together for added rigidity. It will make your ride feel better than you ever imagined it could. suspension dictates ride comfort , if you're looking for comfort loosy goosy style, get a cadillac or isolate ur seat mounts and your steering column with some kind of soft rubber bushing. If ur worried about a hinged bushing like most of the pictures on this thread, you better start with your body mounts because there's no hinges on them.....%)yet

 

[suckerpunched]

From what I have heard the bodys on these babys are notorious for separating from the frame in highway type crashes. If the cage is tied to the frame and the body separates what is the out come? I am looking at doing a cage myself and follow these threads closely. I don't want myself or my passengers being the cushion between the cage and the body.

My bronco already has been in a hard "on highway" crash. Thats why i ended up with it and had no choice but to completely rebuild it. I can see by looking at mine that there is a possibility that all the body mount bolts could be ripped through the floor causing the body to flop around seperate from the frame. none of the factory body mount bolts or brackets on frame failed, but there is some repair that will have to be done to the floor. Mine was hit hard, and was not close to having this happen, but it is possible. dont know they address this with a fiberglass tub, seems like it would be worse. I think any type of frame to cage tie in where the body gets sandwhiched between two plates has to help. That much more of floor has to get torn out before the body tries to leave. also with a bar above the floor from the front hoop to the middle one (see pic) you would have rip the entire floor out before this could happen. I hope no one ever gets to test it out to that extent.

 

[jim3326]

I am using the theory of NASCAR of bleeding off energy. Keep the occupants contained inside the cage, body is attached firmly to cage, if the frame seperates that uses energy but occupants are still firmly inside cage. Now all of this only works as planned if everyone is wearing a 5 point harness at the time, the fewer the points thhe worse the outcome. Personally I don't see the downside of the body seperating from everything that could burn, but maybe that's just me%)

Jim W.

 

[buckintone]

I am using the theory of NASCAR of bleeding off energy. Keep the occupants contained inside the cage, body is attached firmly to cage, if the frame seperates that uses energy but occupants are still firmly inside cage. Now all of this only works as planned if everyone is wearing a 5 point harness at the time, the fewer the points thhe worse the outcome. Personally I don't see the downside of the body seperating from everything that could burn, but maybe that's just me%)

Jim W.

If the frame seperates? I have never seen this? if the cage separates from the frame, you are the energy that will be bled off. the more physical material between you and an un movable mass(earth), the more energy gets scrubbed before it hits you. let's take a roll cage with you strapped in the center of it , and then let's take another roll cage with you strapped in the center of it with that roll cage tied to the frame of an entire bronco. Then lets proceed to drop both of them simultaneously off of a 50 foot cliff! Which 1 would you rather be in when it makes impact ?, its pretty simple stuff.

 

[jim3326]

If the frame seperates? I have never seen this? if the cage separates from the frame, you are the energy that will be bled off. the more physical material between you and an un movable mass(earth), the more energy gets scrubbed before it hits you. let's take a roll cage with you strapped in the center of it , and then let's take another roll cage with you strapped in the center of it with that roll cage tied to the frame of an entire bronco. Then lets proceed to drop both of them simultaneously off of a 50 foot cliff! Which 1 would you rather be in when it makes impact ?, its pretty simple stuff.

Well I don't think it's quite that simple, but if it lands on the roof, I'd rather not have the extra weight pushing on it, E=MC2.

Jim W.

 

[buckintone]

Well I don't think it's quite that simple, but if it lands on the roof, I'd rather not have the extra weight pushing on it, E=MC2.

Jim W.

....? Really? what if a pink elephant sat on a blue mouse? this is the real world. That statement is absurd. A vehicle very, very rarely lands squarely on its roof, unless balanced and dropped upside down from a crane on a windless day. A cage designed to break free from the chassis is a really bad idea. End of story. Any other advise is bad and potentially deadly. When the high profile pro racers start doing it, is when ill consider it. Until then, I've never...ever seen a cage seperate and roll away from a NASCAR or any other race car, other than a disintegrated dragster, and those never end well for the driver.

 

[jim3326]

let's take a roll cage with you strapped in the center of it , and then let's take another roll cage with you strapped in the center of it with that roll cage tied to the frame of an entire bronco. Then lets proceed to drop both of them simultaneously off of a 50 foot cliff! Which 1 would you rather be in when it makes impact ?, its pretty simple stuff.

....? Really? what if a pink elephant sat on a blue mouse? this is the real world. That statement is absurd. A vehicle very, very rarely lands squarely on its roof, unless balanced and dropped upside down from a crane on a windless day.

Which "Real World" are you refering to? As I stated earlier, mine isn't designed to wreck headon into anything, truck or ground, and the theory from NASCAR is shedding parts and pieces burns off energy reducing the impact to the driver compartment. But there also, a NASCAR chassis is one complete component, it doesn't have a separate frame from the cage. If mine was a racing Bronco, the frame would become part of the cage and be fully welded, but it's not. We can agree to disagree on this point and build our respective Broncos as we see fit.

Jim W.

 

[Deano]

Ok here's a question ? If you want your cage to separate from the frame on impact is your steering colum attached to your cage so it comes with you or is it attached to your dash as they all are and rip your arms off when the cage separates from the frame because you are hanging on to it I'm sure for the bracing of your self. Just a thought! And my $.02

 

[jim3326]

As opposed to being shoved through you chest? I don't think my grip is that good. Like I said it's not that simple. With the seats attached to the cage, I feel that is more than adequate for crawling, not many (slow) rollovers are going to rip the body off the frame.

Jim W.

 

[suckerpunched]

yeah thats all pretty awful thoughts of disaster. I think I'm gonna set mine up for slow to semi slow roll overs and keep going to church.

 

[357Bronco]

To the OP'er, you can build mounts like the poly performance ones. Rear control arm bushings for a Mazda RX7 from Energy Suspension, fit 1.75", .120 wall DOM tubing. The sleeve is for 12mm bolt, I have 1/2" shank bolts in mine.If you want the part number for the bushing, let me know, I have the boxes somewhere. I think there's pics in my gallery.

 

[TAC71]

You can't control how the cage/body will separate, which may be catastophic. Tying the cage securely to the frame is the safest, but this also means proper cage design. I have had two of my racecar cages "tested" both drivers thanked me afterward. On my own fiberglass bodied Bronco the cage is directly tied to the frame and the seats and belts are also tied to the frame/cage. It is all one piece. Although this is not really functional for a regular bodied Bronco.

With a street driven vehicle the cage is always an issue. Without triangulation the cage is a compromise of strength vs interior access. Just a small accident can have your head bouncing off one of the upper tubes and without a helmet this could do you some major harm. Those hinged mount points to the frame don't offer much compression/extension strength to the mounting foot of the cage. In a slow roll they would offer some strength.

A friend of mine "tested" his rollbar (not a cage) in a Bronco with reasonable speed offroad. He had it tied to the body only, but very solidly. The roll pretty much totalled the truck but he walked away.

If you mounted the seats and belts to the cage and mounted the cage solidly to the RUSTFREE body. Had the mounts reinforced with a 2x2 tube running across the body between the bodymount and body, replacing your body lift blocks. Used quality hardware with large thick flat washers. This would give you a fighting chance, short of a direct solid connection to the frame.

On other fiberglass Broncos I have built I did away with the stock body mounts and sandwiched the body between the cage to frame mount pads. Again the seats/belts are mounted above the floor directly to the cage.

just my 2 cents

 

[taipeichris]

Good post, good info. Thanks!

 

[patterdale]

I couldn't help but notice the comparisons to race cars. On them the body is built around the frame/cage. The frame and cage are basicaly one and the sheet metal is an add on. That is the difference from a 40 year old Bronco that has a frame and a body. I think that with the sandwiching effect with tubing and or heavy plating that some have mentioned is the best option. It would hold the body and frame together in case of an unfortunate event. My thought was to use 5/16 or 3/8 x 4" plating across the body mounts in the bed (bolted to them) and then weld the cage up from there with some gussets. All the tubing on the floor in the picures I've seen seems unwieldy and impractical.

 

[Jeff76]

im confused on having the hinge on the frame. if the cage pushes through the floor wont the hinge cause the cage to go down even further

Me too. Looks like the cage is set to drop about 6" through the floor before the bracing will even take effect. I think they got the bushing on the wrong side of the bracing on this one. Should be a solid weld tie into the frame. The bushing on the body side could allow for some body roll / flex and still provide a solid brace, depending on the shear strength of the one grade 8 bolt.