tying a roll bar to the frame

[BUCKYOO7]

i have my front hoop in. Now to tie it in to the frame I'm not sure whats the best way to do that.i have the stock main roll bar still in place can that be tyed in to the frame as well or should i look into a aftermarket one And the the e brake pedal is to close to the roll bar can that be moved it is 1983 cj5

[JeepDawg]

It has been talked about....though it has been awhile...

Two basic schools of thought....to tie to the frame or not to tie to the frame...

Some feel that a frame tie in is the strongest....

I personally think it is better NOT to be tied into the frame....reason being, if a roll over is that bad....I would rather the tub seperate from the frame and go it's seperate way. In addition, a frame tie-in will transmit more vibration to the tub...unless you duplicate some type of body bushing to isolate the vibration.

Anyway...here is a pic of how my front hoop attaches....I go through the dash and attach to the floor. When we made the roll cage, we replaced the stock bar with a new one....all of my attachement points are to plates that are at least 4"x4" with simlar plate on the bottom of the tub....if that pulls out, frame tie in is not going to do me much good.....

I love the setup....not only do I not hit my foot on the bar getting in and out....I can roll my window up and down with the door closed.

And, yes, my e-brake is gone....I'll working on putting in a hand operated one.

[jeepdanut]

Yes there is two schools of thought; I fall into the tie it in school. If you choose to not tie it, it is critical you do not use the same size top and bottom plate as it can easily punch through. On unibody cars we usually use a 4x4 inch on one side and a 6x6 inch on the other. Look at a rule book for any type of racing for guidance. If you can make your plate attatch on two planes its even better. For example on your front bar at the floor we make the top plate a 4x6;4x4 with a 90 degree bend leaving a 2x4 to weld to the side of the tub inner structure. We also drill and plug weld our plates in addition to stitching the perimiter. Around here most Jeep tubs have been rotted and poorly repaired. We have been known to run a plate all the way to the dash on them.
IMHO a frame will will rarely separate and get away, just half separate and continue to beat on you with every revolution.

[jdoggmoney]

Also, if you plan on tying your cage to the frame you better darn well have your seats and all seat belt mounting points attached to the cage as well. Regardless of which design you go with, the last thing you want is for your seats to try and go with one part of the jeep while your seat belts try to go with the other!

On an older CJ with rust issues in the body attachment points and frame I could see body/frame separation happening fairly easy. But on a newer or more solid Jeep it would take much more force. I KNOW my current tub and frame are completely rust free and solid. Therefore I did not tie into the frame.

[spook2]

I look at it this way. If your cage is attached only to the tub then you are forcing the tub to absorb all the energy generated during any type of roll as transmitted through the cage, whether major or minor. If you attach to the frame then the frame is absorbing that energy. A much more robust foundation in my opinion. Sturdiness of sheetmetal, body mounts, etc becomes a moot point.

I personally see no argument that justifies mounting to the tub and calling it good. I can envision no scenario that makes it desirable to have the tub separate from the frame with you still in it. Actually I imagine any such scenario to be of such an exceedingly violent nature to begin with that you'd be unlikely to survive in any case.

Beyond all this, the vast vast majority of rolls in our little hobby are mostly just low speed flops onto this or that side with the occasional actual 360 deg. rollover. While more severe rolls do occur they would be in the minority I'd wager, but in any case why not build for the worst case scenario (within reason) to begin with? It's not that much more of a pain.

That's my story.

[LEVE]

Anyone remember that Jeep roll in Colorado a few years ago that killed the driver? The Jeep only flopped down a few hundred feet down the side of a mountain when the driver got off camber while climbing up a small rise. The roll was a disaster; the body separated from the frame and the frame and running gear continued further down the mountain. The driver's dog jumped free and lived. Had the driver installed a full roll cage, attached to the frame as well as the seats to the roll cage and a good seat belt/harness, he would have gotten the ride of his life but lived to tell about it.

IMHO, a roll cage should be mounted to the frame, and the seats to the roll cage. I didn't always think this way till I saw pictures of the above wreck. I like the roll cage to have a little clearance where it goes through the tub to the frame. That lets the tub and frame twist a bit. I'm not a fan of sandwiching the cage mounts to the frame mount with the tub in between. That limits twist and can cause racking of the tub under more extreme conditions.

Check out July 1995 of 4X4 Mechanics, page 61, Caging a 4X4. It's a good primer on building a good cage.

[bandhmo2]

Originally Posted by LEVE

Anyone remember that Jeep roll in Colorado a few years ago that killed the driver? The Jeep only flopped down a few hundred feet down the side of a mountain when the driver got off camber while climbing up a small rise. The roll was a disaster; the body separated from the frame and the frame and running gear continued further down the mountain.

I remember seeing some pictures of that one, they did not stay on the web long, I suspect out of respect. However, it would be good if they were shown more to give people an idea of what exactly can happen.

I am in the school of thought to tie the cage to the frame. However, I will grant that a properly designed body to cage only system would be okay. The problem with such a design is how do you keep the body attached well enough to the frame while making sure that it fails in the body mounts when needed. To me there are just to many unknown's there to make the design easy without a lot of engineering. The sad truth though is that in a long roll down a hill even if the cage holds togeather and the driver is protected there are still issues with impact causing internal bleeding and broken necks. For that reason, I fear long hills with no trees or other things to stop a roll.