Roll Cages

[firestarter]

So I've been looking around at roll cages and am wondering if anyone on this forum currently has one in their XJ? In comparing rally car type roll cages to off-road cages I have a few questions if someone would like to give their opinion on it.

1.) It seems like the majority, if not all, of them bolt in .... doesn't this seem quite weak? I would think that if one were to expect the roll cage to actually function in the time of need that they would spend the extra few hours and weld it on.

2.) It almost seems like the "standard" design (use this as an example CrazyJim's Jeepspeed/Prerunner XJ build - NAXJA Forums -::- North American XJ Association) wouldn't hold up given a good side impact due to all the long sections of tubing. If the intention was to save the driver should more thought be placed into supports, gussets, angled tubing to support key points (such as Four Star Motorsports: Custom Roll Cages)

Without the supporting sections (described by the rally car link) it seems like the standard cage would collapse during a roll and possibly trap the driver, resulting in injury.

Thanks in advance,

 

[MudderChuck]

It's all a compromise between weight and protection is my guess. Many of the full body cages also double as frame stiffeners. They are as much for strengthening the frame as they are for protection.
My personal opinion gained through experience (my wife rolled an XJ) and observation (pictures I've seen of XJ rollovers) is the " A" pillar is the weak point in a roll over and someplace I'd overkill on the engineering a bit. Side protection for the driver is nice, but sure makes getting in and out a pain.
Triangles are pretty much the strongest geometric form in most constructions of any sort.
Lastly I've seen the base of a roll bar go right through the floor (bed) sheet metal on a pickup. The roll bar itself didn't collapse per say, but the legs went right through the floor sheet metal, it collapsed after a fashion.
Maybe a bolt in roll bar with a base plate on the legs may be stronger. There is also a factor in welding, many forget, it's called annealing.

Annealing (metallurgy) - Wikipedia, the free encyclopedia

The area around the weld, say the floorboards, can actually become soft due to the heat from the weld. The heat spreads and you end up with a rough circle of different temperatures. You hit the right temperature and then let it cool slowly and you end up with some pretty soft sheet metal.

 

[Allen's Offroad]

Most bolt in cages are basically sport cages designed to reduce the potential negative impacts of a roll over. Personally, in a high impact roll over, I want my vehicles body to stay as intact as possible, and if something disastrous were to happen, the body to separate from the heavy stuff and still keep me protected..

This is why I am a fan of the better bolt in cages. They are attached to the body only and are designed from the start to have a certain level of allowing for crush points (given adequate mounting engineering so as to not punch through the floor). Meaning that a hard impact on the roof will not hold the passenger compartment perfect from penetration, but will hold it back from completely crushing you while keeping you alive.

I a major impact there are always (3) collisions:

Vehicle with something, you with vehicle, internal organs and the inside of you. Having "some give" built into the product without failure will reduce the overall force of the last two by absorption of energy.

All personal opinion I guess.

 

[54cj3b]

stumbled upon this place cages look like fairly nice cages

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