Exoskeleton question with a minor twist

[MGrobe]

I apologize in advance if this isn't considered an advanced fabrication question.

One of these days or more likely years I'll probably want to add an exoskeleton cage to my XJ as a safety measure for both me and my Jeep. In planning the process in my mind I am curious about a couple of concepts.

Here is background on my Jeep and myself as I know the inclination of some and the type of responses that have been given in the past.

My 98 XJ is in fairly pristine shape with only a couple of minor dents for the 8.5 years of ownership. She still is my daily driver so keeping her intact is still a priority of mine. She doesn’t have an internal cage and really won’t ever have a full internal cage. I may entertain something in the C pillar area but beyond that isn’t likely.

The reason I won’t be installing a full internal cage is due to my physical disability. I have been disabled for 2/3’s of my life and counting now due to severe arthritis which has fused a number of my joints and puts a limit on the amount of lift height of my XJ. Anything higher than my current 4.5”/33” tire and I won’t be able to get into it, especially in the winter when the footing is unpredictably worse. A B pillar support might work if it doesn’t contain any cross-bracing, which makes it questionable for the value of support it would still offer. Without a mock-up I still worry that it would be to intrusive as well.

Back to off-road, my health impairs my ability to arbitrarily attack any ultra-hardcore trail. I have to think about what I am getting myself into prior to entering a trail and sometimes caution is a necessary evil. Reason being is if I roll my Jeep, chances are I will be stuck in the seat in the same position until my jeep can be righted. This can be an agonizing amount of time for someone like me.

Ultimately I want an exoskeleton that can hopefully protect me and keep my XJ in reasonable shape in an unforeseen rollover. Obviously I come first in terms of safety, but I would hope that whatever I build would do whatever it can to spare my jeep from becoming a topless off-road vehicle.

Sorry for the crazy long background and here are finally my two simple questions.

In designing the cage, would it be better to tie the cage in as much as possible to the XJ’s structure their by adding to the rigidity of the uniframe. Or keep it free floating as possible so that the tubing bends and absorbs impact that hopefully won’t be transmitted to the jeep. I realize the answers may vary depending on the type of roll over, but any input is appreciated.

 

[ChuckD]

Why not just buy a CROK cage?

Even the best external cage won't keep your body from getting damaged. The only way to do that would be to keep it at the Mall and only go over the small speed bumps, NO CURBS!

 

[MGrobe]

I appreciate the response. I am aware of the C-ROK kit and I might use that as a basis, but I am leaning towards fabricating one from scratch. Partial reason being is that there is too many minor changes I would make to the C-ROK kit that I doubt it would be worth it in the end. Hence the advanced fab post.

Yeah I am aware that the only way to prevent body damage is to leave her parked. As I said above:

Ultimately I want an exoskeleton that can hopefully protect me and keep my XJ in reasonable shape in an unforeseen rollover. Obviously I come first in terms of safety, but I would hope that whatever I build would do whatever it can to spare my jeep from becoming a topless off-road vehicle.


So you can see what I am trying to figure out is which is the best technique to give me the best edge to saving my neck and hopefully minimizing body damage if possible.

 

[Roxtar]

Would definately tie in the frame rails.
This way the cage strengthens the chassis (badly needed on an XJ) as well as protecting the occupants.

 

[csuxj]

In designing the cage, would it be better to tie the cage in as much as possible to the XJ’s structure there by adding to the rigidity of the uniframe? Or keep it as free floating as possible so that the tubing bends and absorbs impact that hopefully won’t be transmitted to the jeep. I realize the answers may vary depending on the type of roll over, but any input is appreciated.

This is something that I have been wondering about as well. I think pretty much all exos tie into the front bumper, rear bumper and sliders. Some cages tie into the pinch seam on the roof (where a roof rack mounts) and recently someone was talking about tieing their cage into the door hinges.

There is already a relatively high degree of rollover protection built into the cab in stock form. This protection isn't intended to hold up in the conditions we put our vehicles through, but it seems natural to me that tieing in the exo in as many locations as possible would add the strength of the stock rollover protection to the cage, and minimize the amount of tubing and design necessary for the exo cage.

Is this correct? Why don't we see more A/B/C pillar cage tie in's?

 

[MGrobe]

Your thoughts are very similar to mine. On one hand you would think tying into the vehicle as much as possible will add more strength overall. Perhaps it can be overkill if done too much similarly to some of the over triangulated cages you see.

On the other hand I can see some benefit in keeping the attachment points to a minimum which would transmit less energy to the vehicle upon impact. Perhaps similar to the difference between a rubber bushing and an rod end.

 

[csuxj]

Your thoughts are very similar to mine. On one hand you would think tying into the vehicle as much as possible will add more strength overall. Perhaps it can be overkill if done too much similarly to some of the over triangulated cages you see.

On the other hand I can see some benefit in keeping the attachment points to a minimum which would transmit less energy to the vehicle upon impact. Perhaps similar to the difference between a rubber bushing and an rod end.

Where and how were you considering tieing the cage in to the body?