heres the thread

http://www.pirate4x4.com/forum/showthread.php?s=&threadid=127060&perpage=25&pagenumber=1

i didnt notice anything about cherokees (no frame). im planning on putting a full 8 or 10 point cage in my jeep. as soon as i get my tubing bender (not bending tubing for cage, wanna tie new prerunner bumpers, and rock sliders into cage). but where do i mount the cage to the "unibody" im so very confused. pictures would be great help or at least good assumptions. thanks

chad

Check with Rob (Bender), at Shaffer Off Road . He has worked with Cherokee's; bumpers, sliders,cages and such !!

Please refer to them as Cherocars from now on.

Thank you for your cooperation.:D

Originally posted by pmurf1
Please refer to them as Cherocars from now on.

Thank you for your cooperation.:D BWAAAA HAHAHA

http://home.off-road.com/~mithrandir/por_stuff/bitch%20slapped.gif

Originally posted by pmurf1
Please refer to them as Cherocars from now on.

Thank you for your cooperation.:D

Yeah, that might just have to go in the sig line! :D

That's funny chit Pat...

...and didn't I already read this post in another forum? Or is it just virtual deja vu?:confused:

It is kinda complicated with an XJ. I am in process on mine. Most people take the sissy approach and just put exocages on them.

My personaly philosophy is that I purchased a unibody vehicle cause the body is a perfectly good exocage.

For drag racers when they put a cage in a unibody vehicle (or one that doesn't tie to the frame) they use a 6" square by 1/8" minimum 1018 steel plate welded to the chassis (floor pan near one of the pillars) as the tie-in point on the cage.

I also plan on tieing my cage directly to all of my pillars using some heavy guage (14 ga or so) sheetmetal, so that the pillars and cage will both be stronger.

Plate the floor w/ 3/16" &/or make sub-frame tie-ins.

heres the correct link

http://www.pirate4x4.com/forum/showthread.php?threadid=127060

Just make some steel pads and weld them to the floor sheet above the "frame" - my internal ties into my exo by peircing the roof in a whole bunch of places - the only other trick to an XJ is to tie into the suspension mounts via a direct connection or through the rocker protection... Once you have done that you will be all set...

I have also seen folks grab the seat belt bolts (shoulder) and tie the seat w/ mounts into the cage....

Matt

PS: I know mine works as it went all the way over pretty hard (witness said it bounced ~6 or 8" into the air off the ground after the landing on the roof) and the only damage was where the pass side dash down tube connected to the floor - I never got around to connecting the pad into the rocker rail (3/8" below it underneath) - The tube pushed the sheetmetal floor down until it hit the 2" square 0.25" wall rocker rail support and then stopped - I have a small dent in the roof where the tube that connected to the exo pulled the sheetskin of the roof downward a little... :flipoff2:

Originally posted by wanderingwillys
Matt

PS: I know mine works as it went all the way over pretty hard (witness said it bounced ~6 or 8" into the air off the ground after the landing on the roof) :flipoff2:

Nice:D

The prefered method of attaching plate to sheetmetal would be brazing. When done correctly, brazing is extremely strong. At one time, this was how aircraft were put together. This requires some skill though. Welding the plate to the sheetmetal can cause the sheetmetal to crack along the weld. Anotherwat to do it is use 2 plates and sandwich the sheetmetal between them, bolting the plates together. Use different size plates on the top and bottom to prevent cracking at the edges.

You could always put a frame under it like this guy... :laughing:

Originally posted by 05wrightm
You could always put a frame under it like this guy... :laughing:
http://www.pirate4x4.com/forum/attachment.php?s=&postid=1576339


Stock suspension between the two frames?

super soft ride:D

yea. I dont' remember where I got that from.

ya so ive got alotta good ideas but a few are not gonna fly like the frame thing nope not my style i like the unibody its light weight. and it makes people look like asses when they ask my why i didnt BL my jeep. the different size plate thing is one thing i didnt think of its a good idea now with my 220 welder can i just get good penitration and weld the 2 plates? or is bolting a better idea??? never did figure out which is stronger when done right i thought welding was????

Building a cage for a unitbody or monocoque chassis is much like any other except the room to work is limited and you need to watch how attachments are made on the thinner chassis material.

Major external forces should have the force vectors (the force that is transmitted down cage members) grouped to intersect at nodes (group tube junctions to have forces meet at common tube junctions).

Thin member components (thin tube wall and box members) may need to have the force spread out on the junction with plates (face and backing plates: more to add weld inches and room for fasteners, rather than simply add plate edge shear area).

Try to remember a few primitive aircraft manufacturing rules of thumb when working thin sheetmetal. Try to keep force vectors parallel to sheet metal at the connections, or back up the connection with a bracket (one that does transfer the force to a parallel plane or frame member). Use rivets or screws (small bolts and stitch welds) with shear forces, and use bolts where tension or compression forces exist. The safe rule is to use bolts as much as possible, and weld with steel (before WWII, when these rules were learned, aluminum welding was limited to solder and brazing -- before heli-arc).

Understanding how to design components to apply forces in parallel shear planes is necessary with a unitbody because the thin sheet metal construction usually cannot resist direct tension or compression forces (the thin structure folds and collapses).

An example of where this applies is an internal cage member tied into the body floor. The typical body cage is plate mounted to the floor (the typical CJ cage/body on a frame) sometimes with sandwich plates for added strength (added weld inches and shear area due to the limited surface area of the unitbody). The major connection forces are in tension or compression, perpendicular to the sheetmetal body or unitbody (the force vector path of least strength).

This connection can be improved in a unitbody by extending the force path to a location where the forces can be applied parallel to the sheetmetal construction, to the unitframe through the use of an angled lower sandwich plate that captures the tube member plate at the floor and the side of a frame rail. This is a long way of saying that the lower plate should be a piece of angle: with one side of the angle being the sandwiched backing plate for the internal tube plate, and the other side of the angle being attached to the side of the unitframe (where the forces are now applied parallel to the frame sheetmetal, with much more rigidity than the perpendicular connection of the body floor alone).

The other area of design to watch is where you are attaching to thin unitframe rail members (thin formed sheetmetal, rather than thick wall tube shapes). A through-bolt can easily collapse the formed tube rail. The solutions to prevent collapse of the thin rail, and gain a good connection, is to use a crush sleeve (to bridge the thin walls of the formed tube) or use an external thick wall formed plate (wrap the thin formed tube with a thick wall junction plate that cannot collapse and adds shear length area). Jeep used crush sleeves where the steering box is bolted to the unitframe rail, and formed plated where the control arm mounts are welded to the unitframe rail (examples of these design techniques on an XJ).

The last thing to remember is a unitbody can exploit truss construction to span large areas with minimal weight (between the suspension mounts). Consider the traitional frame as a massive beam, and a unitbody as a thin truss structure (an upside down beam or truss, as the forces are applied upwards, compared to a bridge where forces are applied downwards).

An efficient truss needs to have rigid top chord members, and can have a reasonable reduction in weight on the bottom chord without a strength penalty. The few FIA analysis plots seen on this board provide an example of how this works with a chassis: major stress on the lower frame area (the top chord of the upside down truss) and minimal stress on the cage halo (the truss bottom chord). The overall truss rigidity is improved if the top and bottom chord members are attached with as many points as possible (many cross ties or a shear panel).

A unit body cage can recieve considerable added rigidity by connecting the floor/frame into the roof/halo (combine the unitbody and cage at both top and bottom chord members). This technique exploits the combined strength of the cage and unitbody (rather than two independent trusses). The unit body adds considerable shear panels and the cage adds chord strength. Off-road racers have been joining the frame and body with rigid mounts (building a unitbody out of the body on frame assembly) and exploiting the unitbody and integral cage truss construction strength for decades (the body on frame folks can benefit from unitbody construction technique as well).

A good look at unitbody Rally car cage construction and composite panel racecar construction (and aircraft) will point you to techniques that will increase the efficiency and strength of the combined cage and unitbody. Just remember rules dicatate the main hoop and some of the cage members size and thickness, so follow the rules where necessary (even if it is overbuilt, what is needed to strenghten a traditional frame, compared to what is needed for a unitbody).

Happy Trails!

Good explination.
I think the biggest hurdle in trying to work with the XJ or any other unit body vehicle is that it wasn't desingned for the twisting stress that big flexy suspensions and hardcore wheeling put on it. The sheetmatal fatiges easily. This problem is compounded as suspension mounts get moved from their designed locations as is commonly practiced on XJs. If I were building one, I think I would approach the cage design as if I were building a complete tube chassis inside the vehicle, tying the suspension mounts into the chassis. I would then "hang" the body from the chassis at the unit body structural points.