Need bracket ideas for exo-cage type roof rack

[Jim K in PA]

We got our RTT from Main Line Overland yesterday :wings: and are now moving toward the design/build of the roof rack to mount it on our 2005 LJ Rubicon. For a plethora of reasons, I am not interested in any of the aftermarket roof racks. This custom rack will have three down tubes per side. The tubes will mount to the body tub at two points per tube. The body tub is being reinforced with 3/16" steel plate at all the mounting points. The entire rack will be removable from the vehicle. I do not want to rely solely on the shear strength of bolts for the vertical load, and am looking for a bracket design that will utilize a mating design to transfer the load to the body, and bolts to join the brackets to each other. Land Rover racks use a somewhat similar design to what I do NOT want:



I have a couple of designs in mind, but both have drawbacks. One will have stand-off type brackets akin to a body to frame mount, with a pair of bolts to clamp them together. However, when the rack is removed, the fixed side on the body tub will protrude approximately 2.5" from the surface. This is not the end of the world, but they certainly present snag points. The other alternative utilizes a pair of reversed beveled plates for vertical load support. This produces a nice, almost flush mount profile on the vehicle with the rack removed, but requires that the retention bolts pass through the tub wall. Captured nuts on the inside of the tub invite thread damage and potentially sheared bolt that would have to be removed (with great difficulty).

Has anyone utilized a low profile design for mounting an exo-cage or roof rack that does not rely on fasteners in shear and is low profile?

I figured I would throw this out and see if anyone has any idea of what I am babbling on about.

 

[jeepdreamer]

Hmm... interesting challenge

If I follow this correctly, you don't like the Landy cage because its basically not removable due to lots of bolts holding it in place, right? Hmm... This is and interesting design conundrum. I wish I had some better ideas but I'm gonna watch and see where this goes. I'm about the hack the exo- rack off my Scrambler due to not liking its design. I wonder if StumpyXJ or JScherb could offer some insight as they are both highly creative and inventive...

 

[Jim K in PA]

The LR cage has bolts through the tub, which are difficult to get to for removal and reinstallation of the cage. That is the primary problem I have. I also do not like the single mounting point. I am using 1.5" x .120 DOM for the rack, which will be plenty stiff, but I would rather not have the load(s) concentrated on one point where the legs attach to the tub.

Here is another example of an exo-cage that is close to what I am looking for, but not quite. It has single mounting points, and through the tub bolts.

 

[jeepdreamer]

What not to do...

I'll add (if I can find some) a couple pics of how I tried to do mine to keep it removable but its not really what you seem to be after. One thing I wonder is, should the mount be solid or have some sort of bushings to allow for frame and body flex.?.
*addition* Sorry... only two pics I could find off hand quickly....

 

[StumpXJ]

What Jeepdreamer posted is about the only other option I could come up with. I think two things need to be looked at realistically, how often would you actually have to/want to remove this (my guess is not often at all), and whats wrong with mounting in shear? From a physical/mechanical standpoint, there is NOTHING you could put on that rack that would have any negative effect on a properly mounted shear set-up (i.e., backing plates, etc), especially with 3 tubes per side. The backing plates could have the nuts welded to it for fairly easy bolt removal should you need to take it off.

I understand your concerns - and ultimately its up to you- but im personally not convinced they are valid enough to reinvent the wheel, so to speak.

 

[jscherb]

I wonder if StumpyXJ or JScherb could offer some insight as they are both highly creative and inventive...

Sorry, I don't think I can be much help on this one - I'm not a fan of exocages, which is why I designed the Safari Cab to tie the roof rack into the roll bars. No weight is borne by the fiberglass roof, all weight is transferred directly to the roll bars.

 

[squint]

Have you thought about attaching the rear supports to your bumper (not sure of the flex implications though)?.

On the other hand, do you have corner armor? I think I would go with some plates or armor and some weld nuts. It would be strong, fairly easy to remove, and aesthetically pleasing.

 

[Jim K in PA]

Thanks for the input guys.

JD - thanks for the pics of your -8 setup. I see that you intend to leave the lower section of tubing attached to the tub, and seperate the rack at the flanges. I want to remove the all of the tube when the rack comes off.

Stump - your points are totally valid, and I am kicking the same questions around in my head. My LJ is my DD, and will be for the next 3-5 years most likely. That is what is motivating me to take the cage off, during the winter months especially when I won't likely be traveling/camping with the RTT on top. The mounts will be welded to outer armor, and there will be inner backing plates inside the tub. Given the distributed load over three tubes per side and 2 mounting points per tube, the mounts can be reasonable in size.

Greg - I do not want to have the rack mounted partly on the tub and partly on the frame due to the inherent differential movement that can/does occur. In fact, that is one of the reasons I do not like many of the better roof rack designs since they combine a front windshield mount (ABOVE the hinge pin!) and a rear frame mount.

I did some thinking over the weekend and discussed it with a friend of mine who is also a custom fabricator. Rather than rigid mounts, I am now looking into some rubber bushed mounts. The rubber bushings/sleeves will be welded to the down tubes, and there will be a receiving bracket welded to the outer plates bolted to/through the tub. They will be relatively small, and therefore when the cage is removed, there will be little projecting off the surface of the tub.

I'll post up pics when this is finally put together.


Thanks again for the input.

 

[Jim K in PA]

Sorry, I don't think I can be much help on this one - I'm not a fan of exocages, which is why I designed the Safari Cab to tie the roof rack into the roll bars. No weight is borne by the fiberglass roof, all weight is transferred directly to the roll bars.

Jeff - I intend to use my soft top as well as my hard top, with and without the roof rack/RTT. That is why I do not want a through the roof/cage supported rack. I am not a fan of the extensive frame tied exo-cages with the forward tubes either, but this is hopefully going to be similar to the LR type rack, which I actually like. Different strokes, and all that.

 

[jscusmcvet]

Just thought I would chime in. Doubtful I have any experience with designing or fabricating compared to those who have already commented. I just wanted to say that I have a ton of respect for someone who envisions exactly what they want and resists compromised that would make it something less than desired.

I often look to other industries when I cannot find what I want. I wonder if there is some type of mount from another industry where you can leave the mount and remove the rack. Specifically I am thinking of the marine industry where there are racks and such that are made for easy removal.


http://atlantictowers.com/store/tower-parts/standard-tower-mount-fitting/prod_7.html

Might not be perfect, but might spark an idea.

Best of luck. Look forward to what you come up with.

John

 

[Jim K in PA]

Thanks John. Yeah, I generally stick with an idea until I have either reached a point where the path to realization is not worth it, or I have accomplished what I want. I have many Jeep friends that have assured me that as soon as I reached my initial goal, I would be upgrading beyond that (lift/tires). I have my suspension 90% where I want it, and am moving along with the other aspects of the truck that I want to improve or adapt to my liking. I can make decisions easily, and I do waaaay more homework than I probably need to before finalizing my decisions, at least with respect to the LJ. That is why I solicit ideas where I can, and per your suggestion, I look outside the usual places for inspiration. I have a lot of marine oriented electrical components on my rig, for example. Being an engineer makes me think through problems before jumping to solutions.