Cherokee exo..

[BIGdaddy]

I think you are on the right track to incorporate these design elements.

I have seen A-pillar stuff done that is tighter and much less obvious. I want to say at the Advanced section of NAXJA but I'm afraid to send you on a wild goose chase.

I'm not certain I would bring the outside bars out as far as shown on the red XJ. I just don't see the need for the way I'd use my Jeep. I'd focus more on weight carrying, roll over structure and then looks. I'd be inclined to make the front of the halo match the upper arc of the top of the windshield too.

This raises another issue. I'd make the external part of the cage bolt on/off. One of the things that has always bothered me about internal or external cages is the clearances required to change out the windshield. Some guys make them as if you'd never have to do maintenance again. I'm not interested in using a sawzall and welded when changing a windshield. If you make the A-pillar section bolt to a butterfly brace section like I suggest above, and have it bolt through he roof at the rear then the whole assembly can be removed to perform maintenance on the vehicle (changing windshield, repainting, whatever).

I'm really not a fan of that expanded steel bulkhead above. I'd also be inclined to lean the bulkhead back to behind the seat belt top bolts. I might be be keen on the structure with that kind of clearance. Hard to say.

I like the thoughts on the halo. I agree I think something that tucks a bit tighter up top is a better idea for me.

 

[Root Moose]

Another idea to through out there...

There is nothing saying you couldn't take advantage of the "stressed skin" of the roof at the B pillar area via bolting through the roof and somehow making the roof and rack act as one unit. This would add strength of course. Use a plate or whatever is practical above the head liner.

 

[BIGdaddy]

Another idea to through out there...

There is nothing saying you couldn't take advantage of the "stressed skin" of the roof at the B pillar area via bolting through the roof and somehow making the roof and rack act as one unit. This would add strength of course. Use a plate or whatever is practical above the head liner.

hmmmm...that's interesting, but not quite sure I understand, can you explain more? Would this be a different idea that the exo, altogether?

I'm meeting with my buddy tomorrow to measure out total tube ft. and get an estimate going. Love to bring him several idea's.

 

[Root Moose]

Let's see if I can draw a mental picture (all my drawings are a little mental...).

Picture the roof of the Jeep

- picture the headliner... drop it down away from the roof so you see the exposed metal underneath

- picture the structure of the the exo/rack above the roof

- the exo/rack has feet that "bolt" through the metal roof.

- under the the metal roof there is a plate (or plates) with holes that match the exo/rack above. This can either be a stud from the tube of the legs of the exo/rack or bolts that interface with a flange on the exo/rack or whatever makes sense from a fabrication point of view once you get building.

- once everything is bolted together push the head liner back up to hide the plate/nuts/bolts/whatever.

- the plates could in theory be welded in place to distribute the loading... need someone that can weld sheet metal to do it... normal flanged/bolted approach will likely be plenty strong.

You could do something similar at the C/D pillar area too... make the structure distribute the load over the roof more in addition to whatever posts you had in mind originally.

JAT

<btw - this will be expensive to build (man hours)>

 

[BIGdaddy]

Let's see if I can draw a mental picture (all my drawings are a little mental...).

Picture the roof of the Jeep

- picture the headliner... drop it down away from the roof so you see the exposed metal underneath

- picture the structure of the the exo/rack above the roof

- the exo/rack has feet that "bolt" through the metal roof.

- under the the metal roof there is a plate (or plates) with holes that match the exo/rack above. This can either be a stud from the tube of the legs of the exo/rack or bolts that interface with a flange on the exo/rack or whatever makes sense from a fabrication point of view once you get building.

- once everything is bolted together push the head liner back up to hide the plate/nuts/bolts/whatever.

- the plates could in theory be welded in place to distribute the loading... need someone that can weld sheet metal to do it... normal flanged/bolted approach will likely be plenty strong.

You could do something similar at the C/D pillar area too... make the structure distribute the load over the roof more in addition to whatever posts you had in mind originally.

JAT

<btw - this will be expensive to build (man hours)>

ok, yeah, that makes sense...I dig it. it seems like its something that could be added as a phase II type of tie-in, at a later date, so maybe the cost could be spread out a bit.

WAY better than having no connection at all at the B-pillar, or having just a drip rail connection.

One thing that both my dad and my buddy mentioned was body flex. They we're both worried that I'd get stress cracks where the body is supposed to move, but can't due to the exo...

Just can't win..haha! pro and con to everything I guess.

 

[Root Moose]

In theory the body isn't supposed to flex... yeah, an XJ is a wet noodle though.

I figure the more you can restrain the movement the longer the structure will last. The only thing that will change is possibly where the stress cracks occur due to changing the load paths. I keep going on about distributing the load at the front with a butterfly gusset for that reason. E.g. http://www.flyinmiata.com/index.php?deptid=4538&parentid=0&stocknumber=13-71000

On a stock XJ the cracks tend to occur at the front steering box mount n the unirails, around the firewall at various spots where there are holes already in the structure, around the shifter tunnel, etc.

Do the rack, frame stiffeners and rails and it'll be a long time before the cracks appear I figure.

 

[BIGdaddy]

In theory the body isn't supposed to flex... yeah, an XJ is a wet noodle though.

I figure the more you can restrain the movement the longer the structure will last. The only thing that will change is possibly where the stress cracks occur due to changing the load paths. I keep going on about distributing the load at the front with a butterfly gusset for that reason. E.g. http://www.flyinmiata.com/index.php?deptid=4538&parentid=0&stocknumber=13-71000

On a stock XJ the cracks tend to occur at the front steering box mount n the unirails, around the firewall at various spots where there are holes already in the structure, around the shifter tunnel, etc.

Do the rack, frame stiffeners and rails and it'll be a long time before the cracks appear I figure.

I was planning on taking the a-pillar down to the sliders I bought which connect to the unibody rail, as well as the pinch seam below the door.

what do you think about that?

seems like if it's attached at the b-pillar like you've mentioned, and attached behind the rear seats....that it would do well to triangulate the load placed on the A pillar when leaned against by a rock or the ground. (and would also resist flex/preserve the unibody as well)

 

[SWbySWesty]

Here's a slow flop I got to see at Johnson Valley...exo cage. Without the exo cage, he'd have a door to replace...

Does that help? :coffeedrink:

 

[ExpoMike]

Let's see if I can draw a mental picture (all my drawings are a little mental...).

Picture the roof of the Jeep

- picture the headliner... drop it down away from the roof so you see the exposed metal underneath

- picture the structure of the the exo/rack above the roof

- the exo/rack has feet that "bolt" through the metal roof.

- under the the metal roof there is a plate (or plates) with holes that match the exo/rack above. This can either be a stud from the tube of the legs of the exo/rack or bolts that interface with a flange on the exo/rack or whatever makes sense from a fabrication point of view once you get building.

- once everything is bolted together push the head liner back up to hide the plate/nuts/bolts/whatever.

- the plates could in theory be welded in place to distribute the loading... need someone that can weld sheet metal to do it... normal flanged/bolted approach will likely be plenty strong.

You could do something similar at the C/D pillar area too... make the structure distribute the load over the roof more in addition to whatever posts you had in mind originally.

JAT

<btw - this will be expensive to build (man hours)>

Following along on this thread too. I think your idea is fine for the actual roof structure but doesn't really address the pillars, unless you are also including A,C and D bars. If you just have the the roof bars bolted to the roof, even with some internal bracing, in effect you just made a really strong roof rack.

There is no one perfect solution and they all have compermises somewhere. Another thing to keep in mind, in addition to the wind drag of external bars, the additional weight of all the bars (internal or external) will also decrease MPG. I keep playing with the idea of doing some hybrid exo cage but just haven't been able to justify the cons to the pros yet.

Interested to see what comes up in the end though. :ylsmoke:

 

[BIGdaddy]

Here's a slow flop I got to see at Johnson Valley...exo cage. Without the exo cage, he'd have a door to replace...

Does that help? :coffeedrink:

that's beautiful! I'd love to see if he had any bracing at the b-pillar inside...did you happen to look?

 

[ExpoMike]

I was planning on taking the a-pillar down to the sliders I bought which connect to the unibody rail, as well as the pinch seam below the door.

what do you think about that?

seems like if it's attached at the b-pillar like you've mentioned, and attached behind the rear seats....that it would do well to triangulate the load placed on the A pillar when leaned against by a rock or the ground. (and would also resist flex/preserve the unibody as well)

If you really want to get the flex out of the chassis, pick up some of the weld on frame stiffeners first and then weld your rock rails to them. The rock rails alone don't really cut down on flex as much as you think. If I get mine crossed up, I have a hard time getting the rear hatch open because of the flex in the body.

 

[Root Moose]

I was planning on taking the a-pillar down to the sliders I bought which connect to the unibody rail, as well as the pinch seam below the door.

Sure, the big thing is to distribute the load as much as possible. I'm not even sure if is is possible to do much to distribute the load into the firewall/bulkhead.

 

[SWbySWesty]

I think the cage does go inside in the rear of the vehicle, BUT I don't know for sure. PM Karstic on NAXJA and he'll tell you...

 

[BIGdaddy]

Following along on this thread too. I think your idea is fine for the actual roof structure but doesn't really address the pillars, unless you are also including A,C and D bars. If you just have the the roof bars bolted to the roof, even with some internal bracing, in effect you just made a really strong roof rack.

There is no one perfect solution and they all have compermises somewhere. Another thing to keep in mind, in addition to the wind drag of external bars, the additional weight of all the bars (internal or external) will also decrease MPG. I keep playing with the idea of doing some hybrid exo cage but just haven't been able to justify the cons to the pros yet.

Interested to see what comes up in the end though. :ylsmoke:

I thought that, too, but I think Chris is talking about adding that type of connection, especially at the B-pillar, to the existing idea with A,C, D bars.

Speaking of roof racks. I've been pricing out Bajaracks, etc. and came to the decision that a rack on my truck is going to have to work overtime. I don't want an empty rack sitting on my roof doing nothing. If I go the exo route, I'm going to have some amount of roll protection, a low-profile roof rack, and the ability to integrate some vehicle security into the rear load area and possibly the rear doors.

Seems like a good deal, depending on the costs involved.

And no matter what, roof rack or exo, I'm going to be losing mpgs...If I end up going the "lightweight" route with my build, the rack's going to stay up there full time. I'm too lazy to take it on and off all the time...haha!

If this adds 200-300lbs, I may just have to give in, and go to a small cargo trailer, or small tent trailer for our camping gear on longer trips...

thanks for the input, Mike...

 

[SWbySWesty]

If I was just camping and had the cash, yup, I'd have a trailer. Seems easiest. Keep it loaded in the garage and just hook up and go!

What's wrong with wearing a helmet off-road? Don't you wear one to sleep like everyone else? :drool: