Learning to build a rollcage for my Flatty.

Well I have been trying to research some info on building my cage for my Flatfender project but it has been a bit difficult. There are so many opinions and a lot of ego and misinformation to sort through. I tried to search here on early cj5 for some good ideas, especially for the older rigs, but it has been a pain as most of the older threads are missing the picture attachments. Looking over at pirate for info digs up a lot of ridicules hardcore rockcrawler ideas and big egos. I just want to build a safe trail rig for my family and I. I feel I do not need to go nuts with triangulation in 100 directions and 300ft of tubing for a rig that is going to be driven on the street and on old roads and trails with my family. I do want more than the average roll bar though, and I am a skilled fabricator with access to a good hydraulic JD2 tube bender. So in the last couple of days I got at it and started building a cage. I am building the cage out of a combination of tubing sizes. I have 1" and 2 " dies so I have to work with those sizes on anything I want to bend. I am also using 1 1/2" and 1 3/4" tubing for some of the straight runs. All of the tubing that I am using is .120 wall DOM. I do know that 2" x .120" is probably overkill on a lightweight Jeep but I do not have 1 3/4" dies and they cost nearly $400 for a set of dies. (not in my budget) Bending 2" is no sweat anyways as I have a hydraulic bender. 2" also has a beefy look to it as well. The big drawback of 2" is the space it takes up as well as weight. I have done all of the bending freehand without the use of a computer program. (I would have tried a program but I can't find one to work on my Mac) I have made quite a few things with the bender before but this is the first cage I have done. I know that I learned a few things on the way. 1st: is that working by yourself and trying to design and make large pieces is rather difficult. 2nd: is that handling large heavy pieces by yourself in the bender is really hard. 3rd: Compound bends are tough to figure out. 4th: Flatty's are extra difficult to work around as the body gets narrower in the front. 5th: make sure that you consider how you are going to remove the cage to paint it and such when you design it. And 6th keeping the cage symmetrical is a real tricky thing to do. Lucky I like the challenge and enjoy fabricating cause this project makes my brain hurt sometimes. Here is an overall picture of what I have so far.

Greg

 

Here are some more pictures of what I have so far.
















I am going to tie from this pad to the frame on the B pillar.

 

I have made a few mistakes so far. First when I tried to do large pieces I usually screwed up the bends by at least some small amount so I ended up having to design smaller pieces and splice them together with sleeves. This made it much easier to handle by myself and made for less error on the bends. I tried to make any left and right pieces as soon as possible after one another to try to keep things symmetrical. One other thing I figured out now is that I do not think I will be able to remove the cage once it is welded together. I did such a nice job of keeping it tight to the body that the pads that the tubes go to will not slip out of the corners of the body. It is going to make my future progress such as paint and bodywork much more difficult. I will be building the seat support frame to attach to the roll bar and using Corbeau Baja SS fixed back seats. I am liking the shape of the cage so far. I have plenty more pieces to add with gussets, triangulating bars and handles yet to be figured out.
I have a few questions to be asked though.
1st. Is 2 1/2" to 3" enough headroom to the B spreader bar?
2nd. Does anyone have any ideas on how to build a seat frame mount that will still access the tool box under the passenger seat as well as access the back seat area? ( I have a baby on the way and would like to be able to take a little one out in the Jeep in the future)
3rd. How much triangulation is really necessary for a trail Jeep like this?
4th. Any ideas on how to make a mount for a 4 point seat belt shoulder harness without blocking rear seat access?
As you can see with my questions, rear seat access is going to be a problem and may well end up being a fair bit of a compromise.
If anyone sees any glaringly obvious things wrong please go ahead and say something while I can make a change.
Greg

 

Actually Warloch, I downloaded pictures of your cage a year or so ago as reference to what I might do for a cage in the future. I will use 1" round tubing for the seat frame though.

I deviated from your design to the halo bar and an "A" through "C" bent bar for a couple of reasons. One is to keep it tighter to the corners of the interior and two to hang up less in the tight trails that I will frequent. The bush trails in B.C. are very tight with lots of trees. I have seen Jeeps on an off camber trail leaned into a tree and hooked by their cage pillars. This gives me a smooth outside top edge of the cage to slide along a tree if need be.

Thanks for the Hint. I can see how that will be helpful for figuring out bends. I have the tough ones done now so things should go a little easier towards completion but I will definitely use this in the future.
Looking back now what changes would you make to your cage? I noticed you have basically no triangulation to your cage, would you add some looking back now? I believe with 2" x .120 wall you would be hard pressed to fold a cage over in regular trail type wheeling.
Greg

 

Looking good from here. Had a shop teacher that was narrowly saved from being crushed in a rollover by the spare tire. Any cage has to be better than what the military had when these were being used in anger. While trail riding is slow going, are there any steep dropoffs that could amplify your impact?
I certainly don't have your skills or even access to a bender, so my rear child seat plans involve the use of the factory rear shoulder belt bars from a Tracker or Sidekick. Sort of a bolt-in mini-roll cage inside the standard one, that can be removed later when she outgrows it. Which may be before I can get mine on the road.

 

my only question and concern would be about this mounting technique.
I'm no engineer, but in a rollover, what would the stress on these mounting bolts be ?
seems to me from that angle the bolts would shear.
I would rather see the mounting be to a flat surface, like on top of the wheelwell, or flat on the floor.
Other than that, carry on and good job so far.

http://i117.photobucket.com/albums/o...c/DSC04402.jpg

 

The one idea that I had regarding a horizontal bar for the sholuder mounts for the harness, is to have something that can slide up and down the legs of the cage. This would of course need to have some sort of wigned set screw so you can secure it in place in the down position. Then "unscrew" them to lift the bar up, screw 'em back in to secure it overhead for access. Does that make sense?

I like gussets at the joints, simple triangular ones are nice.

I would add padding to the overhead areas, and simple jolts to the Noggin' can really hurt when they are unexpected. Little kids have softer skulls, but my thick cranium doesn't absorb impacts well.

Grab handles make entrance easier. Plus it gives someone something else to hold onto instead of the clasping the bar. Even in a gentle roll, fingers and hands will get smashed that way.

Bicycle water bottle holders make good beverage holders, mount them with a pivot point, so they don't tip over as you lean the vehicle in off camber situations.

Oh, I think your doing a god job.

 

I am confidant, that even though those bolts are in a high angle sheer, they should be fine. I will switch to grade 8 or aircraft bolts on that one mount. Aircraft bolts with a matched grip length (no threads in the hole) should be good. That will be the only frame tie in on this cage. The A pillar will be tied to the rocker sliders on the bottom side. The bottom of that B pillar will be tied to the A with a tube that will also support the seat frame.
Greg
Greg