Builds 86 Xtra Cab Build (4Wheelunderground 3 link front, 4 link rear and 3.4 swap) (4 Viewers)

[aztoyman]

@Broski, I can't do that because I would be going through my rockers and the structure for the cab mounts. Not much room to shift the tubes away from important structure. I'll take another look and see if I can make it work though.

That's why I first tried the halo bar roof. I would have been able to tilt the main hoop forward and down and weld the tops before I put in the A-pillars. I think I can get to those.

 

[littlevulture]

Tube connectors are a no no but joining it back together with sleeves made of 1 1/2" x .120 wall DOM is a better option. If I can weld the tops , I won't cut it.

Why are those bolt together tubing connectors a no-go…I haven’t read any of the rulebooks but I assumed with how prolific they are online they were a legit solution.

 

[aztoyman]

@littlevulture Some of the rule books allow them for harness bars and less critical structure but even then discourage it. Sounds like it's a hinge point?? Maybe an engineer will chime in.

All the rollovers in my groups that I've witnessed were at slow speeds (except one) and the A-pillars caved. They were all Jeeps with whatever factory roll bars they came with. The hard tops got ripped off or really mangled.

I don't haul a$$ off road but I do drive it to the trails. I don't get on the interstate but I'll take the frontage or drive on two lanes at higher speeds so I don't want to chance it.

And then I watched the 4XInnovations videos where they push the Toyota over the bank numerous times and their roll cage holds up well. They use sleeved connections on the main hoop and larger sections for shipping reasons.

The rule books that allow a sleeve connection (usually a repair) specify how it should be done.

 

[aztoyman]

Just to add to the thought process, Marlin Crawler's interior roll cage kit has SIX of the tube couplers, no X-bracing, no back stays and is 1.5" HREW tubing. It does have gussets in the top corners.

Some of the factory tubes in my neighbor's Jeep remind me of the tubing used on my kids swing set.

I have no mechanical engineering education so I'm winging it and hoping I make the right choices.

 

[littlevulture]

I did a little research today…it’s been quite awhile since my statics/dynamics classes and those had a much different engineering focus, although the analysis is similar. I think with the correct hardware torqued properly connectors “could” be acceptable if you used them in the right spot. But I didn’t really see any options on the market that I’d trust.

Here’s some shear and tensile numbers for some standard fasteners, the Barnes 4WD connectors use 3/8 hardware (although they don’t mention thread pitch). McMaster sells similar fasteners with a 170k psi tensile strength. I think the trick to a safe connector design is positioning it in the cage somewhere the interlock takes most of the load instead of the bolts.

Worst case I can see with x2 3/8x16 grade 8 bolts (like the Barnes one) and the load applied in perfect shear on the threads you’d have failure at just under 14k pounds…I don’t think that’s enough to reasonably say the connection won’t fail if ya rolled even though a 100% shear load would be very unlikely. I think at a minimum I’d want larger hardware and a design that interlocks more to transfer more of the load away from the hardware.

Honestly I’m just speculating and not at all qualified but I think you’re probably on the right path avoiding them and using sleeved joins if it comes to it. One other thing I saw mentioned is a failed connector joint could impale you where a sleeved connection would likely just bend.

 

[aztoyman]

@littlevulture , The one set of rules that even mentioned the connectors specified 5/16 grade 8 bolts and locking nuts. No mention of thread pitch or positioning locations. Other than for non critical tubes. So for engine cage and such. Different organizations and race categories obviously have different safety criteria. I don't really fit any but I'm seeing what is "common" for most.