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Pinch seam/rock rail install question

Kejtar

PostMaster General
NAXJA Member
so now that I"m slowly moving towards the rock rails and so on I started to look at how to install the rock rails. I want to tuck them up against the underbody which means that I will have to notch the pinch seam for the legs (not sure if it's going to be 2 legs or 4 legs as I got two sets to choose from). Anyways, when I notch it and fold it should I weld the cut up a bit so that it doesn't have the tendency to tear?
 
Kejtar said:
so now that I"m slowly moving towards the rock rails and so on I started to look at how to install the rock rails. I want to tuck them up against the underbody which means that I will have to notch the pinch seam for the legs (not sure if it's going to be 2 legs or 4 legs as I got two sets to choose from). Anyways, when I notch it and fold it should I weld the cut up a bit so that it doesn't have the tendency to tear?



No

hinkley
 
Kejtar said:
so now that I"m slowly moving towards the rock rails and so on I started to look at how to install the rock rails. I want to tuck them up against the underbody which means that I will have to notch the pinch seam for the legs (not sure if it's going to be 2 legs or 4 legs as I got two sets to choose from). Anyways, when I notch it and fold it should I weld the cut up a bit so that it doesn't have the tendency to tear?


An ounce of prevention, is worth a pound of cure.
 
Remi, why would you want to notch the pinch weld seam, as it weakens the body at the torque box?

Cutting the standing seam (the pinch weld seam) will reduce the strength afforded to the torquebox. When you reduce the strength of the standing seam you allow the torqbox to crush and deform during a hit (deformation that allows your rail to swing up and dimple your rocker panel and door sill).

If you do cut the standing seam back it up with angle to bridge the seams on each side of the rail member spanning to the frame (reconnect the standing seam to restore the strength).



BTW, for those who wanted to see the pieces used to assemble my rails ...

RR1.jpg


To get there you need to weld these together ...

RR2.jpg


These screw to the rocker panel under the door and to the pinch weld seam (if someone has a side or 3/4 photo of my 88 it could help, because I have no good photos handy).

When you drop the XJ on the rails all the screws are loaded in shear, except the screws do not carry the total load, the body carries most of the load. The full underside of the torquebox is loaded.

The pinch standing seam is reinforced (these are 14-ga 1x4 angle), to prevent the deformation that allows a rail to swing up and dimple the rocker or door. The rail cannot swing up because it's not cantilevered outboard of the pinch seam, it's reinforced at the rocker panel directly above the centerline of the rail (by the half-scale 3/4/5 18-ga right-triangle that ties the rail into the rocker panel). The skid rail is 1x3 0.120 wall rectangle tube, that is supported the full length of the rocker by the 3/4/5 right triangle and the 1x4 angle (it takes a major hit to flex or twist because it has no space to bend between the rail and body). The ground clearance is the same as the pinch standing seam, and they stick out 1 1/2 inches past the doorsill.

I made these initial rails three-piece so I could adjust for the taper of the rocker and pinch standing seam. Just clamp them up, set the taper, and weld them. I would make them two-piece (the angle and the rail) in rights & lefts if I was sure the taper was consistent between different XJ's (not too much to worry about). If it were a two piece rail I would make them out of 14 to 10-ga (what the brake tooling will allow) to make them as rigid as possible.

These have taken the full weight of my 88 (both front tires freewheeling) dropping off v-notch rocks, and the only problem was flex at the front fender (the initial run before I added ~ five screws between the right trangle and the fender panel). The fender is not part of the torque box behind the doorsill and it needs more screws (or better yet, stainless rivets) to tie the pieces together. Since adding the extra screws I have had no problems (other than the hangnail widowmaker slivers that will remain underneath after major scraping, a file chore after a run to keep the underside clean of snags).

The photos are of a spare set I have of the pieces (the screw holes are not drilled into these pieces). I made three sets (one for my 88, on for the wife's 89, and one for mistakes). So far, I have been pleased with the one set I welded up (it has not failed in all the crashing and jacking I have thrown at it).

It's just another method of rocker and door protection, without the drawback of cantilever rail loading or the strength or ground clearance loss from compromising the factory pinch standing seam. They have the same advantages of the welded in 4x4 beam rails, without the extensive demo and welding chores (and they hide the dimples in an older rocker panel).

I hope the photos help understand the concept?
 
Reason I was looking at doing the pinch seam incission is because it appears that a set of rails I have seems to require that for mounting. Also I was looking at the situation where doing so would get them up slightly higher and allow for better load distribution: I have pushed my pinch seam UP into the body and tweaked my floor after a sequence of rocks and I am only mounted to the pinch seam using angle iron.
So... my other option is to cut of the angle iron (i'ts 1/2" or so angle iron) and replace it with some square tubing that'd be wider or to add more support upwards so that it doesn't spread the load on pinch seam only.

OK, I guess I'll be going back to the drawing board!
 
Remi,

I'll give you some 1x1 .063 wall tube (or 1x1 angle, I have both).

Have you tried straightening out the pinch seam (eye bolt to the floor, a cable with vice grips or screws, and a jack)?
 
Ed A. Stevens said:
Remi,

I'll give you some 1x1 .063 wall tube (or 1x1 angle, I have both).

Have you tried straightening out the pinch seam (eye bolt to the floor, a cable with vice grips or screws, and a jack)?
LOL.... actually I get to start somewhat fresh with a new vehicle as I rolled the old one so I don't have to worry about the extensive damage to pinch seam (Had to straighten the new one a tad though).
In regards to steel, I'm pretty much ok in that departmnet as I bought quite a bit a while back, but thanks for the offer though :D.
 
CharlesS said:
Buy a quality set of Rock Rails (ORGS, C4x4F, Summit OR) and be done with it.....
I got a set of slightly custom ORGS (they came with the new jeep in a box) and for as much as I'd like to use them they stick out too much (they don't bend up but go out like a step: that's the custom part) and they seem to require notching of the pinch seam as they tuck up high against the floor. I'll have to look at them again though to be sure.
 
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