Another slider idea,

[63chevyll]

If the frame is boxed, it would pick up strength from a piece of tubing passing through and welded to both sides.

does make things better than just welding tubes to the outside of the C-channel.

Now if your tube could pass all the way through BOTH frame rails you would really have something.

You see my point. Exactly what I'm trying to do in a sense, is widen the frame, it just so happens that the widening of the frame turns into a usable slider.

I mean If I have 4 or 5 horizontal bars from each slider, through frame, and through the boxing it would support some weight. And the leverage will be spread along the whole frame, not just on a couple of spots.
I dunno, I'm still not 100% sold on mounting to the body, but defiantly not sold on just welding to the outside C of the frame and calling it done.

 

[63chevyll]

And along the topic of building a cradle/ belly pan. I would been better if the whole frame was stonger to the belly pan didn't support all the load of I was to be high centered, or bashing on rocks.

 

[owenst7]

The longer the boxed section is, the more torsional resistance the frame will have.

Do a free body diagram at the ends of the boxed sections. Unless you span a crossmember (in which case you'd be 100% correct), the force is still spread over the same area (assuming the boxing ends in a frame section that does not have more rotational inertia) because it is still acted upon by two points of frame.

I'm not saying the boxing is pointless. It will make the boxed area more rigid, which will reduce deflection along the whole length of rail. BUT, it won't reduce stress, so if the rotational force is enough to tear the c-channel or deform rivets at crossmembers, it will happen regardless of whether or not that area is boxed. That boxing can be used to reduce deflection, but it won't reduce stress at the end of the boxed areas.

If a guy really wanted to go to the frame, you'd probably be pretty decent if you took the stock tcase crossmember and triangulated the sides to the top horizontal plane of both frame rails. Especially if you added another member behind it (such as for a doubler) that was triangulated the same way, you probably wouldn't get that much twist in the rails when you laid the slider on something. You could then run a donut like a body mount bushing to the rocker/floorboard/etc to prevent the slider from smashing up in to the body. That was how I was originally going to do my sliders, until I realized how much ground clearance I'd gain from chopping out the rockers and welding straight to the pillars.

 

[Blue85]

Yes, I agree that the overall torsion load placed on the frame is the same no matter how many stringers there are (to the sliders) or how long the boxing is. My point is that the further you go up and down the frame (with boxing) the more crossmembers and stuff you will hit. Even a body mount will help a little. Plus as you go rearward on the frame you will eventually hit a place where there no is driveline in the way of adding a simple crossmember. For a given torsion load, the closer you are to crossmember, the less total twist there will be (i.e. less chance of hitting the body), but if you're talking about loads that can damage ther frame, crossmembers are about the only thing that will help.

Still, mounting to the body works pretty good.