What tubing size for roll cage ?

[Doug]

Pictures are worth a thousand words...I'll have to stop by there again and remember to take my camera. It's an app 24" long kicker for the hoop.

It's not split from a shear load, IMO, it split because the weld caused an anomaly in the metal...kinda like scoring a piece of brick. I can only geuss, but I figure it started as a small crack in one place and then spread the full length following the easiest path.

[tacoma]

NONE of the rockcrawler guys here in Rockcrawler Central are using anything other than DOM tubing. If you've seen a rockcrawling competition, you'll know how much abuse those cages take, and hold up to.

ERW fails along the seams in compression or, more rarely, tension, stresses you find pretty frequently in a roll.

[LuckyPabst]

So there's no confusion for anyone - DOM is NOT seamless. It starts just the same as ERW but goes through a secondary process to make the wall thickness consistent.

On the contrary to the 2" looking goofy, I think 1-3/4" looks too spindly for the size of our trucks. But it's all opinion in this regard. I'd like to see what a real engineer has to say about it.

Chris

[tacoma]

Lucky's right.

I agree w/you about the spindly look of 1 3/4".

So there's no confusion for anyone - DOM is NOT seamless. It starts just the same as ERW but goes through a secondary process to make the wall thickness consistent.

On the contrary to the 2" looking goofy, I think 1-3/4" looks too spindly for the size of our trucks. But it's all opinion in this regard. I'd like to see what a real engineer has to say about it.

Chris

[LuckyPabst]

OK, pics of 3 cages I built for 3 different trucks, each one a little different, all of 2"x.120 DOM:

#1 - SOCAL(Sally)'s quasi resto truck on spring over. I like this one the best as far as aesthetics because it only has 3 overhead stringers This truck got sold and the cage cut apart before finishing.


#2 A.D.D.Frapguy's nice looking however greatly abused mod truck. This one also only has 3 overhead stringers and dosen't drop down in back to fit his lanky stature and to match the height of a future bed cage. As you can see, it fits within the softtop framework. This project is on hold with me since I live in H E double hockey sticks.


#3 - My truck and the test pig to see if I actually knew what I was doing. This one has 4 overhead stringers, intended to have a console built between the 2 innermost tubes to house CB, HAM, and Satellite radio. Right now I think it looks too "oldschool baja bug" style. Second pic is how it sits now but highly unfinished. I still need to bring it to the frame with poly bushings and add a bit to the rear half, maybe incorporate a swing down spare tire mount out back. For the softtop, I'll need a zippered panel around the rear window to allow for the rear downtubes.



Chris

[Doug]

So there's no confusion for anyone - DOM is NOT seamless. It starts just the same as ERW but goes through a secondary process to make the wall thickness consistent.

Yes, and more importantly it normalizes the grain in the metal where it was welded...more or less cold forging the tube. Eliminates stressed areas.

On the contrary to the 2" looking goofy, I think 1-3/4" looks too spindly for the size of our trucks. But it's all opinion in this regard. I'd like to see what a real engineer has to say about it.

Chris

Opinion, yeah, 1-3/4 looks too small to me to.

[Elohim1]

Great info. as usual !!!!!!

Will be going 2" for sure. Will use the DOM or Chromoly. I may check and see if I can get (5/32) .156 wall ........

If anyone has shots , how they connected to frame, that would be great too.

I am thinking removable..... But any shots would be nice.

[LuckyPabst]

Here's what I have planned. I only have the one frame point almost finished -it's 3/16" plate, rosette welded in a few spots and welded around the perimeter with some premade tabs to hold a 2" poly bushing. Somewhere I came up with the plate size needing to be about 25 square inches (some racecar fab book at the local bookstore), so that's about what mine is, probably a little larger. From there I'll use the same 2" tube to a 4x4x3/16 plate (exactly like HUMMER103) that's sold in the fencing department at the local steel supplier for like dirt cheap, precut, pre-beveled corners, pre-punched holes.





Chris

[ColHart]

Chris, those are great pictures that tell a ton. The frame point looks a bit behind the cab and not directly under the point where your cage would mount. The poly bushing is a great load transfer point idea. Are you using poly bushings in the body mounts? My only concern would be that there is the same spring constant and shock distance for the body mounts and the cage points. great work... I like the style of Frapguy's cage and will do something similar. Even with the window frames off, the cage gives the truck the same stock look. It would look good with cut doors and a double upright like Tims too.

I love this stuff....

[LuckyPabst]

Yea I had to shuffle the mounts back at that point to fit between cab and bed mounts. It's still "in-line" enough with the rear cage hoop that I think it'll be safe.

One thing I made sure to do before starting the cage was install new body mount bushings, which I made from some poly stock (Frapguy used a CJ poly kit that saved a bunch of time and didn't cost much more) but the cage bushings are considerably harder than the cab bushings - I figure it'll keep the cab bushings alive longer. We'll see how that works.

Chris