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Roll Cage Discussion

blazinzuk said:
I am fond of saying HREW will save your life once.

DOM will save your life more than once
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I would tend to agree with this too. My main thought on my specific build is I have a cab around me that acts as a little more structural support added to the cage. And if I have a roll-over bad enough that it pretty much destroys the rest of the truck, then I will most likely take all the parts off mine and throw it on to another truck anyways, so as long as I walk away from the one bad roll-over then I'm ok with it. In all likelihood all I see in my rig are slower flops where I have total confidence I can keep going after being rolled back over.

If I was building something more along the lines of Horton, or like @FOR MUD's truck, then for sure I would be using DOM for the whole thing, without a doubt
 
nvrenuf said:
I always wondered why more people don't brace from the top of the "C" pillar thru the "B" pillar to the bottom of the "A" pillar
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I would think it would be hard to get in and out of, mostly around the foot and leg area. Also would not help the A pillar strength being much being all the way at the bottem. Maybe if you ran it from the B to about half way in the door opening, you would help the B being pushed backward and you would gain a bigger entrance opening.
 
I was just thinking it would transmit any C pillar force thru the B and A pillars, spreading the love around. :D
 
So if we are actually talking tech let's talk tech.

First design. Rectangles and squares are not very resistant to bend triangles are substantially more resistant to bending.

Why you hear needs more triangulation.

I have seen beefy cages built in all squares or rectangles get pushed over a couple inches in a mild roll over.

X braces or V or /\ type braces should fill up any square or rectangular bits.

B pillars should have an x brace. At a minimum they should have a diagonal brace. I realize this makes for difficult entry egress. At very minimum the B pillar should have substantial diagonal gussets at all corners.

A pillar should have gussets as it is difficult to brace properly. It typically sees less forces than the B pillar. But a middle brace in a V shape is very very important. The a pillar must have a dash height bar. Without you have a very long unsupported span. Unsupported spans are bad.

Notching. Proper fitment of tubes is important. Filling a large gap puts alot of heat into the tube causing the joint to become brittle. In addition allowing much more opportunity for improper joints. At best these will crack. At worst a weld breaks and kills you.

Spreading the load. I cannot stress this enough. Every single joint I imagine all force being applied right there. Then I try to make that force propagate to at very minimum 3 other sub structures. Sometimes it's possible sometimes not. Every time you add a tube it should be to spread the load out more. Dead nodes or a T joint concentrates the load. Doing the opposite of what you want.

Floor plates and gussets IMHO are way too thick in the off-road world.

Most sanctioning bodies require 36 square inches and a 1/8 thickness. This is for unibody cars. For frame cars ( what we all have. They still require either the top plate or bottom plate sandwiching the body to be 36 sq inches. Now the caveat here is that is a 6x6 plate that contacts the floor everywhere. Hence if you don't want to take the time to add things to make a flat surface thickness is your answer.

Imho cages should be tied to the frame. Not only for the save your life function but to increase the rigidity of our wet noodle frames.

I'm sure I'm leaving stuff out.
 
I think you got most of the main Idea of how to construct a cage safely.

The diagonal is the primary reason I am going to only have three seats.. it allows the span from b pillar to the rear frame rail which ties my box together.
 
Great tech Eric, that's exactly the stuff I hope to consolidate here!


With respect to B pillar bracing, like you said rear access is important for my family wheeler. It seems to me the V brace might work best (for me) since it supports the outer corners yet you could still go under or between the bars. If I were to make a floor plate that fit the contour of the trans tunnel, Would it be a huge deal to let the bars land on each side of the tunnel as opposed to a single nod? This would spread the the bars apart an extra 6"-8", just thinking every inch counts if I use the center void for back seat access.
 
Gussets... tubes or tacos? I like the cleaner look of the tacos but they are considerably smaller than say a 8"-12" piece on tubing spanning the corner. It seems like the taco would ultimately be stronger since it makes one big joint instead of several points closely tied together.
 
I like the tacos. It gives alot of surface area. The longer tube gussets give you a shorter unsupported span distance.

So I think it's a toss up.

I have done alot of creative B pillar solutions over the years. Just getting something in there is important. Some sort of angled tube. I really hate saying something is better than nothing but as long as it gives some sort of traingle it is better.

I have used smaller tube a lot on B pillar braces to help with lost room. Done weird bends. Even removable bracing, just gotta do something
 
What's a good resource for those of us who have never dealt with a cage? I do get the "triangle in a rectangle" aspect...
 
There is a very lengthy discussion on my build thread about this...most of which has been reiterated here. But I know yall only care about pics...also I used 1.75" .120 DOM for main cage sections and 1" DOM for support tubes. I originally was building this as a go fast rig but now it's just a dune/rock destroyer, which allows me to get away with a little more on the inexperience.

IMG_7845.JPG

IMG_7872.JPG

IMG_7916.JPG
 
Read Blazinzuk's post above over and over.

A half cab gives you a lot of protection to start with so you don't have to get as carried away with the cage as with a full convertible. Those B pillars in the half cab are pretty beefy as are the doors and windshield frame. Keep the windshield from smashing down too far, protect the back seat and connect the two and you're doing OK. The half cab is also good in that the sheet metal keeps you contained if things get hairy, it keeps stuff from getting in with you like a tree stump in just the right place, and it spreads point loads over a bigger area to some degree. There's a reason Ultra4 cars have at least a 1/8" roof skin fastened securely to the cage, along with window nets.

As someone said above; in a full body rig, a good roll will total the truck. If you survive this, you're good but no matter what you're chances of recovering more than a few parts are slim. I saw the full convertible K5 that rolled on the UA trip in '14 and it was ugly. The 205 was about the only part that was usable after the roll. Axles bent, engine parts and trans case broken, frame trashed, no good body panels. It fell over backward on a pretty steep hill and the cage barely did the job. It could have been built from bigger tube since I think a lot of it was 1.5" and it didn't have many complete triangles. With that same cage in a half cab the truck would still be totaled but he would have had a much bigger margin for error in surviving.

Dropping through the floor to the nerf bars is a good idea since it beefs up the nerf bars to where they become functional to hold the truck up and not bend everything and it also beefs up the frame and provides extra cage support.
There are a bunch of pics of my k5 when it was full body near the bottom of this page. I would consider this cage to be a good minimum with a half cab.
You can see the A pillar to nerf bar tie in the upper right corner of this pic:
front%20suspension2.JPG

That's a 2" tube on the bottom and a 1" tube that runs to the top of the frame. It was all bushing mounted which I would not do again since it doesn't do enough for vibration absorbtion to be worth the hassle and weak point.
This pic has a peek of the rear cage legs tie to the bumper outrigger on the frame:
rearshackles.JPG

You can see the bumper tie here also, along with the tabs that accept the bushing assembly for the B pillar tie that was being rebuilt and raised up before BlazerBash '02.
shop%20pic-coil%20rear1.JPG


Obviously the rig progresses toward the top of the page but the main cab cage structure is still the same as I built in the full body half cab. Looking at the pics, if it had stayed a full body full convertible we would have added some diagonals in the B pillar bay and probably overhead in the A-B bay similar to what we did after the full body was cut off. Access was really good with the original cage system and the only real sticky point was headroom in the back seat was not good for adults. OK for kids but that was it. Frame stiffness was WAY better with even the basic cage. I went from tearing out body mounts and cracking sheet metal in the half cab to a pretty stiff overall chassis. Definitely good for long term recreational use.
One thing that makes me feel a LOT better about that cage was the rear upper corner to bottom-of-B-pillar brace tube. That one tube goes a long way toward keeping the B pillar upright and the C pillar from smashing down. It didn't dead end by very much, I couldn't get it perfect because of the body corner it dropped into but it came close to picking up the bar that ran along the floor pan to the A-pillar.
 
On a converted full convertible K5, would you tie the A pillar of the cage to the windshield pillar? I'm inclined to but a little worried about movement and if it might crack the windshield. I plan to tie the cage A pillar bar to the body under the dash too but haven't figured that out yet (it's kind of congested under there).
 
We have been tying everything together as much as possible, full unibody style. So I'd say tie that A-pillar hoop system to everything it runs close to: side panel, A pillars and the top of the windshield frame. Stuff doesn't squeek and rattle when it can't move. You get a lot of road noise but that's it.
There are some pics of our Convertible K30 here:
http://s1181.photobucket.com/user/ORD2/library/UA14 truck build?sort=3&page=1
I need to see if we have some less cluttered cage pics, most of what I have is from after we've lived in it for a few days and it's hard to find the cage!
 
After seeing how much these trucks flex under load when coilovered I'll agree completely with @Stephen and his comments, heck mine doesn't even have a motor in it right now and the fact it's all tied together now is so obvious it's crazy. Just shut the door.. that gives the evidence pretty blantantly how much stiffer the cage makes the truck.

One other thing to keep in mind, when deciding what material to use the dom vs erw debate is strictly a consistency thing, the dom just is drawn over a mandrel and has a closer tolerance. There are different grades of the steel like 1018 vs 1026 but to find that is almost impossible around here at least and using small 3/4 or 1 inch so guesset corners can make a marginal cage into something that may survive vs maybe killing you because it failed in a unpredictable manner.

So no dead nodes, triangles, spend the money on the metal, do it once and forget about it.. cause safety..
 
Thanks to this thread....I guess I will be adding some more bars and gussets this winter.:D

Actually I did sit there and review my cage the other day...24 triangles, 12 frame tie ins and 6 gussets.....And that is only from the A pillar back Might be adding 2 more bars.
 
My dad developed those in the 60s for race cars. He was working for Bill Thomas racing in So. Ca. He built all of his vorvair powered buggies with those at each corner. Every car was rolled at some time. Every corner held up.

My next cage will have them.
 
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