Roll Cage Failures

[94toytruck]

I feel like the picture with the A-pillar failure is more from no support bar than lack of windshield spreaders. Unfortunately this isn't uncommon on rigs with bodies or functioning doors. Mine are tied in much like the BFR chassis above.

 

[Rockwood]

I guess my thought process is that neither one was optional. The A-pillar supports help deal with fore and aft loads and the windshield V helps deal with lateral loads. I was thinking that without the V the roof would just pushover sideways in a hard hit. However, the roof bracing should really prevent that so its not the issue I was thinking it would be.

Weren't you criticizing his cages earlier?

Hey, I can change my mind to suit my argument! It’s the Internet!

 

[gt1guy]

@mobil1syn

That was well done. I wish like hell I had room to do that.

 

[Woody-LXXXVIII]

Lots of beef in that cage. Only thoughts would be sheetmetal/nets to protect limbs and fingers from getting into the suspension and some roll bar padding on surfaces the occupants can touch. Shit's cheap and is a literal life saver.

Yeh lots of beef. Many angles working in different directions. There are no pinch points in the rear suspension area. I have wanted to sheet metal that area to gain some protection from the environments.

 

[bdkw1]

See, even Robby agrees:

Dakar cars are a different animal. Weight is everything on those, if the FIA don't mandate it, it doesn't get put in. RG's TT's are split between single bar and A. But they all have some sort of windshield bar. The SST's which he designed and built all have A's.

 

[Isdtbower]

F1 and Indy cars have deferred to centered window bars...limiting vision? I have also seen the "window bars" attached to horizontal bars on the driver side of Dashboards...so clearly not meant for intrusion 100%.

The decision to run doors as opposed to climbing over shoulder height tubes probably automatically limit whatever you want to call it. Speed. Crashability. Exit. Entry. etc.

Run what ya brung..................be smart as possible with driving decisions.

 

[Rockwood]

F1 and Indy cars have deferred to centered window bars...limiting vision? I have also seen the "window bars" attached to horizontal bars on the driver side of Dashboards...so clearly not meant for intrusion 100%.

The decision to run doors as opposed to climbing over shoulder height tubes probably automatically limit whatever you want to call it. Speed. Crashability. Exit. Entry. etc.

Run what ya brung..................be smart as possible with driving decisions.

F1 and Indy do it because that's where the driver is though. No one is behind windshield bars, which is why other sanctioning bodies focus on requirements on the perimeter of the cage.

 

[gt1guy]

I think what we're calling the window bar on F1 cars should be called the actual A-pillar. It's only there to hold up the front of the halo. Which on a F1 car is made from titanium. Remember, they never really had a cage before.

That said, nothing F1 or Indy cars do really relates to what we do. They're worried about their own front tires taking their heads off in a crash.

 

[SLOWPOKE693]

That said, nothing F1 or Indy cars do really relates to what we do. They're worried about their own front tires taking their heads off in a crash.

Exactly, those are 100% completely different in every way.

 

[Rockwood]

I think what we're calling the window bar on F1 cars should be called the actual A-pillar. It's only there to hold up the front of the halo. Which on a F1 car is made from titanium. Remember, they never really had a cage before.

That said, nothing F1 or Indy cars do really relates to what we do. They're worried about their own front tires taking their heads off in a crash.

Yep. The runner up design was similar to a regular car, but F1 drivers use tear-offs and they were concerned with visibility towards the end of a race.

 

[gt1guy]

 

[gt1guy]

Yep. The runner up design was similar to a regular car, but F1 drivers use tear-offs and they were concerned with visibility towards the end of a race.

That at least looks better. But they'd have full screen tear-offs for it and then try to toss them into each others air intakes.

 

[Rockwood]

That at least looks better. But they'd have full screen tear-offs for it and then try to toss them into each others air intakes.

Lol, imagine one of those jockeys trying to lean forward and pull that off…

 

[Wisconsinite]

My Mom had a little whoopsie the other day wheeling their JK. She bounced a little too hard, blew the bead on the passenger front and flopped. Low speed, hardly moving, and the windshield hit the lip of the trail.

I thought it was pretty wild that the windshield is the only front support structure.

 

[SLOWPOKE693]

My Mom had a little whoopsie the other day wheeling their JK. She bounced a little too hard, blew the bead on the passenger front and flopped. Low speed, hardly moving, and the windshield hit the lip of the trail.

I thought it was pretty wild that the windshield is the only front support structure.

Pics of mom?

We want to make sure she's OK.

 

[94toytruck]

Momma was getting it!

 

[gt1guy]

That was the perfect hit on to literally no support.

How's the break from working on Jeeps going?

 

[Wisconsinite]

Pics of mom?

We want to make sure she's OK.

I assure you she is okay. Thanks for your concern.

Momma was getting it!

She was! She is now asking me to look into bead locks.

That was the perfect hit on to literally no support.

How's the break from working on Jeeps going?

Right? Not much damage besides the windshield. It pushed in the rear quarter a little bit, but that is about all.

And to answer your second question, the break has been good, but I am getting excited about working on it again! It has been three months since I have touched it, and am ready to start hammering out some projects........after I make some aluminum spacers.

I love my old man to death, but he is the world champion at making mountains out of mole hills. He said the flop tweaked the frame, it's totalled, it's going to be a year before it's back on the road, yadayada. I spearheaded the repair just to get it done so he wouldn't continually be bummed about it. He moved it from his three car garage to the shed so he didn't have to look at it...

A new windshield, frame, and an add-a-cage (that I have been storing for him for two years), and he is back on the road.

 

[chaplinfj60]

sweet

 

[chaplinfj60]

dude i freaking love the skid plates on that jeep. that is legit. sucks about the damage. but your got after it and got it done.

 

[gt1guy]

I see the add a cage tied into the factory B-pillar overhead portion, which isn't that bad of a piece. Did the down tubes for it tie into tie into the factory b-pillar tube coming up out of the tub?

The reason I ask, is because I've had the pleasure of digging way into the B-pillar on my JKU through the spot welded portion on the inside. I was shocked to find that inside the sheetmetal the tube was only held in place by about an inch of weld in 3 different places. The end of the tube just stops in the rocker and is connected to nothing. It seemed like all the little welds are where the seat belt mounts and door hinges are.

I wasn't impressed with what I saw and was the reason I removed the factory tube and replaced it with a 2"x.120" DOM tube that tied into the frame.

I'm assuming the JK's and JKU's are the same from the top of the tub down. I could be wrong though, I've never cut apart a 2 door.

Here's a few pics of what I found. These may not change what you're doing, but may help someone down the road in the future.

This is what you're left with when the factory tube is removed.

Which made it nice to get the hoop tucked in away from my head.

And you all know the guy who is peaking through the windows.

What it doesn't allow, is to run the X bars without bends in them......and I will not build a cage with bends in the X.
So I had to do a double B-pillar that allowed a X without bends.

 

[rattlewagon]

from facebook:

 

[YJ-6 Unlimited]

gt1guy why do you refuse to build a cage that has bends in the X bar? I know straight is ideal and the strongest but with space constraints sometimes you have no choice. It’s definitely better than nothing.

 

[gt1guy]

gt1guy why do you refuse to build a cage that has bends in the X bar? I know straight is ideal and the strongest but with space constraints sometimes you have no choice. It’s definitely better than nothing.

First off, let me say I don't build cages for a living. I'm just a idiot in his garage. So it's not like I'm refusing work or something like that. Though for another project I have, I've spent hours reading rule books from NASA, SCCA, NASCAR and a couple others. NONE of them allow bends in the X. ALL of them deal with big hits.

I won't build a cage for myself with bends in the X-brace.

The X-brace in the main hoop is the most important part of the main hoop itself. It's what gives the main hoop all it's strength. In short, it turns the main hoop into a series of triangles that converge in the center point of it.

Being that the main hoop (including the X) can be thought of as the foundation that the rest of the cage is built off of, it only makes sense to have the absolute strongest foundation you can have.

Bends in the X are weak points, or potential failure points. That's potential failure points in the single most important part of the entire cage.......the part directly over your head.........that everything else is built off of.

Do people put bends in their X? Absolutely. Jeeps, Scouts, Blazers, you name it, you see it all the time. Main hoop gets installed forward of the back of the seats. 99% of the time the fix for that is to add bends in the X to move it back behind the seats. 1% of the time either the main hoop gets moved back, or a second main hoop is added (the double B) so the X can be made without bends.

Are bends in the X better than nothing as you said? Of course they are. My question to you would be, how much better than nothing are they? We don't know that answer. Could be very little or could be a lot. But we do know what the best way is.


When I built the cage for my JKU, I asked myself what was the worst case wreck I could foresee, given what I planed to do with it.
The honest answer was getting cut off on the freeway and barrel rolling at 80mph. That was very eye opening and changed my whole approach. My thinking went from slow motion roll on dirt, to high speed roll on concrete with the possibility of secondary hits from other high speed vehicles.

So I'd say ask yourself the same question and let your conscious be your guide.


We don't get to pick when or how we wreck.

 

[YJ-6 Unlimited]

I get it it and understand load paths. If I could have zero bends I would have. The fact that you made it work for your cage is awesome. I did ask myself if I was willing to sacrifice some strength to keep the cage design I wanted given the constraints I had. I was ok with it. I beefed up places elsewhere. I think I have around 20 or so taco gussets throughout the cage. It’s been on its lid 2 times (one violent) for 3-1/2 total rolls. So far no racking and not even a bruise to me or may passengers. I thought you built them and wouldn’t do it for a customer with one.

 

[Steve300xcw]

I just wanna see the oversize clay pigeon thrower thats throwing that tire

 

[bdkw1]

First off, let me say I don't build cages for a living. I'm just a idiot in his garage. So it's not like I'm refusing work or something like that. Though for another project I have, I've spent hours reading rule books from NASA, SCCA, NASCAR and a couple others. NONE of them allow bends in the X. ALL of them deal with big hits.

I won't build a cage for myself with bends in the X-brace.

The X-brace in the main hoop is the most important part of the main hoop itself. It's what gives the main hoop all it's strength. In short, it turns the main hoop into a series of triangles that converge in the center point of it.

Being that the main hoop (including the X) can be thought of as the foundation that the rest of the cage is built off of, it only makes sense to have the absolute strongest foundation you can have.

Bends in the X are weak points, or potential failure points. That's potential failure points in the single most important part of the entire cage.......the part directly over your head.........that everything else is built off of.

Do people put bends in their X? Absolutely. Jeeps, Scouts, Blazers, you name it, you see it all the time. Main hoop gets installed forward of the back of the seats. 99% of the time the fix for that is to add bends in the X to move it back behind the seats. 1% of the time either the main hoop gets moved back, or a second main hoop is added (the double B) so the X can be made without bends.

Are bends in the X better than nothing as you said? Of course they are. My question to you would be, how much better than nothing are they? We don't know that answer. Could be very little or could be a lot. But we do know what the best way is.


When I built the cage for my JKU, I asked myself what was the worst case wreck I could foresee, given what I planed to do with it.
The honest answer was getting cut off on the freeway and barrel rolling at 80mph. That was very eye opening and changed my whole approach. My thinking went from slow motion roll on dirt, to high speed roll on concrete with the possibility of secondary hits from other high speed vehicles.

So I'd say ask yourself the same question and let your conscious be your guide.


We don't get to pick when or how we wreck.

This was a bolt in Schimdty built cage with no X braces at all. We were going 70ish on the blacktop. Rolled 2 or 3 times and went end over end.

Cage broke the body mounts off the frame. We took the cage out, did a little work to it and bolted it in another Yota. Most cages are way over built and the only issues come from poor design. That cage with no bracing flexed. If it had poorly placed X bracing the HAZ from the welds probably would have made cracks in the main tube. Having bends in the X bracing isn't the end of the world, sometimes a little flex is better than cracking things or straight up ripping them apart.

 

[gt1guy]

I get it it and understand load paths. If I could have zero bends I would have. The fact that you made it work for your cage is awesome. I did ask myself if I was willing to sacrifice some strength to keep the cage design I wanted given the constraints I had. I was ok with it. I beefed up places elsewhere. I think I have around 20 or so taco gussets throughout the cage. It’s been on its lid 2 times (one violent) for 3-1/2 total rolls. So far no racking and not even a bruise to me or may passengers. I thought you built them and wouldn’t do it for a customer with one.

I had a feeling that's what you were thinking with the way you worded your question. That's why I started out saying I don't do it for a living.

I'm sure there are cage builders that mostly work on door banging race cars for specific sanctioning body's that wouldn't do it. They wouldn't want their name associated with that kind of work. By that I mean doing it technically "wrong".
The offroad world seems to be more of a free for all

This was a bolt in Schimdty built cage with no X braces at all. We were going 70ish on the blacktop. Rolled 2 or 3 times and went end over end.

Cage broke the body mounts off the frame. We took the cage out, did a little work to it and bolted it in another Yota. Most cages are way over built and the only issues come from poor design. That cage with no bracing flexed. If it had poorly placed X bracing the HAZ from the welds probably would have made cracks in the main tube. Having bends in the X bracing isn't the end of the world, sometimes a little flex is better than cracking things or straight up ripping them apart.

Sounds more like you got really fucking lucky, as opposed to the bolt in Smitybuilt cage performed some kind of miracle. I'm glad you walked away. That doesn't look like it was a fun ride.

Most cages are way over built and the only issues come from poor design.

Agreed.

Nothing wrong with an over built cage. Well, until you're adding bars just to add bars that aren't really doing anything. At that point, you're adding weight that the working part of the cage will have to deal with.

Poor design is just that though. The biggest problem with a poorly designed cage is that it can end up killing you.

I've never seen a store bought cage that I thought was over built, most seem to be the bare minimum. A lot have sketchy design aspects to get around tearing up the drivers compartment.

That cage with no bracing flexed. If it had poorly placed X bracing the HAZ from the welds probably would have made cracks in the main tube. Having bends in the X bracing isn't the end of the world, sometimes a little flex is better than cracking things or straight up ripping them apart.

Disagree on the flexing part. You don't want the drivers compartment to flex at all. Everything inside of the A and B pillars should not flex. Flexing can let seats move and belts to loosen, which in turn can allow the passengers to hit things that can kill them................like the cage. Or the B hoop becomes lower than head height. That's bad too, for obvious reasons.

Everything in front of the A-pillars can be destroyed, everything rear of the B-pillar can be destroyed. That's just absorbing energy that would have been transferred to the passengers. But inside the A&B's shouldn't be moving around.

I could be splitting hairs here between flexing and absorbing energy. But to me it's two completely different things.

 

[bdkw1]

Landing on your roof and nothing flexing is a hard time. A lot of builders myself included make the roof X brace stick up a little higher than the cage main tubes. I've seen roof bars ripped out of giesers, the impact if they hadn't come loose would have been much worse. Everything needs to give at some point. When and how much are the debate. I have been a crash test dummy more times than I like, I can tell you that "strong" cages hurt worse than energy absorbing ones.

 

[gt1guy]

I think we agree more than we don't. Just differing thoughts on the terms.

A 100% completely rigid immovable cage, will transfer every bit of energy from a hit to the passengers. This is not optimal.

A properly constructed cage can be both strong and absorb energy at the same time without failure. This is what we are shooting for.

A flexy cage has members moving in ways that can lead to over stressing, over stressing other members, or cause a cascading effect leading to complete failure. This is where seats begin to move and harnesses get loose.

NASCAR mandates all roll cages to be made from mild steel for the energy absorbing aspect. CroMo will transfer more energy from a big hit directly to the driver due to the strength increase over mild steel. So same car, same cage, same crash. CroMo cage will be more rigid and therefor hurt more.