gt1guy
Apparently a racist
I just wanna see the oversize clay pigeon thrower thats throwing that tire
3:23 in this vid. Looks to be some sort of air cannon contraption.
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Roll Cage Failures
- Thread starter '84 Bronco II
- Start date
3:23 in this vid. Looks to be some sort of air cannon contraption.
A 4130 cage of the same diameter and wall tube is definitely going to be stiffer. That is why SCORE used to let you run thinner wall 4130 than mild. It kept the strengths about the same. The new cage rules coming down the line will cause more issues than they solve. The minimum structure mandate for weight is way to high in my opinion. The cage will be intact but the driver won't. They are baising the new rules on feelings and preferences over actual solid data and testing. But, Roger is always right........
Air cannons are used in lots of testing. There outdoor one is probably one of the chicken cannons used for plane fuselage testing.
aczlan
Good Morning!
I am curious.
How much of a difference does it make having the cage inside of a cab (like in the picture from bdkw1 ) vs something like a tube buggy where there isn't another layer between the cage and the ground?
I am assuming that having the cage inside a "stock" cab would spread the loads out a little and make the point loads on the cage itself a little less (either from the cab acting like a slider, or just from having another layer of metal to deform and then to spread out the impact to the tube itself over a larger area) vs a tube buggy with some panels between/over the cage bars on the roof, or just the roof tubes).
Aaron Z
gt1guy
Apparently a racist
Having any kind structure outside of the roll cage will always absorb "some amount" of energy as it deforms. I think your other points are valid too. Spreading the load and the slider effect.
Most stock roofs are not much more than a thin flat piece of metal with very little structure to it. The factory A&B pillars are what will absorb energy until the roof is smashed down to the cage.
I'd think the biggest benefit of having say a roof above the cage is that the roof can stop things from making intrusion into the driver compartment and also keeping your arms inside and away from danger.
Don't underestimate the benefits of those roof panels slapped on top of the buggies. If mounted robust enough, they can act like a giant gusset encompassing the whole roof.
All off road racing orgs have roof panel rules. If you are in soft sand like the dunes, tubing will sink in if you are sliding upside down on the face of a dune. Had a buddy get his neck broken that way. Cage was in perfect shape, belts were tight. His head hit the ground inside the cage.
'84 Bronco II
El Chingón
Pretty much all steels have essentially the same modulus of elasticity, so within the elastic regime, 4130 is no stiffer than 1020. It has a higher yield point and ultimate failure stress though, so it will take significantly more force before it bends, buckles, or rips.
Your point is completely valid though, and I have read about the NASCAR material rules before. The problem is characterizing the load to the structure. Obviously hitting a wall at 200 MPH has a lot more energy than taking a tumble recreationally wheeling. Energy absorbtion is critical for reducing injuries and improving survivability (why modern cars have crumple zones and 100 airbags
), but survival space needs to be maintained for the occupants. It's a balancing act in high-energy crashes between absorbing energy and not folding up and crushing the occupants. However, crumple zones are highly engineered and require extensive testing and R&D to design effective ones, something that is well beyond the scope of the average home fabricator.This kind of feeds back into the earlier discussion about how a rigid cage should go hand-in-hand with harnesses and seats with enhanced containment.
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One of my pet peeves at the moment is the extra vertical bar in the A pillar making it an A. Yes the A pillar will deform in a hard hit. But, it is just about as far from the driver's head as you can get in the roof structure. Front impacts here are what cause head and neck injuries Ala Dale Earnhardt. To me having this area deform under a heavy hit is beneficial. But the people with input to the new SCORE rules feel differently. Neither of us has hard data to say which way is better, both are working off gut feelings and past crash experience. To me having a cage that will never give is the wrong answer.
Yes and no. You want the cage surrounding the occupants to be as rigid as possible so nothing moves and potentially harms/kills them but you also want the front and rear of the chassis to "crumple" to absorb impact. Id imagine it's a tough balance for offroad chassis builders to manage while designing a chassis.
Earnhardt died because he was old school and too thick headed to wear the proper and modern safety gear of the times. It had nothing to do with the chassis.
And running no A pillar braces is a sure way to have the front of the roof come down on you in a hard roll. There is no instance in my mind where not having A pillar braces would be a better idea.
And to add....... When the cage surrounding the driver takes a hard hit and doesnt give, the high dollar race seats should be the next thing in line to absorb some of that energy before reaching the occupants.
Seats are like helmets, is your life worth $300 or $3000?
Seats are like helmets, is your life worth $300 or $3000?
Brace yes. Another full sized tube?
I do a brace out of 1" or 1-1/4" .095
In the new rules proposed by Morgan Clark he states it needs to be the same diameter as the main cage tubes. But if you're concerned about weight you can go down on the wall thickness. WTF? .049 wall 2" is OK? Tell me it's about structure and not about looks.....
I do a brace out of 1" or 1-1/4" .095
In the new rules proposed by Morgan Clark he states it needs to be the same diameter as the main cage tubes. But if you're concerned about weight you can go down on the wall thickness. WTF? .049 wall 2" is OK? Tell me it's about structure and not about looks.....
Forward impacts don't bring the seat into the equation. Especially if your endoing and landing flat on the roof line. This is all on the belts and will leave you with bruised shoulders.
If (2) 15" or so vertical tubes made of the same diameter and wall thickness as the main chassis make or break the handling on the vehicle, I hate to say it, but the chassis builder fucked up something majorly somewhere else in the chassis design and it ain't those two tubes..... 
aczlan
Good Morning!
Wouldn't a bigger concern be rolling over at speed (barrel roll) and having something (a large rock?) impact along the top front (top of windshield bar, top of the A pillar, etc) and causing the cage to fold back somewhere on the A pillar, crushing the driver?
I would think that would be more energy to deal with than endoing, then landing on your roof as that spreads the load out across more of the roof.
Aaron Z
Having the front of the roof give isn't a solution to that problem but could compound the chances of severe injury or death if it comes down to far. Some hits you will never be able to make safe and people will get hurt or die, it's just part of the game we love playing.
You saying I wasted my time bracing the A pillar bars?
Is that the same size tube and wall as the cage. If so, overkill. Also, door bars should intersect the dash bar. The windshield A's should have lined up with the verticals to the dash bar. But as you are working around a body none of that may have been possible without serious butchery. The extra beefy A pillars will make up for it.You saying I wasted my time bracing the A pillar bars?
Golf carts kill me, the whole front of that thing doesn't look like it's attached to the main cage. The whole thing looks like one big crumple zone.
EXACTLY!! I'd rather buy/build a new chassis than hurt or kill myself by not having the chassis crumple. I seriously thought about adding a bunch of bars up front but in the end decided new tubing was cheaper than medical bills or funerals.
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And it's the same size.(1-3/4") as the main cage and vertical door bar. Main cage is .095, vertical door bar is .083 and so it the A pillar brace. The /\ bars below it are 1-1/2 .083
Rockwood
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FIA has been doing this for decades now, and they’ve learned a lot of hard lessons in the mountains and trees. Cage’s job is to protect the occupants from getting hit/smooshed. The harnesses, helmets, SFI/FIA padding, seat and HANS are there to help the driver deal with the G-forces of a wreck.
Rally cars are a little different being full body. That body absorbs a lot of energy before it hits the cage. There cages are pretty light duty compared to what we see. They are made to survive 1 crash then get scrapped. TT's see many crashes.
arse_sidewards
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All the more reason not to listen to the Reddit types who think the cage should also function as a crumple zone.
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Who pays attention to anything on Reddit?
Rockwood
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I'm not talking just WRC, but even WRC level has the cage right against the exterior sheetmetal. There isn't really a "crumple zone" except for the stock sheetmetal on the back of the car (since hatchbacks/wagons generally compete).
Crashes? Have you seen WRC?
They crash a stage, the crowd rolls it back over, limp it through the rest of the course, then frantically repair it to continue on with the next stage.
Only time they scrap it is if they went into the trees at 100mph, which a TT isn't coming back from either.
I was talking Dakar though, which is very similar to Baja 1000, except there aren't as many people around to help. Either way, TTs aren't exactly the best example of crumple zones being necessary.
gt1guy
Apparently a racist
I'd think any TT that takes a big hit gets a very thorough inspection when it gets back to the shop and any compromised tube gets cut out and replaced.
The rally car, the cage and body are basically one piece so the choice to scrap would come much faster. Just from a work involved standpoint.
gt1guy
Apparently a racist
Miller's Pro Chassis is what I'd want the A-Pillar area to look like, for an offroad machine.
That's well thought out.
And the drivers elbow isn't going to be banging on the angled door bar.
But more importantly...........look at the size of that bead roller
Bebop
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Usually is even tied to it with big ass plate gussets
Agree to disagree.
The car needs to finish the race but they absolutely will re-shell it before the next race.
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I'm talking multiple crashes in the same race. TT's are mostly a rich guy sport, some of them should not be driving something that fast.
I've been in 2 rollovers in the same race. We finished, but the were several wrench welded on to various suspension parts...
gt1guy
Apparently a racist
Shit. I totally missed what you were getting at.
That leads me to a question though.
Have you ever seen anyone get black flagged that had wadded their rig to the point of basically being unsafe for the driver and co-driver?