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Why a proper roll cage is important...


rturbo 930

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I've seen quite a few cars that where rolled with cages like that, most of them either had bars sheered off, or the cage just folded in on itself. the solstice in the forza motorsport challenge on speed did the same thing then it wrecked, the top of the cage was just folded to the side and the cage itself was just twisted like a pretzel.

 

here's to vid.

 

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They must have 240z floor pans. John, no trying to put you on the spot here......but true race shops that build "track prep" cars....what would you reinforce the floor with so that doesn't happen or do you just go with a completely different style cage?

 

I can't comment on the roll bar installation or type (bolt-in or welded) without looking at the car.

 

From the pictures it appears that how the car hit the roof is a one-in-a-million shot as Josh alluded to in a previous post. In a roll over the car normally rolls onto the roof and doesn't just flop down square. That most likely contributed a lot to the roll bar failure.

 

For that kind of hit the bar would have been better tied to the floor pan and the rocker panel to spread the load. But, again, that's a one-in-a-million type of roof hit and maybe that wouldn't have been enough.

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Like John mentions, multiple structure ties are the key to keeping a rigid roof bar from punching through the floor. Each sanctioning body has requirements for this criteria, and what goes in one place may not be enough in another.

I was at an FIA/KNAF Registered Roll Cage Engineereing Works the last weekend in September and took some snaps of their tie-ins on a 240. It was interesting how they worked the floor through and rocker panel into an integrated structure to accept the roll structure.

I can post them on the site (the photos are on my laptop) or post them in another thread titled roll bar. I thought the 240 specific photos might be helpful later on when I was doing my cage...

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I was at an FIA/KNAF Registered Roll Cage Engineereing Works the last weekend in September and took some snaps of their tie-ins on a 240. It was interesting how they worked the floor through and rocker panel into an integrated structure to accept the roll structure.

I can post them on the site (the photos are on my laptop) or post them in another thread titled roll bar. I thought the 240 specific photos might be helpful later on when I was doing my cage...

 

I'd be interested in seeing a separate thread with these photos. It's been very hard for me to start on my cage because I'm always worried about getting the cage doubler pads to cover as much area as possible, and in the right places.

 

PM me when you start the thread.

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Sounds Good John,

I'm running to an emergency job in Garyville LA at Marathon Oil, so it will be a day or so before I can load up the photos.

 

So much for having two or three weeks in the office before going on furlough.

 

Seems the only time I'm getting off this year is when I'm not getting paid for it!

 

DAMN!

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Sounds Good John,

I'm running to an emergency job in Garyville LA at Marathon Oil, so it will be a day or so before I can load up the photos.

 

So much for having two or three weeks in the office before going on furlough.

 

Seems the only time I'm getting off this year is when I'm not getting paid for it!

 

DAMN!

 

Wow, Garyville, I used to work there for 2 years. My sted-dad still does. It's a nice plant, heavy on the "polotics".

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i would like to see a cage design for a z that was built on some kind of computor added design to use the less tubing but installed in the correct position to get the most rigid chassis and be safe in a crash.something that could be lived with on the street.and maybe help save your a$$ against a drunk in an escalade.i have seen cages built that were built more for looks -used extra tubing that wouldnt really work.a unit body car is just a tin can with wheels on it.i parted out a fox body mustang completely once.it only took me and 2 other guys to load the unit body onto a trailer-by hand.a z shell must be only 300-400 lbs.

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i would like to see a cage design for a z that was built on some kind of computor added design to use the less tubing but installed in the correct position to get the most rigid chassis and be safe in a crash.something that could be lived with on the street.and maybe help save your a$$ against a drunk in an escalade.i have seen cages built that were built more for looks -used extra tubing that wouldnt really work.a unit body car is just a tin can with wheels on it.i parted out a fox body mustang completely once.it only took me and 2 other guys to load the unit body onto a trailer-by hand.a z shell must be only 300-400 lbs.

There isn't enough headroom in a Z for a streetable cage IMO, unless you're really short, in which case it's fine so long as you don't carry passengers who are taller than 5'4" or whatever turns out to be safe. If you're not short, I think you're more likely to get killed in a very minor accident with an Escalade (or a Toyota Echo) when you smack your head on the cage.

 

I think the Z is pretty good in accidents, for as old a car as it is. I was in an accident with my first 72 240Z where I was hit from the rear at ~50 mph (driver of the Firebird never saw me and never even touched the brakes). I was then pushed across the street into head on traffic where I hit an Acura Legend who was going probably 30 mph. The Z performed pretty admirably. My wife hit her head on the dashboard despite wearing the shoulder harness and I broke my nose on the steering wheel (wearing lap belt at the time). The unibody was tweaked pretty bad, but the passenger compartment was relatively intact. In fact the rear end of the car was pushed in about a foot and a half and when the cops got there they asked if my lights and turn signal were on, I looked at my car in the street and said "They still are!" The lens was broken but all of the bulbs were still lit and the turn signal was still flashing.

 

As far as the cage goes, I think it's tough to model the entire unibody in a computer program, but you can model the cage for strength pretty easily in the computer and you can also physically model the cage with wood or wire and test it for rigidity in scale. I came upon my weird cage design after reading Herb Adams' Chassis Engineering. My cage is in there on page 90 only I have X door bars and an X from the rear strut towers to the bottom of the main hoop. I agree wholeheartedly that sometimes designs have a bunch of extra tubes for nothing, and sometimes it's hard to tell at first glance that those tubes really are doing something. I think the basic ideas of cage building are pretty well established and you can do a "monkey see monkey do" cage that does a fine job. If you want to get really anal about it, there are places online for that as well. Read any post by "blainefab" on corner-carvers.com, for instance...

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