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Thread: Factory Installed Roll Cages

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    Factory Installed Roll Cages

    I was learning about the building of rally cars and I read about the importance of a roll cage in these cars. Road cars that normal people like myself drive don't have these and I know most these aren't going used under the same conditions as a rally car would be, but there are a lot of road cars that are flipped or get in bad accidents. Rally car drivers who get into some of the same accidents have a greater chance of walking away from the crash. The purpose of the roll cage is to protect the driver, so why aren't they be installed into road cars?
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    well, newer car are much better designed for rollovers and the like. comparing my 81 rx-7 and my relatively new g35 you can see the different in the A pillar. on the rx it is very thin and hardly obstructs your vision at all. on the G it is a thick as cage. additionally, there are huge amount of supports in the door, so it weighs a ton unlike the older car. all around it is more stout and certainly provides much greater safety margins.

    most people woulnt put up with the headache of a full cage. they are hard to maneuver around, and occupy a lot of space in the vehicle. additionally, if you are not strapped in with a harness, they provide a hazard for your head to collide with, and can hurt you more. so there are a lot of reasons they arent used in road cars, but the lesons of cages are certainly used in the design of modern road cars.
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    Quote Originally Posted by cmcpokey View Post
    most people woulnt put up with the headache of a full cage. they are hard to maneuver around, and occupy a lot of space in the vehicle. additionally, if you are not strapped in with a harness, they provide a hazard for your head to collide with, and can hurt you more. so there are a lot of reasons they arent used in road cars, but the lesons of cages are certainly used in the design of modern road cars.
    Precisely.
    Also, the presence of a roll cage makes almost impossible to access to the rear seats (if they are present that is), while at the same time it would also incrase the costs or road going cars.
    Eventually, driving among, or "close to" the limits wouldn't require a roll cage in most of possible scenarios. Then shit happens, but that's a whole different story.
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    in some cases you only have a rollcage to compensate for flimsier lightweight panels (the doors on a cup car for example).
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    Cages also reinforce the chassis, which makes them stiffer. So that would eliminate benefits of crumple zones and other built in safety features. Also, drivers wear fire retardant suits, hans devices(or something similar) and helmets which aid them in crashes.
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    Yeah everything you've all said is very true. My topic fails haha, wouldn't you think its something to think about? I mean a roll cage or something that works in the same sense could make a difference in a crash.
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    Quote Originally Posted by johnnynumfiv View Post
    Cages also reinforce the chassis, which makes them stiffer. So that would eliminate benefits of crumple zones and other built in safety features. Also, drivers wear fire retardant suits, hans devices(or something similar) and helmets which aid them in crashes.
    Not sure if a roll cage would really interacts with crumple zones. Since they are there to absorb most of the energy generated during an impact trying to leave the cockpit area intact, and given a roll cage is mounted and working inside of the cockpit, I would actually assume that a roll cage would be useful in the moment when the crumple zones aren't enough (you're alreadyd dead probably, still).

    Virtually the central part of the chassis should be intact after an accident (not lateral of course), so what's inside of it should irrelevant as its stiffness is already higher than that of crumples zones, so increasing it should only help.
    Then if the impact involves directly the cockpit area, and if nothing absorb the energy, then that's your brand new role, playing the shocks absorber.
    Sort of.
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    That's actually a very good question. If the passenger cell is the most vital area when it comes to safety, surely it only makes sense to make it as rigid and protected as possible. What better way to do it than with a rollcage?
    Maybe not a complete plumbing job, but some form of reinforcement, especially across the roof, makes sense?
    Maybe rollovers relatively aren't that high of an occurrence to justify spending a lot on R&D to the manufactures, but I'd rather them spend their money on making the passenger areas as safe and secure as possible before trying to bring electric cars to fruition.

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    I think it's not a matter of costs, but of weight and roominess. After all safety cages (so not interacting with the stiffness of the structure) are used for most of the development time of a car, so no R&D required.
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    Maybe there's no R&D required for traditional cages, but how about new kinds made with better materials that do not interfere with interior roominess (by as much at least) or that carry a lower weight penalty?
    Sure there's a rollover test as part of the Euro NCAP now (I think), but personally, I wouldn't trust anything higher than the windowline on any modern car fitted without "scaffolding" to offer much protection in the event of a rollover at anything above, say, 80 km/h.

    EDIT: Probably worth adding even with a factory-fitted roll-cage, I still wouldn't trust a roll-cage fitted car without a helmet and a 6-point harness to offer adequate protection in a roll-over, but anyways.
    Last edited by Kooper; 02-21-2010 at 02:51 PM.

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    They already do reinforce the pillars and roof for rollover protection, as cmcpokey said up there newer cars have much thicker pillars in order to provide more protection in a rollover and whatnot. With today's cars, 99% of the time a rollcage would be unneccessary, and in the other 1% you're probably stuffed anyway. And most of that 1% can be avoided by not driving recklessly anyway.
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    most subaru's for example are already reinforced to the point emergency services have difficulty getting people out of the car.. though they are unharmed.
    if i was to replace the doors with flimsy lightweight carbon fibre items, then i would put in a rollcage to take the place of the integral side intrusion bars.
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    Installing a roll cage in a production car wouldn't be sensible. We have two issues here. The first is passenger cell intrusion prevention. The second is what level of safety makes sense.

    So the first is what a roll cage actually does. It prevents a wreck or impact from closing up the passenger compartment. Well, why would any manufacture actually want to use a roll cage to perform that job? It's much better to reinforce the unibody such that it is strong enough to provide what ever level of protection is needed. As an example most roll cages have bars right behind the A-pillars. That's because the factory A-pillars aren't strong enough to meet the sort of crash protection a cage is meant to handle. Well, if the factory was required to meet the same standards they could simply make stronger A-pillars. Roll cages often have immovable door bars. Well the factory could simply make smaller door openings with more unibody protection rather than messing with adding a tubular cage.

    In real easy terms, the only reason why we add a roll cage to the factory structure is because the factory structure isn't as strong as we need it for racing. However, if the factory was required to build it to racing standards they could integrate that better protection into the unibody instead of having to add what amounts to a second cage inside of the factory unibody cage.

    The second issue is the level of protection that's reasonable. Race cars make all sorts of sacrifices for speed and safety. Drivers have helmets, six point belts, arm tethers, etc in the name of safety. The doors are often partially or even fully blocked in the name of improving side impact protection. These are simply not acceptable trade offs for a daily driven car. I'm not going to get my grandmother through the window of a Focus. Some level of safety must be sacrificed in favor of practicality. Thus we have larger door opening and we wear 3 point belts and no helmets. We have airbags to pad our movement toward the wheel rather than HANS and belts to keep us in the seats. Basically we have a balance between the need for safety and the utility of a car as a tool. Race cars have a higher level of safety because of the environment they operate in. Road cars operate in an inherently less dangerous environment thus they can have less in the way of restraint type safety. If safety regulators felt that the added safety of a cage with respect to passenger compartment collapse was needed they would likely pass laws to that affect. Since they haven't, it's likely that our auto safety dollars (and all these safety things are dollars on the price tag) can be better spent on other safety features.

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    Quote Originally Posted by LeonOfTheDead View Post
    Not sure if a roll cage would really interacts with crumple zones. Since they are there to absorb most of the energy generated during an impact trying to leave the cockpit area intact, and given a roll cage is mounted and working inside of the cockpit, I would actually assume that a roll cage would be useful in the moment when the crumple zones aren't enough (you're alreadyd dead probably, still).

    Virtually the central part of the chassis should be intact after an accident (not lateral of course), so what's inside of it should irrelevant as its stiffness is already higher than that of crumples zones, so increasing it should only help.
    Then if the impact involves directly the cockpit area, and if nothing absorb the energy, then that's your brand new role, playing the shocks absorber.
    Sort of.
    There are tubes that usually run off the central cage to the ends of the car for added stiffness. They usually mount to the ends of the frame rails/chassis. So those would make the crumple zones useless. You know I work on race cars for a living right?
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    Quote Originally Posted by culver View Post
    So the first is what a roll cage actually does. It prevents a wreck or impact from closing up the passenger compartment. Well, why would any manufacture actually want to use a roll cage to perform that job? It's much better to reinforce the unibody such that it is strong enough to provide what ever level of protection is needed. As an example most roll cages have bars right behind the A-pillars. That's because the factory A-pillars aren't strong enough to meet the sort of crash protection a cage is meant to handle. Well, if the factory was required to meet the same standards they could simply make stronger A-pillars. Roll cages often have immovable door bars. Well the factory could simply make smaller door openings with more unibody protection rather than messing with adding a tubular cage.
    This reminded me of the Bertone Mantide.
    Here they did add a (modified) FIA-homologated roll cage, but they wrapped it with the new bodywork. For as regards the driver, it doesn't matter if under the bodywork panels, there is a roll cage or a solid unibody in that specific area.

    Pics attached. As you can see that doesn't look like a Corvette's sill anymore.
    And let me say once again that I love that A-pillar.

    EDIT:
    Quote Originally Posted by johnnynumfiv View Post
    There are tubes that usually run off the central cage to the ends of the car for added stiffness. They usually mount to the ends of the frame rails/chassis. So those would make the crumple zones useless. You know I work on race cars for a living right?
    Of course I know
    I was more thinking about safety cages rather than roll cages, so that makes sense.
    So yes, we are the shocks absorbers then.
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