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  • Cage Design

    Hey guys,

    Looking to get a cage installed in 3-weeks and want to iron out the design. Planning on continuing HPDE once the car is running and doing maybe TT in NASA.

    X-bars, is it worth having them do two bars continuous (bending) vs the traditional x setup?

    FIA bars, any issues with NASA/SCCA?

    No halo bar

    Trying to decide what to have them do off the rear strut towers, low on main hoop or high?

  • #2
    2 bent bars is much stronger in an impact. You're deforming twice the material in the center of the X, and are not loading a weld very heavily like a single bar X has to.

    I would go high on the main hoop for connection to the rear strut bar, that provides much greater strength in a roll over. Basically attach them on the outer portion of the flat top part of the main hoop (top of the B-pillar to roof connection in car).
    '18 Chevrolet Volt - Electric fun hatch for DD duty!


    DefSport Koni Sleeve and Spring Perch Buy!!!
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    • #3
      Originally posted by Def View Post
      2 bent bars is much stronger in an impact. You're deforming twice the material in the center of the X, and are not loading a weld very heavily like a single bar X has to.

      I would go high on the main hoop for connection to the rear strut bar, that provides much greater strength in a roll over. Basically attach them on the outer portion of the flat top part of the main hoop (top of the B-pillar to roof connection in car).

      That makes sense thank you

      I saw some pictures of the cup cars starting to protrude into the door panel. seems counter-productive to the x bar design and starting to get in the realm of the nascar style.


      this is for a civic but the design seems solid

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      • #4
        You want the X to go as far out as possible. The Cup car design has it right. 2 bars would provide more protection at a tiny weight penalty.
        '18 Chevrolet Volt - Electric fun hatch for DD duty!


        DefSport Koni Sleeve and Spring Perch Buy!!!
        http://www.nissanroadracing.com/showthread.php?t=5902

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        • #5
          Originally posted by Def View Post
          You want the X to go as far out as possible. The Cup car design has it right. 2 bars would provide more protection at a tiny weight penalty.
          The bars at the rear of the door appear to get that S bend though



          here is another cup car designs from Porsche

          Comment


          • #6
            I did my car a lot like the cup car design, but I had the X meet with bends welded around where they meet and then boxed in. The X can provide a stiffer chassis. Boxing in around the X is very strong

            The thing I don't like about NASCAR bars is you generally have a long distance that is unsupported. I did a lemons Sentra with NASCAR bars but plated the rocker panel and added 3 braces from the NASCAR bars. It's also really hard to avoid the S bend without going through the B pillar with either type of door bar.

            Also, make sure all tubes terminate so the load path goes into another tube or the chassis. You don't want tubes welded more than 3" away from each other.

            Another thing to consider is adding FIA rollover tube. It triangulates the A pillar and prevents it from collapsing in a rollover.
            98 240SX SCCA STUish

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            • #7
              It's always better to have the material out away from you rather than having everything straight. I guarantee you it takes more energy to move that Cup car design with the S curve in the back of the X door bar to the seat, vs. a straight X that's maybe 1" from the edge of your seat.


              Maybe the straight X takes more ultimate load to fail, but at that point, the door bar is already up your butt and you're likely severely injured.
              '18 Chevrolet Volt - Electric fun hatch for DD duty!


              DefSport Koni Sleeve and Spring Perch Buy!!!
              http://www.nissanroadracing.com/showthread.php?t=5902

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              • #8
                If you're only going to have one rear strut member it needs to be high on the main hoop, just like Def stated.

                Things move in a proper crash. Give yourself SPACE, again, like Def stated. Get the bars as far away from you as possible into the door. If you have S-bends, they can be supported by having verticals like in a NASCAR style cage and then ultimately tie it into the rocker panel or rocker cage member if you have one.

                With Joe D's cage description you could fortify it even more by having a vertical running to the vertex from the rocker panel. If I were to build a new cage right now, I would do this method.

                The biggest benefit of NASCAR bars is protrusion potential. They are usually skinned and provide a ton of space. And correctly done, they don't have S-bends and tie into a straight lower member that runs along the rocker.

                Don't be scared of going through the unibody B-pillars. They are pathetic on an S-chassis anyway. Take a good look here from my old car/cage (where I would now change quite a few things):

                Core4 Motorsports
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                • #9
                  Yea, I don't know why more cages don't put a large notch in the b-pillar seam to get a straighter shot for door bars. Then weld all that together (if rules allow). The b pillar is flimsy, and you get way more strength tying it into a cage tube than leaving it intact and out of the path of a tube.
                  '18 Chevrolet Volt - Electric fun hatch for DD duty!


                  DefSport Koni Sleeve and Spring Perch Buy!!!
                  http://www.nissanroadracing.com/showthread.php?t=5902

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                  • #10
                    Def,

                    Totally agree. Always make everything as far away from the driver as possible.

                    When I did the Sentra I actually came around the lower part of the B pillar with the nascar bars. The door striker was between the two bars and the they came all the way out to the door skin. Then added 3 supports to the rocker. We built a brand new car due to a side impact in the left front wheel area that moved it over a foot. It only had to be one foot back or so and the driver could have been seriously injured. It was an easy decision to go with nascar bars.
                    98 240SX SCCA STUish

                    Comment


                    • #11
                      Originally posted by Joe D View Post
                      I did my car a lot like the cup car design, but I had the X meet with bends welded around where they meet and then boxed in. The X can provide a stiffer chassis. Boxing in around the X is very strong

                      The thing I don't like about NASCAR bars is you generally have a long distance that is unsupported. I did a lemons Sentra with NASCAR bars but plated the rocker panel and added 3 braces from the NASCAR bars. It's also really hard to avoid the S bend without going through the B pillar with either type of door bar.

                      Also, make sure all tubes terminate so the load path goes into another tube or the chassis. You don't want tubes welded more than 3" away from each other.

                      Another thing to consider is adding FIA rollover tube. It triangulates the A pillar and prevents it from collapsing in a rollover.
                      When would a tube not be into another or the chassis? Just trying to understand in instances where that isn't true.

                      Originally posted by gills View Post
                      If you're only going to have one rear strut member it needs to be high on the main hoop, just like Def stated.

                      Things move in a proper crash. Give yourself SPACE, again, like Def stated. Get the bars as far away from you as possible into the door. If you have S-bends, they can be supported by having verticals like in a NASCAR style cage and then ultimately tie it into the rocker panel or rocker cage member if you have one.

                      With Joe D's cage description you could fortify it even more by having a vertical running to the vertex from the rocker panel. If I were to build a new cage right now, I would do this method.


                      The biggest benefit of NASCAR bars is protrusion potential. They are usually skinned and provide a ton of space. And correctly done, they don't have S-bends and tie into a straight lower member that runs along the rocker.

                      Don't be scared of going through the unibody B-pillars. They are pathetic on an S-chassis anyway. Take a good look here from my old car/cage (where I would now change quite a few things):

                      Guys are spitting knowledge at me, trying to understand. What is a vertex?

                      Seems like every NASCAR "style" door bar I've seen has an S bend.

                      Is there any issues with NASA/SCCA and going through the B pillar? seems smart to me, likely more labor intensive as well.

                      Fabricator I planned on going through told me he didn't feel comfortable not doing a halo bar. I'm guessing a lot of these guys are doing standard 4 and 6 points intended for drifting only.

                      Would it be worth doing an 8-point? One fabricator asked forward of the A pillar at the firewall.

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                      • #12
                        Sorry to confuse you. I'm not sure how to write it so it makes sense. You want to look at the load path. I'm not saying its not connecting to a tube. I mean it needs to have another tube on the other side to distribute the load.

                        The vertex is the middle of the X. I actually have another straight tube that has the tube from the vertex to the middle of it. The car was originally built for SCCA IT and NASA PT and it's not allowed to have an extra attachment point to the rocker.

                        Mine is similar to this with a vertical tube in the middle and it bends out into the door:

                        Then I plated it in with taco gussets similar to this:

                        I did a halo in the sentra. It is a little easier in some ways. I do like the look of one continuous a pillar bar from the main hoop forward and it isn't all that big of a deal to make.

                        You need to understand the rules for any class you may want to run in. In general most classes don't want you going through the B pillar or cutting it up. If you have a fairly well prepped car with some higher horsepower it won't matter because you'll be in a more open class anyways.

                        You do have to do some pretty extensive surgery to the door if you go through the B pillar though. It becomes pretty flimsy but we made it work with some extra bracing.

                        Go on google and look at pics of cages. Make sure you understand the rules for whatever organization is inspecting your cage and make sure the builder understands them.

                        Eventually I'll build another one because you always learn what you would do different when you finish one.
                        98 240SX SCCA STUish

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                        • #13
                          https://www.youtube.com/channel/UCcx...rjTVSSUkzZ2Jlg

                          This is not a terrible place to start either. This guy has a whole play list doing a time attack cage.

                          Ch

                          Sent from my SM-G955U using Tapatalk

                          Comment


                          • #14
                            Originally posted by Joe D View Post
                            Sorry to confuse you. I'm not sure how to write it so it makes sense. You want to look at the load path. I'm not saying its not connecting to a tube. I mean it needs to have another tube on the other side to distribute the load.

                            The vertex is the middle of the X. I actually have another straight tube that has the tube from the vertex to the middle of it. The car was originally built for SCCA IT and NASA PT and it's not allowed to have an extra attachment point to the rocker.

                            Mine is similar to this with a vertical tube in the middle and it bends out into the door:

                            Then I plated it in with taco gussets similar to this:

                            I did a halo in the sentra. It is a little easier in some ways. I do like the look of one continuous a pillar bar from the main hoop forward and it isn't all that big of a deal to make.

                            You need to understand the rules for any class you may want to run in. In general most classes don't want you going through the B pillar or cutting it up. If you have a fairly well prepped car with some higher horsepower it won't matter because you'll be in a more open class anyways.

                            You do have to do some pretty extensive surgery to the door if you go through the B pillar though. It becomes pretty flimsy but we made it work with some extra bracing.

                            Go on google and look at pics of cages. Make sure you understand the rules for whatever organization is inspecting your cage and make sure the builder understands them.

                            Eventually I'll build another one because you always learn what you would do different when you finish one.
                            Thanks for clarification

                            Originally posted by a250gpguy View Post
                            https://www.youtube.com/channel/UCcx...rjTVSSUkzZ2Jlg

                            This is not a terrible place to start either. This guy has a whole play list doing a time attack cage.

                            Ch

                            Sent from my SM-G955U using Tapatalk
                            Watched a few episodes, seems helpful for those guys building their own cage.

                            Comment


                            • #15
                              crazy the price gap between quotes but sounding like I'm a week out

                              What is your opinion, on the design of this cage?

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