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  • roll cage building techniques

    For unibody cars that are getting a roll cage added how do you weld fully around the joints that run right up to the existing sheet metal?

    I've seen inside rally cars where the roll cage is very well integrated with the unibody frame concept. Sometimes it seems spot welds were drilled out and the body was re-assembled around the cage. It would add a ton of strength if the body panels were actually welded to the bars.

    I don't have any current plans to attempt a roll cage like that, but reading the post "another roll cage nightmare" has got me thinking about how I would do it.

    Sometimes the best way to learn about something is to study somebody else's disaster. Now that we have all poked fun at that guy that obviously doesn't know what he's doing, I would like to hear how you guys would do it better (other than having the proper tools for the job).
    ________
    Marijuana Vaporizers
    Last edited by eric75; 05-12-2011, 03:03 AM.

  • #2
    One thing I would do (I am not the greatest pipe fighter,, ha) but I would make a cardboard template first and fit it exactly before cutting any metal, some you could reuse on identical joints. Do your trial and error with the cardboard, then wrap it on the pipe, transfer the marks and cut the joint. Use something about the thickness of a cereal box.

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    • #3
      Sberry:
      Printers call that material, chipboard, and all printers have it. Large sheets are available-23"x35" or 26"x40" are the common sizes. Handy stuff for patterns.

      Peace,

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      • #4
        Originally posted by eric75
        For unibody cars that are getting a roll cage added how do you weld fully around the joints that run right up to the existing sheet metal?

        I've seen inside rally cars where the roll cage is very well integrated with the unibody frame concept. Sometimes it seems spot welds were drilled out and the body was re-assembled around the cage. It would add a ton of strength if the body panels were actually welded to the bars.
        .
        But rally car body parts must be replaceable in 20min, hence them remaining unattached. I can only speak to the methods used in rally cars, but there should be some carry over....

        * Removing sheet metal, wherever possible, is always handy. Especially on tight fitting roof bars, where you need to weld the complete perimeter of the tube, drilling out the spot welds that hold on the roof skin allow you the best access. A more hazardous option would be to drill a hole under your front mounting points, allowing the tube to drop forward, and tilt the whole cage forward inside the car, allowing you to weld the tops of the joints, then pull the thing back up into position. It does mean you're cutting a hole in the sill you later want to take impacts, so the roof method is generally better.

        * When you mount tubes to the sill, you generally require a spreader plate, but welding the back half can be tricky, since you want that bar to be right up against the pillars of the car. There are various ways to handle this, but the best I've seen is to make up the spreader box first, and then cut the top off. You then generally have enough slack to weld just this flat plate to the tube, and then slide the rest of the box in underneath and weld it up.

        In any case, to get a really tight fitting cage, you need one of two things. Experience in having done lots of them before, or lots of patience!

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        • #5
          Ive also seen alot of people drill a hole in the floor after the cage is tacked, then drop the whole cage down and weld up the tops. I dont think that is real safe, but alot of people do it, I guess if you weld another plate on the bottom of the car, it would help. I like the idea of the Micro Tig torch from Arc-Zone, that will allow you to get in real tight places.
          Lincoln Precision TIG 375
          Lincoln Power MIG 255
          Lincoln Pro Cut 80
          Miller Elite Red Flame

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          • #6
            Everyone has their own techniques that work for them. I tend to make myself lots of patterns and templates to work from. I use quite a few different methods and tricks to figure out my bends. No "one way" works every time. Every car is different as every customer is different.

            On main hoops I like to draw out the rough dimensions of the B pillar contours and figure out my bends before I ever even touch a tube. I've used degree wheels, flexible exhaust tubing, pre bent tube sections, string, and brake line tubing to figure out bends, and everything from toilet paper rolls, pre notched tube scraps, to notching software for figureing out my notches. I've also used a 3d bending software to figure out my bends and lengths although I haven't had too much luck with the software.

            I tend to make things hard on myself by making the fit too tight to the body but in the end the cage is tucked away and provides as much room as possible.

            I complete the entire cage and tack it together as I go before I ever weld anything solid. This allows me to see any problem areas or tubes that I might have to weld outside of the car before I "get stuck."

            Once I've got all the fab work done, I pull it all back out and clean up the tubes and the weld areas. I also measure the lengths, degrees and notches of each tube as well as label all of my pad patterns for reference when a similar car comes in.

            I'll reassemble the main hoop/downbars/doorbars and crossbars to make sure everything is lining up and then tack the hoop in place. Tack the front crossbars or halo to the downbars and weld what I can from the bottom. I'll then drop the front half down (by either pulling the ends together or cutting the hoop tacks) and weld the tops. The Main hoop is sometimes the last major bar that I'll final weld just in case something needs to move or be tweaked.

            Gotta love building Spec Miatas. They've got a removable hard top. You build the cage with the top on, take 2 minutes and pull the top off and you're standing up welding the tops of the tubes
            Scott Rhea
            It's not what you build...
            it's how you build it
            Izzy's Custom Cages

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            • #7
              notching software

              Speed Raycer, you mentioned notching software. Where can I find it? Did it work good? Thanks

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              • #8
                Originally posted by stinkinlincoln
                Speed Raycer, you mentioned notching software. Where can I find it? Did it work good? Thanks
                www.tonyfoale.com Look for the "Download Free Software" link

                Still needs a little grinding to fit. Not as quick as a PipeMaster but they aren't always easy to use in certain situations.
                Scott Rhea
                It's not what you build...
                it's how you build it
                Izzy's Custom Cages

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                • #9
                  Thanks Much Speed Raycer

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                  • #10
                    Originally posted by Speed Raycer
                    www.tonyfoale.com Look for the "Download Free Software" link

                    Still needs a little grinding to fit. Not as quick as a PipeMaster but they aren't always easy to use in certain situations.

                    I bought the Pipemaster stock car kit and have not tried it yet. Do you use it as the directions say? That looks very time consuming.

                    Thanks,
                    Mike

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                    • #11
                      I just recently saw the actual directions for the Pipemaster. I never had any with mine so I just went by the seat of my pants. I've got the 1.5" unit. For anything more acute than a 35 angle, the collar starts to get in the way which means you need more stick-out of the needles... which leads to them spreading and becoming more of a headache than a help. The next one I buy is going to be from Mittler Bros. I saw their version and it uses much thicker ga. needles that look like they'd stay straight rather than wandering off.

                      Don't get me wrong... the Pipemaster is a great help. Especially on notches that are in the middle of a bend or multiple tube joints.
                      Scott Rhea
                      It's not what you build...
                      it's how you build it
                      Izzy's Custom Cages

                      Comment

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