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How to weld a mild steel roll cage

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  • #46
    SCCA rules for roll cages, etc.

    I am an SCCA tech inspector that has seen some VERY bad welds. First, in the SCCA General Competition Rules (GCR) the roll cage tubing size is determined by the car weight and class. In the case of Spec Miata the minimum size is 1.5 x .095 DOM tubing- NO ERW. These rules take bends into account. The bends must be a minimum of three times the diameter of the pipe. The number of attachment points is determined by the car class, in my case STU is limited to eight. The maximum area of attachment plate in all planes is 144 sq. in. and the maximum thickness this year is 1/4 in. (After several SM's put 1 in. plate in the right rear to get better corner weights.)

    Wall thickness can now be measured with an ultrasonic thickness tester BUT, as was mentioned, it can be difficult to use properly. If the wall thickness is measured by drilling a hole make sure the bit does not strike the far wall as that will make the measurement too thin. Maximum hole size is 1/4 in., 3/16 in. preferred and anything smaller will not accept the depth rod of the caliper.

    Second, all points mentioned about practice are good. In my case practice doesn't seem to help and I will have a professional welder do all the welds except for the attachment plates. I would definitely recommend building the cage but having a professional welder do all the tubing joints. If possible get a tech inspector to recommend a welder because not all road race car shops have good welders. If a car builder insists on welding his own cage I recommend going to a Community College welding program. He should also cut apart his practice joints to check for penetration, etc.

    Gussets have not been mentioned but I highly recommend them. My car will have the maximum number of gussets per joint allowed which is two (SM is also two but other classes have no limits). Also any number of braces are allowed as long as they attach to only the attachment plates or the cage tubing and triangulation really helps.

    Finally, what ever competition you are in be sure and get the rules, read them and ask questions before doing something that might have to be undone. If you ever think that you might change classes or sanctioning bodies try to prepare the car so that you don't have to tear every thing out and start over. We had a lawyer that thought he could do his own thing and found out that he couldn't change the rules to suit him.

    John Cooper
    SCCA national license tech
    Millermatic 250X
    1985 Toyata MR2 being prepared for STU

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    • #47
      John,

      So.... what do you do when someone shows up with their fresh cage that they just paid 3-4K for and is nothing but booger welds and missed backside welds???

      Always wondered how these cars get through SCCA tech. I've just become a NASA tech shop and I'm really not looking forward to explaining to Joe Racer how he just paid for a scrap heap from another shop.
      Scott Rhea
      It's not what you build...
      it's how you build it
      Izzy's Custom Cages

      Comment


      • #48
        Originally posted by Speed Raycer View Post
        John,

        So.... what do you do when someone shows up with their fresh cage that they just paid 3-4K for and is nothing but booger welds and missed backside welds???

        Always wondered how these cars get through SCCA tech. I've just become a NASA tech shop and I'm really not looking forward to explaining to Joe Racer how he just paid for a scrap heap from another shop.
        In the case of PCA it is what you don't do. You don't issue a log book. I have only had one poor looking welds car presented for a log book but have seen plenty of cages that could have been thought out a bit better. Pro shop and home built alike. Some of the most well thought out cages were home built. I guess when it is your can in the seat you sweat the details.
        Weekend wannab racer with some welders.

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        • #49
          Izzy,

          I think I've seen some of your work on 7 Club, Id swear I've been to that website before.

          You have to tell him that he needs to have those welds fixed if you deem it unsafe. And that you wont give him a log book till he does. If he wants...he can go to another inspector to see if they'll sign off on it...but always CYA first.
          Precision is only as important as the project...if you're building a rocket ship...1/64" would matter. If you're building a sledgehammer...an 1/8" probably wont.

          Comment


          • #50
            Sorry, I should have been more specific. What do you do when it's already logbooked and just swinging by for the annual?

            I have no qualms about letting someone know that there's some subpar work that needs to be fixed. I've had several come in for updates that have had horrible or missing welds from some well known shops. Just haven't done it officially yet where I'm telling someone "nope, you can't race this weekend until you have this fixed"

            Fire... I used to post over at 7club quite a bit. Sold my 1st Gen about 2 or 3 seasons ago so I don't get back there much.
            Scott Rhea
            It's not what you build...
            it's how you build it
            Izzy's Custom Cages

            Comment


            • #51
              huh, interesting question...

              I've always wondered something similar with drag cars: it seems like you're always worried about your own work passing, which is pretty decent and as far within the rules as possible (there are times that the chassis or the driver force you to make decisions that are not _exactly_ within the letter of the rules even though they try to follow the intent as close as possible) and then it always seems like there is a decent percentage of cars at the track with certified cages that have booger welds, the wrong size bars, bars in the wrong places... and don't seem to have any problems with tech.
              Mark
              (aka: Silverback, WS6 TA, JYDog, 83 Crossfire TA, mpikas, mmp...)
              Synchrowave 180 SD | MillerMatic 211MVP + Spoolmate | Hobart Handler 135 | Everlast Power Plasma 50
              1960 Bridgeport J-head | Grizzly 10x22 | HF bandsaw | Rigid 4.5” angle grinder (+2 cheapie HF ones)
              BFH

              Comment


              • #52
                Originally posted by Speed Raycer View Post
                Sorry, I should have been more specific. What do you do when it's already logbooked and just swinging by for the annual?

                I have no qualms about letting someone know that there's some subpar work that needs to be fixed. I've had several come in for updates that have had horrible or missing welds from some well known shops. Just haven't done it officially yet where I'm telling someone "nope, you can't race this weekend until you have this fixed"

                Fire... I used to post over at 7club quite a bit. Sold my 1st Gen about 2 or 3 seasons ago so I don't get back there much.
                In PCA we can note in ther log book. Unless it is something that was changed and real bad the original log book was issued the driver races that weekned but has to get it fixed before his next race.
                Weekend wannab racer with some welders.

                Comment


                • #53
                  All good info here! Make sure your not one of those guys who welds down and around. I have seen so many people weld from the top down. Talk about no penetration! Bottom up and around and make sure you get in a comfortable position and are able to get full motion around the pipe. I always hated seeing people stop every 1/2 inch and re starting the weld. Looks like crap!

                  Get a tubing notcher. Its your best investment by far. Tight joints will save you from horrible gaps to fill.

                  I have always liked to tig my cages due to the fact you always get a nice hot peice in your ear! No matter how well you think your covered. I hate ear plugs.
                  Brian C.
                  Turbobrian Fabrication LLc.
                  Miller D165
                  Miller 140
                  Miller Digital Elite

                  Comment


                  • #54
                    Originally posted by turbobrian View Post
                    All good info here! ...
                    Get a tubing notcher. Its your best investment by far. Tight joints will save you from horrible gaps to fill.
                    I'm kind of a software geek. I rewrote the tubenotcher software to help alignment, length and accuracy. If you aren't doing a whole bunch of notches, or can't afford a nice mechanical tubenotcher, or just want to verify your work and alignment, check this out.

                    Its free, runs in any browser & operating system, and includes offsets, gauge thickness, tube pass thru info, .DXF output, tubular brace calculations. Prints out full scale on your local printer. Cut out the pattern, tape it to the tube. Cut metal and file to fit.

                    Tubenotcher Software

                    Here's a picture of an offset pass thru of two tubes of equal size.

                    One addendum: Because of the .DXF out option, this program requires a recent java version to the browser. If you have an Apple computer or a Linux OS, and the system needs to upgrade java, you may need to install manually. Instructions for those platforms, as well as online java testers located here.

                    Would appreciate any feedback on the program if you are so inclined.
                    thanks,
                    zip
                    Attached Files
                    Last edited by zipzit; 04-09-2010, 09:38 AM.

                    Comment


                    • #55
                      Roll cage tips

                      I have welded a bunch of stock car cages and chassis over the years. Here are 2 ideas to make your life easier.

                      -purchase a smaller nozzle to get into the tight spots
                      -build a roll over device for the chassis, it is allot easier than laying upside down in the cockpit trying to do overhead welding

                      Scott
                      http://www.welders360.com/

                      Comment


                      • #56
                        Originally posted by zipzit View Post
                        I'm kind of a software geek. I rewrote the tubenotcher software to help alignment, length and accuracy. If you aren't doing a whole bunch of notches, or can't afford a nice mechanical tubenotcher, or just want to verify your work and alignment, check this out.

                        Its free, runs in any browser & operating system, and includes offsets, gauge thickness, tube pass thru info, .DXF output, tubular brace calculations. Prints out full scale on your local printer. Cut out the pattern, tape it to the tube. Cut metal and file to fit.

                        Tubenotcher Software

                        Here's a picture of an offset pass thru of two tubes of equal size.

                        One addendum: Because of the .DXF out option, this program requires a recent java version to the browser. If you have an Apple computer or a Linux OS, and the system needs to upgrade java, you may need to install manually. Instructions for those platforms, as well as online java testers located here.

                        Would appreciate any feedback on the program if you are so inclined.
                        thanks,
                        zip
                        Both times I clicked on that link firefox crashed...
                        Mark
                        (aka: Silverback, WS6 TA, JYDog, 83 Crossfire TA, mpikas, mmp...)
                        Synchrowave 180 SD | MillerMatic 211MVP + Spoolmate | Hobart Handler 135 | Everlast Power Plasma 50
                        1960 Bridgeport J-head | Grizzly 10x22 | HF bandsaw | Rigid 4.5” angle grinder (+2 cheapie HF ones)
                        BFH

                        Comment


                        • #57
                          My first major MIG project was my 8pt roll bar.. (still not done a year later but that's a different story) and I can tell you, nice tight joints..

                          Comment


                          • #58
                            Originally posted by Silverback View Post
                            huh, interesting question...

                            I've always wondered something similar with drag cars: it seems like you're always worried about your own work passing, which is pretty decent and as far within the rules as possible (there are times that the chassis or the driver force you to make decisions that are not _exactly_ within the letter of the rules even though they try to follow the intent as close as possible) and then it always seems like there is a decent percentage of cars at the track with certified cages that have booger welds, the wrong size bars, bars in the wrong places... and don't seem to have any problems with tech.
                            I saw a ferrari cup car with a "Factory" cage "made in maranello". I would not have felt comfortable saying i welded it! i would call it junk.
                            Dynasty 200 DX
                            Millermatic 175
                            Spectrum 375
                            All kinds of Smith OA gear

                            Comment


                            • #59
                              Try to get good fit ups in all your connections. Move around while welding so as not to get to much heat in one area. If your not sure of your welding skills then get someone who knows.
                              Microsoft Office 2007Microsoft Office Home And Student 2010Microsoft Access 2010

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