66_GT350_R Posted September 3, 2004 Share Posted September 3, 2004 (edited) My plans are to run HPDE and time trials for a period of time and progress both driver and car to AI/AIX over time. The car (a '66 Mustang fastback) currently has a roll bar with two down bars reward and a cross bar that the harness uses. My question is about adding the diagonal bar running from the drivers side (top of roll bar) to passenger side (bottom of roll bar). Because I already have a cross bar, unless I cut out the cross bar, the diagonal would have to be made in two pieces. Is the diagonal allowed to be made up of two pieces joining at the horizontal cross bar, or must it be a single piece? If it's allowed, would it seem to compromise the strength of the diagonal to do build it this way? Edited September 3, 2004 by Guest Quote Link to comment Share on other sites More sharing options...
SDR_John Posted September 3, 2004 Share Posted September 3, 2004 Most diagonals are built that way (2 piece). There really isn't any other way to do it. John Quote Link to comment Share on other sites More sharing options...
66_GT350_R Posted September 3, 2004 Author Share Posted September 3, 2004 If the drivers diagonal were built first, the diagonal would be one piece and the horizontal would be two pieces. An additional diagonal would have to be two pieces, obviously. My guess is I'm asking a newbie question. I didn't really think a two piece diagonal would be an issue, but when I went to last NASA race at Road Atlanta and looked at some of the cages, I noticed that most every, if not every diagonal, was one piece with a two piece horizontal bar. It's probably just a little simpler to make a two piece horizontal than a two piece diagonal. Quote Link to comment Share on other sites More sharing options...
Frank Corkran Posted September 3, 2004 Share Posted September 3, 2004 As always, it's best to read the CCR and AI rules available for download online. While section 15.5.7 of the 2004 CCR doesn't *explicitly* say the diagonal must be one piece, the required mounting points certainly imply it. Quote Link to comment Share on other sites More sharing options...
swhiteh3 Posted September 3, 2004 Share Posted September 3, 2004 I always went under the assumption that either the diagonal or the crossbar had to be continuous, with the other obviously having to be split. It's somewhat like the rules about the front halo area, either the top hoop can be continuous all the way around -OR- the downtubes can be continuous back to the main hoop. (Actually, you can also do it with both front down tubes continuous to each other along with the front bar of the halo, but I can not imagine any installer in the world who would choose to do it this way.....) Quote Link to comment Share on other sites More sharing options...
Frank Corkran Posted September 3, 2004 Share Posted September 3, 2004 The diagonal is a required bar, a horizontal is not - though it's not called out as optional in the "typical" diagram, which shows the horizontal as 2-pc. The three forward cage options are explicitly specified, no option for a 2-piece diagonal is mentioned. I've seen a number of things in "legal" cars that don't appear to meet the letter of the rules, so before building the rest of the cage with a 2-pc diagonal I'd suggest getting a ruling directly from your regional AI director. Fitting and welding a diagonal and 2-pc harness bar will be a lot easier while building the cage compared to going back inside a completed racecar. Quote Link to comment Share on other sites More sharing options...
Jeff F Posted September 6, 2004 Share Posted September 6, 2004 I have seen MANY legal cars that have a two piece diagonal. I wouldn't be concerned. I'd prefer to see the diagonal one piece, but if the welding is good there shouldn't be any worries. By the way, my diagonal AND horizontal are one piece... Quote Link to comment Share on other sites More sharing options...
66_GT350_R Posted September 6, 2004 Author Share Posted September 6, 2004 By the way, my diagonal AND horizontal are one piece... Ok, I'll bite, how did you make them both one piece? To have a legal diagonal, your horizontal must either be bent or it does not attach to the roll bar on both sides(?). Enlighten me. Quote Link to comment Share on other sites More sharing options...
Jeff F Posted September 7, 2004 Share Posted September 7, 2004 Ding-ding-ding, we have a winner! The horizontal has a slight bend at each end where it meets the main hoop. The offset is exactly the diamter of the tubing (1.75") so it touches the diagonal as it passes behind it, and the two are welded together. Quote Link to comment Share on other sites More sharing options...
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