Zzeal Posted September 21, 2009 Share Posted September 21, 2009 I'm prepping a solid '73 for an LS2, to do some auto-X, lapping at Nelson Ledges, and for just a good hoot on the street. This old chassis is pretty floppy to begin with and it's gunna be absorbing 250 more lb./ft. of torque than it was designed for, so I thought some chassis stiffening was a must. Luckily, I know Mark McMahan (rollcageguy.com). He's known for his precise, tightly conforming cages, and his smooth consistent welds top it off. Mark's a very creative, innovative guy whose cages are more like rolling art. I dropped my rolling chassis off to him and we agreed that the cage should be as inconspicuous as possible (i.e., no diagonal on the main hoop), not block outward vision, and I didn't want to climb over bars to get in. The top side bar, coming off the main hoop starts high, hugs the top, then matches the curvature of the "A" pillar, providing space for noggins and retaining good forward vision. The awkward looking bars, running down to the diff. mount area were an afterthought (mine). Had to start 'em there so they wouldn't interfere with the seats. We'll finish it up with gussets later, where there's paper now. The stock seat mounts were removed (not a whole lot of fun) so that the replacement seats can be mounted as low as possible. There's a total of about 77 ft, of 1-1/2", .095 wall DOM tubing, which, at 1-1/2 lbs. per ft. equals about 116 lbs.. Add another 15 or so for the mounting plates and that's a porky total of about 131 lbs. For those of you not saddled with an archaic system of weights and measures, that's 23.5 meters of 38.1 mm dia., 2.4 mm wall tubing for 60 kilo's of pork. A fair trade off, in my mind, for a much more stable platform. Steve Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted September 21, 2009 Share Posted September 21, 2009 Very nice job. It wouldnt pass regs here though. Must have a diaginal and must not extend past the rear wheel center line. I would have thought you would have similar regs? Douglas Quote Link to comment Share on other sites More sharing options...
rturbo 930 Posted September 21, 2009 Share Posted September 21, 2009 That looks like a very nice, tight fitting cage. Quote Link to comment Share on other sites More sharing options...
Roostmonkey Posted September 21, 2009 Share Posted September 21, 2009 Very nice cage indeed. Quote Link to comment Share on other sites More sharing options...
johnc Posted September 21, 2009 Share Posted September 21, 2009 Sorry, I don't like to be the bearer of bad news, but it won't pass SCCA or NASA tech because of the missing diagonal unless the main hoop tubing wall thickness is .120" instead of .095". Hopefully Mark upgraded the main hoop wall thickness. Although its a matter of opinion, I'm also of thought that the main hoop rear braces should not extend past the rear strut towers. That rear crush zone is important and directly imparting rear impact loads into the roll bar increases the loads on the driver. For an open track, lapping car the cage is probably fine. If you ever go to sell the car and you want to expand your market to the wheel-to-wheel guys, you should make the changes listed above. Quote Link to comment Share on other sites More sharing options...
MREDDLE Posted September 21, 2009 Share Posted September 21, 2009 Not that it matter or that anyone cares... I agree with jhonc^. Though this is one of the nices cages I have seen and I will be going with the same design but with the above revisions. Quote Link to comment Share on other sites More sharing options...
big-phil Posted September 21, 2009 Share Posted September 21, 2009 that looks beautiful!!!! Quote Link to comment Share on other sites More sharing options...
MoNkEyT88 Posted September 22, 2009 Share Posted September 22, 2009 Very nice! Makes me want to go put the monkey bars in my track car, too bad I have so many other damn projects. I was interested in the bars in the rear of the car, but I understand the need to have some crumple area in the event of an impact. Quote Link to comment Share on other sites More sharing options...
rsicard Posted September 22, 2009 Share Posted September 22, 2009 Zzeal: Really appreciate your posting these photos. Really helps to visualize just what can be done to protect the driver. Thanks MUCH. Quote Link to comment Share on other sites More sharing options...
SATAN Posted September 22, 2009 Share Posted September 22, 2009 Sorry, I don't like to be the bearer of bad news, but it won't pass SCCA or NASA tech because of the missing diagonal unless the main hoop tubing wall thickness is .120" instead of .095". Hopefully Mark upgraded the main hoop wall thickness. Although its a matter of opinion, I'm also of thought that the main hoop rear braces should not extend past the rear strut towers. That rear crush zone is important and directly imparting rear impact loads into the roll bar increases the loads on the driver. For an open track, lapping car the cage is probably fine. If you ever go to sell the car and you want to expand your market to the wheel-to-wheel guys, you should make the changes listed above. I was unaware of the Main hoop rule being .120". Is that just if it is .120" Cr-Mo or is that mild steel? I also have my main hoop braces actually running TO the rear strut towers. It seemed like the best thing to do for load transfers and for safety. I hardly EVER see cars like that though? They usually run all the way to the rear of the car. Why is that? Original Poster... How did you manage to weld around the entire bar where the A-pillar bar meets the roof hoop? I looks very tight in there. Looks like it could only be welded all the way around if the roof were removed. Actually, it looks to be that situation in a lot of the corners of the cage. It looks like a very nice cage though, very pretty. Quote Link to comment Share on other sites More sharing options...
johnc Posted September 22, 2009 Share Posted September 22, 2009 I re-read the new version of the GCR (section 9.4) and the previous rule that allowed a main hoop or other element to not meet the rules if it was the next size larger in material requirements is gone. My recommendation above regarding next sized main hoop tubing no longer applies. All roll cage elements have to meet the SCCA spec to be stamped and allowed to run at a SCCA Club Race. Quote Link to comment Share on other sites More sharing options...
Zzeal Posted September 22, 2009 Author Share Posted September 22, 2009 Yeah, I know we didn't meet anybody's tech requirements, didn't even think about it. I'm just having a blast building what works for me. Maybe I should be considering what a prospective buyer would want... nah, the next guy can tailor it to his own liking. I just want that stealthy cage to sharpen the handling, not look boy-racer'ish, and provide a whiff of crash protection. Mostly, I wanted to show you what an extraordinary craftsman Mark is. Steve Quote Link to comment Share on other sites More sharing options...
Challenger Posted September 22, 2009 Share Posted September 22, 2009 So is being safe "boy-racer'sh?" Either way the cage does look very nice. I imagine it took awhile. Quote Link to comment Share on other sites More sharing options...
Xylemer Posted September 23, 2009 Share Posted September 23, 2009 77 feet, wow, I never really thought about how much tubing went into a full cage. It definitely looks sexy, regards if its to spec. Man, thats an awesome rotisserie. I have been looking at cages a lot lately and for some reason the rotisserie caught my eye. Quote Link to comment Share on other sites More sharing options...
pantera74 Posted September 28, 2009 Share Posted September 28, 2009 one freaken beautiful cage. Quote Link to comment Share on other sites More sharing options...
RS Speed Posted October 1, 2009 Share Posted October 1, 2009 How much does all that weigh if you don't mind me asking? You did and excellent job so far and I feel like it would be a shame to not have it pass inspection, although I don't know if its reversible at this point. Either way it looks freakin sweet!!!! Quote Link to comment Share on other sites More sharing options...
piston Posted October 31, 2009 Share Posted October 31, 2009 cleanest cage job i have seen on a z. everything lines up so perfect. Quote Link to comment Share on other sites More sharing options...
jerryb Posted October 31, 2009 Share Posted October 31, 2009 ?? I was thinking the same thing......Is it in fact welded all the way around? Original Poster... How did you manage to weld around the entire bar where the A-pillar bar meets the roof hoop? I looks very tight in there. Looks like it could only be welded all the way around if the roof were removed. Actually, it looks to be that situation in a lot of the corners of the cage. It looks like a very nice cage though, very pretty. Quote Link to comment Share on other sites More sharing options...
Zzeal Posted November 1, 2009 Author Share Posted November 1, 2009 ?? I was thinking the same thing......Is it in fact welded all the way around? Sorry about not addressing the question, I did PM SATAN an answer but should have posted it! The only bars not completely welded are those in the engine compartment, going to the strut towers. All the other bars are welded completely around. Mark has some techniques to pull it off, as do most professional cage installers, I'm sure. Steve Quote Link to comment Share on other sites More sharing options...
Lucifersam Posted November 1, 2009 Share Posted November 1, 2009 When you think about (not that I have experience with this sort of thing) if you were building a cage this intricate you would weld up the impossible pieces outside of the car and weld the easy ones in the car, to make the cage solid. Just my theory. besides the fact that it may or may not pass regulations, it is still what th OP wanted and shows of what is undeniable amazing welding skills of the creator of the cage. Quote Link to comment Share on other sites More sharing options...
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