Forces Posted February 8, 2007 Share Posted February 8, 2007 I'll be recieving the S&W 6 point cage in about a week, and I am not sure if I want to use the down bars in the back.... I was thinking of doing an "X" brace from the corners of the main hoop to the front of the rear strut towers and add a rear strut tower brace. I know the S&W cage isn't the best one out there, but local shops in my area are either too 'swamped' to make a cage in a timely manner, or "don't DO one time projects" .....a$$holes. I am looking for rigidity more than saftey in case of an actual roll. Would it make a more stable cage with an X brace in the rear? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 8, 2007 Share Posted February 8, 2007 I would just put a diagonal in the main hoop. That's what the SCCA rules call for these days, and it's less weight up high. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted February 8, 2007 Share Posted February 8, 2007 I wonder how an X-brace made from lighter weight material would compare axainst a heavier weight single diagonal brace?? It seems like a fair comparison... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 8, 2007 Share Posted February 8, 2007 I don't think there is a sanctioning body that would allow that, even if it was as strong. If you don't care about rules, then yeah, you might have a point. Would take some testing to see what works best. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted February 8, 2007 Share Posted February 8, 2007 ^^^ I should have made my point clearer... sorry. Yes, I meant if one doesn't care about rules. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 8, 2007 Share Posted February 8, 2007 Yes, I meant if one doesn't care about rules. Or safety. There really are sound engineering and field tested reasons why SCCA and other sanctioning bodies specify tubing material, OD, and wall thickness in their cage rules. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted February 8, 2007 Share Posted February 8, 2007 ^^^ Point well-taken, John. Still, I'd like to see the theory tested. I'd wager good odds that a well balanced X-brace made of "slightly" thinner tubing would add as much protection or more than a "slightly" thicker diagonal brace. I'll bet the (?better?) X-brace would only cost a couple extra pounds. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 8, 2007 Share Posted February 8, 2007 I talked to the guy who bent my main hoop about all of this. He mostly does rally cages. His opinion was that you weren't going to do better than a diagonal that attached to the main hoop on both ends. SCCA rules call for a diagonal in the main hoop that attaches to the floor or as close to the floor as possible, but it was this guy's contention that having the diagonal attach to the hoop was a lot stronger than the floor right next to the bottom of the hoop. I think the point for him was that any distortion of the top of the main hoop has to bend the diagonal as well, where if the diagonal attaches to the floor it still props up the hoop but isn't as integrally attached and one can bend without affecting the other (as much). As far as the X in the back goes, it also props up the main hoop but does so from an angle and so it is weaker, which is why you need an X instead of just one piece for equivalent strength. Probably the best strength-wise would be an X in the main hoop instead of just one diagonal. The problem with that idea is that there won't be enough room for the driver's seat unless your under 5'6" or so. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 8, 2007 Share Posted February 8, 2007 In the past, SCCA allowed an "X" in the main hoop rear braces in lieu of a diagonal bar on the main hoop - the roll bar in my old car was built that way. The allowance was eliminated in the late 1990s I think. FIA also used to require an "X" in the main hoop rear braces with the main hoop diagonal optional. They have since changed that to require a main hoop diagonal. The "X" in the main hoop rear braces is optional unless the car can achieve some level of speed and then the "X" in the main hoop rear braces is also required. Quote Link to comment Share on other sites More sharing options...
Forces Posted February 8, 2007 Author Share Posted February 8, 2007 I would just put a diagonal in the main hoop. That's what the SCCA rules call for these days, and it's less weight up high. I'm not as worried about SCCA rules as much as NHRA. It would be nice to have a cage that won't let the body twist under sharp cornering though. Are you saying that a diagonal in the main hoop is as rigid as having ANY brace in the back? Or simply that the S&W cage with a diagonal in the hoop will provide the same strength as using an X brace? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 8, 2007 Share Posted February 8, 2007 I'm not the expert (see all my threads with questions about my own cage) but the guy who did my cage seemed to think that the diagonal was better at preventing distortion of the main hoop than an X to the rear strut towers. I didn't ask him about ANY combination of braces, just about the X as that was the other "usual" thing that I had seen. Quote Link to comment Share on other sites More sharing options...
Roostmonkey Posted February 8, 2007 Share Posted February 8, 2007 Forces, I gather your more interested in stiffening the chassis and John and JM are thinking more driver saftey which is all SCCA and other organizations are concerned about. I will be building a cage for my car very soon and will be using SCCA approved design but my main concern is stiffening the chassis to handle an RB26 swap.This is not to say that saftey isnt also a priority but this car will never see any SCCA inspections. I plan on dooing the X from the top corners of the main hoop to the strut towers just to stiffen things up. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 9, 2007 Share Posted February 9, 2007 For stiffness' sake you might want to consider an X between the strut towers and the BOTTOM of the hoop. That anchors the strut towers to the rockers. Attaching to the top of the hoop isn't as sturdy unless you tie the roll bar into the roof, even then the roof isn't nearly as sturdy as the rockers. Here's a pic of Steve Parmley's (zlalomz) car. This is basically what I'm going to do (note Steve also has the X to the top of the hoop): Quote Link to comment Share on other sites More sharing options...
Forces Posted February 9, 2007 Author Share Posted February 9, 2007 ^^^Jesus. Planning on getting into a game of chicken with a freight train?^^^ - Is that all seemless? Forces, I gather your more interested in stiffening the chassis and John and JM are thinking more driver saftey which is all SCCA and other organizations are concerned about. I will be building a cage for my car very soon and will be using SCCA approved design but my main concern is stiffening the chassis to handle an RB26 swap.This is not to say that saftey isnt also a priority but this car will never see any SCCA inspections. I plan on dooing the X from the top corners of the main hoop to the strut towers just to stiffen things up. BINGO. I don't PLAN on ever needed all the saftey that the cage will provide, and my car won't ever see the SCCA inspection either. I just don't want to warp and distort the frame. That, and I don't want to make it to the track, make 1 run and have them tell me to go home and come back with a cage. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted February 9, 2007 Share Posted February 9, 2007 Yes that's a well-tightened chassis. Quote Link to comment Share on other sites More sharing options...
zlalomz Posted February 10, 2007 Share Posted February 10, 2007 I had a diagonal in the main hoop but I didn't fit so I went with the X bar to add some clearance and also protection for a passenger. I'm 6'4 and fighting for every inch of room. Here are some pics of an x bar used in the Devendorf IMSA GT/U car in 1978. Zsane posted these in this thread http://forums.hybridz.org/showthread.php?t=116774&page=16&highlight=school+photos Quote Link to comment Share on other sites More sharing options...
260DET Posted February 13, 2007 Share Posted February 13, 2007 Below is an alternative, note how the cage is tagged into the body to give extra rigidity too. Gives excellent rear vision that arrangement. Decided not to go for a full cage for various reasons but the basis for one is there. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted February 13, 2007 Share Posted February 13, 2007 260DET... You've really M-braced your Z, haven't you? Quote Link to comment Share on other sites More sharing options...
260DET Posted February 14, 2007 Share Posted February 14, 2007 260DET... You've really M-braced your Z, haven't you? Yeh, both the X and M have angled legs though Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted February 14, 2007 Share Posted February 14, 2007 ^^^ That's okay, Richard. You probably like bow-legged women too ^^^ Quote Link to comment Share on other sites More sharing options...
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