johnc Posted August 28, 2006 Share Posted August 28, 2006 I'll be doing a roll cage in a car this week and I have to make sure there's head clearance. I'm going to do a Halo bar that bends up from the main hoop and is tight on the roof and the A-pillars. I'll post pictures after I figure it out and put it together. BTW... I agree with Katman and would be very concerned about driving that 240Z linked on classiczcars.com. Quote Link to comment Share on other sites More sharing options...
DavyZ Posted August 28, 2006 Share Posted August 28, 2006 If you can get away with it and still be comfortable, try lowering your seat a little bit. That's far too practical, Richard. j/k Davy Quote Link to comment Share on other sites More sharing options...
zlalomz Posted August 28, 2006 Share Posted August 28, 2006 Katman or Johnc, would an X bar betwenn the down tubes to the rear strut towers be sufficient or does a diagonal need to in the plane of the main hoop to be safe? I have a horizontal bar side to side welded at the bend of the main hoop.This question is for a non SCCA track day car. Quote Link to comment Share on other sites More sharing options...
johnc Posted August 28, 2006 Share Posted August 28, 2006 The last time I looked at the FIA rules for a tarmac car it required an "X" brace in the main hoop rear braces. SCCA requires a diagonal brace in the main hoop. I've heard through the grapevine that FIA is now also requiring a diagonal brace in the main hoop in addition to the "X" brace in the rear braces. I don't know if that's true or not. I put diagonal braces in the main hoops of all the cages/bars I build. Quote Link to comment Share on other sites More sharing options...
bjhines Posted August 28, 2006 Share Posted August 28, 2006 Johnc.... I have mocked it up with tubes up high against the roof skin.... It seems to cause even more trouble because as you get the bar up higher it also must move toward the center.... the helmet takes up more vertical space as the bar location is moved higher and inboard... I simply cannot find room for my head.... My alternatives are... 1. lower the seat... easy enough.. I already did that... but it needs to be VERY LOW... the problem is.. I cannot properly see the front of the car... I am just barely looking over the steering wheel... windshield wipers absolutely must be removed for visibility... and besides... This is WAYYYY TOO LOW for autoX... cant see the cones 10' in front... 2nd option... put more bends in the A pillar bar... Illeagal yes... I could get another inch of clearance by finding a way to more closely match the profile of the roof... without moving the bars inward any... I could also cope the bars into the factory sheet metal... I am not going to do this though... 3rd option.... live with it... this is my most likely option... I have several 240Z bodies to mock this up in... one has an SCCA legal bolt in cage.. Autopower.... it has even worse headroom clearance.... in fact the bolt in cages look terrible.. they cut down visibility, the are weakly mounted, they leave very little headroom, they interfere with larger steering wheels, they bite your ankles because they stick out into the pedal area.... I am trying to improve upon this design with my own custom cage... but.. they headroom issue is a killer... I measured a friend's BMW M3... there is 43" vertical space from seat mounts to headliner... the Z only has 38" with my modified seat mounts.... I went through the shop and parking lot with a tape measure... most cars have considerably more vertical space 4" to 6" more than the Z car... I cannot imagine what a Z car with a chopped/lowered roof would be like... you would have to lay down to drive it... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 28, 2006 Share Posted August 28, 2006 Could you cut your A pillar bar and make a halo bar instead? The halo bar could then be more closely fitted to the roof. Quote Link to comment Share on other sites More sharing options...
johnc Posted August 28, 2006 Share Posted August 28, 2006 I just finished bending and fitting the main hoop and the halo bar in this 1982 Toyota Corolla I'm working on. Unfortunately the halo bar is about 1" narrower then necesary at the front and a little too pointy for the Toyota windshield header. This is a low buck quickie 6 point cage so I used my 240Z templates. Worked well for the main hoop, not so well for the halo bar. I'll post pictures later. I need to drink some water and get back at it. Quote Link to comment Share on other sites More sharing options...
bjhines Posted August 29, 2006 Share Posted August 29, 2006 JM has a good idea... I will see what I can do with this... unfortunately I cannot complete welding the cage until this issue is resolved one awy or the other. I spoke to 2 guys this evening about their experience with the S-30 roll cages... They both said this was the same in their cars... they both said it was not a problem... riding around with your helmet knocking against the roof bar isn't as distracting as you would think... Quote Link to comment Share on other sites More sharing options...
Drax240z Posted August 29, 2006 Share Posted August 29, 2006 It is a problem. If your helmet is hitting the bars, you might as well just drive without one for all the good it is going to do you. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 29, 2006 Share Posted August 29, 2006 It is a problem. If your helmet is hitting the bars, you might as well just drive without one for all the good it is going to do you. Agreed. I know I've said all this before, but here it goes again: I did a tank slapper into a 360 spin at an autox once, and when the car stopped I smacked my head against the roof above the door really hard. Hard enough that I saw stars with the helmet on. This is the main reason why I don't feel like you're safer riding around with a full cage in your street car. There already isn't enough room for your head as it is, last thing we want is to encroach on the remaining space. I think this is also the reason why cars keep getting taller and taller. You might have "headroom" when your head is an inch away from the roof, but see what happens when the car flips upside down! The push for safety means that the roof and door pillars keep getting farther and farther away. I guess the downside there is the center of gravity gets higher and higher, probably more so because the windows are also getting larger and larger. Quote Link to comment Share on other sites More sharing options...
katman Posted August 30, 2006 Share Posted August 30, 2006 Main hoop diagonal vs X brace to rear: I think a properly located diagonal in the plane of the main hoop is the most efficient and stiffest way to protect the driver's head against a rollover. You basically form a truss with the peak at the driver's noggin'. An X-brace to the back with no diagonal has some lateral stiffness for the case where the roll contact is on the side, but for pure vertical you have to rely on the bending stiffness of the hoop bar. Not good. With the diagonal both lateral and vertical impacts are resisted- no need for the X-brace IMHO. I don't see the X-brace as very efficient for any anything- a waste of tube. Not sure what the sanctioning bodies who require it are thinking. Quote Link to comment Share on other sites More sharing options...
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