Roostmonkey Posted May 6, 2009 Share Posted May 6, 2009 Thats very true John but being a street car, I dont want any cage around my head.Any frame I put in will be behind the seats and down low across the doors.These low bars will also tie into the rockers in at least 2 spots.They will have to be low enough so I can get my big butt in and out without breaking a hip every time. When I get to that point, I'll be looking for some advise from you and others. Quote Link to comment Share on other sites More sharing options...
jtl260z Posted May 6, 2009 Share Posted May 6, 2009 Thats very true John but being a street car, I dont want any cage around my head.Any frame I put in will be behind the seats and down low across the doors.These low bars will also tie into the rockers in at least 2 spots.They will have to be low enough so I can get my big butt in and out without breaking a hip every time. When I get to that point, I'll be looking for some advise from you and others. Something like this? Quote Link to comment Share on other sites More sharing options...
rsicard Posted May 6, 2009 Share Posted May 6, 2009 rsicard- are you planning on welding the 2x3 tube to the bottom of the floorpan? If so, as Jon pointed out, you will lose 1.5" of ground clearance. ( stock rails are approx 1/2" tall ). You fellows are absolutely correct. I went out and took the 2x3 tub with then looked and found the floor pan is lower than the horizontal portion of the lower rocker panel by 1+ inches. Adding 2 inches to that and there are serious issues with ground clearance. Search the forums and found EMWHYR0HEN had done something similar but with 1x3" rectangular tube. Even at that it would be wise to cut the floor pan 3" wide and project the 1x3" rect tube upward by 1/2" into the cabin. Then the original clearance underneath will be maintained. Already have shortened all struts on the 240Z and installed Koni Shocks and 2.5" coil springs per John Coffey's instructions. Just wondering about how to get tubing immediately behind the rocker panels and join it up with outriggers from the 1x3" subframe connectors. Maybe it would be easier overall to just go with Bad Dog subframe connectors. Still concerned about torsional rigidity. Quote Link to comment Share on other sites More sharing options...
Roostmonkey Posted May 6, 2009 Share Posted May 6, 2009 (edited) Heres how I'm doing it. The tube is 1.5" X 3" with an .090 wall. ( thought it was .120" ) As I said , its half in and half out and has a .75 X .75 angle welded down the center to help position it and give more to weld to the section floorpan. The main hoop will weld on top of the tube frame behind that wire harness.This tube is welded to the rocker.Its also welded to the rear factory subframe. Edited May 6, 2009 by Roostmonkey more info Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 6, 2009 Share Posted May 6, 2009 Still concerned about torsional rigidity. Pick up the book Chassis Engineering by Adams. It's not the most in depth book ever, but it really goes after torsional rigidity and talks about how useless a ladder frame is in torsion. It has balsa wood models to test rigidity of different cage ideas. Quote Link to comment Share on other sites More sharing options...
rsicard Posted May 7, 2009 Share Posted May 7, 2009 Roostmonkey: Very nice photos. This is exactly the way I want to do my 240Z. I see the outriggers just ahead of the rear wheel well and gives a place to weld the roll cage in the interior. You mentioned .75 x .75" angles. Are these angles on either side of the 1.5x3" rect tube. If so then I understand it completely. Is so, that appears to add more strength to the floor panels. VERY NICE JOB you have done! Quote Link to comment Share on other sites More sharing options...
rsicard Posted May 7, 2009 Share Posted May 7, 2009 Pick up the book Chassis Engineering by Adams. It's not the most in depth book ever, but it really goes after torsional rigidity and talks about how useless a ladder frame is in torsion. It has balsa wood models to test rigidity of different cage ideas. Jon: I think I already have that book. Just need to go back and study it CAREFULLY. Quote Link to comment Share on other sites More sharing options...
rsicard Posted May 7, 2009 Share Posted May 7, 2009 Fellows: Thank both of you. Now I can order 1.5 x 3" .090 wall rectangular tube and enough of it to accomplish the strenghening of the 240Z. First per John Coffey's recommendation, is to remove the engine, trans etc. to put remove the strain on the structure and then cut and weld the subframes and outriggers. Quote Link to comment Share on other sites More sharing options...
Roostmonkey Posted May 7, 2009 Share Posted May 7, 2009 rsicard, the .75" angles are on both sides of the tube running lengthwise.They are something I bent up in my shop.You can find hot rolled angle iron in either 1/2" X 1/2" or the 3/4". Quote Link to comment Share on other sites More sharing options...
rsicard Posted May 7, 2009 Share Posted May 7, 2009 rsicard, the .75" angles are on both sides of the tube running lengthwise.They are something I bent up in my shop.You can find hot rolled angle iron in either 1/2" X 1/2" or the 3/4". Roostmonkey: Thanks, now I have a plan of attack. Next is to study the Adams book carefully and gain another angle of attack for the Roll Cage. Quote Link to comment Share on other sites More sharing options...
Domenic Posted July 14, 2009 Share Posted July 14, 2009 I used 2x2 tube on a friends 240z. Worked Very well. Quote Link to comment Share on other sites More sharing options...
rsicard Posted July 14, 2009 Share Posted July 14, 2009 Domenic: I have refined my plan of attack and will go with 2x2" or 2.5x2.5" square tube. Additionally, the tube will be above the floor and through it at the ends joining the original subframe. Quote Link to comment Share on other sites More sharing options...
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