dsommer Posted May 2, 2002 Share Posted May 2, 2002 Would this help with stiffening things up? I am considering running some 1"X 2" square tubing inside the car. Under the seats, behind the front seat bracket from the outter frame support (Below the door) to the tranny tunnel (attach the tubing to a steel plate to the tranny tunnel) All welded in. Would this help stiffening the cahssis, or just be a welding lesson for me. Also do strut tower bars help (front and rear) to help stiffen? What about an one of those SCCA rollbars VB sells (anybody out there running one?) I need to know before I start putting the interior back in. As always thanks for your help. David Quote Link to comment Share on other sites More sharing options...
Guest AlsoRanFPrepared Posted May 3, 2002 Share Posted May 3, 2002 I suppose what I really need to know is what specifically you are stiffeneing the chassis for. Would that box help stiffen the chassis? Yes. Would it stiffen it enough to be substantial or be in the correct areas? No. Given the seat bracket is already performing a similar task there it would likely be the welding lesson you mentioned. The best method you mentioned to sftiffen up the chassis would be from the roll bar. It would still be limited in its effectiveness given its limited attachment points (bar not cage). Generally speaking the benefit of an SCCA roll bar or cage is the cross support that is required in the main hoop. This support forms a large triangle which improves stiffness. (rant) As for the strut tower bars I have been in many debates concerning the effectiveness in improving handling. It will improve the stiffness of the front end somewhat but considering that it is forming a "square" between the crossmember, strut towers and the brace itself the stiffness gained will be marginal. There is also some debate as to which direction the strut tower actually deflects under cornering load. I am of the opinion that the tower would actually deflect outward under load given the free body diagrams I drew of the wheel/strut system. Based on how the geometry of the suspension is under load what the roll angle/stiffness of the chassis is and the relative stiffness of the strut towers it may not deflect a significant amount at all. This is espically true of the Z front end with the TC rod attachment point being able to support moments making calculations much more difficult. Without any real deflection measurements or a clear load path for the chassis there is really no way to determine the effectiveness of the brace. Many times when installed people will say the car feels better or stiffer but may also be expecting just that change which clouds any actual improvement.(i'm done with the rant). If the brace were triangulated to the frame/structure or crossmember somehow the stiffening gained would then be significant. -Mark Quote Link to comment Share on other sites More sharing options...
dsommer Posted May 3, 2002 Author Share Posted May 3, 2002 I’m concerned with the additional stress/twisting of the body by adding the 350. I don’t, overtime want to start finding stress cracks in the body of the car. The reason I am considering the tubing under the seat is because the material (seat supports) appears to be of thin gauge and doesn’t offer a great deal of lateral support. PLUS I have some rust in these areas under the seat supports (which I didn’t mention before sorry) that is repairable (small holes but still good metal) POR-15 patch repair will fix it. I think I’ll give it a shot because it won’t hurt a thing having some extra supports in there. Thanks for the info on the roll bar and strut supports. I’ll probably run them all because I’m trying to build a complete “system” all at once, not just drop in the 350 and run it and gun it. Thanks Mark Any other ideas out there? David Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 3, 2002 Share Posted May 3, 2002 My subframe connectors stiffened the body in a big way. I noticed a difference with the rear strut brace more than the front but I feel they both contribute to chassis stiffness. I think it is a good idea to run some tubes back to the firewall from the shock towers also... just havent gotten there yet. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 3, 2002 Share Posted May 3, 2002 BTW, I also replaced the floors with thick gauge sheet metal (16g) That could contribute greatly to the stiffness of the chassis. Quote Link to comment Share on other sites More sharing options...
dsommer Posted May 3, 2002 Author Share Posted May 3, 2002 Jumbo, I like the set up of your interior. What brand roll bar is that in there? If it's the MSA or VB how did it mount up? I know they are bolt in bars how difficutlt was the install? Also do those bars just mount to the rear shelf or to the floor behind the drivers and pass. seat? Also what strut tower bars are you running? Thanks, David Quote Link to comment Share on other sites More sharing options...
Tim240z Posted May 3, 2002 Share Posted May 3, 2002 I also replaced my floors with thicker gauge sheetmetal and put in 1x3 rectangular tubing front to back. If nothing else, I can at least jack up the car without wondering if the jack is going to end up going through the floors . With the sub-frame connectors and the 8 point cage, the chassis is PLENTY stiff, I will wait to see if strut brace are even necessary later. Tim Quote Link to comment Share on other sites More sharing options...
fl327 Posted May 3, 2002 Share Posted May 3, 2002 still havent finished all my subframe work, like the idea of the tubes from the strut towers to the firewall. im working on boxing the crap out of my car, subrames front and back with left to right reinforcements as well, i figure now is the best time since i have only about three feet of exhaust and no mufflers. Quote Link to comment Share on other sites More sharing options...
RB30-ZED Posted May 4, 2002 Share Posted May 4, 2002 I agree with Jumbo 240, i too found the rear strut brace, made a bigger differance than the front. The biggest improvment i found was with a brace between the chassis just behind the supports for the tie bars (compression rods).This improved braking stability to a large degree. Steve Quote Link to comment Share on other sites More sharing options...
Guest Azel Posted May 4, 2002 Share Posted May 4, 2002 You also might want to try structural foam. foam Quote Link to comment Share on other sites More sharing options...
QWKDTSN Posted May 4, 2002 Share Posted May 4, 2002 I have been seriously considering using expanding foam for a while, after reading that using it in an AE86 (corolla) can stiffen the chassis 45% while using a roll bar can only stiffen around 25%. I am curious if a combination of the two might be ideal. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 5, 2002 Share Posted May 5, 2002 beware of moisture absorbing foam . there is an ideal type that does not draw moisture Quote Link to comment Share on other sites More sharing options...
Guest 1fastz Posted May 5, 2002 Share Posted May 5, 2002 HMm just how stiff could this stuff make a be ? Quote Link to comment Share on other sites More sharing options...
DavyZ Posted May 5, 2002 Share Posted May 5, 2002 If it doesn't absorb water, it would be the bomb to fill up the pillars and rockers. More research on our end is needed--sorry, but magazine articles have to be taken with a grain of salt Still, the stuff seems fairly inexpensive. I'll look into the stuff when I'm ready to do chassis work. Davy Quote Link to comment Share on other sites More sharing options...
Guest Azel Posted May 5, 2002 Share Posted May 5, 2002 I've seen this stuff used in a lot of race cars, even some of the IRL, CART and Formula 1 use it, I believe. Steve Mitchell's 500hp Z31 uses tons of it and he's said it made the flexy chassis rock solid now. Seems like a rather inexpensive chassis stiffener as opposed to some of the 6,8-point roll cages. I'm hoping that this stuff in addition to the front + rear strut tower bars will significantly lower chassis flex and deflection. IF it is water-absorbing, you could probably use some sealants found at Home Depot to seal off the foam. I always use undercarriage rubber spray to seal off noise-dampening foam in my car. Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted May 5, 2002 Share Posted May 5, 2002 Seems like a rather inexpensive chassis stiffener as opposed to some of the 6,8-point roll cages. One usually needs a chassis stiffener because the Z needs it for high HP applications, but the foam should never be considered an alternative to a roll-cage. Roll-cage is more than just a chassis stiffener. Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted May 6, 2002 Share Posted May 6, 2002 Hmm...what if you put the foam in the roll cage Quote Link to comment Share on other sites More sharing options...
Guest Azel Posted May 6, 2002 Share Posted May 6, 2002 Originally posted by Scottie-GNZ: quote: Seems like a rather inexpensive chassis stiffener as opposed to some of the 6,8-point roll cages. One usually needs a chassis stiffener because the Z needs it for high HP applications, but the foam should never be considered an alternative to a roll-cage. Roll-cage is more than just a chassis stiffener. I can understand the necessity of having a roll-cage, especially for someone like you terrorizing the dragstrips and the rules and regulations. But I was speaking for people like myself, who, won't be doing any dragracing or any other sort of competitive racing to warrant the need for a rollcage. I think down the road I might want to install a 6-point cage but I'm not sure I'd need it but then again, the Z's doors don't seem very assuring. Quote Link to comment Share on other sites More sharing options...
Guest Perry Posted May 14, 2002 Share Posted May 14, 2002 Foam is used in some production cars now for stiffening and noise. It can be very difficult to fill a space that is long and narrow, which is usually the case in a car. Be VERY careful if you try this, sheetmetal will not stop the foam if you put too much in. What commonly happens is the foam skins over, trapping liquid inside, which keeps expanding until something gives. I saw a fibreglass boat deck seperate from a V hull by this stuff once. Just a side comment, Auto OEMs haven't used foam until recently because they couldn't get a consistant density with a normal pour-in process. Perry Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 14, 2002 Share Posted May 14, 2002 dsommer, sorry this is so late. The roll bar is made by Autopower, purchased through Motorsport Auto. It has the helmet strap bar and the scca triagulated brace. Cheers. Jon Quote Link to comment Share on other sites More sharing options...
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