JMortensen Posted February 1, 2007 Share Posted February 1, 2007 Looking for your thoughts and input. I am just about to paint the bottom of my car. My task list was: a. finish rear control arms b. mount fuel cell c. cut and weld rear fenders for flares, and then I figured I could paint the bottom. Those things are now done. I started to work in the front and ended up stripping the engine compartment, so I was thinking of painting it as well, and that's when I hit a snag. What to do about the strut tower bar??? I cut off the crappy firewall clevises I had a friend weld on during the previous build, although I still have the clevises on the strut towers. Now I'm considering cutting those off too, and redoing the whole thing completely. My original plan was to reuse the original clevises where they mounted to the firewall, but after looking at where they were welded to I've decided I'm definitely not going to do that. The driver's side clevis hit one of the cowl supports. I think I ASSumed that there would be another support on the other side, but there isn't. The passenger side wasn't attached to a reinforced area of the firewall at all. So now the issue is whether to use the existing clevises on the strut towers and attach them to a mount at the center of the firewall, or whether to integrate the triangulated brace into the cage itself. I'm really thinking that I should cut the clevises off of the strut towers as well, and integrate the clevis into the reinforced area that the cross bar bolts to. I think the original idea worked in a rudimentary way, but in retrospect really wasn't that great and could have been done a lot more cleanly. The major concern I have about doing something like John Coffey did with the mount in the center of the firewall is that the firewall really doesn't seem very sturdy. Even if the mount was fairly large and spread the load over the top and bottom sections of the cowl, it still doesn't seem like a very good spot. I was really excited about bjhines' solution of reinforcing the cowl structure, but now I'm not so sure that it's a good idea to attach anything to the firewall. Maybe if I ran a bar from the dash bar straight through the cowl to the firewall... seems like a PITA... The major concern I have with integrating the strut towers into the cage is that if I eventually get around to an engine swap I'd hate for those bars to be in the way and then to have to cut them out. If I did this I would triangulate from the strut towers to a dash bar, and the two bars would intersect at the dash bar and go straight through the cowl area. Some pics: WRONG strut tower attachment points!!! Don't put them here like I did! Blank slate: Bars through the cowl to intersect dash bar: Bars attach to firewall bracket in center: This is what the strut towers look like currently: This is how I would move the strut tower bar attachment point: Quote Link to comment Share on other sites More sharing options...
bjhines Posted February 1, 2007 Share Posted February 1, 2007 as far as the clevises on the strut towers go... I would not move them... I would keep all forces passing through the center of the strut tower.. not offset inboard to the tang for the crossbar... Quote Link to comment Share on other sites More sharing options...
bjhines Posted February 1, 2007 Share Posted February 1, 2007 some pics of my side reinforcement... It clears the clutch hydraulics, it ties the wheelwell, tower, firewall, and side together along with the front of the A-pillar bar... .... Quote Link to comment Share on other sites More sharing options...
bjhines Posted February 1, 2007 Share Posted February 1, 2007 More Ideas for the center supports... There is supposed to be one more trianglular gusset on the front of my firewall brace tang... But I am getting ready to hack this one off and make it completely removable... for distributor clearance with a Chevy SB V-8 incomplete tang ... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 1, 2007 Author Share Posted February 1, 2007 Hey thanks for all the pictures. Does this bar bend or is it a straight shot? Any interference with the pedal box? Quote Link to comment Share on other sites More sharing options...
johnc Posted February 2, 2007 Share Posted February 2, 2007 The major concern I have about doing something like John Coffey did with the mount in the center of the firewall is that the firewall really doesn't seem very sturdy. That's funny because that firewall mount and the entire traingulated STB setup on my old car had some actual engineering via FEA software behind its design. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 2, 2007 Author Share Posted February 2, 2007 Did they engineer the mount with the software? I'm not questioning the mount... I'm questioning what it is mounted to. I've stitched my firewall to the cowl box and I'm bringing this up because of the flex in the firewall that I was feeling while removing paint with a scouring pad. I mean if I can flex it by hand (all sections, not just right at the top or right in the middle), that makes me think that when the strut towers try to deflect the mount won't have a chance... Quote Link to comment Share on other sites More sharing options...
bjhines Posted February 2, 2007 Share Posted February 2, 2007 I used John C's pictures as a reference for my design... as soon as I test fit the tubes.. I noticed that the tubes to the firewall did not cinch up tight at all... I could see the flex in the center firewall... Now that I have tied everything together it is MUCH STURDIER... My inside bar does not iterfere with the pedal box.. It is straight.. It also allws me to bolt int the original vent flapper and I can still hook up the cowl vent tube... Quote Link to comment Share on other sites More sharing options...
heavy85 Posted February 2, 2007 Share Posted February 2, 2007 Jon I think the 'wrong' location is the best at least on my car. For one there is a vertical gusset on both side right behind that area (you can see this in bjhines pics) and you can tie into the top horizontal plate of the cowl. Other reason is it's far enough out that you can weld the bars in instead of using rod ends. I think welding would provide a far stiffer structure. Just my 2 cents after studying it for a while. Here's where I'm planning on attaching. It's centered in front of the vertical support and tied into the top plate. Just tacked in temporarily to get the idea and mock up the tubes. And I agree the tabs on the strut tower should be spread out like they are now. Cameron Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 2, 2007 Author Share Posted February 2, 2007 Hmm... mine has no support on the passenger side. There is a vertical support on the driver side. Maybe yours is a later chassis and they put one in later on??? Quote Link to comment Share on other sites More sharing options...
tube80z Posted February 2, 2007 Share Posted February 2, 2007 The major concern I have with integrating the strut towers into the cage is that if I eventually get around to an engine swap I'd hate for those bars to be in the way and then to have to cut them out. If I did this I would triangulate from the strut towers to a dash bar, and the two bars would intersect at the dash bar and go straight through the cowl area. Bars through the cowl to intersect dash bar: This is how my old car was done. I don't thick you'd have any issues with putting another motor in. A Ford 5.0 fit fine and looking at Kipperman's LS-1 I didn't see where it would be an issue. I actually had more room this way as the V was larger. I also think this is stronger. The only other option I'd offer if you were looking for a bolt in design is one I've never seen. That would be an X that hooks into the rear corners of the engine bay and then to the strut towers. Similar to what you'd see in a Viper competition coupe. This seems stronger to me than going to the cowl. Cary Quote Link to comment Share on other sites More sharing options...
johnc Posted February 2, 2007 Share Posted February 2, 2007 Did they engineer the mount with the software? I'm not questioning the mount... I'm questioning what it is mounted to. They built a simple FEA model of the car from the transmission mount forward including the suspension links. The model was used to develop the transmission mounting, STBs, radiator mount/front ARB reinforcement, and the brake MC bracket. Per the model (if I remember correctly) the loads on the center firewall STB mount are shared between the two bars and 20% of the loads are shear loads across the face of the firewall and 35% are tension loads from one STB pulling against the other. Less then half the load is compression. Quote Link to comment Share on other sites More sharing options...
bjhines Posted February 2, 2007 Share Posted February 2, 2007 The middle of my firewall including the lower seam with the cowl box flexed fairly easily... much easier than the slight flex between the 2 strut towers... I reinforced my cowl box and it became stiffer than the 2 strut towers... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 2, 2007 Author Share Posted February 2, 2007 Cameron, I think I see the difference in our two cars. In this pic you see the support on the passenger side of the cowl. Mine did not have this vertical support underneath the cowl, although it did have one on the driver side. I think after all the discussion I'm going to go through the firewall to a dash bar. It just seems like the best most rigid solution. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted February 2, 2007 Share Posted February 2, 2007 Very good thread here. I think this is the first thread that Iv'e seen that deals with how an interior cage could tie into the nose of the car. I always try to visualize how to get the front bars through the firewall and where to come through. This thread answers that basic question. Nice work. All this talk about bars on Friday makes me thirsty. Mmmmm. Tanqueray and Tonic coming right up! Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 2, 2007 Author Share Posted February 2, 2007 The only other option I'd offer if you were looking for a bolt in design is one I've never seen. That would be an X that hooks into the rear corners of the engine bay and then to the strut towers. Similar to what you'd see in a Viper competition coupe. This seems stronger to me than going to the cowl. I was only able to find one picture for the Comp Coupe strut tower brace. It's at the bottom of this page: http://www.caranddriver.com/specialtyfiles/8120/specialty-file-dodge-viper-competition-coupe.html I can't tell because the corners are cut off but it looks like it attaches to the roll bar, and not the cowl or anything else in the engine compartment. It also looks like the X is bent up to clear the intake. While it may be possible to do this differently in a Z, I still don't see a good place to attach it to, and the curve in the brace seems like it would be less stiff than a straight bar that goes through to the dash bar. Quote Link to comment Share on other sites More sharing options...
LLave Posted February 2, 2007 Share Posted February 2, 2007 a lot of talk about John Coffey's car. Can anyone give me a link to some pictures? Thanks Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 2, 2007 Author Share Posted February 2, 2007 There are some pics on his website: http://www.betamotorsports.com. If you go to the bench racing section and then to the OTC stuff, I think there are some pics there. Various other pics scattered around the site. It was a one off FI NA L31 with ~290whp, sequential trans, Penske shocks, etc. No expense spared, really fast Z car. He parted it out and sold the shell a couple years back. Quote Link to comment Share on other sites More sharing options...
Mayolives Posted February 3, 2007 Share Posted February 3, 2007 Food for thought. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 3, 2007 Share Posted February 3, 2007 I can't tell because the corners are cut off but it looks like it attaches to the roll bar, and not the cowl or anything else in the engine compartment. It also looks like the X is bent up to clear the intake. While it may be possible to do this differently in a Z, I still don't see a good place to attach it to, and the curve in the brace seems like it would be less stiff than a straight bar that goes through to the dash bar. You're correct regarding the Comp Coupe engine compartment X brace. Bondio Fab makes a replacement X brace that's made out of 4340 tube, 095" wall that doesn't move even with me standing on it. Quote Link to comment Share on other sites More sharing options...
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