rc's240z Posted June 11, 2002 Share Posted June 11, 2002 see photos & information at http://www.240z.org/photopost/index.php?photo=1184 Quote Link to comment Share on other sites More sharing options...
katman Posted June 11, 2002 Share Posted June 11, 2002 Well, it's cool, but claims that it eliminates all strut tower movement are a stretch. The "ultimate" brace would have a single triangle from the towers to the center of the firewall, not two individual triangles. Here's why: What we are trying to prevent on the front half of an early Z is twist due to torsion and sideways motion due to lateral forces. Vertical loads are already well accounted for by the frame rail/inner fender/hood ledge assembly. All strut bars basically keep the two struts together at the top. Now to react sideways motions of the strut towers we need to react a sideload somewhere. Using the two trusses shown with this setup, a sideload applied at a strut tower is reacted back at the firewall as an equivalent and opposite sideload at each truss attachment, PLUS a moment equal to the sideload times the distance to the firewall from the strut tower. Now this moment is reacted by fore and aft loads at the firewall attachment, which would be fine if the area behind the firewall had anything behind it, but it doesn't, so there's almost no fore/aft capability up there. Consequently this setup is not very stiff for lateral movement of the strut towers, which is the whole point of having the brace. A single truss, tower-to-tower-to-firewall uses the fore/aft capability of the hood ledge in a mo' better than the device shown, effectively becoming a 3 truss system. Better angles, more efficient, much stiffer. I'd draw a freebody diagram to make it clearer if I had a napkin and a beer. Quote Link to comment Share on other sites More sharing options...
S30Z Bushido Posted June 11, 2002 Share Posted June 11, 2002 looks cool, i'd like to see it installed... Quote Link to comment Share on other sites More sharing options...
pparaska Posted June 11, 2002 Share Posted June 11, 2002 katman, if I you lived closer I'd invite you out for a beer so you could draw that. But I'm still interested if you care to sketch it up, scan it and upload it. Quote Link to comment Share on other sites More sharing options...
Kennysgreen280zt Posted June 12, 2002 Share Posted June 12, 2002 I'd draw a freebody diagram to make it clearer if I had a napkin and a beer. Im interested in seeing this beer drawing too Quote Link to comment Share on other sites More sharing options...
Drax240z Posted June 12, 2002 Share Posted June 12, 2002 Katman you must be an engineer, that's exactly the first think I noticed as well. Maybe I can clarify your thoughts a little though, to prevent any crazy napkin drawings. Basically because the two strut tower braces aren't meeting in the center of the firewall, and instead are placed what looks to be about a foot and a half apart, there isn't nearly as much additional lateral stiffness as there would be if the two center braces attached to each other. (used each other for rigidity) Not trying to slag someones product for the Z car, we know there just isn't enough stuff like that out there now... but I'd be happier with the one bleach posted. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted June 12, 2002 Share Posted June 12, 2002 Kinda like this I think? img Quote Link to comment Share on other sites More sharing options...
johnc Posted June 12, 2002 Share Posted June 12, 2002 Everyone asumes the strut towers move side to side and front to back. They actually twist with the right side turning in a clockwise direction and the left side turning in a counter clockwise direction. In fact, the shock or strut towers on most cars twist in the same directions. That's why a big triangle works so well (like the Mustang/Falcon export brace and a lot of the factory braces on older big cars.) Quote Link to comment Share on other sites More sharing options...
BleachZee Posted June 12, 2002 Share Posted June 12, 2002 Is this triangular strut tower bar more what you are talking about? This one is from Top End Performance. $189 shown here on a 280zx, they also sell them for the S30 models. Quote Link to comment Share on other sites More sharing options...
katman Posted June 12, 2002 Share Posted June 12, 2002 Originally posted by blueovalz:Kinda like this I think? Yup. Quote Link to comment Share on other sites More sharing options...
Guest jcp240z Posted June 13, 2002 Share Posted June 13, 2002 One thing to note is that on this bar ( The one Ron C. showed) the mounting points at the fire wall coincide with the braces which run from the fire wall back to the cross bulkhead. I hope that I am describing it correctly. If you take off your cowel covering you'll see the bracing which goes between the firewall. Quote Link to comment Share on other sites More sharing options...
rc's240z Posted June 13, 2002 Author Share Posted June 13, 2002 james nice to hear from you! katman you are very knowlegable but incorrect about the bracing at the bulkhead, pull your cowl off to verify bracing back from the firewall. the difficulty is in mounting any brace to the center of the firewall because of the factory hood latch. Top End has tried, but does not support their product to the factory bracing built into the firewall, nor does it support the tie into the way bar. Most importantly, this bar picks up the twisting energy of an oversized sway bar-something most of us have, and transfers that energy to the triangulated assembly.... Having the prototype of this bar and driving the car extensively I can say that it works well, and does what is claimed. I DO NOT make a profit from the sale of this bar nor did i design it. It was designed by a guy who used to build chassis for NPTI and Neumann Haass. I know he knew what he was doing and the proof is in how the car handles....you are welcome to draw your own conclusions..... Quote Link to comment Share on other sites More sharing options...
rc's240z Posted June 13, 2002 Author Share Posted June 13, 2002 more photos: http://www.240z.org/photopost/index.php?user=932&thumb=1&cat=500 As I Expand on Katman's comments: If you take into account that the center section works as a triagulated section then you have two small triangles supporting one large central triangle preventing lateral as well as twisting movement of a 30+ year old chassis. Katman we are always looking to make this product better. Got an idea, send it to me.... Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted June 13, 2002 Share Posted June 13, 2002 I have the TEP strut bars installed in my S30. As delivered, the firewall triangle will not do much good, but I laid a strip of 1/8" thick steel in the channel across the top of the firewall and bolted it down in several places, including the tabs of the strut brace. It seems to be extremely rigid now, and I'm quite happy with it. BTW, I'd love to see that free-body diagram, it makes sense to me about the one big triangle being more effective than the two small triangles separated by the width of the flimsy firewall. Quote Link to comment Share on other sites More sharing options...
pparaska Posted June 13, 2002 Share Posted June 13, 2002 Those "supports" behind the firewall that go to the windsheild area and down to the bottom of the cowl box are very thin. Although they have a cup shape, bends etc. in them for more stiffness, I doubt that I'd want to depend on them alone. I think the idea of reinforcing the firewall like Terry did makes the most sense - to distribute the load over that 22 gage sheetmetal firewall to get to the ends where it's supported for/aft. Quote Link to comment Share on other sites More sharing options...
katman Posted June 13, 2002 Share Posted June 13, 2002 Yeah, now I remember there being some sheet metal behind the firewall in some places up there in the cowl area, I stand corrected. Regardless, I stand by my statement that it's not very effective that way. Agreed there is a challenge to a single truss emanating from the center of the firewall because of the hood latch. There is no fore/aft reacting load necessary with the single truss if the connection at the hood latch is designed to react side loads only (the real beauty of that concept). Easily done. Side loads imparted anywhere on the firewall are easily reacted. Fore/aft loads to balance the moment are then reacted by the hood ledge area of the inner fender as I alluded to earlier (my original microfiche calls this a "food ledge"). Lemme run some numbers with each design including the bracing aft of the firewall. May be in practice there's not much difference in stiffness. I'll keep ya'll posted. Quote Link to comment Share on other sites More sharing options...
johnc Posted June 13, 2002 Share Posted June 13, 2002 FYI and FWIW I'm having Bill Savage at TMag Racing (he built the suspension uprights and many of the other chassis and suspension components for NPTI and their GTP cars) build some strut tower bracing for my car. In addition to the bar going across the strut towers we are also running two diagonals from the strut towers to the center of the firewall (my hood latch is removed.) What's important, based on our flex tests with a hydraulic ram, is to tie the firewall mount of the strut brace to where the lower panel inside the cowl meets the firewall (you can see a line of spot welds inside the engine bay) with the upper lip on the firewall. This is true regardless of where (horizontally) on the firewall you are. It requires a fairly tall plate with a couple gussets. We looked at adding some internal bacing inside the cowl area but our tests indicated that a tall plate fitted as stated above was strong enough to accomodate the expected loads. Quote Link to comment Share on other sites More sharing options...
pparaska Posted June 13, 2002 Share Posted June 13, 2002 John, I like using that lower part of the cowl area box - it sould be pretty stiff for/aft. It's about 6" below the cowl panel. Do I have this right? : You're putting a plate of the engine side of firewall that goes from about that spot weld line that indicates the bottom of the cowl box, out toward the hood ledge? Then I guess the gussets are longitudinal (for/aft) tieing in the firewall like those wimpy stamped steel ones that we were referring to above? Quote Link to comment Share on other sites More sharing options...
katman Posted June 14, 2002 Share Posted June 14, 2002 Originally posted by johnc:What's important, based on our flex tests with a hydraulic ram, is to tie the firewall mount of the strut brace to where the lower panel inside the cowl meets the firewall (you can see a line of spot welds inside the engine bay) with the upper lip on the firewall. This wouldn't be necessary if you eliminated the fore/aft component of the connection here (trickier to fab no doubt), but I like your thinking. That's exactly what I'd expect with a traditional "hard in all degrees of freedom" connection, that the place you want to hit is the intersection of that shelf with the firewall. All around an excellent idea. I love it when somebody has the gumption to run a test. I can see I'm gonna hafta dig up my finite element model of a HLS30 unibody and dink around with some strut bars. I wonder if we still have that old Cray XMP out in Rye Canyon....? Quote Link to comment Share on other sites More sharing options...
rc's240z Posted June 14, 2002 Author Share Posted June 14, 2002 Katman, soundslike you'll need some bandwidth for those calculations.....Let us know what you come up with... John C Ask you buddy who used to work for NPTI if he knows Carl Azevedo.... I think we are missing a key point, no other "manufactured" bar offers a tie on to & through the frame rails to the front sway bar. this link is what adds a large amount of stability strength to this design by transfering that energy away from the frame rails and to our assembly and strut tower, thus stiffening the entire front subframe. Quote Link to comment Share on other sites More sharing options...
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