260DET Posted February 13, 2009 Share Posted February 13, 2009 Sorry about my blunt responses but why build a cage without forming the bars so they are snug to the body? Then any tagging to the body can be much lighter yet stronger in all planes than where there are substantial gaps to be bridged? That Jap example is just nonsense, its all about show, the Japs love that hand made look Quote Link to comment Share on other sites More sharing options...
drmiller100 Posted February 13, 2009 Share Posted February 13, 2009 ummm, the springs push UPWARDS. Those braces in the engine compartment aren't going to do much to stop the strut towers from continuing. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 13, 2009 Share Posted February 13, 2009 The strut towers don't move upwards under load. Per some FEA done by Bill Savage at T-Mag the strut towers on an S30 twist and bend inward under load. If I remember right, the driver's side strut tower twists counterclockwise and the passenger side strut tower twists clockwise as viewed from above. The twist is caused by how the strut tower is attached to the inner fender. A triangulated strut tower brace setup as pictured by bjhines is the most effective way to combat that twist. It puts the braces in tension and compression. A good setup will allow a 50% increase in front spring rate. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 13, 2009 Share Posted February 13, 2009 The strut towers don't move upwards under load. Per some FEA done by Bill Savage at T-Mag the strut towers on an S30 twist and bend inward under load. If I remember right, the driver's side strut tower twists counterclockwise and the passenger side strut tower twists clockwise as viewed from above. The twist is caused by how the strut tower is attached to the inner fender. A triangulated strut tower brace setup as pictured by bjhines is the most effective way to combat that twist. It puts the braces in tension and compression. A good setup will allow a 50% increase in front spring rate. What load again? They pull OUT under cornering loads. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 13, 2009 Share Posted February 13, 2009 I think I got the twist wrong. Its been a few years since I saw the animation. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 13, 2009 Share Posted February 13, 2009 I think you had said previously that bumps cause the strut towers to bend in towards the car centerline which makes sense. I was just making the point that the bend out under cornering loads, because the pressure on the tire is pulling the bottom of the tire in. Quote Link to comment Share on other sites More sharing options...
drmiller100 Posted February 14, 2009 Share Posted February 14, 2009 ummm, well, No. For sure the tops of the struts move in and out. Tying the tops together turns it from a basic U shape where the tops flop in the wind to a Box or paralleagram where it all twists less, and altogether, but none the less, still moves. If we are going to the HUGE effort to put in a cage, and we trying to pretend the cage is going to stiffen something, shouldn't we be trying to stiffen the suspension pick up points? To do that, we should tie the cage into the front cross member (not done in any pics I have seen) and tie vertical forces at the top of the strut tower into the halo (again not in any pics I have seen.) Unless you are saying you are tying the cage into the front suspension via the rocker panels under the door hinges. Quote Link to comment Share on other sites More sharing options...
bjhines Posted February 16, 2009 Author Share Posted February 16, 2009 Well.... The front crossmember is a fairly stout piece on the later chassis. This is the reason I chose a later model crossmember that still fit the early rack. Then I stiffened the chassis rails and tied the added longitudinal rials into the TC buckets I used 2 diagonals outside the frame-rails as well. The inside has considerable gusseting to tie the various parts into the 14gauge reinforced frame-rails. The frame reinforcement goes all the way around and even has an added lip where the crossmember bolts to the chassis. The rear got similar treatment. added upper frame reinforcement plate upper tower reinforcement rear diagonal reinforcement There is also a rear cross-brace between the towers, AND the main hoop is tied into the diff-mounting crossmember with diagonals to further stiffen that mounting point ... Quote Link to comment Share on other sites More sharing options...
drmiller100 Posted February 23, 2009 Share Posted February 23, 2009 ok. Lets pretend the struts go up and down as the car turns this way and that, and hits bumps. Further, lets pretend the primary forces involved with these struts going up and down are that the tops of the strut towers go up and down. You have all those bars keeping the tops of the bars from going back and forth which is handy cuz they don't move anyway, but what keeps the tops fo the struts from flexing up and down???? 35 year old tackwelded sheetmetal, bars in bending, and happy thoughts. Quote Link to comment Share on other sites More sharing options...
bjhines Posted February 23, 2009 Author Share Posted February 23, 2009 OK. You need to realize that this was only a partial discussion of a build that was further outlined in another of my threads. You are starting to sound like a broken record compared to the people in here that are posting real ideas and solutions. JM, JC, I, and others also have had discussions in other threads. I suggest you look them up. The welds are reinforced by seamwelding, possibly the hardest part of that entire project. There are also a few extra layers of metal where things were weak from the factory. If you look carefully, you will see the there are nearly vertical tubes on the front and rear towers in the pictures I have posted. Please feel free to show me what you would do on this drawing ... Quote Link to comment Share on other sites More sharing options...
johnc Posted February 23, 2009 Share Posted February 23, 2009 but what keeps the tops fo the struts from flexing up and down???? Proper design and engineering from Nissan. How much vertical load you think those strut towers see in a 2,400 lb. car? Quote Link to comment Share on other sites More sharing options...
drmiller100 Posted February 25, 2009 Share Posted February 25, 2009 Proper design and engineering from Nissan. How much vertical load you think those strut towers see in a 2,400 lb. car? 10,000 pounds per corner when you hit a good sized bump??? Quote Link to comment Share on other sites More sharing options...
drmiller100 Posted February 25, 2009 Share Posted February 25, 2009 so you are saying you did all that work, and then are counting on seam welded joints to control the suspension??? Sure would be easy to run a brace from the top of the rear strut bar up into the back of the roll bar, directly opposite where the halo bar comes in. Sure would be easy to use substantial bars to tie the towers together across the body, and weld them in place, not just counting on heim joints to locate them. Sure would be easy to look at real loads coming into suspension points, then tie the roll cage into them, rather then pack a bunch of weight around cuz it looks cool. Sure would be easy to build bars connecting the cross member to the tops of the strut tower. What would be REALLY hard would be to build a bridge or ladder or sheer panel to tie the cross member weights and tops of the strut towers back into the cage in a vertical stress. With the stock cars, the inner fender wells are what carry the loads back. They carry them in sheer, but there are lots of bends and bad angles. Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted February 25, 2009 Share Posted February 25, 2009 drmiller100, Can you draw some pics, I'm having trouble following anything that you're saying. Sure would be easy to run a brace from the top of the rear strut bar up into the back of the roll bar, directly opposite where the halo bar comes in. Look at the upper centre of this pic: http://i46.photobucket.com/albums/f127/bjhines/V8%20240Z%20project/bodywork/paint/interiorpaint1.jpg Note the bar running from the outer edge of the flat surface the strut mounts to (which isn't really flat, but rather has embossed lips for strength I guess) into the upper outside corner of the main loop. I assume this is what you're talking about? That combined with this: http://i46.photobucket.com/albums/f127/bjhines/V8%20240Z%20project/roll%20cage/Towerbraceboxinstalled.jpg Would seem to provide pretty good vertical support of the rear strut towers to me. Unless you are talking about the small section of embossed flat the strut tops actually mount to flexing? As for the front, its a similar story as shown in this: http://i46.photobucket.com/albums/f127/bjhines/V8%20240Z%20project/suspension%20mods/steeringintermediateshaft.jpg Note the two triangle-shaped braces tying the extra strut tower sheet directly to the frame rail, in addition to the large tube tying it at the sway bar mount. Again, the only place I could see any substantial flex occurring is on the embossed flat the strut towers actually mount to. And thats only because I have no idea how strong an embossed steel plate like that is? As for your other points: Sure would be easy to use substantial bars to tie the towers together across the body' date=' and weld them in place, not just counting on heim joints to locate them.[/quote'] Do you have any reason to suggest that heim joints + a strut tower brace as BHJ is allowing for is in any way weaker than ``a substantial bar welded in place'' ? Sure would be easy to look at real loads coming into suspension points, then tie the roll cage into them, rather then pack a bunch of weight around cuz it looks cool. Show us how, as clearly noone here has any idea? Sure would be easy to build bars connecting the cross member to the tops of the strut tower. Doesn't the crossmember mount solidly to the frame rails, and then the afore-mentioned triangle braces and sway-bar-mount-brace tie the frame rails to the strut tower (at both the bottom and the top)? Or are you saying that whatever gauge steel in the main wheel well + whatever gauge in the overlaid strut tower is not strong enough in tension to support the required vertical loads? Dave Quote Link to comment Share on other sites More sharing options...
EMWHYR0HEN Posted February 25, 2009 Share Posted February 25, 2009 10,000 pounds per corner when you hit a good sized bump??? How the hell did you come up with those numbers? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 25, 2009 Share Posted February 25, 2009 How the hell did you come up with those numbers? You know... 600 lbs/corner and a 16.6666666g bump. There you go, 10,000 lbs per corner!!! It's like when you've got Roscoe P Coltrane on your tail and you see that dirt ramp. You just gotta take it!!! YEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEHAAAAAAAAAAAAAAAAAAAAAAAAAAW!!! Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted February 25, 2009 Share Posted February 25, 2009 hehehe Quote Link to comment Share on other sites More sharing options...
S15 200sx owner Posted February 25, 2009 Share Posted February 25, 2009 Hey guys, i thought you might like to see these pics of a fairly serious track car i had a good look at a couple of weekends back. Note, it has three bars from the cage to the strut towers (under the hood) and another bar under the front fender from lower front corner of cage to the front rail, with a smaller diameter verticle bar tieing the lower bar and one of the upper bars together. The diagional bars from the strut towers heading towards the centre of the firewall, actually pass thru the firewall and join the upper dash bar. In the rear It also had diagional bars going down from the bar running between the strut towers, down thru the floor, and mounting the rear of the diff. There were similar bars passing thru the floor forward of this providing the mount for the front of the diff. Also note the rear susp. The owner made a really good point, once i started asking him about this. He quoted that 'others' join both sides of the rear susp together with a cross brace, he said that for a track car that isnt smart, as when you take a biff in the rear you end up damaging both sides of the susp. makes sence. I got lots of good ideas from this car, hope the owner doesnt mind me posting these. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 25, 2009 Share Posted February 25, 2009 Looks like a lot of careful thought and attention went into building that car. I see very few nits to pick. The bar from the strut tower down to the sway bar area would be better if it were straight, but he would have had to cut into the fenderwell to do it. A curved bar is less stiff. Also in the front I think the bar from the strut tower that presumably attaches to the dash bar node is in my opinion redundant. I looked at doing the same thing, but the upper frame rail is right there and attaches basically the same parts in the same plane. Not sure the load path is the best for the tube that goes from the strut tower to the TC rod/rocker arm bar. Those are all pretty small issues though. Interesting rear suspension solution. Looks like he has no front diff crossmember either. Diff changes must be a snap. Is this guy a member here? He should be... Quote Link to comment Share on other sites More sharing options...
S15 200sx owner Posted February 25, 2009 Share Posted February 25, 2009 Looks like a lot of careful thought and attention went into building that car. I see very few nits to pick. The bar from the strut tower down to the sway bar area would be better if it were straight, but he would have had to cut into the fenderwell to do it. A curved bar is less stiff. Also in the front I think the bar from the strut tower that presumably attaches to the dash bar node is in my opinion redundant. I looked at doing the same thing, but the upper frame rail is right there and attaches basically the same parts in the same plane. Not sure the load path is the best for the tube that goes from the strut tower to the TC rod/rocker arm bar. Those are all pretty small issues though. Interesting rear suspension solution. Looks like he has no front diff crossmember either. Diff changes must be a snap. Is this guy a member here? He should be... Hey Jon, These points you mention above, how could they be improved upon (I am about to get into mine shortly) Any pics/drawings etc you could show me/point me at? I will post some more pics of that car. Quote Link to comment Share on other sites More sharing options...
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