Roll Cages and Roll Bars

[pparaska]

Ross, good point on how to tie to the towers. Like everything else, I asked for it to be installed a certain way (like tied better to the tower top) but they put it on the upper front face of the tower, although with a decent sized plate. I may add to it and gusset it.

 

Terry, my view is that many of the larges loads are vertical through the tops of the strut towers. Granted there are others and tieing them all together with tubes (now you have a space frame car) would be best. But pickint up those tower loads as they the tires try to push the tower upwards is a worthwhile thing.

[Guest Anonymous]

Stony I belive you r right. That's how I counted

[blueovalz]

I guess I don't understand the towers only cage system. To me the vertical movement of the suspension would be transfered to the unibody (frame rails, etc) by the verical tension/compression strength of the towers themselves, and very ineffeciently through horizontal bars. but if inertia in a corner is trying to force the mass of the car outward, than the tower tops are going to follow suit (assuming the tires and hence the lower control arm picup points maintain grip), or all the towers if they are all tied together without any bracing to the bases of the towers (or control arm pickup points). It appears to me to be a parallelogram (spelling?)flexing rather than a parallelogram with a travers brace (tying the towers to the lower points on the unibody thru a cage). I've never seen this set-up of towers only before, and I may be missing something on this.

[Guest Anonymous]

That's a nice looking cage andy.

 

jon

[pparaska]

Terry, I agree a vertical tube to the top of the tower, if it were tied well into the rest of the structure of the car, would be the best bet. Unfortunately, the stiff thing to tie it too seems to be the roll bar, which is forward. I asked the guy to angle them down from the top of the hoop, and well, got them shooting back from the sides, at a more horizontal angle. Damn, if you want something done right, you have to do it yourself!

 

I also run a simple tower strut bar, but something that is rigid like an X between the towers would be better to keep that parallelogram from flopping around.

[blueovalz]

Dang Pete, I feel your pain. That's why I limit the out-work to the very very minimum, which at times is more agravation to do it myself, but in the end I know it's done right.

[Guest Anonymous]

One quick question on this topic of roll cages. What does the number mean in 8 and 10 point roll cages? I kinda get that the high number has more bars but is the number actually the number of bars used?

[Guest Anonymous]

quote:

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Originally posted by radtad:

One quick question on this topic of roll cages. What does the number mean in 8 and 10 point roll cages? I kinda get that the high number has more bars but is the number actually the number of bars used?

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When says, for instance, 10 points, that means that it connects to the frame in 10 different places. The points have nothing to do w/ how many bars there (if you look at a 6 point roll cage, there's only 5 bars).

[Guest Anonymous]

Why not curve the back bar like mine and tie it too the wells .Open my page and open your eyes ! what did you all say triangled rectangled , something, pentangled ,octangled Just look lat bars touch in front of the tail lights. Is 350.00 a good price for a LSD ?

[Modern Motorsports Ltd]

quote:

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Originally posted by blueovalz:

I guess I don't understand the towers only cage system.

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I didn't intend that to be interpreted as towers only. Design was a full tower cap, an X b/t tower's, pity bar on main hoop etc if one can 'tolerate' all that (ie. depending on your car's use). As well the bars are fully welded to the heel plates BUT heel plates are NOT fully welded to the frame/rails/towers...intermittent welds spaced around the plate, this allows some flex of that tie-in and it'll stay part of the cars structure far longer than a fully welded plate that is so rigid the car will part ways with it sooner as it's essentially more 'brittle' and will shear/tear away as the actual car's structure is not as stiff(for lack of a longer explanation). The longer your cage remains part of your structure the safer you are. I"ve seen v. few do it this way (maybe it's more common than I know) but I know the incidents a few walked away from with above design and it's what I'll want when it's done (the cap and weld details etc).

[blueovalz]

Thanks for clearing that up Ross.

[BLKMGK]

Cerberus - my chassis guy did NOT put the bars all the way back intentionally. His feeling was that in an acident I'd be better served by having a "crush zone" behind me. This way I would have some cushion and not have the shock tied into the cage so directly. Hopefully I'll never have to test this design decision!

 

Hrm, I do have a strut tower brace in addition to the cage being tied to the towers. That was mostly because I've got it and saw no reason NOT to use it. I'll have to sit down one day and docment the cage design. I would like it if th efloors were a little more reinforced over the plates I've got but that's a future addition I think.

[pparaska]

I've seen the bent seat belt bar done before (Andrew did something like this.) It just doesn't look as clean to me, and I couldn't handle the roll hoop NEXT to the seat - it had to be behind it for my seats.

 

Jim, I don't know - I think it MIGHT be better to take that crush zone out of the rear of the car - the gas tank/cell is where that crush zone is! Mike Kelly is living proof that having the bars go all the way back keeps that from happening! I may add some from the top of the tower to the back of the car later. I also run a removeable strut tower bar.

[ZROSSA]

Roll cages, man have i put a lot of thought into those over the years. there are a couple things to remember that i dont think have been mentioned yet. No mater what the application try to tie the front and rear suspension with the cage. Triangulate (?) it as much as you can and never put a load into the middle of a bar. On my old corolla race car the cage is almost a space frame it could run without the shell at all and picks up every suspension mount and strut tops. It is also attached to the body buy tabs to try to get as much stiffness as possable. Then you could always seam weld the car. Lots of fun. The local z race cars Tie in the cage to the strut tops then add another bar from the bottom of the main hoop back up to the strut top. Welded into this is a bar which goes between the two rear strut tops. this then gets a diagonal bar back to the main hoop. You could do this from the other side to form a x. Look at some current Aussie super touring cars or the old british touring cars for ideas. They have awsume cages that tie into the shell as the rules are a bit different then in the states. You guys just buy a spec space frame and slap any old body one it. Both work fine but the poms cages better fit our applications.

[BLKMGK]

Not to worry Pete, I'm not thrilled about the cell being in a crush zone either but it's foam filled an should break away or go down in an accident. At least that's what I hope occurs! I'm seriously conidering doing a bigger cell with a steel safe like Mike's got now - I'd have done it the first time if I could've found one that I thought would fit We'll see, for now I just try hard not to dwell on it.

[johnc]

Here's the roll bar in my 240Z. It ties in the rear strut towers very well.

 

 

[Modern Motorsports Ltd]

quote:

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Originally posted by BLKMGK:

Not to worry Pete, I'm not thrilled about the cell being in a crush zone either but it's foam filled an should break away or go down in an accident. At least that's what I hope occurs!

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I'd prefer a stiffer rear as well, foam or not I'd be concerned about hot exhaust/sparks from the carnage/electrical to pump and other items back their etc. Let alone if you can't get out easily that could be a lot of fumes moving your way that might find a spark/short somewhere.

 

Then again, I have a hugely long list of what I'd prefer on my own car as well

[Guest Anonymous]

the amount of bars that go to the floor determines the count i believe.

 

 

Correct.

 

 

Alot of the pic links have died.

 

Hey Pete, would you mind posting some pics of your cage/bar?

 

I plan on doing a full 10 point cage on my Z, plus a fab'd front strut tower brace running into the firewall.

 

Right now I am trying to decide on how to set up the rear half of the cage. I agree that the rear towers should be tied into the cage, just not sure exactly how would be best.

[74_5.0L_Z]

Here's how I tied my cage to the rear struts.