Jon's 2 year roll cage saga...

[JIM73240Z]

Oh, you mean the amputee thing. That was a triangle between the A pillar, center of the dash bar, and the rocker panel where the A pillar hits it. I have NO idea where that guy plans to put his feet.

 

 

umm no. i meant across the roof. from the drivers sun viser to above and behind the passenger seat. that is what i was thinking. looking at some of the stuff that they are talking about, are we sure they are not a evil kinevil(sp) dare devil group that drops themselves off of large buildings with them inside. i mean i look at johnc's cages and yours and think $hit that can take some damage. but theirs is the next set or 2 down that road. i think johnc is smarter than the average bear but what kind of responce would he get from over there with his cages?

 

jimbo

[sweetride2go]

eh, nice work jon!! just for kicks and the sake of curiosity, how many lenial feet of tubing do you have in there???

 

cheers

ryan

[bjhines]

LOL, CC are so damn proud of themselves. I won't even speak of the tiff I got into with a local police officer over there. Needless to say I am still a member of CC, but I have nothing to add to their site.

 

 

 

Jon,

You are building a time-trials car... right. You simply cannot make an E-prod cage and have room for a passenger. I am an instructor and I am constantly asked to give rides to other instructor's students because their instructor has a "petty-bar" and no passenger seat. I love the attention and the fact that so many people have been around in my cars.

 

I chose to reinforce the "torque box"/cowl box and firewall to do much the same thing the dash and center dash bar do in your car.

 

 

...

[dj paul]

 

Did you change this since this picture? i didnt get a chance to look through and see. I think i saw a picture where it was different but i cant remember. Im assuming your going to be running a bar perpindicular to this or something because this will not support the load of a rollover, it will just go right through the floor. Im pretty sure you know that, but i just wanted to be 100%

 

Edit: I would place a decent thickness steel plate on the floor itself, and put a small piece of pipe to extend it to that plate, to spread out the load. Maybe even a piece of angled steel up against the floor and the rails. (cant remember the real name for them ATM)

[JMortensen]

Im assuming your going to be running a bar perpindicular to this or something because this will not support the load of a rollover, it will just go right through the floor. Im pretty sure you know that, but i just wanted to be 100%

Do you have any idea why this won't work, or are you just saying that it is so because YOU said it? When I made this same argument one guy at cc.com (the "give me something better than 'No because no' argument"), he did some FEA on it. The FEA showed that it would be OK. Even to the point of another guy over there assuming that I did the FEA to prove that the design was good enough.

 

I took this part of the cage directly from Keith Thomas (screen name katman). He wrote a magazine article on how to build an ITS cage, and this was in that article. The rocker where the bar attaches is MUCH stronger than the floor. The guy who bent my main hoop claimed that having the tube open on the bottom was the problem. The guys at cc.com claim that I need a box to transfer the stress to the 24 gauge floor. You are apparently saying that there needs to be another bar tied in here. Why?

 

For the record the plan is to build a box under the end of this tube. With that done it will be tied vertically into the rocker and the floor and should be a hell of a lot stronger than tying it directly into the floor. I'm not putting any other tubes into the attachment point, although the X for the door bar should be relatively close to this point.

[JMortensen]

eh, nice work jon!! just for kicks and the sake of curiosity, how many lenial feet of tubing do you have in there???

I don't recall, but it was like 168 lbs of tube with the door bars figured in. This addition will add another 7 lbs or so (1.625 x .060 DOM tube is about 1.1 lb/ft).

[katman]

"I took this part of the cage directly from Keith Thomas (screen name katman). He wrote a magazine article on how to build an ITS cage, and this was in that article. The rocker where the bar attaches is MUCH stronger than the floor. "

 

On the ITS cars we did take the plate down the rocker box and onto the floor to help shore up the connection between the rocker weldment and the floorboard. It's not the vertical loads you do this for- Jon is right the floor adds virtually no strength in that direction, but instead you want the plate to continue onto the floor to help shear out the side loads from a T-bone, which are introduced via the door bars to this vertical member.

 

I've done this two ways- by intersecting the rocker box with the vertical tube at the corner of the rocker, such that the outboard half of the tube disappears and the inboard half continues down to the floorboard plate (very lovely), and also by using a plinth.

 

And for the record, Jefferson Speidel wrote the Z Car Mag series on "Building an ITS 240Z". That rat bastard sleeps with my wife.

[johnc]

For the record the plan is to build a box under the end of this tube.

 

That's what I remembered, but when I saw this picture today I got scared. Why? Because a rollover load would put the welds on the side of the tube in shear and they could peel away from the plate from something as simple as a little dirt in the weld, a gust of wind blowing the shielding gas away for second, or any number of other little things. Adding a box underneath to handle rollover loads in compression is a good idea.

 

EDIT: When I use the term "compression" I'm referring to how the load moves through the tube. Roll bar tubing works well in comrpession/tension and not as well in bending or shear.

[JIM73240Z]

i was takling to jon about an "S" shaped plate to go over the rocker, down the rocker and over the top of the floor pan to help with this. obviously jon can not do this now, so the box is the best fix for that. for those that have not put it in yet, i think the "S" plate will cover all of the issues.

 

jimbo

[JMortensen]

More progress. This last leg was giving me fits yesterday. I got it cut today and notched the tube, but it didn't look right. So I did it again. It still didn't look right. So I did it again. The third time I measured the angle between the strut tower bar and the V to the diagonal, and also the angle from the X to the V on both sides, and it's within 1 degree everywhere. It just looks really wonky. I think the problem is that it is intersecting the main hoop which is laid back and the diagonal which is at an angle. You can see from the straight behind pic it looks like the left side is lower than the right, then from the above shot it looks pretty good.

 

I think I'm ready to weld it in, I just wish it looked more even.

 

 

 

 

[tube80z]

Good work on those compound tube junctions. They aren't easy and never look right.

 

Cary

[EMWHYR0HEN]

What's next on the cage/structure to do list Jon?

 

Comin together nicely.

[JMortensen]

Pedestals under the tubes, then door bars. And that will be it. Looks like a simple X door bar that doesn't go into a gutted door is now legal, so that will be the way I do it. I think it's superior from a stiffening perspective than a bent X to go into the door, and it's a heck of a lot easier from an installation perspective. I was going to do a bar just above the rocker panel and tie it in with a shear panel. I think I've given up on that one, figuring the X door bars will provide the necessary stiffness there.

[tube80z]

I was going to do a bar just above the rocker panel and tie it in with a shear panel. I think I've given up on that one, figuring the X door bars will provide the necessary stiffness there.

 

I would rethink that. I've seen a couple bad accidents and in each case how the driver was hurt was from the rocker crushing between the X and getting to him. While these weren't Z cars they had similar weak rocker areas. If you look at newer cars you'll see these areas have been really strengthened. This is also a good location to create an external jack point, which at some point you'll wish you had.

 

That's one area where the nascar door bars are a little better. For my XP car I'm probably going to do the X too, but I will have a bolt-in nascar type structure for when the car is hillclimbed. If you happen to look at one of the recent race car engineering mags you'll see this is the type of thing the FIA has been testing for rally car side impact protection. Having one tube try and crush through another has been shown to dissipate a fair amount of energy.

 

Cary

[JMortensen]

I went back and messed with the right leg instead of the left and had better results. Biggest mismatch in angles is now .5 degrees, and I think it looks a bit better, if still not perfect.

 

Here's the finished product:

 

 

 

 

 

 

 

 

Cary, I hear what you're saying but I'm not going to be doing any hillclimbs and the amount of effort involved makes me think that it is just not worth it. If I had known then what I know now I would have started by cutting up the rockers and installing a 2x2x.120 square tube. If I did do the rocker tube, it was just going to be across the door opening. I think you had previously suggested that it go all the way forward to the firewall and I think that would be a real bitch to get in there and weld it in.

 

EDIT--Just re-read your post Cary. You're saying that bracing the floor in between the X prevents something from coming under the X and crushing the bottom of the seat basically. That's pretty good reasoning. I guess I'll have to reconsider this...

[JMortensen]

I was going to do a jackpoint straight through the rocker with a plate on either end and a tube through the middle. How would you suggest incorporating a jack point into the tube above the rocker? Seems like the jack would have to go right through the door...

[tube80z]

I was going to do a jackpoint straight through the rocker with a plate on either end and a tube through the middle. How would you suggest incorporating a jack point into the tube above the rocker? Seems like the jack would have to go right through the door...

 

When you put in the tube between the cage legs I would add a tube underneath (say 5/8 ID) that allows you to slip in a remote jack point. You'll need to notch the rocker and you can then back this up with plates on the inside of the rocker to the tube and on top of the rocker. If this isn't clear I'll attempt some Cary CAD to make a visual version. Just an idea. I'm going to a go a little farther and do this at the ends too so I can put the car on stands with nothing under it very much like a rally car.

 

Cary

[JMortensen]

When you put in the tube between the cage legs I would add a tube underneath (say 5/8 ID) that allows you to slip in a remote jack point. You'll need to notch the rocker and you can then back this up with plates on the inside of the rocker to the tube and on top of the rocker. If this isn't clear I'll attempt some Cary CAD to make a visual version. Just an idea. I'm going to a go a little farther and do this at the ends too so I can put the car on stands with nothing under it very much like a rally car.

Someone here posted their setup which had a jack point at the front and the back of the rocker on each side (sorry, can't remember who you were) and I was thinking of doing the same thing you were, with the stands like a rally car. But then I was thinking about how often I really needed to get the car up on stands like that, and for the few times I replace a clutch or whatever I think I'll just jack it up and put it on regular old jack stands. I would very much like to have one jack point on each side so that I could make a ride height adjustment or change out a tire without having to go underneath the car to jack it up.

 

Are you sure you need to notch the rocker like you're describing? Seems to me this other guy just had plates on either end of the rocker panel and the tube welded through, and that was it. Seems like an easier install that way. I was thinking about 4" or 5" behind the last flanged hole in the rocker panel.

[tube80z]

I'm all about easy

[dj paul]

The guys at cc.com claim that I need a box to transfer the stress to the 24 gauge floor. You are apparently saying that there needs to be another bar tied in here. Why?

 

For the record the plan is to build a box under the end of this tube. With that done it will be tied vertically into the rocker and the floor and should be a hell of a lot stronger than tying it directly into the floor. I'm not putting any other tubes into the attachment point, although the X for the door bar should be relatively close to this point.

 

Sorry to not be clear. Im not saying there needs to be another bar here, that would be unnesassary to very little gain. Im talking about the shear horizontal load, i was in a hurry and didnt mean to word it like i did. the box you are talking about will do just fine, i was simply wondering if that portion of the cage had plans to change. By the way, the cage looks great if i didn't mention it before.