SC400 Lightweight Roll Cage material??

[spf_lexus]

I just spent a solid day brush wheeling my entire interior to bare metal. Before I spray everything black I want to install a rollover hoop just behind the front seats with 2 straight return bars running from the top of the hoop, straight thru the rear deck, onto the rear trunk frame rails.


Whats the most light weight material I should use that still has good rigidity? Chromolly? Mild steel? Aluminum?

What size wall should I be shooting for? 120 wall? 90 wall?


I want to keep weight down as much as possible and cost isnt a major concern because im only planning to run the hoop and 2 straight bars. I have a local shop that can mandrel bend the hoop, and my neighbor will let me use his lincoln electric for the weekend so it just comes down to a material decision. I think im looking at around 25 feet total for all 3 bars. I installed a full cage into my 99 tacoma years and years ago and weight wasnt an issue. I used 120 wall mild steel all over and man was it heavy stuff.

 

[spf_lexus]

Oh yeah, whats a better size? 1.5" or 1.75"? Should I be looking at ID or OD?

 

[stevieg]

For the weight of an ls400 I'd go with 1.75" 0.120wall DOM tubing, you need to TIG weld chromoly. No need for mandrel bent tubes as long as it's a good quality tubing bender with the correct bending dies

Steve

 

[spf_lexus]

Its actually going in my 3100lb sc400. Can I get away with a smaller wall than .120? Also, how much weight per foot would a 1.5-1.75" DOM tubing cost me?

 

[stevieg]

For most sanctioning bodies .120 wall Dom is required for vehicles over 3200lbs (with driver) as well as a straight hoop provides zero protection without an accompanying diagonal brace as well. For a fully built car like yours your best bet is to do a full 6point that's either scca or nhra, their specs are pretty much bare minimum safety wise and are designed to triangulate and disperse the energy around the occupants

Steve

 

[spf_lexus]

Ok that sounds like I should stick with the 120. Now is there any wiggle room weight wise? I dont know much about the common types of metal used for cages. I am planning the main hoop with 2 return bars. I need this half cage (if you want to call it that) for chassis stiffening, and to mount harnesses. I would like to keep the complexity to a bare minimum. If I decided to just go with generic 120 mild steel, would I be adding unneccesary weight?

 

[XR8tt]

Are you going to drop main loop through the floor to weld top section ??
Just doing a cage now in Celica with mild steel..
It sure tightens body stiffness !!!

 

[spf_lexus]

Are you going to drop main loop through the floor to weld top section ??
Just doing a cage now in Celica with mild steel..
It sure tightens body stiffness !!!

Through the floor? i think i'll take the headliner out to keep the fire hazard to a minimum but I am hoping to leave a 1/2"-1" gap between the sunroof and the top of the hoop. I never considered the welds up top but your right, if I get carried away with fitment I could have a big issue with the return bars.

Can you give an idea of how heavy the main hoop is for your celica? I think my curb weight is very close to a celica with my weight loss so im curious to find out what size wall, OD, and the hoops'-weight for this cage. Im sorta pissed because I have 100 feet of 120. wall mild steel in 2" (which is a little too big) sitting in storage.

 

[XR8tt]

NOT familiar with correct sizing ..
We used ..
2.9mm X 41.3 mm [1 5/8]

Side and cross bar 1.9mm X 31.8... [1 1/4] in mild steel...
As per rules down under..

 

[Spinnetti]

Feedback is good... .120 dom 1.75.. Don't run your rear stays to the frame rails past the rear shock towers - makes them too long, and don't do much for stiffening. Run them to the base of the shock towers and tie them in to the towers, or with plates mount directly to the top of the shock towers. Def. Need a diagonal brace in the main hoop too. Typically as stated, you use a hole saw, cut holes in the floor, drop the hoop down to get 360 degree welds. The tighter the cage is to the unibody, the better job it will do - ideally you would tie it (i.e. weld it with tabs) to the roof rails too.

 

[spf_lexus]

Thanks for the ideas spinetti, much appreciated. Your tip on running the return bars to the shock mounts makes sense. I plan on running them to the wheel well arches, an inch from the shock mount w/ a steel plate in between for support. As far as welding the top of te hoop, are you sure I wont have any access up top? I have a massive folder of supra/sc300/400 roll cage builds and most of them have an inch or 2 between the top of hoop to the bottom of sunroof. I know exactly where I plan to run the bar thru the rear deck and on paper, I should have room for the top welds. I mean, the return bars come off the hoop on a 45 degree angle so its not like I need to flushly weld the bar parallel to the roof but I get where your coming from. I do plan to place the sides of my hoop very close to the sides of the cab so I can run gusset plates for added strangth. I also need to mount 3" harnesses so I also plan to run a cross bar horizontally across at shoulder level, with an added 4" depth before it corsses so I can still recline the seats a bit. I need to include some comfort just because its daily driven ride and driven 1/2 way across the country 3-4 times a year.

 

[spf_lexus]

Ok so I just re-read all the replies again and I guess I can mock everything up, tack the return braces in place, and THEN drop the floor and fully weld before actually welding to the chassis?

 

[stevieg]

If it's a daily driven car I highly recommend against a roll-cage, I have a buddy who got t-boned in his fully caged Miata. He now has a 6" scar across the side of his forehead and down the side of his head (yes the cage was padded) cages are designed to be part of the safety system not all of it. Hence a 5point harness, helmet and nowadays a HANS device. A production car is designed to have crumple zones to shed off velocity in a slow and controlled manner during an impact. Rollcages ar designed to direct force around the driver and not reduce it in any way by crumpling. If you are not properly restrained you will be travelling at a much greater speed and you become the crumple zone along with your head that is only inches from that roll cage.

For me it's an all or nothing. FYI my buddy was wearing a full 5point harness and was only missing the helmet so it could have been a lot worse but looking at the damage on the car it wasnt a very big impact and if he hadn't had the cage he would've walked away without a scratch

Steve

 

[spf_lexus]

If it's a daily driven car I highly recommend against a roll-cage, I have a buddy who got t-boned in his fully caged Miata. He now has a 6" scar across the side of his forehead and down the side of his head (yes the cage was padded) cages are designed to be part of the safety system not all of it. Hence a 5point harness, helmet and nowadays a HANS device. A production car is designed to have crumple zones to shed off velocity in a slow and controlled manner during an impact. Rollcages ar designed to direct force around the driver and not reduce it in any way by crumpling. If you are not properly restrained you will be travelling at a much greater speed and you become the crumple zone along with your head that is only inches from that roll cage.

Thats the biggest reason why I do NOT plan to run any bars that I can smack into. I dont want any bars that run parallel, above or in front of me. This cage work is mostly for chassis stiffening and harness support. To keep it basic, 1 hoop, 2 rear shock return, 1 horizontal harness bar and maybe a horizontal floor bar. Also, when im in CA, if the cops spot a cage, its almost an instant pullover. Its not like its illigal to run a cage but profiling might as well make it illigal because I dont run emissiojn controls and the cage could be an easy way for cops to spot my illigal mods.

I have flipped a stock sc300 pretty bad with the car landing on the roof and bouncing again and the roof never caved and I was travelling at 90mph at the time of the accident. It would be nice to have a full 10 point, but its just not feasible for my application.

 

[Spinnetti]

Thats the biggest reason why I do NOT plan to run any bars that I can smack into. I dont want any bars that run parallel, above or in front of me. This cage work is mostly for chassis stiffening and harness support. To keep it basic, 1 hoop, 2 rear shock return, 1 horizontal harness bar and maybe a horizontal floor bar. Also, when im in CA, if the cops spot a cage, its almost an instant pullover. Its not like its illigal to run a cage but profiling might as well make it illigal because I dont run emissiojn controls and the cage could be an easy way for cops to spot my illigal mods.

I have flipped a stock sc300 pretty bad with the car landing on the roof and bouncing again and the roof never caved and I was travelling at 90mph at the time of the accident. It would be nice to have a full 10 point, but its just not feasible for my application.

Hmm.. Lots of good dialog here... I did a test spin around my 'hood in my "real" race car (full road race AE86), and I jabbed the gas, it got sideways instantly and I racked my head on the cage - OW! lol.... I just laughed at myself. After understanding your intended use, do you really need a roll bar? This chassis is pretty good as is... I'm putting a full cage in my LS, but its a race car.. prolly not worth it for a street car; you can't put enough load on street tires to get it to flex anyway I bet.... If just for fun, then as long as its all behind you, you can build it however looks best

 

[spf_lexus]

hehe I hear ya, this car is sort of a mad max machine. I picked it up for $1300 w/ salvage title and almost no interior. I will never put the interior back in and I never use the space behind the seat as well as the trunk (only long trips) so I guess you could say its expendable space? I am also planning to swap blowers from my LS this winter so the chassis will be dealing with another 100-150hp. I also have beein sitting on 50 some feet of clean 120wall mild steel in I want to say 1 and 3/4" (i think) so the material is free. I bought it for a bed cage for a 1999 tacoma project that never happened. It could be argued that its extra weight, but it will stiffen the back end and it will compliment the gains when I closed cell poly foam the rest of the chassis. Both of these mods will really stiffen this chassis up and with my current materials shouldn't cost more than a couple hundred. I attend an automotive college so this car is always being experimented with. Thanks for your help Spinetti, Stevieg and Xr8, your input helped a lot. I always seem to be working on something, I was brought up in a populated suburban environment where I was constantly involved with something and out here, its a small town, small population, and small potatoes as far as anything exciting so I keep myself going with this car and my local track.

 

[Spinnetti]

hehe I hear ya, this car is sort of a mad max machine. I picked it up for $1300 w/ salvage title and almost no interior. I will never put the interior back in and I never use the space behind the seat as well as the trunk (only long trips) so I guess you could say its expendable space? I am also planning to swap blowers from my LS this winter so the chassis will be dealing with another 100-150hp. I also have beein sitting on 50 some feet of clean 120wall mild steel in I want to say 1 and 3/4" (i think) so the material is free. I bought it for a bed cage for a 1999 tacoma project that never happened. It could be argued that its extra weight, but it will stiffen the back end and it will compliment the gains when I closed cell poly foam the rest of the chassis. Both of these mods will really stiffen this chassis up and with my current materials shouldn't cost more than a couple hundred. I attend an automotive college so this car is always being experimented with. Thanks for your help Spinetti, Stevieg and Xr8, your input helped a lot. I always seem to be working on something, I was brought up in a populated suburban environment where I was constantly involved with something and out here, its a small town, small population, and small potatoes as far as anything exciting so I keep myself going with this car and my local track.

Lol.. Rock on bud... My stuff is the eyesore of the neighborhood! I don't have the cage in yet, but here's the LS track beast (for 24 hrs of Lemons). I have vid up too...

Maybe this vid link will work...
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[spf_lexus]

I love it, I bet your LS is the only luxury brand at the 24hrs of lemons race? It may be an old car but it wont let you down when your beating the crap out of it. Great choice for your event, I would be very surprised if anything failed on it! So I must ask... how much weight do you think has been ripped out of it? The glass alone has got to be a few hundred. When does your event start?

I will start putting my rear cage together in about 6 weeks. I need to finish this semester off before i will be back in CA.

 

[Spinnetti]

I love it, I bet your LS is the only luxury brand at the 24hrs of lemons race? It may be an old car but it wont let you down when your beating the crap out of it. Great choice for your event, I would be very surprised if anything failed on it! So I must ask... how much weight do you think has been ripped out of it? The glass alone has got to be a few hundred. When does your event start?

I will start putting my rear cage together in about 6 weeks. I need to finish this semester off before i will be back in CA.

I promise to get in on the scales after the cage is done. I'm dying to know too. I'd like to hit 3,000# with the cage in it, but maybe just dreaming. I gutted the doors, and even gutted the underside of the trunk lid, removed the hinges and latch.. just bolted it to the body. I got rid of the a/c, one of the idler pulleys, the clutch fan, front bumper reinforcement etc.... lots of stuff tossed out... Battery is in the passenger side rear seat. Handles awesome. Plan to race it next year, maybe in May in South Carolina..

This link should work better for the video... http://img704.imageshack.us/img704/1319/file2604.mp4

 

[Spinnetti]

I know, another oldie, but thought you might like to see the finished cage....