any roll cage suggestions

[abdul]

hello every body
i am thinking of changing my roll cage to a light weight full welded one
, i need it to be cut and ready for welding .

any suggestions please

[T-Rex]

My suggestion is to find a fabricator and have one custom made. Any pre bent, sectioned cage is not going to fit as tightly in the car, or allow for any variances that your chassis has. It will be more expensive but well worth it.

[abdul]

the problem I am having we don,t have one that do Chromoly roll cage !

[Def]

Just do it out of DOM tubing. I don't trust the torch+crayon method of post-weld heat treating chromoly, and it's impossible to get some joints unless you cut and drop the cage.

The weight savings for the same strength for 1020 DOM vs. 4130 chromoly is maybe 6-10 lbs for a full cage(depending on how much tubing you use), and a TON more work.

[veilside180sx]

Just do it out of DOM tubing. I don't trust the torch+crayon method of post-weld heat treating chromoly, and it's impossible to get some joints unless you cut and drop the cage.

The weight savings for the same strength for 1020 DOM vs. 4130 chromoly is maybe 6-10 lbs for a full cage(depending on how much tubing you use), and a TON more work.

2nd...not worth the extra effort for brittle tubing.

[Markku Kiviniemi]

I think that DOM 1020 is same tube what we have use at our cars. carbonsteel seamless. We had excel file where we count tube weight and if we have done chromoly gage save have been about 5kg and chromoly tube its really hard to weld+ its expencive. But what you are going to do, do its safe. If i crash i like to get out whit my own feets.

[Umai Kakudo]

MotoIQ.com has some good roll cage articles. They are also proponents of DOM tubing vs CroMo.

Scion Tc - http://www.motoiq.com/MagazineArticl...0/Default.aspx

B15 Racecar "Dog Car II" - http://www.motoiq.com/MagazineArticl...-V-Part-1.aspx

Z32 - http://www.motoiq.com/MagazineArticl...-Part-One.aspx

In steel terms DOM means drawn over mandrel. When DOM tubing is made, a flat sheet of steel is drawn into a tubular shape while cold over a mandrel and electrically seam welded to make a complete tube. This cold drawing makes the grain of the metal finer and gives it better mechanical properties. A cheaper form of mild steel tubing is called ERW which means electrical resistance welded. ERW tubing is hot rolled into tubular form and resistance welded. It does not get the grain refinement that cold worked tubes get and thus has worse mechanical properties. NASA, the racing sanctioning body we run with, does not allow ERW tubing for roll cages, another good reason to use DOM!

Although mild steel does not sound as exotic as the higher strength chrome moly steel, it has several advantages for a roll cage. Chrome moly is steel with a high percentage of chromium and molybdenum. These elements impart superior mechanical properties including a 40% higher tensile strength than mild steel. The heat from welding weakens chrome moly more than mild steel. Chrome molymust be post weld heat treated to retain the same level of strength in the heat affected zone of the welds. Chrome moly tends to be more brittle in the zones around the weld. Chrome moly is also less ductile and tends to crack when its limits are exceeded. Mild steel however is less affected by the heat of welding and is more malleable.

What this equates to is a cage that can deform, bend and absorb energy better in a serious crash while staying together and not cracking apart. You may hear contrary opinions by other highly qualified fabricators but we feel that for us, mild steel is safer. Many race sanctioning bodies feel the same way and sometimes chrome moly is not allowed by the rules, a good reason to check the rulebook first before starting on a project.

[img]http://www.motoiq.com/Portals/0/Magazine/Articles/Kojima/300ZXTT/part1/38.JPG[img]





The famous Kajoma Crash Attenuator

[2Fass240us]

I heart Mike. I talked to him (on the phone) several times and he is definitely good people.

[racepar1]

WOW, that 300zx cage is seriously overdone. There is no need for that many braces in such a small area. There's gotta be at least 25lbs of crap that could be removed there with little or no effect. And to think, I was worried about overdoing my cage as I plan to dimple die gusset the hell out of it. It's kind of amusing how small the dimple die holes in the gussets in those cages are though, it is almost pointless to have even bothered to punch those holes. The tubes running along the bottom of the door sill are an interesting idea though.

[Matt93SE]

WTF mang. that cage is waaaaay overkill in the back. not enough support in the doors, too much in the back. I'd hate to have to work on anything behind the driver's seat (i.e. where my battery and fire suppression system are...)

as for the gussets and dimples, how thick is that sheet metal? I learned after I got my cage done that bracing to the chassis is legal in my class, so I was going to do all that myself. just need to know how thick that steel should be so I can buy some and start cutting.

[racepar1]

as for the gussets and dimples, how thick is that sheet metal? I learned after I got my cage done that bracing to the chassis is legal in my class, so I was going to do all that myself. just need to know how thick that steel should be so I can buy some and start cutting.

The gussets do NOT need to be thick. You want to use about the same thickness sheetmetal as the roof. You will want to dimple die punch your gussets though. I plan to roll the edges of mine as well. The gusset's point is not to be very strong on it's own, just to basically take up the space between the substructure (cage) and the main structure (unibody) which increases the rigidity and strength of the enrire car greatly.

[Matt93SE]

Yeah, I didn't figure they would need to be that thick. They're all basically in tension and/or shear, not compression or torsion. you can pull pretty hard on a piece of sheetmetal in those directions.

So what's the roof metal made from 18ga? 20? I've never bought sheet metal by specs before- just chopped up scraps I had laying around for whatever.

I have a bunch of old wheel bearings and other things laying around I can use in my press to make dimples with.. that's easy enough.

[Def]

1/16"/16 Ga is sufficient for gussets. That's the thinnest I'd go, but can't see going thicker except in some very high stress areas(like corners etc.)

[Matt93SE]

coo. tanks. I'll have to pick some up from the local scrap yard. buddy of mine works there and I can get sheet metal for pretty much free. too bad they don't get DOM tubing.... (He says they do on a regular basis, but there's a custom bike shop on one end of the building that snipes all the good tube as soon as it comes in!)

[Def]

They use stuff like 1.75x0.095"? Kinda big for a bike.