cages
 

I've heard of poeple making their own roll cages, but it seems like they'd be weaker than one built for you, right? I mean shops go out and spend $$$ for these high tech tools to make bends and weld it all cleanly together.

Well I guess the question is has anyone made a cage and still turn out really nice?

The ones I've seen were made from the pipe benders at like harbor frieght and mig welded, is this even legal in some classes, or is it more so the construction and materials?

thanks
rip

Bolt-in roll cages are flexible; they do give you some extra crash protection but they do not stiffen the chassis and improve handling. A welded in cage is the only way to go if you want to stiffen your chassis and make it handle better.

Harbor Freight pipe bender + roll cage tubing = junk
It takes a tube bender, not a pipe bender, when you are working with roll cage tubing.

MIG welding is just fine on a properly prepared joint on mild steel DOM tubing.

The strength of a home made cage depends on your fabricating skills, your welding ability, and your structural engineering knowledge. It takes all three to design and make a good cage. Some people do possess all three skills, and they can make a good cage at home. If you are weak in any one of those three areas, and you don't get experienced help in your weak areas, then you will produce a poor cage.

Just judging by your post, I'm going to advise you have someone else do your cage.

yea, i wouldn't build the cage, but I might try finding a kit that just needs welding. I've been welding for awhile.

I would suggest useing 4130 cromoly for the material of the cage. stronger, lighter the DOM i would also TIG weld the cage together for sure. higher quality. If you can do it give Nick a call @ 805- 527-9899. hes a kool guy and he would be happy to help you out with any question you have. he owns a race fab shop.

Have someone build you a custom cage. Money well spent. You'll spend $4-600 (plus shipping) on a AP or similar cage and get a heavy, generic fit cage for your money.

Get pics or names of clients and inspect the companies cages in person if possible. Make sure they notch their joints and weld them 360 degrees. I've seen downbar joints that were filled over 1/2" with weld and I've seen big name shop cars w/o 360 welds.

MIG or TIG... 6 of one, half dozen of the other when we're talking DOM. Someone who knows what they're doing is the key. Actually, in my experiance very few tight cages can be 100% TIGed

Personally, I would take a DOM cage over a 4130 if I was going to be in a situation where I was going wheel to wheel. Yes, 4130 is stronger and lighter, but with that strength it also becomes more brittle. I'd rather have a cage bend then break. Drag race cage??? 4130 is a great option as the odds of a 3200 lb car going 60+ coming in the door to say hello is much less.

4130 is TIG only. Thoughts vary on whether you HAVE to normalize it or not since the wall thickness is so thin.

wow thanks for the help, I'm definatly going to do my homewrok on this one, time to start searching. Thanks again

rip

cages
 

i think izzys a little confused.....any quality shop will alway have the joints welded 360degrees weather they have to remove the roof of the car or not. and as far as tig and mig welding being 6 to one half a dozen the other.. do your homework!

No, there are a lot of shops that don't do 360 welds because they're half-assed or just stupid. I've seen my fair share of cars get kicked from tech because Cooter McDumbass didn't 'figger he needed to weld all the way around.

I'm not confused in the least, and I've done plenty of homework including destructive tests on my own work. With the tubing thickness that is used in a roll cage, a MIG weld can achieve as good a penetration as a TIG weld with the proper prep and technique.

I've personally seen cages from some very big name shops that were missing welds at the downbar to halo joint because it was a tough spot to get to.

Don't many sanctioning bodies stipulate that the cage MUST be DOM?

Obviously you have not done your homework. Izzy builds the nicest cages I have seen.

The original poster would serve himself well to ask Izzy as many questions as he can before making the incorrect decision.

-billy

It should also be mentioned that 4130 (aka Chromoly) weighs *exactly* the same as 1020 (aka mild steel), though it is much stronger. The weight savings only comes if you use a thinner-wall tubing, which gives you *comparable* strength for less weight. You really don't get both lighter and stronger; pick one. Also, be sure to read your rule book closely. Not sure if it's still the case, but SCCA moved away from permitting thinner-wall 4130, since so many people were lying (using thin-wall 1020 and saying it was 4130). You can still use 4130, but the cage would be way over-built and expensive. As I said, check the rule book to be sure you don't waste your money.

As opposed to ERW or Chromoly? AFAIK, all sanctioning bodies dissallowed ERW a few years ago, but NASA/SCCA still allow DOM or Chromoly.

Let's be careful here...DOM means Drawn Over Mandrel and is a kind of "seamless" tubing; it is not synonymous with Mild Steel (aka 1020 or similar variant). Chromoly may also be DOM construction. ERW is an electrically welded (seamed) tubing of whatever variety. So when someone says "Don't many sanctioning bodies stipulate that the cage MUST be DOM?" that is a question regarding *manufacturing* of the tubing; not the materials used (e.g. 1020 vs. 4130). The answer is yes, though I believe they refer to it as "seamless tubing" (I could be wrong...my rulebook is not at hand, right now). Perhaps "Raceruss" -- owner of Racetech Fabrication -- will chime in, though I know he doesn't come here that often.

Damn, I was enjoying lurking in the shadows. Blake is mostly correct, Most Sanctioning bodies do require DOM, or seamless.

DOM was a Electric Welded Tube with all weld flash removed. Tested for weld soundness, drawn over a mandrel and retested. This product is superior in finish and wall uniformity to seamless tubing Normally drawn OD and I.D. dimensions.

Definition from manufacturer
DOM tubing to ASTM Specification A513, types 5 and 6, using the Electric esistance
Welding (ERW) process. This process produces the highest weld strength possible.
Because it is cold-drawn after forming, DOM also offers a number of other advantages:
• The uniform wall thickness of DOM, with closer OD and ID tolerances,
provides maximum concentricity. • Thermal treatment prior to cold drawing
crystallizes the grain structure of the tubing and weld area, giving it a
uniform, controlled hardness. • Cold working gives DOM higher yield and tensile strength than aswelded product. Thermal treatment following drawing can give increased ductility when desired. • The OD and ID surfaces of DOM are cleaner, smoother and more dense than as-welded product. The reduction of the tube during cold drawing removes all dimensional evidence of the weld.
• DOM tubing can be manufactured to an almost infinite range of diameters
and walls by varying the sizes of the die and mandrel. This size range allows end users to achieve material savings and lower machining costs through selection of a size that matches the dimensions of the finished product.
• The tight tolerances, controlled mechanical properties and uniform,
dense surface of DOM all result in good machining characteristics".

This should answer everyones questions.

Blake is correct on the 4130. Same weight, so you can use thinner wall material.

I didn't realize that; thanks. I know little about cages and from what I had heard in the past I always equated DOM to mild steel.

DOM is mild steel, so you were correct.

4130 is not also produced seamlessly, using the DOM process? If not, how do they do it?

The SCCA used to group "DOM" and "Alloy Steel" seperately, although they now have more vague wording as if they heard the same thing but want to remain ambiguous (at least according to my .pdf GCR). I don't even remember what the NASA rule says.

It's probably because all 4130 is produced seamless, while only some mild steel is made that way. Saying DOM 4130 would almost be redundant. And, when talking about mild steel, people just specify ERW or DOM, taking the material for granted. At least, that's my theory. All I know is that ERW and DOM are processes; not materials. 4130 and 1020 (et al) are materials; not processes. Maybe they use some other means to make 4130 seamless (I thought it was DOM, but that's a guess), but it really doesn't matter. Russ grasps the vernacular better than anyone I know, so I will defer to whatever he says. Oh, yeah, he's my shop landlord, so that may also play a factor ;)

cagedruss
 

im impress cagedruss has some knowledge.. its nice to here some one not talking out of there brown eye.

Not only does Russ fabricate race cars professionally, I have it on good authority that he has personally rolled about 5 of his own cars -- back in the day, he used to do a lot of circle track...in an R100! :)

Nice to see that he can spell too. I'm curious redzone... exactly how many cages have you built and how long have you been welding?

izzy
 

about 45 cages, 4 chassis cars, and 7 years welding...