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...

Hmm.. With the above statement insinuating that you could use 4130 and not TIG it... or TIG it only for better quality over MIG , I'm surprised by your resume.

I'll yield to your #'s as I haven't got that many under my belt, but I'll stand by every statement that I've made.

izzy
 

i would never MIG weld 4130 and i can only think of one of the cages that i have done that i mig welded. in that case the material was ERW.

I think everyone has strayed from the question. The real answer is get the rulebook for the sanctioning body you plan to race with(don't rely on fabricators to have all the rules, these guys build stuff for many different applications and can be expected to know all the rules). Use the materials and construction procedures required by the sanctioing body. If you don't understand what the rulebook is saying be sure to call or email the sanctiong body with your question. most are very helpful when contacted. All the techniques mentioned can and have been used with good results to build cages. as with alot of things there are many different ways to skin a cat. My personal suggestion: go to a couple events in your area with the sanctioning body you want to race with and talk with the local racers and ask who does there work, drop by the shops recommended, ask the shop some questions, and participate in the build. making sure you have proper clearances for helmets, window net mounts, steering wheel disconnects, seat mounts, and seat braces(if required). getting all the small stuff done right first will save you money down the road. if you want to do it yourself do the same thing only observe what some of the other racers have done to their cars to help give you a direction with your project. ask the shops what type of machinery they use. most racers are very proud of there cars and love to give all details including how they did it. go to the track and make some friends. good luck on your project

Tim, I agree with everything you said, except the part about not relying on the fabricators to know the rules. The good fabricators know the rules as good or better than the techs, though it are the techs who obviously have the last word. Anyway, the experienced fabricators have had their stuff scrutinized hundreds of times and know the nuances to the rules that can't be picked up by simply reading the lines; a lot of stuff is between the lines, owing to intent of or even a lack of clarity in the written rule. For example, until this year, there was the issue of minimum tube size when one or more tubes could not meet the bend requirements (e.g. a main hoop cannot have more than four bends, totalling 180 degrees). If you, say, put a peak in the center (fifth bend) or had to jog the tubes to conform to the body, or whatever, the rules said something about requiring the use of the tube spec'd for the next higher weight class (thicker wall or larger diameter). However, it was not totally clear if only the affected tube or the whole cage had to be upgraded. The fact of the matter was that the whole cage needed to be upgraded, but damned if I could find that definitively spelled out in the rule book in 2004! Russ, of course, was addament that it meant the whole cage. Low-and-behold, the 2005 GCR is very, very clear on this point, proving him right (...not that I doubted him). Russ also shows me a lot of work that comes into his shop that had been approved recently, despite obvious and very serious flaws...crimps in bends, poor welding, or just plain bad design. Not just old work from a more lax period that is grandfathered-in, but new stuff by back-yard cage fabricators (and even some "legitimate" shops) that got past the techs. Some of these examples include GT1 cars!

What I'm saying is, if you find a good, experienced fabricator, you may put your trust in them to guide you through satisfying the letter and spirit of the rules as well as to convince the techs of that fact. And, you can't rely entirely on the techs catching poor design or fabrication, so be wary of inexperienced or underskilled fabricators. Talking to the other racers, as you suggested, it a great way to find the people you can trust.

Russ, by the way, has hosted the Oregon Region SCCA annual tech day in his shop for the last few years, so you can understand that he is on a first name basis with the techs and often calls them about a particular project just to get clarification on a sticky point before a tube is bent. That is the kind of fabricator you should look for in your area. Ask to see their GCR (or whatever applicable rule book for you form of racing and sanctioning body) before hiring them. Even the 2005 copies should be dog-eared and dirty with fingerprints by now, probabaly with a bunch of notes in the margins. They should also be able to refer you to many of their customers so you can go check out their cars at the track and ask them questions about the experience. In Russ's case, that would be almost the entire front half of the regional Spec miata grid, just for starters.

that is is great that your area has a top notch fabricator that is heavily involved with the SCCA, but what if I needed a cage and some work done for and NHRA car or NASA, the rules are not always the same? Some areas have great fabricators and welders that can build most anything, but they specialise in one area and this might not be the area you intend to race in. Do your own homework and if parts of the rulebook are unclear, such as the roll cage bend specs, contact the sanctioning body. What if the fabricator is wrong? will he redo the work to make it right for free? doubtful. I am glad you have someone you can trust and it looks like the guy stays on top of stuff, but others may be to busy to read up on the rule changes. just make sure you do it right the first time it will save you alot of money.

Blake is almost embarrassing me, but I do appreciate the accolades. I am currently working on 3 projects in the shop now. (1) SCCA Prod. Alfa Romeo, (2) NHRA 9 second Supra, and a (3) 69 Camaro Street Touring Mini Tub Project. I have been to a lot of Shops in the country and most fabricators I have met have with a broad range of experience. Most shops need to be open mined in doing more than one type of cage. Shops go through busy and slow periods in a year like other business do, versatility is a must .

If you are needing a cage done or race car fabricating work, check out the local tracks, asked around and get some recommendations from other car owners and the tech's. Find the shops, asked for customer recommendations from the type of class you are interested in. See if the shop will guarantee the work to pass Tech. Look at pictures of past projects or see what the shop is working on at that time. Don't be to discouraged about a bad reference from somebody about a past project, most fabricators get better with time, and you simply can't make everyone happy.

I have see some awesome Road course cages fabricated by stock car shops and vice versa. Look for well thought out designs and try to keep away from exotic bends, gets the techs nervous, And each tech is different in his or hers evaluation or interpretations of the rules.

Russ

Exactly. That's why I specified "good" and "experienced" fabricators; not Joe Blow Fabricator who just hangs out a shingle. Finding them is the trick, so you have to do the networking at the track with other people who have been through the same experience. Certainly some good fabricators specialize to the point they couldn't help you outside their expertise, but they will tell you up front and be able to refer you to someone who is qualified...and a peer referral even better than a customer referral, as it would be based on a larger reputation; not just one job.