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Old 07-31-2010, 09:37 PM   #1
dpbgst13
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Have a few questions. I'm looking to build a cage in a 2002 wrx. Does anyone know the cost of buying tubing and building it yourself vs. buying a prebuild cage and welding it in.

Also what type of tubing do you use for the cage? Type? Thickness?
I will be using a MIG welder to build this cage.

Also is there a special bender or is an exhaust bender strong enough to bend the thicker metal?
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Old 08-01-2010, 11:34 AM   #2
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Originally Posted by dpbgst13;
I'm looking to build a cage in a 2002 wrx. Does anyone know the cost of buying tubing and building it yourself vs. buying a prebuild cage and welding it in.
It varies greatly. I've built a cage for as little as $550 for myself. A professionally built cage can cost $4500-$6500 or more however. You're paying mostly for the fabricator's labor and knowledge. Tubing can cost $3.00 to $7.00 per foot depending on your local supplier's costs and the specifications.

I usually figure 60-100 hours to build a cage, but then again I TIG weld all my joints which takes a lot longer than MIG. And the extensiveness of the cage makes all the difference in the world in terms of time and costs. I tend to add a lot of gussets and tie-ins, and my cage baseplates alone take me a day to fabricate.

Quote:
Also what type of tubing do you use for the cage? Type? Thickness?
I will be using a MIG welder to build this cage.
What sanctioning body's rules are you building the cage to? Rally America? NHRA? SCCA? NASA? It helps to know what you are trying to do with the car. A few racing organizations still allow chromoly tubing, but most specify DOM (Drawn Over Mandrel) or CDS (Cold Drawn Seamless) 1018/1020 mild steel tubing. I don't think anyone allows ERW (Electronic Resistance Welded) tubing any longer, except maybe for some local circle tracks.

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Also is there a special bender or is an exhaust bender strong enough to bend the thicker metal?
An exhaust tube bender will likely crush the tubing at the bends, unless it is a mandrel type bender, however it is physically capable of bending the tubing. This creates a weaker bend than a structural tubing bender or a mandrel bender, and won't pass tech due to deformation.

Bob
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Old 08-01-2010, 07:41 PM   #3
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if you want a tubing bender

takacs cycles sells a plan for one.. I built one for my senior project at welding school.. still gotta finish it up though...
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Old 08-15-2010, 09:24 PM   #4
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i used to build drag race cars... full tube chassis', we always used chromoly tubing all different sizes for different things, it ranged from .035-.095 if i remember correctly
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Old 08-16-2010, 07:38 AM   #5
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^^^

chromoly is pretty often not allowed for cages. It's too rigid, and it doesn't deform nicely. It tends to fail catastrophically.
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Old 08-17-2010, 03:50 PM   #6
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^^^^^***I used to build professional drag cars that were 3000 hp plus.... We ran a 6.14 at over 230 mph with our chassis'. All of our chassis' were nhra ihra certified, and they were all chromoly, chromoly is all that's used for us. You can get away with running very thin light tube and yet it's still WAY stronger then normal untreated mild steel, just my .02 cents, btw I am still very much involved in nhra and ihra stuff, including the welding of many of the race car parts and chromoly is still pretty much all that's used... The end lol
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Old 08-18-2010, 10:24 AM   #7
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^^^^^***I used to build professional drag cars that were 3000 hp plus.... We ran a 6.14 at over 230 mph with our chassis'. All of our chassis' were nhra ihra certified, and they were all chromoly, chromoly is all that's used for us. You can get away with running very thin light tube and yet it's still WAY stronger then normal untreated mild steel, just my .02 cents, btw I am still very much involved in nhra and ihra stuff, including the welding of many of the race car parts and chromoly is still pretty much all that's used... The end lol
I think Sniper's point is that with the exception of drag racing and some off-road racing, chromoly has been disallowed by almost all other race sanctioning bodies.

I don't deny that it is stronger and stiffer for a given dimension, however is it noticeably more prone to fracture when subjected to repeated stress and especially when incorrectly welded...please be aware I am in no way stepping on your toes here, but chromoly is not for a newbie welder/fabricator. It needs to be welded by an experienced professional (as you seem to be), not someone setting out to build their first rollcage.
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Old 08-18-2010, 11:59 AM   #8
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That could very well be true, I have always been involved in the drag racing side of things as well as off road not much road course stuff tho, it's somewhat new to me I guess you
could say, and you have a good point it's usually a good idea to be a very proficient welder before using chromoly or in my opinion building a cage period haha
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Old 08-18-2010, 03:34 PM   #9
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Yeah. Rally america, for example, explicitly outlaws chromoly cages with the exception of FIA homologated weld-in cages.
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Old 08-18-2010, 10:36 PM   #10
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Wow hmm Definitly didn't know that! That's good info, so what material is dominantly used in that case then?
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Old 08-18-2010, 11:07 PM   #11
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With talk of chrome-moly failing catastrophically in a crash, would this be at the welds principally? Because can't it be treated to a spring temper? (4130 treated to Rockwell C 35 hardness)
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Old 08-18-2010, 11:25 PM   #12
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It all depends on what you are trying to do. It you want a roll bar, with like a 6pt configuration for road racing and such you are looking at $200-300 in bar. It took 2 full sticks at $5 a foot to build mine. I opted out from adding the front bars and door bars now because I drive the car in the street. A roll cage can do more harm than good if you put one in and dint have on a helmet ALL the time. Sooo if you plan on street driving this at all, don't plan on having your helmet and 6pt strapped on all the time go roll bar, add a 5th or 6pt to it and you will still be plenty safe.

Now when I buy another car and this goes race only I'll add the front in. We left everything setup to add those parts.

As far as the rest goes a simple manual bender that you just pull the tube into form is all you need. That and a tig welder. Than you need some plate 6in X 6in to weld to the floor. That will work as your mounts. You will have to mig these in place, you can also bolt it or both. Next I think we used .120 wall black steel tube. It was heavier gauge than we needed for the weight of the car, but stronger is better and when we add on it will be rally spec. As far as time the bar only took 14hrs to build. I don't know where the one guy is saying 40-60hrs to tig it. We tiged 100% of mine except the main plates to the floor. I bet when we finish the the roof bars and front down tubes it will take another 14-20. So we will have maybe 30-35 total in it and 400ish in pipe and plate.

I hope some of this helps. I think 4 full sticks will work for ya if you are careful.
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Old 08-19-2010, 07:24 AM   #13
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I don't know where the one guy is saying 40-60hrs to tig it. We tiged 100% of mine except the main plates to the floor. I bet when we finish the the roof bars and front down tubes it will take another 14-20. So we will have maybe 30-35 total in it and 400ish in pipe and plate.
I wouldn't want to compare the time it takes to do a cage. I'd probably be more comfortable in a cage that took 60hrs to build than one that was only 35hrs..... Afterall, it's been proven time and time again, that the quality of the cage is only evident at the worst possible moment.

For the OP: Doing a cage is something best left to experienced eyes and hands. Yeah, you can't get experienced without doing it....but in the name of safey, seek out someone who has a good background in designing and building them to help....preferably, watch over each step so you don't have to remove and redo sections or have a failure when it counts the most.

Jay
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Old 08-19-2010, 09:15 AM   #14
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Originally Posted by Storm View Post
I wouldn't want to compare the time it takes to do a cage. I'd probably be more comfortable in a cage that took 60hrs to build than one that was only 35hrs..... Afterall, it's been proven time and time again, that the quality of the cage is only evident at the worst possible moment.

For the OP: Doing a cage is something best left to experienced eyes and hands. Yeah, you can't get experienced without doing it....but in the name of safey, seek out someone who has a good background in designing and building them to help....preferably, watch over each step so you don't have to remove and redo sections or have a failure when it counts the most.

Jay
Agreed. Cage design is a science, and the one time you need the cage to save your life, you don't want to end up paralyzed or dead because you didn't understand all the trade-offs involved in a proper design.

The cage needs to be designed to deform predictably and absorb the tremendous amount of energy involved in a crash. If it's too rigid, or welded in the wrong places, it will either fail catastrophically, or it will stay completely intact and kill the driver from internal injuries anyway, because it didn't absorb any of the energy from the crash.
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Old 08-19-2010, 10:11 AM   #15
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Quote:
Originally Posted by Storm View Post
I wouldn't want to compare the time it takes to do a cage. I'd probably be more comfortable in a cage that took 60hrs to build than one that was only 35hrs..... Afterall, it's been proven time and time again, that the quality of the cage is only evident at the worst possible moment.

For the OP: Doing a cage is something best left to experienced eyes and hands. Yeah, you can't get experienced without doing it....but in the name of safey, seek out someone who has a good background in designing and building them to help....preferably, watch over each step so you don't have to remove and redo sections or have a failure when it counts the most.

Jay

No I agree, but I just did not want to scare him if he had to pay someone labor to do it all. My cage too less time because we had 2 people working on it, one bending fitting parts and one welding parts in place as we went along. We have also built a few others and he is practically a machine at welding, worked for John Deere as a welder. So I guess it all depends on who is building it and how much skill you have. Biggest thing for us is EVERYTHING fit first try, so we did not have to keep going back to adjust bends, or lengths of things. That saved us many hours right there.

All and all I would say expect somewhere between 15hrs for just a basic roll bar all the way up to 90hrs if you go all out, cut the roof off, weld in all sorts of crazy gussets, etc. Just make sure your mounting surfaces are large enough and strong enough as I talked about. I have seen far too many cages just welded to the body, no reinforcement at all on unibody cars. Not so good.... it will pop right out the floor pan that way.

Last edited by RedefinedTR; 08-19-2010 at 10:17 AM.
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Old 08-19-2010, 10:53 AM   #16
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My cage too less time because we had 2 people working on it, one bending fitting parts and one welding parts in place as we went along.
Ummm, two people working on a car for 35 hours would be 70 billable hours at any shop I've ever seen. Just FYI....
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Old 08-19-2010, 11:21 AM   #17
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The OP should really decide on what sanctioning body he'll be building for first, then read up on those requirements, then check out other cages from that series to see what the general consensus is...take pictures. One doesn't have to reinvent the wheel in cage design, and if the fabrication skills are there....it's completely possible to do this yourself and still have a safe (and legal) car when finished.

My $.02 anyway.

Jay
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Old 08-19-2010, 11:50 AM   #18
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Ummm, two people working on a car for 35 hours would be 70 billable hours at any shop I've ever seen. Just FYI....
I guess you are right, I was not even thinking like that. Oh well. My buddy's shop in Dubuque did it, and I helped with all the bending and cutting. But he gave me such a good deal I kind of forget about the price it would normally cost.
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Old 08-19-2010, 09:29 PM   #19
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As said just need to decide the primary purpose of the car. If you are doing mostly drag then you can use 1 5/8" x.120 mild steel and mig all the joints/floor plates. If it is moly then you can mig wherever the moly meets mild steel but all other stuff is tig. We do a wide variety of fab work where i work. We have been doing a lot of road course stuff lately which has been DOM tubing.
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