|01-19-2011 03:25 PM|
Sorry, pulling it through a mandrel does not change the molecular structure, it just changes the shape. It's not near hot enough. It becomes more rounder and more uniform - much more accurate and consistent, - good for hydraulic systems using a piston etc. The process of pulling and twisting through the mandrel work hardens it. It's much the same as bending it.
Hammering, squashing, folding it doesn't change anything on the molecular level either.
DOM is much harder to bend - that why it's often used for tie rods, control arms etc. But it also tends to shatter.
To prove or disprove it, simply put a piece of it in acid for a few minutes. The stress cracks become obvious - you can see the spirals where it was turned and pulled and all the tiny cracks around it.
Now bend it - - you are bending an already work hardened material - those stress cracks get bigger and lots more of them. It's not unlike bending a steel wire - then re-bending it at the same place. It becomes weak. The first bend is like the mandrel does to the tube, then the 2nd bend is harder to do since it's work hardened, and after the 2nd bend it becomes very brittle. A third or 4th bend it may even break. Try it!
Now weld it - even more cracks.
Put it in a press and you can break it.
It's so simple - use pool acid (Hydrochloric) or even Sulfuric acid.
To get rid of the stress cracks it must be heated then properly cooled - best to leave that to the heat treating boys. You aren't going to do that to a weld-in cage.
I've done it, and I've seen it. Talk to a metallurgical engineer about it.
I don't know about anyone else, but I sure wouldn't want to depend on something that's already pre-broken.
There are lots of opinions about DOM vs ERW - racing associations rules are often very different from each other. Many are based on wives's tales.
For example - most of them won't accept aluminum - yet when I owned part of Don's Chassis we specialized in Formula I race car chassis - that was all we did. Our world famous chassis' were all made of aluminum and carbon fiber. We had about 12 "engineers" working for us. Most specialized in the actual design of the structure, but 2 were metallurgical guys. By most racing clubs rules they would not be acceptable.
Welding itself even on ERW is a problem too. If it cools too slowly it becomes soft - annealed. To fast it gets hard and brittle. Try cooling a hot weld with CO2 gas or Freon - way too fast - it's easy to shatter, but it's so hard a regular hacksaw has trouble cutting it. Keep it warm with a torch and let it cool slowly, it stays soft and malleable. Try it!
But - proper design, triangulation, gusseting etc - is super important. Probably more important than the material itself - within reason. No, spaghetti won't work.
|01-19-2011 02:12 PM|
But, I do agree with you that no matter what cage is used, anything is better than the stock set up. The picture of the Jeep that rolled down hell's pass and held up is impressive.
|01-19-2011 01:57 PM|
|01-19-2011 01:25 PM|
The strength needed depends on how you roll it. I've seen stock cages work pretty well - yes the windshield folds down partway, but the occupants are still OK. The rig looks bad afterwards, but it worked. But again, it's how hard you roll it and how it impacts.
No cage is going to last through a 200 foot drop on it's top. The stock cage holds well in a mild easy rollover. Anything that increases the strength is going to help out.
The OR fab helps keep the windshield from folding in - the floor supports also will help it.
They bolt right in easy. There's no reason you cannot enhance it by welding the connections, or adding a cross bar along the windshield top, and or another bar along the dash. Those are easy mods after it's installed.
The side bars that connect from the hoop to the windshield can be enhanced simply by slipping a hunk of tube inside them. I think it takes a 1.5" tube. Welding isn't even necessary to do that.
As far as the material goes ERW is my choice. It welds decent without making many stress cracks. DOM is exactly the same steel, (it's made from ERW tube,) but it's been work hardened by pulling it through the mandrel. That's why it seems harder. It already has stress cracks from the drawing process. When you bend it you make even more stress cracks, inviting failure. Welding also make more cracks - failure points, unless it's been heat treated after.
CM tube needs to be Tig welded, even then it takes a very skilled welder to not create stress cracks.
I always use a stub inside a tube connection - if I'm using 1.75 x .120 tube, I slip a short piece of 1.5 inside at the connection - it's a slip fit inside. Then when welding it allows higher heat and keeps oxygen off the backside for more and better penetration. You can turn the heat way up! It also keeps the connection from being totally weld dependent.
The design, welds, and gusseting is the most important thing.
Get an aftermarket rollbar or cage from a wrecking yard - cut across the welds - it's downright scary the way they don't get decent penetration.
Welding is NOT dribbling metal on a seam - welding IS heating the base metals enough so they flow together to become one. The filler is just to add a little material to fill the voids.
Cut across their welds, then dip the cut in acid - you'll see how little they penetrated the steel. It's no wonder they are afraid of lawsuits!
If a company claimed a cage or bar was designed to withstand rollovers, they would be wide open for lawsuits. Some will not say it on the phone, some will. Ask for it in writing - you'll never get it.
Be careful when buying a Jeep with a cage already installed. I talked to a guy at a coffee shop that just bought a very pretty CJ with lots of goodies on it. He was bringing it home on a trailer.
As we were talking I leaned against the cage - it moved! The Previous owner had made the cage from PVC pipe then covered it with foam! It looked good, but it would have been a killer!
I was at the Hammers when a guy rolled his CJ. He'd been playing on the dry lake doing donuts. He had the typical store-bought hoop and side braces onto the rear wheelwells. When he tumbled it the left rear brace's weld broke off the hoop, the brace's end went through the back of his seat and through his chest - sticking out his front! He was still alive!
The Life Flight Helicopter came to get him - we had to cut the brace and leave the piece in him - else he'd bleed to death. I heard he recovered - amazing!
No matter what you put in or enhnce what you have, it will make it safer than nothing.
And - think about it - a toolbox or jack flying around is just as deadly as the top crushing you - maybe more so. Lash everything down!
|01-19-2011 12:21 PM|
Each clamp uses 1/2" thick and 6 - 5/16x24 socket head cap screws to secure one piece to another.
The weakest part of a Rock Hard cage is the welds between the DOM tubing and the clamp. Not the clamp and exsisting cage.
|01-19-2011 12:13 PM|
|01-19-2011 12:11 PM|
|01-19-2011 12:08 PM|
|SABATY||when all else fails find a good fabracator and have them make a cage out of 2in diameter cromoly tubing and then your set|
|01-19-2011 11:58 AM|
|DevilDogDoc||Precisely so if neither are rated how much difference is there? I looked on the ORF page and saw nothing of the materiel used either.|
|01-19-2011 11:39 AM|
Hint: You will NEVER find one. "Rating" something like this a multi-million dollar lawsuit waiting to happen. And there would need to be a standard "rating" system or classification system in place...there isn't one...for the same lawyer reason.
|01-19-2011 11:16 AM|
|01-19-2011 11:05 AM|
|01-19-2011 11:00 AM|
|Schmo||If you want to go with a bolt in, check out RockHard . . . they seem to be the most popular when it comes to the bolt in version . . . not cheap, but I've seen some videos of some pretty nasty roll overs where they held up well. Be sure to add on the extra pieces that go down thru the floor . . . they also sell frame tie-ins that can be added for even more strength.|
|01-19-2011 10:52 AM|
If you watch that video, you can see that thing rolling down Hell's Gate twice and then landing upside down. Pretty brutal.
Having seen the bolt on cage withstand that, I would still say a welded cage is superior. But apparently, your "cheap" bolt on cage isn't exactly a porcelain teapot.
|01-19-2011 10:47 AM|
I also have the OR-FAB cage and like Devil Dog Doc mentioned, there is evidence that it will provide some protection.
This is the Jeep in Stu's website:
The rest of the pictures and a video of the roll can be found here.
TBT Sports Bar Rollover
|01-19-2011 10:34 AM|
|dan188||I did a LOT of research on this when I was looking into a cage for my TJ. I called or-fab and the first thing out of the guys mouth was "this is a sport cage. Not meant for a roll over"... WTF, why would I want it then? Also, I'm not trying to talk down on the bolt-in cages, but they don't use DOM (drawn over mandrel) tubing. They use HREW (hot rolled electric welded) tubing which is less strong than DOM... Poison Spyder makes a really nice trail cage, made of DOM, designed to give you an A-pillar support, cross windshield support, and across the dashboard support. The whole kit is 8 pieces and something like $500. You have to weld it in, but it is all cut to fit and it IS rated for roll overs.|
|01-19-2011 10:15 AM|
|DevilDogDoc||I have the ORF front cage, bolted up easy had no issues with install. Stu Olson had a review with pics on his site of a lady who flopped it on a trail and it held up fine. Just my 2 cents!!|
|01-19-2011 09:59 AM|
I've seen two different MORE bolt in cages take pretty violent rolls in Moab and hold up beautifully. One of them tweaked a couple bars, but the driver was totally unharmed. The other cage wasn't damaged at all. Both cages had frame tie-ins. Don't think that bolt in means it can't take a hit.
That said, personally I like the A-Z fab cage. But only because it has a cleaner install.
|01-18-2011 06:49 PM|
|01-18-2011 06:43 PM|
|cavediverjc||Check with any local circle track racers. It's big in Kansas, so there's a circle track racer on every block it seems. Find out who welds their chassis. Around here, full caged chassis for certain race classes have to be certified (I have no idea what is entailed in getting certified, I don't circle track), so you know the guys welding them have to be good. I've got a local chassis fabricator here who is supposed to be doing some cage work for me when he gets around to it. It was supposed to be sometime this winter, but it might end up being sometime this spring. Either way, I feel comfortable having a guy with that kind of experience weld up my cage. Just check around your area for a racer, strike up a conversation and find out who does his rollcage work.|
|01-18-2011 04:02 PM|
You can get a weld in sport cage kit from A to Z Fabrication for under $500.
They are about a 5 hour drive from MD if you want them to install it. Give Zach a call.
|01-18-2011 03:53 PM|
|TJe0454||anyone fab or know any good places to get a cage welded up? PM me please!|
|01-18-2011 03:35 PM|
|UnlimitedLJ04||weld the cage in.|
|01-18-2011 02:46 PM|
|TJe0454||i wasnt planning on spending more than 500 really. so looks like itll be on the backburner till i can afford it!|
|01-18-2011 02:15 PM|
|jimmy-90||Having a shop bend and weld up a competition rated cage might not be alot more expensive than one that you order out of a catolog after shipping. It depends on how many bars you have them add to it. A basic cage is usually about $1000 or so and then 30 or 40$ for each additional bar. Find a shop that specializes in rollcages and get them to give you a quote and then compare that to the price of a bolt in after shipping. It may cost a couple hundred more dollars but If I pulled out in front of a tractor trailer or something I would definately want a welded cage.|
|01-18-2011 01:50 PM|
|bobjenkins||Bolt holes weaken pipes a lot its the cheap way out|
|01-18-2011 01:47 PM|
|derekshep||i would have someone weld in a cage, i would never use just a bolt in.|
|01-18-2011 01:46 PM|
|TJe0454||i dont do any serious wheeling where i would be prone to rolling, i want it more for street rollover protection especially because of the weaknesses in the windshield area.|
|01-18-2011 11:53 AM|
|01-18-2011 11:51 AM|
If you wheel, don't go cheap. Especially on something that could save your life.
Look at Genright.
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