Ft of tube for a cage?

[Mcstiff]

Looking to make a family like cage an I'm trying to figure out how much tube to get. Anybody make one for a 2 dr?

Tired of waiting for PUV;)

~Ed

[FatXJ]

I was just about to ask the same thing!

I was going to build mine as an 8 point with lots of reinforcement (triangulation). So how much do I need? I had planned on about 140' being enough.I am also building a prerunner style winch bumper for my new winch so that's an estimated 16' of tube.

Also I have been doing some research on DOM vs HREW and it looks like 1.5"x .109wall DOM is what the FIA requires for their rollcages so I am assuming that 1.75"x.120 wall HREW will be just about as strong/suitable?

[Rev Den]

1.75 x .120 DOM

JMHO


Rev

[Beezil]

Hard question to answer without getting an idea of what your design looks like....

can you describe?

what bender are you using?

there's a little step you can do right in the beginning to reduce mistakes in bending........you might have done it already.......

start with a 24" tube, mark the middle of the tube (12" from either end) alighn the mark with some point on your bender, usually on the "output" side of your die, and make a 20 degree bend, and in a sketchbook or something, demension the tube and write it down so you can predict how the tube stretches during bending.....re-insert the tube the same way in the bender and keep bending the tube, stopping now and again (30* 45* 60*) sketching and demensioning the tube each time until you get to 90 degrees.......place the "L" tube on the inside of a framing square. you will see that one leg will have grown, and the other leg will have shrunken......mark these dims down in your sketchbook, and you'll be able to "predict" the finished dim of any tube you bend, so you don't need to waste tube making mistakes, or bending longer lengths of tube and re-cutting. Its pretty cool to know exactly how long your un-bent tube should be, where to bend it, so you have EXACTLY the right finished lengths on either leg of the bend.

[Loose_Nuts_Enterprises]

I've got the Bendtech 2.0 program. It works great, no wasted tube at all, but you need to know your exact dimensions and angles. Here's a link to a good method that I have had sucess with as well.

bending 101 (http://www.pirate4x4.com/tech/bendin_tube/index.html)

Happy bending. But how are you gonna get beezil's mom to doyour welding?

Dan

[Beezil]

great link dan, I forgot about that one!

[XJZ]

Hey Rev, Beez or any other knowledgable soul;

Would it be a good idea to do the main structure (the hoops, etc) with the heavier wall tube and go with lighter wall tube in some of the secondary/reinforcing area's in an effort to keep the weight down? Or would the weight loss be so insignificant that it's not worth the effort?

What wall thickness would you recommend for the thinner?

[FarmerMatt]

How much you use depends on your design. Figure out where you want to place your bars & measure each length where the bars will be placed. Add it all up & you have how much tubing you need.

Matt

[Rev Den]

1st....I am NOT qualified (thanks anyway) to be mentioned in the same sentence as Beezil on this subject.

Now....I used 1.75 x .120 DOM for all main tubes, except 2 x .120 for the B hoop (Rusty), and 1 x .120 for gussets. I did this following advice off this board by those who know better than me...and thats just about everyone.

Do a search for Roll Cage and see what comes up, also look at Beezil's rig.

Rev

[Beezil]

Like farmer says, its all in your design....

there are plenty of cages made from .188 2" out there, that are weaker than some made from 1.5 dia .090 wall......

design and geometry are primary.

choose your materials based on the design......

on mine, i chose .120 throughout, and used a combination of 1.5 and 1.75 dia DOM tubing.....

[Goatman]

There's no way for us to tell you how much tube to buy, you need to design your cage, measure, and calculate how much tube to buy. For my cage and rear bumper, I used 200', mostly 1.5" with some 1.75", all .120 wall.

As far as DOM or HREW, it's up to the builder. There is no question that a cage built from DOM is going to be stronger than one built from HREW, if the designs are similar. I built mine with HREW, which the local race car fab shops and metal suppliers just call rollbar tubing. I'm not planning to roll, or hit a wall, at 100+ mph, so I figure that the HREW will do me just fine. The design and the quality of the welds are the most important thing.

I hope I never have to find out how well mine is built, and how good my welds are. :D

[RCP Phx]

The bottom line here is first decide what your trying to protect yourself from.Then do your design work(the most critical) and then base your materials on that and any weight concerns.Ive been building/designing chassis since the late 70's.The newest trends are all chromoly using minimum wall thickness.General rule is that form is the most critical,after that weight.In the order of HREW,DOM,and Chromoly you can generally reduce the wall thickness by one size!

[Loose_Nuts_Enterprises]

In the SCORE rule book, it says you can use 1.5" HREW .120 wall for vehicles 3000lbs and under. Any heavier, you have to step up to 1.75" .120 wall, or 1.5" 1.20 wall cromoly. These specs are to keep a driver alive after a crash in the desert at 100+ mph. If it's designed well the HREW shouldn't be a problem even with the 1.5" variety. My jeep won't even go that fast anyway, LOL.
Food for thought...

Dan

[Mcstiff]

Of course you guy's cannot tell me how much tube to buy. I was looking to hear how much others used. I may have a hook up for 150' of HREW (1.5od .098 wall) I do not have a finalized design or a bender yet. Just tryign to think ahead and save some cash.

[Beezil]

In the SCORE rule book, it says you can use 1.5" HREW .120 wall for vehicles 3000lbs and under

Hey Dan, I'm certainly not trying to bust on you at all, you always bring up great points, and I don't like to snag a quote, especially if its out of context, but you reminded me about a point I feel i need to make.....


JEEPS ARE NOT RACECARS! Jeep rollcages must not be designed merely by following racecar design philosophies, or rules and especially material specs!

Sure, there are many many many similar qualities to pay attention to, and much can be learned, however, one must understand the differences in the energies put on a cage during a hard roll in order to design a JEEP cage adequately. Race cars cages *generally speaking* are designed to RESIST/ABSORB energy in a fore-aft highspeed impact and offer a good amount of protection in a side-impact senario. They are desgined with a certain geometriccal form and triangulated as such......

IMHO, Jeep cages must be designed for a variety of energies, such as tumbling, rolling, pitch polling in all axisis, and must resist collapse in the vertical axis. Your design will reflect this, and while some parts of tha cage will be constructed similarly to a racecar cage, other areas will need a different kind of approach.

The challenge is to design a cage that offers the most protection being careful not to get too carried away so that you do not make your jeep top heavy. It would be ridiculously ironic to build a cage and have it be just the thing that causes you to go turtle.

[rixXJphx]

Originally posted by Mcstiff
Of course you guy's cannot tell me how much tube to buy. I was looking to hear how much others used. I may have a hook up for 150' of HREW (1.5od .098 wall) I do not have a finalized design or a bender yet. Just tryign to think ahead and save some cash.
Seems like all the previous advice recommends AGAINST anything thinner than 0.120.

Be wary of mixing thicknesses of steel in a welded design. The heat required to fuse to the heavier walled material may burn the crap out of the thinner wall.
Net result is weight-saving members that don't fail because their welds blew apart.

[Loose_Nuts_Enterprises]

Beezil, no offense taken, I was just trying to give an example of tubing size/ thickness vs. strength, as long as you have a good design. However, I think and offroad truck's cage would probably survive with the types of loads that we could put on our jeeps, even in the nastiest of roll overs. But I do understand that this goes both ways, and a trophy truck cage in an XJ is way overkill and would probably render the station wagon quality of our beloved XJ useless as well as topheavy.

Dan

[XJZ]

Of course if you build it a little top heavy, you could always get D60's front and rear to keep it grounded. :)

[Beezil]

Be wary of mixing thicknesses of steel in a welded design. The heat required to fuse to the heavier walled material may burn the crap out of the thinner wall.

this shouldn't be a concern....

any welder who hasn't mastered the technique of welding unlike material thicknesses, shouldn't be welding a rollcage.....

the transition between welding something like .090 to .188 AINT NO THANG........easy stuff

[Goatman]

Originally posted by Mcstiff
Of course you guy's cannot tell me how much tube to buy. I was looking to hear how much others used. I may have a hook up for 150' of HREW (1.5od .098 wall) I do not have a finalized design or a bender yet. Just tryign to think ahead and save some cash.

HREW is not expensive, and you can get it from any metal supply place. It's roughly a dollar a foot, will come in 20 ft lengths, and they should deliver it to you. I get mine delivered to my house for no extra charge. If you're going to use the HREW, I'd get the .120 wall. I don't know how much that .098 is going to cost you, but the difference can't be much.

[vintagespeed]

I agree with the guys on the wall thickness .120 and HREW will work fine for your cage. The reason that some prefer DOM over HREW is that DOM has no weld seam and is one solid piece of steel. The HREW can split at the weld seam (although only in serious impacts) and this is why certain sanctioning bodies will not allow it in roll cage construction. When you build your cage keep the seams facing the inside of the structure whenever possible and never bend HREW with the seam on the outside of the bend (stretch side) as this will thin and stretch the weld surface weakening it. :D

Here's a frame I bent up with my ProTools 105 bender back before I did Jeep stuff.

http://www.rockxj.com/images/rail/frame1.jpg

[FarmerMatt]

I don't see any problem with welding different thicknesses together either. You just have to concentrate more heat on the thicker material. You'll get real good at this when welding the foot plates into the unibody if you go that route. My cage is all ERW 1.75 x 120 wall. I used tube gussets of 1.25 x 120 which is overkill for gussets, but I had it already & didn't want to buy another size that I use little of. FWIW I used about 60' of tubing in my cage.

Matt

[XJZ]

Excluding the seam, is the HREW as strong as DOM?

What are the pros and cons of either?

Inquiring minds want to know....

[vintagespeed]

I'm sure the DOM is a little stronger altogether being a more uniform piece of metal and formed as a tube not rolled into a tube like HREW.

[FarmerMatt]

From what I understand & I am by no means an expert, DOM (Drawn Over Mandral) is only ERW drawn over a mandral. Basically it just presses the ERW to make it more uniformed & possibly denser. Like I said before I'm no expert & this is just how it was explained to me. Please correct me if I'm wrong.

Matt

[XJguy]

DOM is ERW drawn over mandrel but let me say this, there is a body of thougt that considers DOM inferior to ERW. Reason being that the machining that makes DOM also impregnates the steel with oil; that is, the mandrel bending forces oil into the metal, hence the DOM 's distinctive darker and oily surface its just part of the process. This oil interferes with the welding process, so it is said. So in this sense ERW may be as strong or stronger than DOM (welding wise)...but I personally do not know...I go by the books..and the powers that be claim DOM superior in strength to ERW. When in doubt go 4130 MIL spec...thats my cream of the crop, no doubting that bad boy but it comes at a premium.

XJguy

[XJZ]

May I ask the Bonehead of the Day question? :dunce:


Is ERW and HREW the same thing? Ouch!!

[Beezil]

xj guy, that oil impregnation is at the SURFACE LEVEL AND DOES NOT IN ANY WAY, CAUSE DOM TO BE WEAKER.


DOM is stronger than HREW plain an simple.

[FarmerMatt]

Yes, ERW = HERW

Matt

[Ed A. Stevens]

Originally posted by Beezil
xj guy, that oil impregnation is at the SURFACE LEVEL AND DOES NOT IN ANY WAY, CAUSE DOM TO BE WEAKER.


DOM is stronger than HREW plain an simple.


True, and true.


The oil is from the DOM quenching process, post mandrel forming. The steel is red hot when it is drawn over the mandrel, well above a temperature that oil can withstand.

DOM is work hardened in the mandrel process. Work hardening increases the strength by packing the cubic structure of the steel tighter, and the grain structure into a more uniform pattern. The process is the same as forging, except for tubing (and few novices claim forgings are inferior).

Is HREW good? Yes (but heavy).

Is DOM better? Yes (a little, strength & weight).

Is CrMo better? Yes (but only if you know how to Tig weld and use post-heating to stress relief the welds).

If you want a quality recreational cage to enhance the XJ unitbody 1.75x.120 HREW is more than adequate for the main hoop, and 1.5x.120 for the halo and A/C-pillars. If you want something lighter then use DOM (or CrMo).

Don't get too hung up on the materials, as any enhancement is a safety benefit.

[XJguy]

You da man Ed...the guy I spoke to, a chassis and roll cage manufacturer, told me that the processing of DOM squeezed oil into the metal, similar to the impregnation of carbon in cast iron. He told me no matter how well you clean or sand the surface that oil is still in the metal itself, almost like cintered bearings. I thought it was a bit odd since DOM is considered by most to be a superior choice of tubing..but his reasoning sounded logical enough (though in my research I never encountered this information). Never the less, I follow the rest and deem DOM superior to HERW especially in light of what racing sanctions rule. All my personal Jeeps use only DOM mild steel and 4130 in their cages and suspension/steering.

Oh by the way Ed, one correction, ERW is not heavier than DOM or 4130 for that matter (difference is negligable). DOM and 4130 tubing are stronger and so allow for the use of thinner gauge tubing without sacrificing the strength of the component, therein lies the weight savings. Im sure you knew that but you may have just worded it wrong.

XJguy

[Beezil]

"that guy" doesn't know what he's talking about.....

maybe he was thinking about HRPO, and even then he'd be a little inaccurate.....

[4ward]

Don't be "that guy"

I run a multitude of varying OD's and wall thicknesses. My cage is ERW and has held up well so far. The race car is DOM cuz we couldn't get it under 3000 lbs. yet.

I have 1.75 .120, 1.625 .095, 1.5 .095, and 1 .120.

[Beezil]

BTW......

there is a big difference in strength between hrew and dom.......

when you looka t the numbers......... strength to weight ratios between the two, its kinda tough NOT to use DOM.

xjguy is correct, hrew and dom weight the same, however....

DOM is TWICE as strong in tension, and MORE THAN TWICE as strong in bend resistance compared to HREW....

Chro Mo is only around 20-percent stronger than DOM.....not enough of a STRENGTH improvement, but the weight savings is substantial.......material cost and fabricating concerns is my reason for choosing DOM for cages.......

[Ed A. Stevens]

Originally posted by XJguy

Oh by the way Ed, one correction, ERW is not heavier than DOM or 4130 for that matter (difference is negligable). DOM and 4130 tubing are stronger and so allow for the use of thinner gauge tubing without sacrificing the strength of the component, therein lies the weight savings. Im sure you knew that but you may have just worded it wrong.

XJguy



Correction noted (thanks for the help, and assisting in what I wanted to say), HREW & DOM are made from the same stock with the same weight per foot for size and thickness.

The DOM is stronger in tension and bending, and raw numbers claim almost twice as strong, but after welding the strength increase should be discounted except in tension only members (X-style cross bracing). Exploit the DOM increase in strength by using smaller material in bracing, but not major members.

The ride stiffness is the difference you will feel in a buggy cage between these metal choices, with a gradual increase in natural frequency as the stiffness increases (less plush ride feel as stiffness increases, it's hard to describe).

[Ghost]

This thread though intresting gave me a headache!

[TN William]

Okay I have heard more DOM vs HREW debates than I can count. All the DOM arguements point out the raw material strength differance.

I want to see:

1) Practical application data. 1.5x.120 DOM is stronger than 1.5x.120 HREW. But what about comparing 1.5x.120 DOM to 1.75x.120 HREW? Or 1.5x.120 DOM vs 1.5x.188 HREW?


2) Real life strength requirements. Not what competition organizations require; they have liability issues so their lawyers have told them what to spec. With a sound cage design, what are the material strength requirements and how were they calculated. Scientific data here, not heresay.