pipe vs. tube

[camarolover]

I went to metal-mart to check prices for a roll cage and they told me to use pipe over tubing, they said that tubing is welded on one side only and that pipe is welded on both therefore is stronger. Everything I have read states that for cages etc. to use DOM tubing-what is the case for and againest useing pipe for a cage? I willbe tying into the stock bar and am thinking using .120 or .190 pipe which they said alot of wheelers use.

 

[Meat_]

DOM tube is not welded at all. Don't know wtf they were talking about but it wasn't DOM

 

[BioNuke1]

I thought DOM was welded then drawn over a mandrel which smooths it out and forges it

 

[Caleb]

alright, more info then you'll ever need...and deffinitely enough to go tell them to stick it up their arse

http://www.rockymountainextreme.com/showthread.php?t=2886

check out the animation I linked to in that thread, it shows the difference between erw and dom. Granted yes, dom is welded but it's then drawn over a mandrel to make it a uniform size and make it harder (tougher, stronger, whatever you want to call it). Meat, it would have to be welded at some point since it all starts as flat plate.

 

[Meat_]

...Meat, it would have to be welded at some point since it all starts as flat plate.

I ment no weld seams but anyway...

And CDS isn't welded at all

 

[Crawler]

Also, keep in mind that if you have a bender, or are going to borrow/buy one, the outer diameter of tubing (hrew, dom, etc...) is slightly different than that of pipe. The black pipe that they sell at metal mart will NOT fit a tubing bender die set properly and will cause problems. Tubing is more expensive, stronger, and definately the way to go for roll cages etc...

If you check with any race sanctioned organization the will not allow any cages built with black pipe.

Just my .02

 

[troutbum]

either will work, most people will tell you tubing is the only way to go, but I know several people (myself included) who have beaten the piss out of Sch. 40

That being said my current cage is DOM and HREW

 

[78mitsu]

It's really up to you, Point being, that cage will save your A$$ one day, A good design out of Pipe is better then nothing or a poor designed cage out of anything else. I used .120 wall 4130 Chromo I want my a$$ staying right where it is.

 

[cruiseroutfit]

either will work, most people will tell you tubing is the only way to go, but I know several people (myself included) who have beaten the piss out of Sch. 40...

Pipe is different than Tube, we all know that...

Has anyone ever looked at the strength numbers of sch40 versus DOM or HREW? You would be surprised , and yes DOM is much lighter than Sch40 (which happens to be its main advantage).

I know alot of people that have built compete cages out of sch40, HF benders, etc (Olly, Tracy Evans for example), they rolled more than the average and the cages did hold up fine.

Sure some may argue "if your going to do it, do it right...". I want to know who is actually heat treating their 4130 cages post TIG'n the joints...

If your building a comp buggy, then DOM is a no brainer, weight savings and high strength. But if your building a ROP structure for a weekend wheeler, then a properly designed and built structural steel (such as sch40) cage will work fine.

 

[cruiseroutfit]

It's really up to you, Point being, that cage will save your A$$ one day, A good design out of Pipe is better then nothing or a poor designed cage out of anything else. I used .120 wall 4130 Chromo I want my a$$ staying right where it is.

How did you weld the joints and heat treat the material surrounding the weld interference?

 

[cruiseroutfit]

...If you check with any race sanctioned organization the will not allow any cages built with black pipe...

Which ones?

I know several UROC competitors (albeit a couple years ago) that competed with sch40 cages.

I just raced in the SAE (Society of Automotive Engineers) Mini-Baja race in Portland a couple months ago. We had a FULL day of tech inspection, including a chassis check for material and thickness specs. The SAE inspectors (Engineers from Polaris, Honda, Freightliner, etc) allowed structural steel of all types assuming it met the pre-sepecified requirements. Carbon content of at least 0.18, bending stiffness & strength = or greater than that of 1018, yeilds strength of 370MPa +, Mod of Elast of 205MPa +.

If your referring to the cast "black pipe" such as used for plumbing, then we are talking about two different things.

 

[78mitsu]

How did you weld the joints and heat treat the material surrounding the weld interference?

the cage was Heliarced, I tached the parts I did together with a mig The cage was heat Treated by a friend of mine who built Chromo cages for years, Come look @ it the welds are pretty.

 

[78mitsu]

Which ones?

I know several UROC competitors (albeit a couple years ago) that competed with sch40 cages.

I just raced in the SAE (Society of Automotive Engineers) Mini-Baja race in Portland a couple months ago. We had a FULL day of tech inspection, including a chassis check for material and thickness specs. The SAE inspectors (Engineers from Polaris, Honda, Freightliner, etc) allowed structural steel of all types assuming it met the pre-sepecified requirements. Carbon content of at least 0.18, bending stiffness & strength = or greater than that of 1018, yeilds strength of 370MPa +, Mod of Elast of 205MPa +.

If your referring to the cast "black pipe" such as used for plumbing, then we are talking about two different things.

I used black steel to build the cage in my chevy, raced it once at RMR, The sanctioning bodies there didn't even look at the materials, more design and welding.

 

[cruiseroutfit]

the cage was Heliarced, I tached the parts I did together with a mig The cage was heat Treated by a friend of mine who built Chromo cages for years, Come look @ it the welds are pretty.

Well, your the exception then... Very few chromo cages get heat treated as needed. I'll have to take a look at yours one day.

 

[RockMonkey]

DOM is for cages. Pipe is for drive shafts.

 

[cruiseroutfit]

DOM is for cages. Pipe is for drive shafts.

Actually, my shafts are DOM...

 

[Unimog]

For a good strength comparison of Pipe, HREW, DOM, and Chromoly, see the February (I think) issue of Peterson's 4 Wheel and Off road. There is a good article about 'tubing basics' that describes the differences as well as relative strengths, including some crude strength tests.

 

[troutbum]

Well, your the exception then... Very few chromo cages get heat treated as needed. I'll have to take a look at yours one day.

I read somewhere (RDC maybe) that thin wall (.120) Chromo did not really benefit from heat treat, or at least it was not as critical. The same artical said you can MIG weld 4130 just fine.

 

[troutbum]

here it is

Wire Size-Amperage Range- WFS Range Relationships for Short Circuit Transfer on Steel
Wire Size Amperage
Range Wire Feed Speed
Range
.023" 30-90 100-400
.030" 40-145 90-340
.035" 50-180 80-380
.045" 75-250 70-270

Cleanliness is critical when welding 4130. Make sure that all mill scale and oils are removed using mild abrasives and/or acetone. When you strike an arc, keep your heat input low to reduce stresses in the metal.

Post-weld heat treatment of 4130 varies from one application to another. If ductility and toughness are your goal, post-weld heat treatment is recommended up to 1,200°F. If the material you are welding is thinner than .120 in., stress relief through heat treatment is not as critical.

WFS Rule of Thumb:
1 ampere for every .001 thickness
1/8" material=.125=125 Amperes
Wire Burn Off:
.023-3.5" wire/amp - 125 amps=437 IPM
.030 - 2" wire/amp - 125 amps=250 IPM
.035 - 1.6" wire/amp - 125 amps=200 IPM
.045 - 1" wire/amp - 125 amps=125 IPM

Welding 4130 is a lot like welding mild steel and is easy if you know how. These are just some of the reasons 4130 is considered so flexible and is used on everything from airplane engine mounts to bicycle frames.

from http://www.race-dezert.com/forum/showthread.php?t=18152

 

[78mitsu]

I read somewhere (RDC maybe) that thin wall (.120) Chromo did not really benefit from heat treat, or at least it was not as critical. The same artical said you can MIG weld 4130 just fine.

According to my friend Chromo needs to be heat treated for consistency, apparently at the edge of the weld penetraton there is an area where the heat tempered metal forms a interface with the non-heat tempered metal and there is a significant weakness there, tends to crack there, by heat treating, you can bring all the metal to the same hardness and it is better.
Maybe it's overly simplified, and I'm sure there is a better explaination, but this one worked for me, I can see the point. Cruiser... As an engineer...