pipe vs. tube

[troutbum]

MIG 4130 article
http://www.millerwelds.com/powerclick/powerclick_0307.html


Oh yeah and to stay on topic, pipe is for poo :lol:

 

[cruiseroutfit]

"If the material you are welding is thinner than .120 in., stress relief through heat treatment is not as critical."

1. Who's definition of "not as critical:
2. Who is using less than .120" on a cage? Next common size is .095"/.083", that is a pretty drastic step down in wall thickness.

We used .095" & .060" on our Baja vehicle, but it weights 400 lbs total

 

[ZUKEYPR]

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.

You crack me up Kurt, way to much info in that cranium of yours.

 

[ZUKEYPR]

here it is

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

Great info, more important than what material you use is the fitment of the peices and the manner in which it's designed. You should have no more than 1/32 gap around those joints before welding, that came verbatim from the brother of my boss just last night who welds on NASCAR cages. If you have more and you are attempting to bridge it you are just creating a major week point in a critical area. As for the design it's all about triangelation (I spelled that wrong, didn't I). MIG or TIG, it doesn't amtter. For what a cage is designed to do neither has a significant advantage as long as it's done right. Don't "spot" weld it if your Migging, Use a stitch method or a few continues beads. "Spotting" it, normally an attempt to make it look pretty, causes cold spots and weakness. I've seen quite a few welds now that look fantastic that aren't worth a crap. Looks aren't everything.

 

[camarolover]

I still don't see any hard facts as far to strengths, weight yes but tube vs pipe is still looking like most people just follow the herd and say that pipe is bad-dom is great, this is going to be a daily driver offroad capable rig. No I don't want to die with the first roll-over but I don't want to spend more than I have to. On I8mud there is a thread on if the factory bar is crap most say it is not worth saving but no knows of someone gitting killed with one in a roll-over when they are belted in. I just want to add to the factory bar and add a little more safety to my cruiser. Again what I see it is more the design than the materal. Thanks for the info and I will keep looking for the specs asfar as advantages with tube over pipe but I am leaning towards sending the money for the tube and building it in stages instead of the hole thing at the same time.

 

[Caleb]

I still don't see any hard facts as far to strengths, weight yes but tube vs pipe is still looking like most people just follow the herd and say that pipe is bad-dom is great, this is going to be a daily driver offroad capable rig. No I don't want to die with the first roll-over but I don't want to spend more than I have to. On I8mud there is a thread on if the factory bar is crap most say it is not worth saving but no knows of someone gitting killed with one in a roll-over when they are belted in. I just want to add to the factory bar and add a little more safety to my cruiser. Again what I see it is more the design than the materal. Thanks for the info and I will keep looking for the specs asfar as advantages with tube over pipe but I am leaning towards sending the money for the tube and building it in stages instead of the hole thing at the same time.

search around here for strengths, I know cruiseroutfitter (Kurt) has posted numbers before, and I also know it's been posted on PBB as well. From what I remember schedule 40 is actually stronger BUT it weighs a whole lot more as well.

 

[RockMonkey]

I still don't see any hard facts as far to strengths, weight yes but tube vs pipe is still looking like most people just follow the herd and say that pipe is bad-dom is great, this is going to be a daily driver offroad capable rig. No I don't want to die with the first roll-over but I don't want to spend more than I have to. On I8mud there is a thread on if the factory bar is crap most say it is not worth saving but no knows of someone gitting killed with one in a roll-over when they are belted in. I just want to add to the factory bar and add a little more safety to my cruiser. Again what I see it is more the design than the materal. Thanks for the info and I will keep looking for the specs asfar as advantages with tube over pipe but I am leaning towards sending the money for the tube and building it in stages instead of the hole thing at the same time.

My first comp rig was a sorta YJ and I built the cage off the stock hoop. It was well triangulated and all the tube I added was DOM. The cage held up great to many many many hard hard hard rolls. Like you say, design has a lot to do with it. I think there are worse mistakes you can make than building from the stock roll bar. One of those worse mistakes would be using pipe to do it.

 

[Tacoma]

I love this topic, it never dies.

you'd think that at this point, people would just KNOW the difference, and know better. I guess not.

 

[muleskinner]

I love this topic, it never dies.

you'd think that at this point, people would just KNOW the difference, and know better. I guess not.

Yep, I still challenge someone to show proof (pic) of a failed sch40 cage that is built correct.

 

[anvil]

There are plenty of good uses for pipe in a rig. Each design is unique so you can't make a blanket statement like "always use DOM." Pipe is deffinitely weaker than DOM so design accordingly. Steel pipe is covered by ASTM A53 Fy=35 Ksi Fu=60Ksi. Here is a chart I made as a reference.



Pipe dies are availabe for the JD2 and Pro Tools benders. 1.5" schedule 10 is great stuff for bumpers and braces in a cage. I probably wouldn't use it for a main hoop or pillar, but in low risk or show only applications it would be fine.

To compare bending yield strength
If you call 2" OD .120 wall HREW 100%
1.5" schedule 10 pipe is 71%
1.5" schedule 40 pipe is 89%
1.75" .120 wall HREW is 75%

I'll add some numbers for DOM later.

 

[Rusted]

The justification for using pipe always seems to come down to price. Anyone have a price quote to compare the two? How much more expensive is a DOM or a HREW?

 

[cruiseroutfit]

There are plenty of good uses for pipe in a rig. Each design is unique so you can't make a blanket statement like "always use DOM." Pipe is deffinitely weaker than DOM so design accordingly. Steel pipe is covered by ASTM A53 Fy=35 Ksi Fu=60Ksi. Here is a chart I made as a reference.
...

To compare bending yield strength
If you call 2" OD .120 wall HREW 100%
1.5" schedule 10 pipe is 71%
1.5" schedule 40 pipe is 89%
1.75" .120 wall HREW is 75%

I'll add some numbers for DOM later.

What material props did you use for the DOM/HREW? Same as the sch steel?

Your numbers look very close to the ones I came up with awhile back, sadly I think the thread with all the number crunching was lost (it was in chat I think).

What bending yeild fomula did you use to equate the numbers? Modified in anyway for a seam (I've never found one that does but it would be cool).

 

[greenjeep]

All I know is that I have Sch 40 for my cage and have no complaints at all. I've rolled it twice and it hasn't moved/bent at all. If you want proof, THIS is the thread about my roll off White Knuckle Hill.

I wouldn't hesitate to use pipe as long as it's done right!!!

 

[anvil]

I used 42000 Ksi for the HREW and 36000 Ksi for the pipe. I haven't run any numbers for the DOM because I keep finding conflicting information. If someone wants to call Marmon Keystone and get the yield strength for the DOM they carry I'd be happy to run the numbers. I used the beam loading formulas in Machinery's Handbook. There is no correction for a seam. I like rusted's idea of getting some prices. We could make a chart of price, weight and strength.

 

[cruiseroutfit]

...I used the beam loading formulas in Machinery's Handbook. There is no correction for a seam. I like rusted's idea of getting some prices. We could make a chart of price, weight and strength.

What was the formula?

 

[troutbum]

You should have no more than 1/32 gap around those joints before welding

I am screwed then...

 

[ZUKEYPR]

I am screwed then...

Me as well, I've done stuff before that had up to a 1/8" gap at some points or another that I've filled and bridged. Thank god it wasn't on a load point. He said that the two welders that he works with (Childress Racing) uses (I forget at the moment what size) a wire from a mig in between the pieces to be welded to gap it properly. Of course he TIGS them, but on that note he did agree that being we are not crashing into concrete walls at 200 mile an hour MIG is fine for our application. I asked him about the pipe/DOM issue and he whipped some stuff off on me like Kurt and some others on this board does and just made my head hurt. X + Y * pie to the second power, yada, yada, yada just what is the maximum wind velocity of an unladen swallow carrying a one pound coconut?

 

[anvil]

what is the maximum wind velocity of an unladen swallow carrying a one pound coconut?

African or a European?

 

[anvil]

What was the formula?

stress at center = W*l/(4*Z)
W=weight
l=span between supports
Z=I/.5*OD
I=.049*(OD^4-ID^4)
all units are inches and lbs.

To compare strength just compare Z value. If you'd like to go a step further you could choose a distance like l=120" Plug Fy of material in for stress and then calculate the maximum weight W that could be supported before the beam yields. The maximum supported weight indicates the beams strength.

 

[ZUKEYPR]

Scary, I actually understand that.