Todays quick lesson Square vs Round

[Krawl]

Just a little info for you who would like to know. Square is stronger than round. Now consider this round control arms with bends in them, they will want to continue to bend, not saying they will, but once bent it easier to continue to bend. Square control arms cut and welded are stronger, if you know how to weld. Most control arms are round for aesthetics.

Another tip when building something bumpers rock rails ect, always keep the seam of the material away from the impact side, as it is the weakest point. So when building a bumper put the seam closer to the vehicle.

 

[5-90]

"seem" /= "seam". I think you wanted to use the latter.

It's also worth noting that, when doing "hard" fabrication, DOM should not have a seam - and should be available in common "mill shapes" for tubing. The "seam" found in most tubing indicates that the tubing is either HREW - Hot Rolled Electrically Welded - or CREW - Cold Rolled Electrically Welded. The latter is slightly stronger, because of the work hardening taking place during forming. Also, CREW can be used when aesthetics are important, because most hot-rolled steel shapes develop scale while cooling (while cold-rolled does not.)

If the seam cannot be seen on the outside of the tubing, just clean a short section of the inside (about an inch or so) - which should show up the welded seam neatly.

DOM (Drawn Over Mandrel) is hot-formed tubing. They take a bloom or a billet of steel (both are mill shapes, no matter what marketing wants you to believe "billet" means,) heat it until it becomes readily plastic, and then force it through a die with the desired outer shape (and a mandrel with the desired inner shape.) Then, it is allowed to cool. Typically, there is a second heating process that causes the steel to "form closed" where there would be voids due to the mandrel supports.

Now you know why DOM costs more - it's more energy-intensive to manufacture, and there is a certain amount of wear that takes place on the mandrel and the die.

5-90

 

[Krawl]

Yes your right, seam.

 

[MaXJohnson]

"DOM tubing is roll-formed, electric-welded and sized on modern mills designed especially for high-quality, high speed tube production. Inside and outside weld flash is removed during the process and every foot is tested for weld integrity with sophisticated in-line equipment. Tubing is cut to length as it comes from the mill.

The tubing then goes through a cold drawing process which creates a uniform, precision product with substantially improved tolerances, surface finish and tensile strength, increased hardness and good machinability.

Prior to the cold drawing operation, tubing udergoes a thorough cleaning in a casutic wash; normalization in a continuous, controlled-atmosphere annealing furnace; cold pointing of one end of each length; pickling and lubrication.

The tubing is then cold-drawn over a mandrel and through a die. This operation transforms it in size, appearance and homogeneity and improves its dimiensional accuracy and strength. The best characteristics of the as-welded tube are retained and refined, and the DOM product assumes dynamic new characteristics.

The cold drawing operation reduces the diameter of the as-welded tube shell and thins its wall to required dimensions in a controlled fashion to provide the properties desired in the finished product. This process improves the tube's concentricity, tensile strength, hardness and machinability. Close dimensional accuracy is achieved through positive control of both inside and outside diameters."

 

[5-90]

"DOM tubing is roll-formed, electric-welded and sized on modern mills designed especially for high-quality, high speed tube production. Inside and outside weld flash is removed during the process and every foot is tested for weld integrity with sophisticated in-line equipment. Tubing is cut to length as it comes from the mill.

The tubing then goes through a cold drawing process which creates a uniform, precision product with substantially improved tolerances, surface finish and tensile strength, increased hardness and good machinability.

Prior to the cold drawing operation, tubing udergoes a thorough cleaning in a casutic wash; normalization in a continuous, controlled-atmosphere annealing furnace; cold pointing of one end of each length; pickling and lubrication.

The tubing is then cold-drawn over a mandrel and through a die. This operation transforms it in size, appearance and homogeneity and improves its dimiensional accuracy and strength. The best characteristics of the as-welded tube are retained and refined, and the DOM product assumes dynamic new characteristics.

The cold drawing operation reduces the diameter of the as-welded tube shell and thins its wall to required dimensions in a controlled fashion to provide the properties desired in the finished product. This process improves the tube's concentricity, tensile strength, hardness and machinability. Close dimensional accuracy is achieved through positive control of both inside and outside diameters."

Ah - thanks! Shortly after I'd posted that, I was thinking there was some error in my thinking. I'm more into metallurgy than process, I'll admit (save machining.)

Must correct that shortcoming... However, the "cold-drawing" should also result in a slight increase in strength due to the work-hardening I mentioned.

Might I ask what your source is? I'd like to peruse it further...

5-90

 

[xDUMPTRUCKx]

im building my dissapearing 3-link with square tubing.....

A because troy(mr. overkill) has some in his garage

B because he says its stronger

 

[Dirk Pitt]

Just a little info for you who would like to know. Square is stronger than round. Now consider this round control arms with bends in them, they will want to continue to bend, not saying they will, but once bent it easier to continue to bend. Square control arms cut and welded are stronger, if you know how to weld. Most control arms are round for aesthetics.

Another tip when building something bumpers rock rails ect, always keep the seam of the material away from the impact side, as it is the weakest point. So when building a bumper put the seam closer to the vehicle.

Would you lead me (astray) to believe that square is stronger in all loading conditions?

 

[Mike L]

Just a little info for you who would like to know. Square is stronger than round. Now consider this round control arms with bends in them, they will want to continue to bend, not saying they will, but once bent it easier to continue to bend. Square control arms cut and welded are stronger, if you know how to weld. Most control arms are round for aesthetics.

Another tip when building something bumpers rock rails ect, always keep the seam of the material away from the impact side, as it is the weakest point. So when building a bumper put the seam closer to the vehicle.

Are your driveshafts built out of square?

 

[XJ_ranger]

Would you lead me (astray) to believe that square is stronger in all loading conditions?

:confused1



for everyone who reads things on the internet and believes them to be true -

Square is stronger for the same size OD and wall thickness and alloy, if the direction of loading is:
a. known
b. in one of 4 planes, or very slightly out of them, perpendicular to the flat faces of the square.

Just a little info for you who would like to know. Square is stronger than round. Now consider this round control arms with bends in them, they will want to continue to bend, not saying they will, but once bent it easier to continue to bend. Square control arms cut and welded are stronger, if you know how to weld. Most control arms are round for aesthetics.

also - rectangular is stronger than square - a 3x3x.188 1018 hot roll square is weaker than a 2x4x.188 1018 hot roll in one direction... but what about the other?

Round tube is the same strength in all loading directions perpendicular to the lenght of the tube...

Take your cut and welded square and load it on an edge and watch it fail LONG before a round tube that is bent would fail in ANY loading direction...

My Lower control arms have missing powdercoat on the bottom, and both sides... (and where the corners of square would have been) maybe that is cuse i dont know how to drive... but it is proof that they were in contact with rocks in a situation where square would have been weaker...

 

[vetteboy]

Square is stronger than round.

You need to be more specific here. There's a lot more to material sections than outside shape.

 

[Mike L]

Damn, Opie is smarter than he looks........................

 

[Dirk Pitt]

:confused1


for everyone who reads things on the internet and believes them to be true -

You are preaching to the choir here.

Thanks for explaining my point.

 

[vintagespeed]

You need to be more specific here. There's a lot more to material sections than outside shape.

yeah, this seems to be a very "simple" thread.

subway tunnels aren't square, neither are domed arenas, if their roofs were flat they'd collapse.

 

[vintagespeed]

.....round control arms with bends in them, they will want to continue to bend, not saying they will, but once bent it easier to continue to bend. Square control arms cut and welded are stronger....

and do we know why this is?

when you bend round tubing you stretch the outside of the bend and shrink the inside of the bend. The leaves the outside material thinner at the bend point than the inside bend material. also why you dont bend seamed tubing with the seam on the outside of the bend.

square tubing that is mitrecut will have more thickness at the cut edges because of the angle at which it's cut, when it's welded back together you're probably doubling the material thickness vs. bent round tubing.

so it would be more appropriate to say that round tubing is bent rather than mitred for asthetics.

 

[nhrocker]

subway tunnels aren't square, neither are domed arenas, if their roofs were flat they'd collapse.

I feel like I'm watching a VW Bug commercial now...

And in reference to the original poster, I'm not too worried about my 1.75"x.25 wall DOM tube lower arms bending any more than they are now. There are plenty of other things on my rig that will bend, break, or tear off before I do anything more than scratch those arms.

 

[Lincoln]

Thanks for the help. I'm going to make a buggy out of square tube or pipe, damn I can't decide.

 

[Jes]

Thanks for the help. I'm going to make a buggy out of square tube or pipe, damn I can't decide.

Go pipe. It's cheaper and my friend's cousin's former roommate said he can get you a super deal.

 

[nhrocker]

Go pipe. It's cheaper and my friend's cousin's former roommate said he can get you a super deal.

And with proper planning and joints you can assemble your entire cage with a pipe wrench, no welding necessary!

 

[vetteboy]

I made my first roof rack out of electrical conduit and those little set-screw connectors, it worked fine. You could probably get away with that.

 

[Lincoln]

With propper planning I could probably use the heat off the motor to smoke my crack.