Would 1.5" .120 wall square tubing be the same strength as 1.5" .120 wall round tubing? This is for a flatbed project for a toyota in case you were wondering.

I'm not worried about looks, b/c i like the look of square tubing, im just wanting to make sure if i rub the bed against a rock or tree that it won't cave in on me or anything like that.

look under your truck. is the frame square or round? look at your engine hoist, the arm that carries the weight horizontally, is it square or round?

Strength (in bending and buckling) comes from the moment of inertia (I)

I (round) = .12 in^4
I (square) = .21 in^4

In other words the square tube is about 70% stronger

go get a book. cylinders (tube) hold the most weight vertically, but with a side load i would think they would be weaker. since you are just building a truck bed and not a bridge, don't over engineer it, and don't make it too heavy going overboard. keep it simple, clean, and think it through completely. square flat beds are more than strong enough to support many times the wieght of the vehicle.

now get to it!

Strength (in bending and buckling) comes from the moment of inertia (I)

I (round) = .12 in^4
I (square) = .21 in^4




depends on the direction of the force upon the obect. from the side, yes, squares are stronger, from the top, cylinders are FAR stronger.

either one will be fine......I don't think he's sweating a dent in his flatbed.....:p :p :rolleyes:

I definatly wouldnt use dom square tubing on yur flatbed. I built mine out of the cheap stuff and I spent like 50 bucks on metal. (Except for the expensive diamond plate sheet I used, but mine was thick compared to many flat beds on the board.)

Anyway, i could build another flatbed on my truck for 50 bucks if need be since I wouldnt use that expensive diamond plate if I did it again.

For my purposes I wouldnt use expensive tubbing even if I did mine agian.

Originally posted by TyTy
I definatly wouldnt use dom square tubing on yur flatbed. I built mine out of the cheap stuff and I spent like 50 bucks on metal. (Except for the expensive diamond plate sheet I used, but mine was thick compared to many flat beds on the board.)

Anyway, i could build another flatbed on my truck for 50 bucks if need be since I wouldnt use that expensive diamond plate if I did it again.

For my purposes I wouldnt use expensive tubbing even if I did mine agian.

Huh? You wouldnt use cheap tubing, but you wouldnt use expensive tubing.

And why wouldnt you use square tubing on a flatbed?

As far as resistance to bending forces, I.E. Axial Compressive resistance, Square tube is approx. 50-60% stronger as the same size and wall thickness round section, but it is also heavier as well. I will give you two examples: Using 350MPa steel, the Mr (Kn-m) for 4"x4"x.188" is 20.3, with a mass of 9.45# per foot, while the round section of 4", .188" wall has a Mr of 14.1 and a mass of 7.67# per foot. 3.5"x3.5"x.188" has a Mr of 15.2 and a mass of 8.17# per foot, while the round section 3.5", .188" wall has a Mr of 10.7 and a mass of 6.66# per foot. Basically a 4"x.188" round section is going to be as strong, and have a mass close to a 3.5"x3.5"x.188" wall square section.

The little extra weight wont hurt anything. I need more weight back there to get my All-pro springs flexing.

ok what about for suspension links?
I have been considering getting some 2" .25 wall round tubing for my 4 link, but I already have enough 2" .25 wall square. should I just go with the square?
and if so should I set up the bottom of the bottom links (the first thing to hit rocks) to be on a flat face or a corner? I would assume the flat face would be stronger, but was wondering what all the engineers think.

Flat face is the way to go - Much easier to construct as well as stronger. A Minor dent in the flat face is only going to affect the strength in one axis as long as the dent did not cause any deformation of the other faces. A dent on the corner will cause weakness in both axi as well as torsional strength will be reduced. A dent in a face can also be repaired with some flat stock, vs. having to replace the tube due to a dent in the corner.

Originally posted by mossberg
look at your engine hoist

You mean look at my old engine hoist :flipoff2:

lol! hey thanks again i love my new hoist!:D

hey seabass, do we really need to go through this again?:flipoff2:

Originally posted by fcfred
hey seabass, do we really need to go through this again?:flipoff2: :flipoff2:lol:flipoff2: why don't NASCAR USE SQUARE THEN, SPLAIN THIS SOMEONE? and yes nascar is fawkin gay!

The chasie is square and the cage is round, the chasie loads are predictable the cage loads can be in any direction that is the difference.

Originally posted by XJJack
The chasie is square and the cage is round, the chasie loads are predictable the cage loads can be in any direction that is the difference.

No it's bcause they don't side-load the tubes in their cage. And for protecting the driver it's more than just tubes. They add plate to the sides and floor as well as many more tubes for that purpose.

Squash

Sounds just like I said tubes for protection because the load can come from any direction and square for the chasie that has load in two plains.

Sounds just like I said tubes for protection because the load can come from any direction and square for the chasie that has load in mainly two plains.

Just be sure not to travel by bus when you go to get whichever tubing you decide on.

:flipoff2: