Need help with ladder bars

Smitty256

Smitty256

Too Much Time
What is everyone making ladder bars out of? Square tubing? Pics and info please! Mine will be on a dodge but any help is appreciated
 
^^^^^Not true...to generic of a statement.

A square vs a round of the same diameter vs width/height with the same wall thickness...the square is stronger in ever measure exempt torsion about its center.
 
zstroken said:
Round will be your strongest geometric shape.
Click to expand...

I'd disagree. Round is going to give you the most torsional strength. Square tube would likely be stronger in the bending moments that'll be put on it.
Remember, the forces on them is almost solely rotating the axle and shoving the end of the bar into the frame.

That being said, I'd build it out of round because it looks so much better!

And I personally like the style with a shackle up front. a 'floating' ladder bar. Much less binding.
 
The way the ends are connected will dictate the force in the bar...whether is is axial...compression/tension or moment...bending or both.

A shackle on one end and fixed at the axle...will make it a bending type.
 
cquestad said:
^^^^^Not true...to generic of a statement.

A square vs a round of the same diameter vs width/height with the same wall thickness...the square is stronger in ever measure exempt torsion about its center.
Click to expand...


Well are we talking 2" OD diameter, and 2" width/height? Or 2" OD diameter and 1.41" width/height?
 
cquestad said:
The way the ends are connected will dictate the force in the bar...whether is is axial...compression/tension or moment...bending or both.

A shackle on one end and fixed at the axle...will make it a bending type.
Click to expand...

Ladder bars are fixed at the axle and have a bending moment on them, assuming no binding (why I called out the floating design).
Traction bars are a single floating bar in compression.
 
Last edited:
What about an I/H beam design?
(I want to go down in oraller history like Rudolph)

Carbon fiber I beams

I thought anything with rounded structures faired better under stress than to have corners (stress risers)

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zstroken said:
So in general is a 2"OD stronger than 1.414" width/height?
Click to expand...

I built a simple calculator real quick. Here's what I found:
2" Solid bar 4' long in bending with a load of 3000N will only have a stress of 284.19MPa.
1.414" Solid Square bar 4' long in bending with a load of 3000N will have a stress of 473.69MPa

2_zps10l985yl.jpg

1_zps4pijxepf.jpg


biggy238 said:
What about an I/H beam design?
(I want to go down in oraller history like Rudolph)

Carbon fiber I beams

I thought anything with rounded structures faired better under stress than to have corners (stress risers)
Click to expand...

Carbon fiber for one, isn't a long term solution. Every time it deforms, it breaks bonds and degrades. If you're using it only in a torsional application, it works pretty well. Bending and tensile it is still alright. Compression is doesn't love.

And I-beams are better in certain applications. This might even be one.
This is what I got for a 4' long, 3000N loaded I-beam that's 2" wide, 2" tall, and 1/2" thick.
It has a stress of 184.72MPa (which is the best yet). These hate torsional loading, but as long as you're not trying to get axle articulation (think off-roading style twisting), this would fight your bending forces really well.

3_zpss7kkl1rw.jpg
 
Carbon fiber was an oraller joke. I'm sorry.

The opportunity to articulate and see compression load should be low I would think.

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biggy238 said:
Carbon fiber was an oraller joke. I'm sorry.

The opportunity to articulate and see compression load should be low I would think.
Click to expand...

I agree with a floating ladder bar setup. Fixed, or a traction bar setup would both have some compression on them.
 
Compression strut is far more simple...lighter and takes advantage of existing strength of the leaf spring.

Period.
 
Yes...mount the lower rod end directly below the axle...3" is a nice offset.

36-48 inch bars are plenty long. 36 on a low truck...48 on a high truck.

1 1/2 Sch 40 Pipe is more than enough.
 
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