Solid alloy rod for suspension links?

[OpTimuS]

Hey guys.
Here I go again with another whacky idea.........
I am putting a front and rear 3-link in my 60-series (that's not the whacky part!), I have trouble getting hold of some DOM? or HT? tube in darwin, but I can get aluminium rod. I am considering using Aluminium rod for my links. I would of used 2" O.D. tube with .250" wall, can anyone tell me what size solid alloy rod I should use for the same strength?

Cheers Davo.

[Bahndo111]

Solid rod is not appreciably stronger then tubing because you are not increasing area moment of inertia. So if you were planning on using 2" OD tube a solid tube of the same strength would not be much smaller in diameter. I will do the back of the envelop calculations when I get home later. The other thing to consider is that aluminum does not have a fatigue endurance limit like steel which basically means that if the rod is subjected to cyclic stresses it will eventually fail. That being said if this is a trail rig and you are using 2" OD solid 7075 aluminum rods, you'll probably be alright.

[Eskimo]

Aluminum links? Who would do something so stupid like that? Oh yeah...me.

You'll want 7075, at least 1.75" diameter, make sure there's a good bit of meat left around the threads after drilling and tapping.. I wouldn't feel comfortable with less than .25" - meaning a 1.25" thread heim should go in nothing smaller than 1.75 rod.

1.75" would be about 25% stronger in bending than DOM, and 2" would be ~90% stronger.

That said, it will bend almost 3x more easily than steel.. it just doesn't STAY bent. it's a weird feeling the first few times you land on the link.

I'm running 2" lowers with a 1.25" shank forged johnny joints, and 1.75" uppers with 1" shank forged johnny joints. no regrets.

As for fatigue endurance.. you won't see it in this lifetime.

[OpTimuS]

Originally Posted by Bahndo111

Solid rod is not appreciably stronger then tubing because you are not increasing area moment of inertia.

Ahh yes continum transfinctioner.

Originally Posted by Bahndo111

So if you were planning on using 2" OD tube a solid tube of the same strength would not be much smaller in diameter. I will do the back of the envelop calculations when I get home later. The other thing to consider is that aluminum does not have a fatigue endurance limit like steel which basically means that if the rod is subjected to cyclic stresses it will eventually fail. That being said if this is a trail rig and you are using 2" OD solid 7075 aluminum rods, you'll probably be alright.

Bahndo, you seem to be the man in the know, so I will go ahead with a few questions if you don't mind; It is my belief that for the same strength alloy section the alloy will weigh 2/3rds of the steel mass, however the physical mass of the steel will be 2/3rds the size of the alloy. Is that correct?
Also thank-you for doing some envelope calc's, I look forward to your results.

[OpTimuS]

Originally Posted by Eskimo

Aluminum links? Who would do something so stupid like that? Oh yeah...me.

You'll want 7075, at least 1.75" diameter, make sure there's a good bit of meat left around the threads after drilling and tapping.. I wouldn't feel comfortable with less than .25" - meaning a 1.25" thread heim should go in nothing smaller than 1.75 rod.

1.75" would be about 25% stronger in bending than DOM, and 2" would be ~90% stronger.

That said, it will bend almost 3x more easily than steel.. it just doesn't STAY bent. it's a weird feeling the first few times you land on the link.

I'm running 2" lowers with a 1.25" shank forged johnny joints, and 1.75" uppers with 1" shank forged johnny joints. no regrets.

Ahh so someone has done it. YAY!
As for the 1.25" threads I guess that is cool as I planned on using 1.25" JJ anyhow.
Eskimo why did you choose to run alloy links over DOM?

Cheers for the input guys.

[coolcruiserfj40]

my buggy has 2" solid 7075t6 with 1 1/4 hiems

[OpTimuS]

7075 is about $400 a 3m length over here in Oz but I think I can get it cheaper. It seems 50mm bar is the way to go.

[OpTimuS]

oh update.......
In Sydney 50mm 7075 T6 is $155 a length

[Bahndo111]

Sorry I didn't get back to this til this morning but things seem to always be busier then I think. Anyway A solid 2" aluminum tube can take a bending moment of about 4000 ft lbs before yield, and a 2" aluminum tube (.125" wall) can take about 3000 ft lbs before yield. So for using all that extra material you only gain 30% strength in bending. The best way to increase strength in bending is to increase the outer diameter of the tube/rod. For sure you are not likely to see an endurance limit failure but these links are subject to cyclic loading in bending and in axial loading so it not something to completely ignore. But hey, I've never needed (or could afford) 2" solid rod for anything so what do I know. The only thing I am trying to point out is that you will gain more strength by increasing the OD then by going with soild rod over tubing. If tubing is not available then it really dosen't matter.

[Eskimo]

Originally Posted by Bahndo111

So for using all that extra material you only gain 25% strength in bending. The best way to increase strength in bending is to increase the outer diameter of the tube/rodIf tubing is not available then it really dosen't matter.

I am seeing 2" .125 being about 40% as strong as the solid rod, or about the same as 1.75" .375 wall DOM. (1797lbs. vs 4343lbs in my length pbending)

But even if you use AL tube, you'll need someone to make some aluminum tube adapters and then you'll have to have someone TIG them in.. gets pricy.

I did the AL because:

• People said it wouldn't work, I'm gonna kill myself, the threads are going to rip out, or that it's going to fail after a year.
• Trying to save weight (saved ~75lbs on the links)
• The 2" .500" DOM I was originally going to use wasn't available at the time, and even so, the logistics of just moving a 20' long, 160 lb. piece of DOM was something I really wasn't looking forward to.
• It's
• Cushy landings when I land on the links.
• Best strength to $$ ratio when the weight, availability, and ease of preparation was factored in. (Yes, I was actually on a bit of a budget)

[coolcruiserfj40]

Originally Posted by Eskimo

I am seeing 2" .125 being about 40% as strong as the solid rod, or about the same as 1.75" .375 wall DOM. (1797lbs. vs 4343lbs in my length pbending)

But even if you use AL tube, you'll need someone to make some aluminum tube adapters and then you'll have to have someone TIG them in.. gets pricy.

I did the AL because:

• People said it wouldn't work, I'm gonna kill myself, the threads are going to rip out, or that it's going to fail after a year.
• Trying to save weight (saved ~75lbs on the links)
• The 2" .500" DOM I was originally going to use wasn't available at the time, and even so, the logistics of just moving a 20' long, 160 lb. piece of DOM was something I really wasn't looking forward to.
• It's
• Cushy landings when I land on the links.
• Best strength to $$ ratio when the weight, availability, and ease of preparation was factored in. (Yes, I was actually on a bit of a budget)

why are you running tube adapters?
you lose all the heat treating the 7075t6 has
why not just tap the link thats waht we did

[OpTimuS]

Originally Posted by Eskimo

I am seeing 2" .125 being about 40% as strong as the solid rod, or about the same as 1.75" .375 wall DOM. (1797lbs. vs 4343lbs in my length pbending)

But even if you use AL tube, you'll need someone to make some aluminum tube adapters and then you'll have to have someone TIG them in.. gets pricy.

I did the AL because:

• 1 People said it wouldn't work, I'm gonna kill myself, the threads are going to rip out, or that it's going to fail after a year.
• 2 Trying to save weight (saved ~75lbs on the links)
• 3 The 2" .500" DOM I was originally going to use wasn't available at the time, and even so, the logistics of just moving a 20' long, 160 lb. piece of DOM was something I really wasn't looking forward to.
• 4 It's
• 5 Cushy landings when I land on the links.
• 6 Best strength to $$ ratio when the weight, availability, and ease of preparation was factored in. (Yes, I was actually on a bit of a budget)

o.k. points 1 through 6 I really really agree with.

I am fricking in!!

[OpTimuS]

Originally Posted by coolcruiserfj40

why are you running tube adapters?
you lose all the heat treating the 7075t6 has
why not just tap the link thats waht we did

I plan on using rod, drilling and tapping the rod. No welding and strong as hell.
38" links and 1.25" JJ

[bustanutley]

My buddies uber bling buggy has aluminum links, drags them over everything, straight as can be. It is pretty common practice, but I thought aluminum links would be quite a bit more expensive that the standard DOM option, interesting.

[OpTimuS]

Hey Busta.
Is that also aluminum front steering links I can see?
What setup does your mate have? are they solid or hollow?

Cheers.