Lower Link Comparison Guide - Page 2 - Toyota FJ Cruiser Forum
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post #11 of 80 (permalink) Old 02-20-2016, 10:40 AM
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Re: Lower Link Comparison Guide

I don't have them yet but CalFab is high on my list

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post #12 of 80 (permalink) Old 02-21-2016, 05:12 PM Thread Starter
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Re: Lower Link Comparison Guide

Need to add Rokmen links, knew I was forgetting one.....
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post #13 of 80 (permalink) Old 02-21-2016, 05:27 PM
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Re: Lower Link Comparison Guide

Out of curiosity, has anyone ever done the math to see what sizes actually make sense for the lower links? You could make a 3" O.D., 0.5" wall link but, is it possible to actually put enough stress on the links to require more than, for example, 1.75" O.D. 0.188" wall? I get that it's cool to have beefy and mean looking lower links but, at what point do you start to see diminishing returns? If you look at the Light Racing links, they look kinda wimpy compared to other links but, SPC tends to design stuff to be as strong as it needs to be. Are other links crazy overbuilt or are the Light Racing ones underbuilt?
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post #14 of 80 (permalink) Old 02-21-2016, 07:42 PM Thread Starter
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Re: Lower Link Comparison Guide

I know the light racing DOM lower links are advertised to be "2x stronger than OEM" which I'm sure is plenty, but I am also curious on the strength of others. An interesting thing I've always wanted to compare would be solid aluminum vs. some of the steel tubing. It would actually be simple to calculate this. Basic beam bending, moment of inertia, stress is about all you need to know along with some Greek. I'll see what I can come up with #'s wise when I've got some free time....
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post #15 of 80 (permalink) Old 02-21-2016, 07:47 PM Thread Starter
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Re: Lower Link Comparison Guide

One thing that would be difficult to figure out, how much load will these see? The weight of the FJ? Half the weight of the FJ? We can compare their relative strength all day long, but we need to figure out the maximum possible force they will see if we really want to determine if they are "strong enough".
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post #16 of 80 (permalink) Old 02-21-2016, 07:57 PM
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Re: Lower Link Comparison Guide

Quote:
Iconic_ previously said: View Post
One thing that would be difficult to figure out, how much load will these see? The weight of the FJ? Half the weight of the FJ? We can compare their relative strength all day long, but we need to figure out the maximum possible force they will see if we really want to determine if they are "strong enough".
I've been thinking about this tonight and I was thinking to maybe compute 3000lbs on each end of a 2ft tube dropped at 1ft onto a point. That seems like an extreme condition and the variables could be backed off to find approximate failure points from there. Having said that, I'm not a materials engineer so, my methodology is likely to be naive or just plain wrong.
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post #17 of 80 (permalink) Old 02-21-2016, 09:16 PM Thread Starter
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Re: Lower Link Comparison Guide

Quote:
sdennie previously said: View Post
I've been thinking about this tonight and I was thinking to maybe compute 3000lbs on each end of a 2ft tube dropped at 1ft onto a point. That seems like an extreme condition and the variables could be backed off to find approximate failure points from there. Having said that, I'm not a materials engineer so, my methodology is likely to be naive or just plain wrong.
That sounds close, usually with basic beam bending for this type of scenario you calculate the force it will see (in this case directed towards the middle as worst case scenario) and treat the ends as 100% statically supported. After this is completed, another interesting thing to look at in the system is the strength of the bolts they are attached to:

Some links and link skids come with 9/16" Grade 8 bolts. Grade 8 minimum yield strength = 130,000 psi (this is the force to bend, not break) Shear strength is approx 60% tensile strength: 130k x .60 = 78,000 psi. Tensile stress area for 9/16 bolt= .182" squared. Multiply this area by 2 because of two bolts, and by 2 again because they are in double shear= .728 in sq of area.

Ubiquitous formula:
Force (lbs) = P (psi) x A (sq in)
F= 78,000 x .728
F= 56,800 lbs to bend the bolts that mount the lower links given an evenly distributed force.
Divide this # by two to see what a single bolt can do if the load was on one end.

Now the factory metric hardware should be close to this # too.
There is yall's basic statics lesson for today. Part two is the strength of the lower links...
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post #18 of 80 (permalink) Old 02-21-2016, 09:21 PM
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Re: Lower Link Comparison Guide

Quote:
Iconic_ previously said: View Post
That sounds close, usually with basic beam bending for this type of scenario you calculate the force it will see (in this case directed towards the middle as worst case scenario) and treat the ends as 100% statically supported. After this is completed, another interesting thing to look at in the system is the strength of the bolts they are attached to:

Some links and link skids come with 9/16" Grade 8 bolts. Grade 8 minimum yield strength = 130,000 psi (this is the force to bend, not break) Shear strength is approx 60% tensile strength: 130k x .60 = 78,000 psi. Tensile stress area for 9/16 bolt= .182" squared. Multiply this area by 2 because of two bolts, and by 2 again because they are in double shear= .728 in sq of area.

Ubiquitous formula:
Force (lbs) = P (psi) x A (sq in)
F= 78,000 x .728
F= 56,800 lbs to bend the bolts that mount the lower links given an evenly distributed force.
Divide this # by two to see what a single bolt can do if the load was on one end.

Now the factory metric hardware should be close to this # too.
There is yall's basic statics lesson for today. Part two is the strength of the lower links...
Rock on.
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post #19 of 80 (permalink) Old 02-22-2016, 09:04 AM
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Re: Lower Link Comparison Guide

Thanks for this info!

I was looking at getting beefier lower links and I have to say I really like the high-clearance design from WildWest.

"building them out of real stout materials isn't enough, we put a bend in the arm to help get it up out of the way to allow your tire to get to the obstacle before the arm hits it."

This makes a TON of sense to me.

https://www.wildwestoffroad.com/cata...s/prod_23.html
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LSSC

Last edited by 81N4RY; 02-22-2016 at 09:16 AM.
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post #20 of 80 (permalink) Old 02-22-2016, 02:47 PM
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Re: Lower Link Comparison Guide

Thanks for taking the time to assemble this!
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