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Old 08-06-2008, 08:33 PM   #11 (permalink)

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Default Re: Roll cage 101

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Originally Posted by jp350 View Post
For the record, tubing is stronger in tension then compression. If you aren't willing to trust your life to the welds & overall design & construction of the car, you shouldn't be in it.
True that.
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Old 08-07-2008, 12:32 AM   #12 (permalink)

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Default Re: Roll cage 101

Old Fart I meant no offense,
I do worry about the design and the thin wall tubing, I understand that you have rolled it...I come from woods country trees and rocks and other buggies on an oval are ALOT less forgiving than sand in a crash...Go to the fisrst page of my adventure thread...Both of those little 460's(built in the 90's) survived corner to corner and barrel roll crashes...natta a tweak...No ego...just glad that I had thought stuff thru and used heavy enouph tubing...The Purple people eater went 3 corner to corner's 3 more barrels and slid to a halt in the tires...Both right side tires were torn off the bead...The rear was a beadlock...pipe was mangled...I was shaken but not stirred...and was fine except for the bruises the harness left on my shoulders and hips...WELL my EGO did take a hit that afternoon

Last edited by renegadespec1; 08-07-2008 at 12:52 PM.. Reason: a capitalized offense... (:
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Old 08-07-2008, 02:28 AM   #13 (permalink)

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Default Re: Roll cage 101

Please explain tension and compression. So Iam clear on it

Thank you
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Old 08-07-2008, 02:51 AM   #14 (permalink)

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Default Re: Roll cage 101

Gee I wish you boys would quit worrying about me I'm a big boy and after all I've been in this racket for 20 years and for the last 12 have averaged 1500+ miles on the sand. Iknow I know with that much seat time I should have canned something by now. But I have been lucky

There is usually 3 or more cars and we stick a big V8 car in the front and let him try to run away from us. How can you possibly get hurt doing that?
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Old 08-07-2008, 03:17 AM   #15 (permalink)

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Default Re: Roll cage 101

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Please explain tension and compression. So Iam clear on it

Thank you
Tension - pulling on each end of the tube
Compression - pushing on each end of the tube

When you put a member (tube) in compression, they have the ability to buckle. If the forces are not directly down the tube, the tendency to buckle can go up dramatically.

When in tension, you're weakest point will be the weld (if it's not a top notch weld). It's damn hard to pull a piece of tubing in two if you've done the design correctly.

Take a drinking straw and push the ends together - it will bend fairly easily. Now try to pull that sucker apart. Lots more force required to cause damage.

Think of an a-arm setup. (This is a generalized point, so let's not beat it to death - it's merely an example, okay? )

Lower arms are in tension as you push up on the arm - because of the location of the wheel, the KPI, etc. These same forces put the upper arm in compression.

Ever break a ball joint? Doesn't matter, top or bottom joint. The bottom of the wheel always wants to go out - hence tension on the lower arm.
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Old 08-07-2008, 03:24 AM   #16 (permalink)

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Default Re: Roll cage 101

We're not worried about you.It's your own ass.However you keep saying you've got a lot of experience and such so why not let us in on what makes you tick and what credentials you have to support your expert opinions.
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Old 08-07-2008, 03:32 AM   #17 (permalink)

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Default Re: Roll cage 101

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Originally Posted by K-fab View Post
Tension - pulling on each end of the tube
Compression - pushing on each end of the tube

When you put a member (tube) in compression, they have the ability to buckle. If the forces are not directly down the tube, the tendency to buckle can go up dramatically.

When in tension, you're weakest point will be the weld (if it's not a top notch weld). It's damn hard to pull a piece of tubing in two if you've done the design correctly.

Take a drinking straw and push the ends together - it will bend fairly easily. Now try to pull that sucker apart. Lots more force required to cause damage.

Think of an a-arm setup. (This is a generalized point, so let's not beat it to death - it's merely an example, okay? )

Lower arms are in tension as you push up on the arm - because of the location of the wheel, the KPI, etc. These same forces put the upper arm in compression.

Ever break a ball joint? Doesn't matter, top or bottom joint. The bottom of the wheel always wants to go out - hence tension on the lower arm.
Question about tube in tension.How severely is a weld in tension that is not in a direct line of pull affected.

Last edited by masterfabr; 08-07-2008 at 03:34 AM..
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Old 08-07-2008, 04:00 AM   #18 (permalink)

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Default Re: Roll cage 101

If you place the load on the tube at a right angle to and through the axis of the tube then you have bending and shear.

The same load but off axis creates bending, torsion and shear.

Now take that load and place it an angle between 90 and axial through the axis and you now have bending, tension or compression, and shear.

Same load off axis and you have bending, torsion, tension or compression, and shear.

So depending on the loading the weld would see many different stresses. The amount of which would depend on the angle and a few other factors.
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Old 08-08-2008, 11:13 PM   #19 (permalink)

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Default Re: Roll cage 101

Found this website. Pretty good reading...

Roll Cages - All you need to know
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Old 08-08-2008, 11:25 PM   #20 (permalink)

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Default Re: Roll cage 101

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Originally Posted by dunerocket View Post
If you place the load on the tube at a right angle to and through the axis of the tube then you have bending and shear.

The same load but off axis creates bending, torsion and shear.

Now take that load and place it an angle between 90 and axial through the axis and you now have bending, tension or compression, and shear.

Same load off axis and you have bending, torsion, tension or compression, and shear.

So depending on the loading the weld would see many different stresses. The amount of which would depend on the angle and a few other factors.
First off so no one thinks I'm trying to goad or bait or belittle anything that has been posted.I'm serious and am just looking for info!Yes I'm digging for more though. I know a tube in tension is strongest but is it stronger in compression or tension considering its weld attaching points?
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