Suspension tubing question

nshefbuch · 08-24-2011, 07:29 AM

I've noticed that on xtreme Ian always uses two piece tubing setups. He always uses two .120 wall pieces together to make .250. Why would he do this instead of one piece .250 wall tubing? I've seen him do this for both suspension arms and steering arms.

Hope Springs Hauler · 08-24-2011, 07:57 AM

I'm not sure why he would do that when he has the choice. Theoretically, it is not as strong because the 2 pieces can flex separately. Think about it like lumber, if you can afford the 4x4, get it rather than sandwiching a couple of 2x4s instead.

humpy · 08-24-2011, 10:21 AM

Quote:

Originally Posted by Hope Springs Hauler

I'm not sure why he would do that when he has the choice. Theoretically, it is not as strong because the 2 pieces can flex separately. Think about it like lumber, if you can afford the 4x4, get it rather than sandwiching a couple of 2x4s instead.

Agreed!! Nice example btw...

nshefbuch · 08-24-2011, 12:29 PM

Thank you. I was thinking it would be weaker but wasn't sure as I'm new to fabrication.

dougg01 · 08-24-2011, 04:47 PM

Quote:

Originally Posted by Hope Springs Hauler

I'm not sure why he would do that when he has the choice. Theoretically, it is not as strong because the 2 pieces can flex separately. Think about it like lumber, if you can afford the 4x4, get it rather than sandwiching a couple of 2x4s instead.

Well, with wood it is likely different to some extent. For a given type of wood, two 2x4s screwed/nailed together are stronger than one 4x4 alone and will warp, twist, and bend less.

I'm not a metalurgy kinda guy and not a chassis builder by a long shot, but the use of twin frame rails, double rail cage hoops, etc is widely practiced. They could have just used larger or thicker tubing, but the effort needed to work that into shape, the cost, and the weight are probably big factors. It's likely why we don't see monster truck frames built with 4" OD .750 tubing. Once upon a time I tried to understand the physics and mathmatics involved with building a TF Dragster chassis so I could grasp why they build them like they do and why some work better than others. It got deep in a hurry so i gave up and said 'it just does and I'm glad for it'. A non-solid frame that can handle that kind of power, flex as a chassis, AND break apart in an accident to save the pilot is an engineering wonder. Definitely one group of engineers that will be allowed to live under my clemency program.

Hope Springs Hauler · 08-24-2011, 09:04 PM

Actually, the mechanics of materials applies no matter what it is. The moment of inertia and section modulus are dependent on the distribution of the material from the centroid.

The exact example that was originally asked about was using 2 pieces of steel and sliding 1 into the other and passing it as equivalent strength as a single piece of steel that has the same OD and wall thickness.

With my example, you brought another dynamic into it. When you screw/nail the 2x4's together, you are beginning to create a composite section; much like glu-lam lumber. Screws or nails that connect the sections experience a shear force that is generated along the interface and thereby connect the two pieces into a single composite section. For that situation to apply to the sleeved tubing, it would have to be plug welded in many different spots along the circumference and length so that the 2 pieces act as 1.

Redriverranger · 08-24-2011, 09:41 PM

Quote:

Originally Posted by Hope Springs Hauler

For that situation to apply to the sleeved tubing, it would have to be plug welded in many different spots along the circumference and length so that the 2 pieces act as 1.

And therefore closer to an actual lamination, which I had understood to be quite strong such as plywood vs a similar solid board of the same thickness. I don't believe just slipping one tube inside another would be as effective as a solid piece, hence I agree.

JeffK5 · 08-24-2011, 10:23 PM

I have no knowledge whatsoever on this subject ... but I do have access to a couple different engineering software packages.

We have a simple little Excel MOI worksheet that generated a .537 MOI with 2.0x.25 DOM ..

It generated .325 MOI on 2.0x.125 and .264 on 1.875x.125... for a total MOI of .589... in theory doubled tube is stronger correct?

check this thread out...

http://www.pirate4x4.com/forum/showt...+tube+strength

dougg01 · 08-25-2011, 03:54 PM

Quote:

Originally Posted by Hope Springs Hauler

With my example, you brought another dynamic into it. When you screw/nail the 2x4's together, you are beginning to create a composite section; much like glu-lam lumber. Screws or nails that connect the sections experience a shear force that is generated along the interface and thereby connect the two pieces into a single composite section. For that situation to apply to the sleeved tubing, it would have to be plug welded in many different spots along the circumference and length so that the 2 pieces act as 1.

I had assumed this would be the case. Anytime you sleeve tubing (in a solid chassis) for repairs or in the construction, plug welding is mandatory. That's the only way I have ever seen sleeving used. A large tube for a frame rail that then extends forward/rear and the desired diameter is smaller then it is stepped down and everything plug-welded. The use of two tubes slid together for the length of a single span, welded on the ends and plug welded, in theory, seems very strong, but also heavy and likely wouldn't flex at all.

I'd have to go see my neighbor (crane engineer) to give me numbers and such.

carwash · 08-25-2011, 10:36 PM

wow... that's a 5 year old pirate thread, funny.

this is a much argued topic... and people will swear on their lives that their answer is right. use what works for you and what you have on hand or available to you.

myself, no sleeving for me. I will only use a solid wall tube. it's stronger. the air gap, no matter how slight, opens the door for failure of the tubing. If you could get a tube to slide into another with ZERO tolerance and gap, then it might be close, but still not as strong. you'd have to have an insane press to get it that tube in there, and the one yer sliding it into would have to have been bored to an exact dimension. Any discrepency would allow for a failure point.

Don't buy 2 pieces of tube, just buy one in the size you want and never look back. Then again, I'm no engineer, I just have some real world experience. There's reasons I run .500 wall lowers on my rigs...

yellowjacket · 09-05-2011, 06:29 PM

Better to bend over time, then have heims pull threads out suddenly.... Imo.

Sent from my LS670 using Tapatalk

08-24-2011, 07:29 AM	#1
nshefbuch Join Date: Jul 2008 Location: piqua, ohio Posts: 76	Suspension tubing question I've noticed that on xtreme Ian always uses two piece tubing setups. He always uses two .120 wall pieces together to make .250. Why would he do this instead of one piece .250 wall tubing? I've seen him do this for both suspension arms and steering arms.

08-24-2011, 07:57 AM	#2
Hope Springs Hauler Join Date: Jul 2008 Location: Hamilton, OH Posts: 431 Images: 16	I'm not sure why he would do that when he has the choice. Theoretically, it is not as strong because the 2 pieces can flex separately. Think about it like lumber, if you can afford the 4x4, get it rather than sandwiching a couple of 2x4s instead. __________________ 1988 Suzuki Samurai on propane FJ 40 axles (4.10) 5.14 tcase 36" TSL SX

08-24-2011, 09:04 PM	#7
Hope Springs Hauler Join Date: Jul 2008 Location: Hamilton, OH Posts: 431 Images: 16	Actually, the mechanics of materials applies no matter what it is. The moment of inertia and section modulus are dependent on the distribution of the material from the centroid. The exact example that was originally asked about was using 2 pieces of steel and sliding 1 into the other and passing it as equivalent strength as a single piece of steel that has the same OD and wall thickness. With my example, you brought another dynamic into it. When you screw/nail the 2x4's together, you are beginning to create a composite section; much like glu-lam lumber. Screws or nails that connect the sections experience a shear force that is generated along the interface and thereby connect the two pieces into a single composite section. For that situation to apply to the sleeved tubing, it would have to be plug welded in many different spots along the circumference and length so that the 2 pieces act as 1. __________________ 1988 Suzuki Samurai on propane FJ 40 axles (4.10) 5.14 tcase 36" TSL SX

08-25-2011, 10:36 PM	#11
carwash pimpin' IS easy Join Date: Jan 2007 Location: Union, KY Posts: 3,344 Images: 605	wow... that's a 5 year old pirate thread, funny. this is a much argued topic... and people will swear on their lives that their answer is right. use what works for you and what you have on hand or available to you. myself, no sleeving for me. I will only use a solid wall tube. it's stronger. the air gap, no matter how slight, opens the door for failure of the tubing. If you could get a tube to slide into another with ZERO tolerance and gap, then it might be close, but still not as strong. you'd have to have an insane press to get it that tube in there, and the one yer sliding it into would have to have been bored to an exact dimension. Any discrepency would allow for a failure point. Don't buy 2 pieces of tube, just buy one in the size you want and never look back. Then again, I'm no engineer, I just have some real world experience. There's reasons I run .500 wall lowers on my rigs... __________________

09-05-2011, 06:29 PM	#12
yellowjacket barely breathing Join Date: Mar 2008 Location: alexandria, ky Posts: 889	Better to bend over time, then have heims pull threads out suddenly.... Imo. Sent from my LS670 using Tapatalk __________________ my next rig will be on the trail before zuk 2.0 will

08-24-2011, 12:29 PM	#4
nshefbuch Join Date: Jul 2008 Location: piqua, ohio Posts: 76	Thank you. I was thinking it would be weaker but wasn't sure as I'm new to fabrication.

08-24-2011, 10:23 PM	#9
JeffK5 Tiny Member Join Date: Jan 2007 Location: Colerain Posts: 798	I have no knowledge whatsoever on this subject ... but I do have access to a couple different engineering software packages. We have a simple little Excel MOI worksheet that generated a .537 MOI with 2.0x.25 DOM .. It generated .325 MOI on 2.0x.125 and .264 on 1.875x.125... for a total MOI of .589... in theory doubled tube is stronger correct? check this thread out... http://www.pirate4x4.com/forum/showt...+tube+strength