Suspension tubing question

[nshefbuch]

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]

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]

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]

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

[dougg01]

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]

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]

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]

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/showthread.php?t=533830&highlight=sleeve+tube+strength

[cheech]

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/showthread.php?t=533830&highlight=sleeve+tube+strength

The second MOI would have to be on 1.75 Dia.

[Hope Springs Hauler]

The idea is technically correct, however 1.875 is too big to fit in 2.0x.125. When it is reduced to the 1.75x.125, he combined MOI is equal. This is assuming that the nominal vs actual diameters and wall thickness are exact. Mind you, I am not advocating that sleeving is never worthwhile; I am only saying that it is not a worthwhile effort to go and purchase the tube to make your own when you can buy the product ready-made.

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/showthread.php?t=533830&highlight=sleeve+tube+strength

[humpy]

Lot if good info in that thread... Crazy to think 1.75x.12 is stronger than 1.5x.25. That means this 1.75x.12 cage I just finished up is stronger than what I used to use for link bars (1.5x.12).... Learn somethin new everyday... Thanks cw and the pirate crew for doin your homework

[KargoMaster]

I'm glad that we're keeping this theoretical.... It's a great discussion topic... MOI is a great indicator for bending resistance...

nshefbuch, I'm not sure of when or which projects these were on ("budget builds" vs "unobtanium"), but I'm guessing that Ian (a former teacher) chose to use the materials that represented what the largest cross-section of the Extreme 4x4 audience might have available... Do I believe that Ian's personal buggy has sleeved tube, umm... NEGATIVE.

[dougg01]

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]

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...

[nshefbuch]

wow, i didn't think this thread would be this detailed. i watch xtreme all the time and i actually have learned some things from ian. he just did this on his supension arms for the current buggy he is building on that search and restore project. i've seen him use this method on steering links as well on his own show.

on his blazer solid axle rig he was working i noticed another part i didn't think was safe. on his drag link bar he has it bolting on top of the tie rod bar on the same knuckle(passenger side) using the same long ass bolt. to me it looked like the sheer point on the bolt would be moved to the distal end and from looks looked like it would snap pretty easy.

[cincygman]

I think it all has to do with the angle of the dangle............

[boomhauer]

as redriverranger can testify to.... i am lost. tooo many big words for my little brain. now on the other hand, if their were some naked girls in there i might understand a little more..lol

[rwells]

If Im mounting shocks to rearend i use 2.250 dia. 7075 solid alu. on lowers and if mounting shocks to arms I use 2.250 dia. with .375 wall chromoly tubing and have heat treated for strength. In my opinion in time the steel arms no mater how thick will bend.

[yellowjacket]

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

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