Steel Fabrication Questions

[HongerVenture]

I have several questions as I'm getting ready to order materials to fab a rear bumper and rock sliders.

1. I'd like to know the difference between steel pipe and steel tube. HREW, DOM, etc. I know that pipe is measured differently than tube and thickness is by schedule rather than measurement. What are the merits of using one over the other? Can some of you smarter folks (guys like Goodtimes) give me a summary of steel pipe and tube? I'm an engineer, so don't be afraid to include the technical details. I geek out on that stuff!

2. What dimensions do you usually use for square stock or round stock on rock sliders? 1.5" OD tube? 1.5" x 1.5" square stock? Bigger or smaller? My buddy who is helping me fab is suggesting 2" OD and 2" x 2" stock which seems a little large to me. I just want to see what kind of stock most sliders use.

I think that is it for now... some answers from ya'll will probably yield more questions.

 

[jnelson4x4taco]

Okay im no pro at this but heres a little info from my experience. I know that its a terrible idea to weld galvanized, the fumes are deadly....seriously. I have built a few sets of sliders for CJ7's and used 2x3 box for the main part and used 1.5" sch 40 black pipe for the kick out. I had heard from a few rock crawling guys that DOM is actually stronger than the frame so if you take a hard hit on them, it will transfer the energy to the frame and damage it. Since i went with sch 40 pipe, if i do take a hard hit on them and manage to damage the pipe, ill cut it off and re-weld another for $15. I can say that i have thoroughly tested my desing and build quality on some 7+ trails (on 1-10 scale) and hey held up beautifully. Because of the cost of pipe i managed to build the jeep sliders for $50 a pair. I will probably use pipe on the side protection for my tacoma because it seems to be pretty strong. My theory is that if the design is good, you can make weaker materials work out ok. Obviously i wouldnt use this method in something serious like a cage or anything like that.

Hope this helps

 

[goodtimes]

. . . Can some of you smarter folks (guys like Goodtimes) give me a summary of steel pipe and tube? I'm an engineer, so don't be afraid to include the technical details. I geek out on that stuff!

Huh? Has someone been spreading lies about me again???? Just because I am a smart-ass doesn't mean I am smart. I am also no engineer (yet...the UofA is still collecting money from me...some day when they think I have given them enough, they will call me an engineer...).

Anyway, there is alot of debate about which is better and why... and I don't know all the answers. I do know that pipe is measured by the nominal ID, where tube is measured by the OD. Because of this, pipe is usually used for fluid transportation/storage, where tubing is used as a structural component, and to my understanding, this is why:

It is easier to design structural components by using the outside dimensions, then increasing wall thickness to obtain the strength we need. The ID is irrevelent...OD and strength are what is important. This is also what makes bending tubing so much better than bending pipe....the consistant OD* allows the use of a forming die which keeps tube from collapsing when it is bent--you can easily get a 180* bend from tubing with minimal OD variation through the bend.

When we design fluid transfer systems (cooling towers, chillers, compressed air systems, etc), we are more concerned with capacity through the system...the OD of the pipe is meaningless here, but the ID is critical. So we start with the ID we need, then add wall thickness to obtain the strength we need. Bending pipe is difficult because of the inconsistant OD**. You cannot use the same type of die as you use with tubing. So you are restricted to relatively large radius bends, or the pipe collapses when you bend it. There is some arguement about pipe being brittle as well...meaning that under severe load, it will crack and possibly break off...leaving a sharp stub of pipe sticking up and becoming a hazard. I don't know if this is true or not...I have never seen it happen, but that doesn't mean it doesn't happen.

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*The OD of tubing is consistant because you start with a solid number for the OD (say 2.00"), and add wall thickness to the ID of the tube. If your OD is 2.00", and the wall thickness is .120 +/- .010"...the OD is still 2.00, but the ID is between .1740" and 1.780".

**The OD of pipe is inconsistant because you start with a solid number for the ID (say 2.00"), and add wall thickness to the OD of the pipe. If your pipe is 2.00" ID, and the wall thickness is .120 +/-.010", your ID is still 2.00", but your OD is somewhere between 2.220" and 2.260".

 

[goodtimes]

2. What dimensions do you usually use for square stock or round stock on rock sliders? 1.5" OD tube? 1.5" x 1.5" square stock? Bigger or smaller? My buddy who is helping me fab is suggesting 2" OD and 2" x 2" stock which seems a little large to me. I just want to see what kind of stock most sliders use.

Honestly, most sliders/bumpers are designed, not engineered. They are usually over-built, and asthetics are very important. Mine are no exception. Usually you use one of two different methods to determine what size tubing to use.

Method #1: Determine the amount of tubing needed (regardless of size), then go look at the rack and see what size you have enough of to finish the job.

Method #2: Determine what size A)"looks right", and B) fits the die sets you have, then go buy enough of that size to finish the job.

I use method #2. For most vehicles, 1.75" round/11ga HREW is what I use for the main pieces. IMO, for anything except full size trucks, 2" looks to big, and 1.5" is bordering on to small. I do like to use 1.5" for smaller components of projects, or for main components on physically small projects. For example, tube fenders on a wrangler look best in 1.5", while sliders on a tacoma look better in 1.75".

Roll cages are actually something of an exception to the rule....larger tubing has better strength when you crunch the numbers regarding the moment of impact...I'll have to look to see if I can dig up the formulas again....but IIRC, when I crunched the numbers long ago, a 3" OD, .095" wall piece of tube would hold significantly more weight than a 1.75" .120 piece (we were comparing a OE roll bar in a CJ compared to a roll cage...only in the aspect of which material was stronger, not which would provide more protection)

 

[crawler#976]

Pipe is cast steel - it's made to withstand static internal pressure vs external forces like bending or heavy impacts. Pipe will work for sliders - it's cheap, so if it gets wasted, it can be replaced. I wouldn't trust it for anything that's "man rated" like a roll cage. It can be weled by stick, MIG or TIG with good results.

HREW (hot rolled electric welded) has a visable seam, and is designed to withstanding external forces and loads. It's usually made from low carbon 1010 Steel. HREW is great for "normal" duty sliders - it will dent and bend in severe use, and can be used for light duty roll cages. Cost is less the half of DOM. It can be weled by stick, MIG or TIG with good results.

DOM (drawn over mandrel) is seamless, so it is stronger than HREW, and is designed to withstanding external forces and loads. It's usually made from low carbon 1020 Steel. DOM is the stuff most serious roll cages is made from. It can be weled by stick, MIG or TIG with good results.

4130 Chrom Moly DOM is the stuff race cars are made from, and requires TIG welding and normalizing after welding.

1.75" dia x 0.125" wall tube is great for sliders. On my rock rig, the main tubes are made from 2", and the hoops from 1.75". The HREW has taken a severe beating and has some subtantial dents, gouges, but hasn't fractured.

On both the other trucks trhe sliders are all 1.75" HREW.

Galvanizing should be removed prior to welding. It makes for bad joints and also emits toxic fumes.

 

[devinsixtyseven]

No professional welder will touch galvanized. Something to keep in mind...the fumes will kill you as jnelson mentioned. Look for the coating if you're buying scrap, it's easy to pick out...shiny matte-textured silver when everything else is dull grey, black, or rusty. Avoid it unless it's small pieces and you have a blasting tumbler or something...it's likely coated on the inside as well and you won't get it off.

The PBB is a GREAT place to read up on different processes (HREW vs DOM), different materials (1010 vs 1020 vs 4130 steels) and different fabrication techniques (GMAW vs GTAW, heat treatment). Discussions there border on religious, with more numbers than most people want to read.

Some interesting things I've picked up there, and from the engineering degree:

Sch40 steel pipe (vs Sch40 in plastic and other materials), HREW 1010 and 1020 DOM will deflect about the same amount for a given OD/wall thickness, even though one is ultimately stronger than the other.

You can make whatever you want from any material you choose as long as it's supported correctly...the advantage of using DOM 1020 vs HREW 1010 vs Sch40 steel pipe vs DOM 4130 is being able to decrease the wall thickness, so what you're building is lighter. Plenty of people have built practical, well-designed, tested, low-speed cages from Sch40...just like a poorly designed structure will fold regardless the material.

Wall thickness resists dents, diameter (actually profile...think of an I-beam) resists deflection.

If you put all that together, it means you can make a perfectly functional set of sliders, bumpers, cage, whatever, from Sch40 steel pipe, but it will be heavy. It also means that you may want to consider wall thicknesses and OD based on unsupported lengths and references such as your skid plates.

Keep an eye on how you attach things to the truck...support the load over as large an area as possible, over as structurally sound an area as you can manage. This doesn't take an engineering degree...it just means that if you can spread the load from top to bottom of the frame, and do it over a crossmember, it'll be more robust than welding a 1.5" piece of tube to the center of your 6" tall frame somewhere between two crossmembers.

If you choose to use materials which are thicker than your frame (I did), make sure the frame is adequately supported (I did this also).

Unless you have a particularly heavy vehicle, 0.120 wall makes a fine pair of sliders. My truck weighs 3T loaded, so I used well-supported 0.180 wall. Your T100 is of similar size to my Tundra, don't know about the GVW tho or anything else, but my sliders are 2x2x0.180 box for the main rail, 1.5x1.5x0.180 box for the ladder bars and 1-1/4" Sch40 for the kicker.

When building bumpers, bear in mind that bombproof construction will kill you and/or anyone you hit if it cannot deform to absorb an impact. Stick to 0.120 wall for bumpers unless you have an extremely good reason to do otherwise, for example if the part youre making isn't something that will take the brunt of an impact, or has a crumple zone behind it. For example...ARB bumpers are made from 1/8". Mine has a few mods here and there, like 3/16" plate replacing the sides where it was trimmed to provide more rigidity and protection. The sides will not take the brunt of a front impact, and the bumper is attached by a crumple bracket that will bend (hopefully before the frame) if the bumper is hit hard from the side. In retrospect I could have used 1/8" and a couple gussets and it would have been fine. My entire rear bumper is 1/8" except for the towing support and subframe, a couple small gussets supporting the hoop on the rear, and the shackle hangers.

-Sean

 

[goodtimes]

See, I told you I wasn't the smart one.

On the subject of welding galvanized steel....as I understand it, zinc oxide (ZnO) is the main problem. Exposure to ZnO can lead to Metal Fume Fever, and can lead to such happy things as bronchitis, pneumonia, pulmonary edema, nasal cancer and even bone damage.

That said, I JUST got done welding some galvanized parts....with no fume extraction here at home. Welding while holding your breath kinda sucks.

 

[Super Doody]

I have several questions as I'm getting ready to order materials to fab a rear bumper and rock sliders.

1. I'd like to know the difference between steel pipe and steel tube. HREW, DOM, etc. I know that pipe is measured differently than tube and thickness is by schedule rather than measurement. What are the merits of using one over the other? Can some of you smarter folks (guys like Goodtimes) give me a summary of steel pipe and tube? I'm an engineer, so don't be afraid to include the technical details. I geek out on that stuff!

2. What dimensions do you usually use for square stock or round stock on rock sliders? 1.5" OD tube? 1.5" x 1.5" square stock? Bigger or smaller? My buddy who is helping me fab is suggesting 2" OD and 2" x 2" stock which seems a little large to me. I just want to see what kind of stock most sliders use.

I think that is it for now... some answers from ya'll will probably yield more questions.

Short and sweet version. Tube is used for carrying poop (plumbing) and pipe is used for strength (its also higher quailty steel, chromoly, ect.)

I think its okay to use tube for light use sliders and bumper but I would not use to build a roll cage unless you dont mind the possiblity of metal tube sticking into your body.

 

[BogusBlake]

Short and sweet version. Tube is used for carrying poop (plumbing) and pipe is used for strength (its also higher quailty steel, chromoly, ect.)

Uhh. It's actually the other way around.



One more thing to consider- For a given wall thickness, the larger diameter tube will dent easier than a smaller diameter. Once a tube is dented, it can no longer be considered a structural member. Not so important for a rock slider, but a rock slider isn't there to save your life, just your paint.

If this is your first tube project, I would recommend using HREW because it's cheap enough that you can afford to make a lot of mistakes.

 

[HongerVenture]

Great input!

This is exactly the type of info I was hoping for... first-hand working experience! Some of the things you mentioned I already knew (don't weld galvanized, pipe is based on nominal ID, tube is based on OD, one used for fluids and one for structures) but most of it was the kind of finer points I was missing. Thanks guys! I'll take any other items you toss out there.

 

[goodtimes]

If this is your first tube project, I would recommend using HREW because it's cheap enough that you can afford to make a lot of mistakes.

Or your second, or third.....hell, HREW is about all I use.

 

[Super Doody]

Uhh. It's actually the other way around.



One more thing to consider- For a given wall thickness, the larger diameter tube will dent easier than a smaller diameter. Once a tube is dented, it can no longer be considered a structural member. Not so important for a rock slider, but a rock slider isn't there to save your life, just your paint.

If this is your first tube project, I would recommend using HREW because it's cheap enough that you can afford to make a lot of mistakes.

sorry my dyslexia has been acting up on me:sombrero:

 

[HongerVenture]

This will be my first project, but I'll be having my hand held by a friend with lots of experience.

My buddy is quite experienced and has suggested steel pipe for the sliders. He indicated that because I do expedition travel, not rock crawling, I can save the pennies and be plenty protected.

From what I've gathered here, that is sound advice. Any arguments?

 

[devinsixtyseven]

Or your second, or third.....hell, HREW is about all I use.

LOL...yeah, I feel the same way . I leave DOM and 4130 work to the pros...

 

[devinsixtyseven]

This will be my first project, but I'll be having my hand held by a friend with lots of experience.

My buddy is quite experienced and has suggested steel pipe for the sliders. He indicated that because I do expedition travel, not rock crawling, I can save the pennies and be plenty protected.

From what I've gathered here, that is sound advice. Any arguments?

poop pipe is even good for rock crawling, 'cause it's cheap! you just wont have the world's lightest construction...

my only argument would be that since it's for expedition stuff, you want it lightweight and strong so you can carry more gear vs more trail armor. this points to 4130, but personally i wouldn't use it for anything that will get beat hard like sliders.

I would use HREW steel as it's the least expensive, best compromise. Were I to do it again, I'd use HREW vs pipe since the HREW tube has a "standard" OD vs the 1.66 (more or less) OD of 1-1/4" Sch40...it's easier to deal with the HREW when you're bending or cutting radii in square stuff to fit the round stuff...you try finding a 1.66 dia hole saw or end mill and lemme know what you come up with . Tho now you can use the online+printout+straight cut method for fitting round stock together.

If you're not going to weld the sliders on, you can build them from pipe now, wait til you're good at fabrication, then build a lighter set when you're ready. It's just that unless you're very in to modding your truck, the first set you build will probably be the only set, so choose materials wisely. With full length sliders from 3/16 wall HREW and Sch40 and frame reinforcements/plating, my sliders weigh in at ~90# each. Unfortunately, there isn't much I can do to reduce that weight without changing material to something exotic with an equally exotic price, as I have seen 1/8" wall (round) sliders deformed by Tundras. The Sch40 is a negligable part of that weight, mostly it's the 2x2x3/16 main rails, frame attachments and bracing.