Input requested: turning angle iron into rectangular tubing

Hmm, didn't get any responses the first time ... not sure if the post didn't
go out, or didn't generate any interest! Here's my second try:
I'm needing to build a pickup truck rack; nothing too heavy duty; it is
mostly for carrying a canoe, maybe the occasional small load of wood or
steel. Probably 200-300 lbs. max.
I happen to have lots of bedframe angle iron, around 1/10" thick, in various
widths ... I've done a little experimenting joining two pieces of angle to
make a tube, as my ascii graphics below attempt to show:
* _______
| |
| |
| |
|______ |
*

The asterisks show where the welds are made. I clamp the two pieces together
to make the tube, and then grind out a vee to allow full penetration. I've
welded the pieces together with 3/32" 6011 running at 65 amps; this seems to
work pretty well, giving a completely fused weld, which I can grind down to
create what appears to be a smooth rectangular tube.
What do you think -- would such a tube be sufficiently strong to make some
or all parts of my rack? Would I use up more money in welding rod than I
would just buying some steel tubing? (It takes about one 3/32" rod to run 6"
of the weld, filling in the vee groove completely.) Is there any reason I
would want to use a different rod to do this?
Comments, suggestions?
Reply to
Andrew H. Wakefield
Loading thread data ...
Buy new.
Steve
Reply to
Steve Taylor
If your time means anything - buy tube.
If you do keep going, you do not need a continuous weld. Continuous will create tremendous warping.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net
duty; it is
wood or
thick, in various
of angle to
pieces together
penetration. I've
this seems to
grind down to
rod than I
rod to run 6"
Reply to
DanG
Thanks for the response ... but I still have the same questions. Are you recommending buying new because it would be cheaper? Are you recommending buying new because it would be faster? (Obviously it would ... but welding is a hobby, so the welding itself is fun, not just the completed project.) Are you recommending buying new because there are safety or other structural problems with making tube this way/from this material?
Reply to
Andy Wakefield
Dan, thanks for the response. You raise an interesting question for someone whose welding is strictly a hobby. Does my time mean anything? Obviously if I were making a truck rack for income, it would be ridiculous to trade several hours of labor for a material savings of maybe $20-30. (But then again, if I were worried about the time/money equation, I wouldn't be making the truck rack in the first place; I'd simply buy one.)
Welding is, for me, strictly a hobby -- a way to spend time relaxing from the stresses of my real job, doing something creative with my hands, just enjoying the time making sparks ... trying to improve my technique, trying to make good, strong, useful things, but absolutely not trying to make any money at all. (The last time that I accepted money for doing something that I do as a hobby -- in that case, woodworking rather than metalworking -- it nearly ruined the hobby for me!)
So, for me the equations work out this way: Time spent welding = time enjoying my hobby. Money saved on buying tube = money I can put into this or other hobbies. However, if money spent on rod > money saved on tube, then I lose some money that I could be spending on hobbies. (My wife keeps me on a strict hobby budget ... or rather, we keep each other on strict hobby budgets :) And of course, if in the end the pickup truck rack that I build proves unsafe and hurts someone, then no matter how much I enjoyed the welding or how much money I saved over buying tube, it was not worth it!
So here are the questions I'm trying to answer:
1) Am I likely to spend more on welding rod than I save over buying tube? (I should be able to answer this question once I get back a quote on some tube, and count how many rods are in a box ... but I thought maybe someone would have experience or instinct that would allow a quick answer.)
2) Is the resulting tubing going to be sufficiently strong for my pickup rack? Issues here include the original material -- bedframe angle, 1/10" thick; brittleness or other factors introduced by the welding; perhaps a better choice of rod; anything else I haven't thought of.
Your point about warping is well taken; I had given some thought to that. I would prefer to have a fully continuous seam, in order to keep water out (I don't want it rusting away on the inside where I can't see it!), but knew that just running a weld from one end to the other would be disastrous. However, what about running stitches of 2-3", spaced a few inches apart, then coming back and doing another stitch to fill in some of the gap, and so on -- would that keep the warping down? Or, hmmm -- what if I did a full-penetration weld (vee-grooving, etc.) only say 2" out of 6", and just did a butt-joint weld elsewhere -- enough to keep water out, but saving some rod and putting less heat into the tube ... ?
Perhaps I should add that the longest piece of "tubing" that I would expect to make this way would be 5' -- I don't have any bedframe angle any longer than that. I figure that I could make the uprights and the side-to-side crossbars this way, but I'll *have* to buy some tube to get enough length for the front-to-back crossbars. (So, yeah, instead of buying two 20' lengths of tube, I'll only buy one -- definitely not saving a whole lot of money, but if I save any, then I'm ahead based on the equations of the hobby :)
Thanks again for the input; keep it coming -- this will help me think through this project!
Andy
Reply to
Andy Wakefield
I am a beginner welder and don't have much experience in this field yet, but as a former auto mechanic and home owner, I think I have fixed and built enough stuff to answer this question.
You will be building something that will be supporting potentially dangerous items if they fall from said support structure while in motion. You could cause someone serious injury or death. Now, if you were that person, the one riding behind your structure at 55 MPH, what type of material would you want it made from? Buy New, and weld it together with every weld being your very best. Weld the bedframe together for practice or for use in some stationary object. Just my 2 cents worth of common sense. Doug
Reply to
Douglas R. Probst
I am a hobby weldor. My 2c: For a project such as this, buy new steel _tube_ or, if you can get enough _tube_ for the complete job at your local metal salvage yard, that would be okay too so long as you can get all you need and it is clean of major rust and paint.
Why new? 1. Bedframe metal is typically made from scrap with very little metallurgical control on the resultant angle iron. Consequently, there are often sections where the steel is more like high carbon steel than mild steel (i.e., you can get significant brittle sections--made worse by welding--which would be awful for a safety-critical weldment such as truck racks). 2. Most of the bedframe stuff I've seen (and used myself for some simple projects) is painted. I hate to work with something that already has paint on it because it increases the metal prep time. Angle iron sucks in this regard because it's tough to get all the paint off the inside of the angle. 3. Unless you got a load of bed angle from the same manufacturer, it will have all different dimensions. On a large job like a truck rack I would hate to deal with all the fitting problems. 4. I love welding as a hobby but, making tube from angle just sounds tedious to me and, this added to all the other issues simply adds up to the beauty of getting new steel for this type of job. Don't get me wrong, I use a _lot_ of scrap/used steel for my projects but for something like this I personally would only use new steel.
BTW, rebar is also made from scrap with little interest in controlling the uniformity of the output (i.e., cannot be counted on to be uniformly mild steel and, therefore, should not be used for safety-critical projects).
Have fun and best wishes, David Todtman
Reply to
David Todtman
Well, if you cost your time and materials yes.
Yes. (Obviously it
Structurally it will be banana shaped.
Look at it this way: if you buy new tube, you can weld up this neat project double quick and get to use it. Then you can make something else: you will have a pile of rods left that you didn't use up, and lots of cool offcuts of RHS to make something else with !!
In the UK I can buy a 21 ft length of 2" x 2" x 1/8" RHS for around 20-30 USD.
;-)
Steve
Reply to
Steve Taylor
First, the safety issue. You have decided to build a welded rack, so be sure you know how to weld. If you feel you are good enough to join purchased steel materials, then go ahead. I, personally, don't trust my own welding enough to do critical welds (where failure could be disastrous.) So I always design in enough redundancy to eliminate the problem.
Second, the question about "manufacturing" your own tubing. I suggest that you look at your design, and try to build it as much as possible out of angle iron. It doesn't HAVE to be tubing throughout. You will eliminate the problem of water leaking inside and causing rust, and all that distortion that is so hard to control.
A rack made of both purchased tubing and the angle iron you now have will probably look good, and be lighter.
I predict that if you start making up tubing out of your bed rails, you will end up wasting a lot of time and materials, and will end up buying more material. Just my 1 1/2 cents worth.
Reply to
Leo Lichtman
Andy:
An old friend of mine used to say, "You can't make ice cream out of horseshit." You can, actually, but the result will not be satisfying to anybody. That's how I feel about "saving" by welding angles into tubes. Can you do it? Sure. But down that path lies building a direct reduction steel plant in your back yard to save gas on trips to the steel distributor.
As far as whether it would work or not in practice, I'd have to see the design for your truck rack. Where and how you plan to use the bed frame material -- and how the loads will be borne -- makes all the difference. I would be glad to look at and comment on a plan if you have one that's email-able.
-Jon Ward
Reply to
Jon Ward
If you try to make full seam welds, chances are you are going to use close to the same amount of rod as the tube would cost you(cost-wise). Steel is still pretty cheap.
Probably, if you do a good job welding. In reality, you are going to end up with a stress area somewhere, and you will crack/break something(probably at the most inopportune moment). Your welds(and the HAZ) are going to very brittle. A lot of this will depend on what type of loading you put on your tube(compressive, bending, etc).
I would actually question if you need to weld these into a tube. With proper construction, I would think you could leave as is and build the structure. This would save you time and money. Everything would be open eliminating the rust concern. Years back, Dad and I built a canoe rack with open angle iron and it worked very well. It was a double wide rack so that we could carry two canoes at the same time(a third could be laid in the bed if need be).
JW
Reply to
Jeridiah
Doug, your point about safety is well taken (and I share it wholeheartedly) ... but let's take it a step further. Some of the commercially produced racks I've seen appear to be made of something like .065" thick tubing. If I buy new tubing, .065" thick, and weld it up, am I going to get something stronger and safer than making my own tubing, .1" thick? Why or why not? I'm asking seriously, not trying to be flip; part of what I'm getting at is whether commercially made tubing is necessarily stronger than homemade, and if so, why. Would a heavier thickness in the homemade compensate for the possibility of some imperfections in the seam? Does the commercial tubing have a different geometry in the corners than I can get by welding together two angles?
Of course, any rack, whether commercial or homemade, has loading limits beyond which it would be unsafe. The normal load that I anticipate carrying is < 100 lbs.; the maximum that I would plan for would be 200-300 lbs. (Even with 100 lbs., I think I'll be more worried about center of gravity and stability of the truck than about the rack itself.) My goal, whatever material I use, is to try to over-engineer it so that it will always have a large margin of safety.
Obviously, just buying new material will not automatically guarantee such a margin of safety; not only does the material need to be sufficiently thick / strong, but also the design needs to be such that one single weld failure does not result in the whole shebang coming down. (I'm still interested in seeing plans or pictures, if anyone else has built a rack :)
Truth to tell, with some of the racks I've seen, I'm more worried about the bolts through the thin sheet metal of the truck body than I am about the rack itself. :)
I guess the answer to your question is, I might rather be behind a rack that I've made out of bedframe, well and over-engineered, than behind a commercial rack that attempts to squeeze out the highest load limits from the least amount of actual steel. After all, bedframe material is used to support 200, 300, 400 lbs. or more every night!
Again, I appreciate the input, and the chance to dialogue and think through this. A disclaimer: though I probably appear to be taking a hard-nosed, I'm-going-to-do-it-regardless attitude, that is actually not my intention. I have no great objection to spending the money for new tubing (though I don't mind saving the money either, if it really is a savings vs. the cost of rod), and certainly may wind up going that way. However, so far the negative responses have not really given a reason why they are negative beyond the assumption that new is better, so I'm arguing the other side in order to try to push beyond that assumption :)
Andy
Reply to
Andy Wakefield
.> BTW, rebar is also made from scrap with little interest in controlling the
I cringe a little everytime I hear this one repeated. All grades of rebar are weldable with the proper procedure. If a lot of welding is intended, A706 or Multi grade A706/A616 will usually be specified. A615, A616 and A617 require more care (preheat, postheat, ect.) but are still weldable. AWS D1.4, welding code for rebar, goes into the subject in great detail if anyone is interested. Southern California (a high seismic area) probably has more rebar certified welders than most locales. But they are everywhere. Your friendly local Ironworkers or Pile Drivers welding school's are testing and turning them out as we speak.
JTMcC.
Reply to
JTMcC
Jim, Okay, okay, it's weldable with proper technique and filler. ;)
Am I off base with the idea that rebar is of quite variable carbon content?
Ciao, David Todtman
Reply to
David Todtman
I don't think so.I'm not an expert on rebar specs but my understanding is that carbon content can be pretty high in some grades.
I'm also not suggesting that home garage welders go down to Home Depot and buy rebar to weld important stuff out of.
Just that reinforcing bars are not the "mystery meat" a lot of people make it out to be, and that it's welded by the freight car load in a lot of places.
I've heard structural engineers, who haven't any experience with welded rebar, argue strongly that it can't be, never has been, and isn't done. A copy of the AWS D1.4 code book is all it takes to "show them the light" : )
regards, JTMcC.
controlling
Reply to
JTMcC
The specs on standard grade 40 and 60 rebar do have a very high carbon content, that is how they get the tensile strength. This does have bad effects on many other properties, such as welding. The weldable bars mentioned are closer to regular steel in bar form.
We weld standard dumb rebar a fair bit - use it for temporary sway bracing and beam bracing in falsework, for example.
-Rich
Reply to
Rich Jones
You can't just compare one steel hunk to another. Your bedframe steel is (at best) 36KSI yield, with lots of carbon and plenty of impurities to make it brittle, reduce the toughness and so on. At least in the US, rectangular formed tubes conform to A500-B, which has a yield strength of 46ksi. These bought tubes will not have residual stresses trying to warp them out of shape.
As for the geometry, yes it is different. Your tubing will have seams at opposite angles. Shrinkage across the welds there can cause the cross setion to twist or to flatten out as if you took two opposing corners and pushed them together. Commercial tubing has one seam in the middle of a side. This is symmetric, and any shrinkage will cause one side to shorten, but leaving the top and bottom parallel. Everything else aside, it's a tested and true configuration, known to work. Your new geometry adds a little more risk. It all adds up.
A trailer, especially a small one, is a high impact weldment - bouncing around and such. The crappy bedframe steel will not have toughness, expecially after you weld it all up. Toughness measures resistance to impact. Reduced toughness will cause your trailer to snap sooner, rather than just bend way out of shape. Bending out of shape is prefered, since you get to see the problem before it is too late.
Yet, in an unwelded condition with supports and designed connections.
As an engineer, homegrown trailers scare me. Let's break down the risks: 1) Faulty Design 2) Poor Materials 3) Poor Workmanship In general, Workmanship comes with lots of experience. During that experience, you see the types of materials used and the typical design details and processes. In defense of homegrown trailers, many (most?) are done very well. If the weldor has years of experience, the risks of faulty design and poor materials can be reduced since he can tell when it 'just dosen't smell right.'
Reply to
Rich Jones
Most of the rebar sold through the secondary suppliers as well as retail suppliers (Home Depot, etc) is indeed 'mystery meat' The only spec on the normally available C40 and C60 grades is 40kpsi and 60kpsi. Actual carbon content can vary a lot but commonly runs in the .4% to .6% range. These numbers are high enough to preclude quick weld joints. The rest of the 'good' components like Manganese and the bad stuff like silicon are not controlled to particularly tight tolerances. None of this makes for consistent welding. I do a demo where I weld samples of 1/2" bar and quench them after most of the red disappears. The whole weld area will commonly shatter like glass when dropped from shoulder height.
The better grades of bar are more tightly controlled, if the specs say they can be welded, have at it.
The local Northstar steel plant makes this stuff by the 30 ton ladle. Quite impressive to watch them melting, pouring, and rolling rebar.
JTMcC wrote:
Reply to
RoyJ
The bed iron tends to be very hard and brittle, feels like it is .4% carbon range. The HAZ is likely to be quite nasty. This translates to a much lower fatigue resistance for the welded up angle iron compared to mild tube.
I'd suggest using new tube of whatever thickness you need. My local supplier sells 10' lengths of the common sizes for around $.55 a pound, take your choice.
New stuff also has the advantage of clean, no paint, no rust, long lengths, all those nice things!
Andrew H. Wakefield wrote:
Reply to
RoyJ
I would box it up leaving the edges to form a small vee for your weld. Weld up your angle in lengths running a one inch weld every six inches along the corners. Now that you have you "tubing" cut it to the lengths you need. I would weld at the corners of your structure so that there is a continuous weld at least four inches from every connection of the tubing. Since you figure your load is maximum of 300 put a six hundred pound static load on it then pull and twist it to see if you have any permanent deformation. You are looking for it to bend. Those are the areas you will need to reinforce. Paint your rack with a good quality enamel. Regularly look for failure of the paint film which will indicate cracking or deformation during service. Randy
Reply to
Randy Zimmerman

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