How do I design or fabricate my <insert project here>?

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Over the last year or so, I've seen numerous posts from a wide variety of people with this subject; myself included.  Some have been expert welders, and some are novice 'do-it-yourself' types.  The projects have ranged from trailers, to welding benches, to flatbeds for work trucks, to steel structures, or in my case an aluminum tank.  A common theme throughout all these posts has been, "How thick should it be?  Should I use square tube, or C-Channel?  What should the wall thickness be for these hollow sections?  Where and how should I brace it?Mechanical and structural engineers learn how to answer these questions with years of college education.  Most everybody else resorts to copying something they've seen elsewhere.(Hoping that the original design was created by an engineer...)As welders we understand(hopefully) the fundementals of creating a sound weld.  But nobody teaches welders how much weld metal to lay down, and where to put it.  Again, hopefully there's an engineered drawing to answer these questions, or a sound design that we can copy for our own projects.  Even those of us who've been lucky enough to go to college and study engineering, often don't learn anything about these topics.Another poster to this forum, David R, frequently references the Lincoln welding procedure handbook, or "the bible" as he's named it.  I'm always looking for good information and trying to learn, so I finally got around to visiting lincoln's website and ordering a copy of the bible for my own use.  While I was there, I found another great reference book that answers alot of these kinds of questions we all have asked at one time or another.  I ordered a copy of 'Design of Weldments' by Omar Blodgett, which answers a great many of the basic questions about design theory.  I spent about half an hour today skimming through my new books, and I needed to post a recommendation for this book on the forum.The book was not very expensive, about $20.  This is a steal for a college level textbook.  I have other books of similar quality that I paid well over $100 for when I was in school.Design of weldments is not a basic book.  It's written for someone with training in engineering.  But the author has done a terrific job of illustrating some basic design concepts.  And there's enough discussion in the text that even a non-engineer should benefit from learning these general theories.  If your math skills are strong, then you can even take what's given and figure out exactly how to design a structure to meet a specific need.  What size and thickness of structural members should I use?  How many and how large a weld bead should I use, and where does it belong on the structure?  Do I need continuous welds, or can I use a series of smaller welds to achieve the desired results?For everyone that designs and custom fabricates steel, I strongly recommend checking out a copy of this book for yourself.  Even if you just go to the library, and borrow a copy first, I think you'll agree with me.  You don't have to get all the math, just skim the examples and discussion of each problem for useful information.  There's real value to be gained from this book.  As I said before, the cost is small for what's contained inside...Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:I have that book and you are right.  it is an excellent reference.  I come from a carpentry back ground and have a strong understanding on design and bracing, but I am weak in material strength.  I found I typically could build a structure lighter with lighter members.  Most newcomers I run into not only don't understand the strength of the metal issue as I struggle with, but they lack design and bracing aspects.  This book is good start on both of those issues.
Reply:Thanks for the tip. I have been looking for a reference book along those lines. my usual solution is to over engineer the design, but that adds to cost and weight.
Reply:@ ADWD - generated your exact thought TODAY, while reading previous threads concerning "how to design x".  Totally agree with your assessment of "Design for Weldments" by Omer Blodgett.  A solid technical review that any tech should keep handy.Another great reference is 'Simplified Design of Steel Structures' by Harry Parker and James Ambrose.  Strongly recommend this text. Almost a mini-version of the ASD Design Manual by AISC, replete with practical examples.Last edited by ManoKai; 08-23-2013 at 01:31 PM."Discovery is to see what everybody else has seen, and to think what nobody else has thought" - Albert Szent-Gyorgyi
Reply:When I had my office, I hired structural, mechanical, plumbing, electrical, etc, & "un"civil engineers, and they were pretty much all book-keepers - just make sure the numbers add up and you're okay, and make sure the drawings have "seals".  "Official" approval was needed to build.  Ironically, or perhaps naturally, people that built things without engineering calculations tended to over-build the project more than the cost of the engineers!  If people/amateurs could/would access the kind of books you're citing, and have the confidence to use them, and verbal skills to defend them, things would get done so much easier.  Thanks for the reference.  I have lots of books, but should add that one to the library.
Reply:Thanks for the tip.  I just picked up a very nice hardcover copy for $13 off Amazon.  Does not appear to have been cracked open much, which I hope to remedy __David Hillman
Reply:Interesting.  I just ordered a copy of the Blodgett book.  You can get it straight from the horse's mouth here:http://www.jflfoundation.com/Product...ProductCode=DWI'm a degreed mechanical engineer and have designed a number of welded structures over the years, the most notable being the nation's largest anechoic stability wind tunnel test section and hemi-anechoic chambers that live at Virginia Tech.  The test section is about the size of a train car and the anechoic chambers were so tall that I had to split them into 2/3 and 1/3 in order to fit them through the decent size roll-up doors and then they join with flanges once they get in the control room (the upper third hangs from a hoist and the lower 2/3 gets shoved underneath it).  The main rails on the test section are 6 x 6 x 5/8" box tubing.  Came in as 40' long joints.  The machinists where I worked stuck a forklift on each end and rolled the horizontal band saw in to cut them.  Good times.  I have some pictures of it during the fabrication and rigging somewhere...http://www.aoe.vt.edu/research/facil...itytunnel.html