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Thread: Jib Crane

  1. #21
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    Quote Originally Posted by kcstott View Post
    The crane needs to support 125% of it's rated load where it will produce the most beam deflection OSHA 1910.179 ref ANSI B30.2 so it needs to support 2500 lb. at the end of the beam. It also needs to be built to a safety factor of at least 2:1. lifting equipment will have a safety factor of no less then 5:1 (that's automatic, all your chain slings and synthetic slings are rated correctly so long as they come from a reputable supplier)
    The LRFD load factors are 160% for live load and 120% for dead load. The live load is the component that is acting at the end of the beam, so I increased the the live load factor by 125%.
    1.6*1.25=2.0 which is what I used.

    It works out differently than ASD - but the results are similar.

    Try the same example using ASD with sf=2 and 125% live load specified and see which beams that method produces.

    80% of failures are from 20% of causes
    Never compromise your principles today in the name of furthering them in the future.
    "All I ever wanted was an honest week's pay for an honest day's work." -Sgt. Bilko
    "We are generally better persuaded by reasons we discover ourselves than by those given to us by others." -Pascal
    "Since we cannot know all that there is to be known about anything, we ought to know a little about everything." -Pascal

  2. #22
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    Default That is an S beam, not a W beam

    Quote Originally Posted by Mega Arc 5040DD View Post
    I am not sure off the dimensions of a W12 or W10 beem can some one tell me what I have and if it will work for any part of the crane I want to build please.
    I have it and have never had a use for it so if it will work I might as well use it.

    I have a 25' or 30' beam i picked up at auction 6 or 7 years ago for like $50. the top and bottom flanges are 5" wide 3/8" thick(at the edge the taper to 1/2" thick at the web). The beam is 12" high with a 3/8" thick web.
    The beam you have is an old style of beam called a standard section, or "S beam." Both varieties of "I" beam look similar, but they are very different. For one, the S beam is probably grade A36 or lower, which means the steel alloy is around 40% weaker than a modern W beam insofar as yield point is concerned. The other difference is that S beams concentrate their mass near the web because of the taper. This results in a lower moment of inertia about their thin axis, which makes them less suitible for use as a column. Also, this makes them more susceptible to a failure mode called "lateral torsional buckling" when used as a beam.

    From the dimensions you give, it could be a S12x27.5, with the following dimensions:
    Depth: 12.00
    web: 0.301
    flange width: 5.061
    flange thickness: 0.464

    This section was rolled by Phoenix Iron Company in 1915,1923,and 1929.

    There are other possibilities, but to be sure, you'll have to give me measurements made with dial calipers. The thickness of flange measurement is always suspect, since it slopes.
    Last edited by Bodybagger; 09-20-2008 at 08:50 PM. Reason: included decimal measurements

    80% of failures are from 20% of causes
    Never compromise your principles today in the name of furthering them in the future.
    "All I ever wanted was an honest week's pay for an honest day's work." -Sgt. Bilko
    "We are generally better persuaded by reasons we discover ourselves than by those given to us by others." -Pascal
    "Since we cannot know all that there is to be known about anything, we ought to know a little about everything." -Pascal

  3. #23
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    Quote Originally Posted by Bodybagger View Post
    The beam you have is an old style of beam called a standard section, or "S beam." Both varieties of "I" beam look similar, but they are very different. For one, the S beam is probably grade A36 or lower, which means the steel alloy is around 40% weaker than a modern W beam insofar as yield point is concerned. The other difference is that S beams concentrate their mass near the web because of the taper. This results in a lower radius of gyration about their thin axis, which makes them less suitible for use as a column. Also, this makes them more susceptible to a failure mode called "lateral torsional buckling" when used as a beam.

    From the dimensions you give, it is an S12x25, which is no longer rolled. If you want to know more about it, ask.
    Where to start with the questions
    How do you know its an S beam (I'm not questioning you I beleive you I just want to learn). I always thought that if it had a taper then it was wide flange and if it was square then it was an I beam.

    And how do you know the grade of the steel just based on the shape (again I am not questioning what you said). and for my small crane can I use it for any part I mean I am not building some huge shop crane. You kinda made it sound like my beam is useless. If it won't work for my crane are there any other uses that it would be good for?

    Sorry for all the questions I never pass on a chance to learn something new
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  4. #24
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    Question where to start...

    Different types of "I" beams...

    The most common are "standard section" or S beams and "wide flange section" or W beams.

    Quote Originally Posted by Mega Arc 5040DD View Post
    How do you know its an S beam?
    S section beams have sloping flanges that are narrow at the outside and thick near the web.

    W section beams have flat flanges. This distinction can be found in the AISC Steel Construction Manual.

    Quote Originally Posted by Mega Arc 5040DD View Post
    I always thought that if it had a taper then it was wide flange and if it was square then it was an I beam.
    If you buy an I beam today at a steel dealer, you are buying a W beam because the vernacular stayed the same while the actual section was superceded by the more efficient modern W series.

    Quote Originally Posted by Mega Arc 5040DD View Post
    And how do you know the grade of the steel just based on the shape
    I know that a W beam is made from a stronger alloy of steel because W sections are rolled to ASTM specification A992 which specifies a minimum yield strength of between 50,000 and 65,000psi, as well as steel chemistry, etc.

    The last common specification that S beams were rolled to was ASTM A36, which specified a minimum yield strength of only 36,000psi. However, your beam probably predates this specification and was rolled to the low 30 thousand psi range.

    Quote Originally Posted by Mega Arc 5040DD View Post
    You kinda made it sound like my beam is useless. If it won't work for my crane are there any other uses that it would be good for?
    That's not to say it's useless. It's just different than what's used today. When that beam was rolled (if it's the one your measurements indicate), high strength structural bolts didn't exist. They used ASTM 502A hot rivets, or welded the connections. That beam is not in the current steel manual and its properties (strength) must be calculated based on the alloy and the section geometry. All I can tell you is a modern W beam of a similar unit weight is much stronger.

    It would probably make a great gantry crane for the loads you want as having another leg SIGNIFICANTLY reduces the maximum stress in the beam. But I can't be sure without knowing the section properties, and for that I'd need very accurate measurements of your beam's cross section.

    Does this help?
    Last edited by Bodybagger; 09-21-2008 at 03:55 PM.

    80% of failures are from 20% of causes
    Never compromise your principles today in the name of furthering them in the future.
    "All I ever wanted was an honest week's pay for an honest day's work." -Sgt. Bilko
    "We are generally better persuaded by reasons we discover ourselves than by those given to us by others." -Pascal
    "Since we cannot know all that there is to be known about anything, we ought to know a little about everything." -Pascal

  5. #25

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    I disagree with quite a bit of that post by "bodybagger".

    If you ask for I beam at any service center I've dealt with you'll be quoted an S shape, ask for a Wide Flange and they'll quote you a W shape, ask for a H beam and they'll quote you a HP shape. These terms are pretty common nationwide between buyers and sellers.


    Most W shapes are rolled to A992 specs, but in the past many were rolled to A36 and A572 Gr. 50. Today all Weathering Steel W shapes are rolled to A588 Gr. 50 or A242 Gr. 42, 46 or 50.
    If you spec higher strength W shapes you'll get A572 Gr. 60 or 65 or A913 Gr. 60, 65 or 70.
    You can still get W shapes rolled in A36 (probably be dual cert tho) A529 Gr. 50, 55 or A572 Gr. 42, 50 or A913 Gr 50.

    Most S shapes will be rolled to A36 but many other grades are available, including the Weathering Steels. Way too many too many to list but A572 Gr. 50 is very common.


    Info on materials not in the current steel manual are still commonly available. Specially to those of us with old steel manuals

    If I was to get real ambitious I'd dig thru my collection and find this guys beam. But it's Sunday and I'm chillin.

    Don't oversimplify complicated topics and don't over complicate simple topics, both lead to more of those pesky internet myths. And nobody likes that.

    My take, take it or don't.

    JTMcC.
    Some days you eat the bear. And some days the bear eats you.

  6. #26
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    How can some one get a hold of all this info. Is there a good book I can buy or a website that breaks it all down. I would prefer a book I don't like reading the computer monitor more than I have to.
    Hobart Mega Arc 5040DD (with built in air compressor)
    MM Passport Plus with Q-gun
    O/A

    sold MM 251

    There are only 2 tools needed in a tool box. 1) Duct tape to fix any thing that moves that isn't supposed to. 2) WD40 to fix anything that doesn't move but should.

  7. #27
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    bodybagger will add to this i hope but a structural steel code book is a good start along with the steel suppliers spec pages they print up for each type of beam
    Kerry
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  8. #28
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    There is alot of info here to absorb.I just ordered a beam last week for a customer per the drawing he brought with a structural engineers stamp on them they spec A992 W10 49lbs/ft 19' with 12"x6" 5/16" wall thk. tube steel under it.Had to special order direct from mill 24' $1200
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  9. #29
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    There are exceptions to every rule.

    I could write 1 page to cover a good deal of what's used 90% of the time, and 100 pages to scratch the surface of the 10% where special steel is specified.

    You can learn some from the internet or books, but the technical books on steel are probably inaccesible to folks without an engineering background. The ones that cover design are geared toward civil and structural engineers and the ones that cover chemistry and sections are geared toward materials scientists. There are a variety of good ones either way. The AISC Manual of Steel Construction, 13th Ed. is the most authoritative source for information on American steel construction and it contains a lot of standards as well. It covers the two methods of steel design (ASD and LRFD) in one book.

    European and Asian steel construction is based on different standards not covered by AISC.

    A good internet site to look up American section shapes is http://www.efunda.com/math/areas/IbeamIndex.cfm

    As far as standards, ASTM is a pay site, but you can browse some things... http://www.astm.org

    You can get a lot of free information from AISC at http://www.aisc.org

    The latest steel manual costs $350. There's not a huge market for this book, but the people who need it would still need it if it cost $1,000. You may find a copy of an older version at your library.

    Well, my wife just told me to "stop being an annoying smart aleck and come to bed." So good luck on your quest for more info.

    80% of failures are from 20% of causes
    Never compromise your principles today in the name of furthering them in the future.
    "All I ever wanted was an honest week's pay for an honest day's work." -Sgt. Bilko
    "We are generally better persuaded by reasons we discover ourselves than by those given to us by others." -Pascal
    "Since we cannot know all that there is to be known about anything, we ought to know a little about everything." -Pascal

  10. #30
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    This might be a realy dumb question but are the standards and specs the same for Canada and the USA? Just want to make sure that In my search for info I get what aplies to me.
    Hobart Mega Arc 5040DD (with built in air compressor)
    MM Passport Plus with Q-gun
    O/A

    sold MM 251

    There are only 2 tools needed in a tool box. 1) Duct tape to fix any thing that moves that isn't supposed to. 2) WD40 to fix anything that doesn't move but should.

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