building a crane...

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I need to build a gantry crane cause im too cheap to buy a forklift to unload stuff. I need to be able to lift 10,000 pounds and the main cross beam or whatever you call it has to be 12 feet long...  I dont build stuff this big and I dont wanna kill anyone so I'm not sure what I need to use for the beam so it can support that much weight without just bending in the middle. also dont wanna just jam the biggest thing I can find up there cause I dont want to make it heavier or cost more than it has to. Its a pretty big span so im just worried itll bend in the center when I load the hell out of it. input anyone? or a better idea for building something cost effective to lift heavy loads off trucks if you think the gantry crane idea is stupid?I like to party!
Reply:Is the bridge on this thing going to move or just the trolley? The size of the beam required to span 12 feet, supported on both ends, with 10,000 hanging in the middle is going to vary, depending on your attachment on the ends, and what kind of trolley you have riding on it.Just off the top of my head, your maximum  bending* moment on that beam is going to be 30,000 foot pounds. I think the safety factor for overhead lifting is 5 to 1.So you will be looking for a beam that will handle 150,000 foot pounds of "bending moment*".Have you ever gone down to Joe Fazzio's in Glassboro to see what he laying around?*(Not to be confused with "moment of inertia")I'm just curious, What would you spend on a forklift? Keep in mind a 10,000 pound machine is rated 24" from the heel of the forks. to get into the center of a flatbed you are going to be 48 to 51 inches out.Last edited by joethemechanic; 02-25-2008 at 08:53 AM.Joewww.CummingsHauling.com
Reply:Quick answer: what he said about more information needed.Longer answer: That isn't a huge load for the span, but it is definately a pretty good load. You will not have ANY beam that bend in the middle. The issue is how much bending. The main concern isn't the beam, it is the support. You don't want the thing to fall over or collapse under  load. This is where design gets a little squirrelly, as dynamic loading can be MUCH greater than static loading in these types of rig. It isn't fun when a footing lifts and the whole setup falls over.If you can come up with a few more details about what you want, there are several people here that can offer experience and advice, but if you build, it will be at your risk.
Reply:Originally Posted by joethemechanicIs the bridge on this thing going to move or just the trolley?
Reply:You might contact some of the hoist manufactuers like Yale and Budgit to see if they have any engineering specs on what is required to do your job. I used to have a bunch of data from Budgit that I used to build a few overhead hoists but I don't remember what I did with it.
Reply:If your top beam is simply supported (pins, so the ends can rotate a little under load)12ft between support points, S-profile (which is why you probably want for a trolley mounted lift)An S12X35 will have a max stress of about 9500PSI when center loaded with 10000LBs, shear being low, and max deflection of about 0.1", for a safety factor of about 3.5 against yeild with A36An S12X50 will have a max stress of about 7000PSI, low shear, and a max deflection of about 0.07", for a safety factor of about 5 against yeild with A36Not small, light beams, but readily available.See Machinery's Handbook for more info
Reply:S12x50, or better.  If a load-factor of 1.5 is used or required, the safety factor in bending drops to about 2.  Most likely safe, but may not meet applicable codes.Note:  this advise worth what you paid for it.Also note, if this is for a business, or business use, or anything other than a home/hobby, you WILL need a PE to stamp off on the design.  OSHA don't like home-built.  And I can't think of too many home/hobby needs to off-load a 10,000 pound load off a truck.  Also think of lift-zone barriers/barricades, OSHA needed or not.
Reply:hi, here is a site by WALLACE GANTRY that my be helpfull. http://www.wallacecranes.com/gantries.htmheres an adjustable one. they have been around along time. Hope this helps, BOBhttp://www.wallacecranes.com/triste3.htm