Building an A-frame???

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I'm looking to build an a-frame gantry.  I need 14' clear overhead (to the bottom of the beam) and 12' clear between the uprights.  I'd like to be able to lift a minimum of 3000 lbs with it.  Really just need it now for a 1500 lb load...but who knows what I'll need down the road.I priced out today doing it with 4x4x1/4 square tube uprights with 3x3x3/16 square tube diagonal braces.   What do y'all think of that?  Overkill, or not heavy enough?  What would you suggest using?  I figure there's something just as good for my use that'll be cheaper.For the beam....from looking at commercially available gantrys, I'm thinking 8 or 10"....got access to some really cheap 6"... is it crazy to stack 2 of them flange-to-flange and weld together??  Any way to calculate that???Any tips/tricks/pics would be appreciated...Thanks.
Reply:Some of the guys have load/stress software.  They ought to be able to come up with a load factor.I have a 20' , 24,000 GVW gooseneck flatbed trailer, and the frame rails are 10" channel.  The longest clear span is from the front of the tandems to the hitch, and that's around at least 18'.  It's an old pintle hook dozer trailer with the beavertail cut off, and a goosencek added so the wheels are set all the way back as it's now setup.I have a sneaking suspicion that an 8" beam would be sufficient for the load you figure on."Any day above ground is a good day"http://www.farmersamm.com/
Reply:You could also gain strength on the 6" stuff my adding plate to the flanges at the midpoint, maybe for around 6' or so.  The midpoint is more apt to deflect than the ends where the beam rests.Better design guys ought to have the answer to that too."Any day above ground is a good day"http://www.farmersamm.com/
Reply:I personally would go with "I" beams over the tube.  You probably will get it cheaper anyway.  I've got one that I built for a firend years ago that is 6" "I" Beam with an 8" across the top.  It's 15' wide and I've never had a problem with it and I have lifted 3000 pounds with it a few time that I know of.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:At the minimum, 8", 12.5-lb I-beam.    I have a formula to figure it out somewhere on the computer...MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Moment at mid-span-M = wL(squared)/8M = moment @ midpointw = weight being supported (3000 lbs)L = span length of the beam (12 feet)3000 x 12'(squared) / 8 = 3000 x 144 / 8 = 54,000 in-lbsThere are more parts to the calculation.  Moment at center all I have found so far.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Here is my over head crane it is a 10 inch s beam with a 8 inch channel on top it spans 28 feet and will lift 1 ton. this came out of a factory that was closing so it was probably engineered. Check my old post there are more pic's from when I installed it.Tim Attached ImagesMiller 330 A/BP Bernard SS coolerMiller cst 250Miller Big Blue 251DCentury 210 Mig (first welder I bought)Hypertherm PowerMax 800Victor torch setRu Fong 31 MilAtlas lathe
Reply:I remember the pics"Any day above ground is a good day"http://www.farmersamm.com/
Reply:I used 10" 35# I-beam for the top rail on mine. For the legs I used some 4 1/2" 11.60# casing. I have picked up over 4500 lbs with it. It spans 15 feet. It has never bent, and I use it often. .............................."Look Good Doing It"!!!!!!!!!!!!!!!
Reply:OK, here's the progress so far....last week a friend borrowed my truck and trailer to pick up some "scrap" from work....got these for a buck a foot....big one is 18' of 8' beam, other 2 are  6" by 15'3" long.Hoping for more for bases and diagonal braces.
Reply:You SCORED on that dealJust take into account the proper load factors when puttin' the weight on the beam Attached Images"Any day above ground is a good day"http://www.farmersamm.com/
Reply:That's an excellent buy for a buck a foot!