Help design an A frame hoist
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  1. #1
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    Default Help design an A frame hoist

    I am looking for a few different machines for my shop, but my holdup is a way to get them off a trailer once here. So my plan is to build an A frame type hoist to be able to back the trailer under it, and lift the machine off it. So I am looking for suggestions on the build. Max machine weight would be 7 tons. I figure about 10’ between the uprights, but wonder how big an I beam I need across the top. Any help is appreciated.

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    lets say you have a 10" high I beam with a moment of inertia of 143 in^4

    7 tons in the middle of a 10 foot span will induce a peak stress of 14600 psi and the beam will deflect .122 inches

    i have found this site to be accurate
    Simply Supported Beam with Point Load (when using this calculator make sure your distance from neutral axis to extreem fibers is accurate (usually it is half the thickness of the beam)

    Second Moment of Area Calculator

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    Quote Originally Posted by gmark1 View Post
    I am looking for a few different machines for my shop, but my holdup is a way to get them off a trailer once here. So my plan is to build an A frame type hoist to be able to back the trailer under it, and lift the machine off it. So I am looking for suggestions on the build. Max machine weight would be 7 tons. I figure about 10’ between the uprights, but wonder how big an I beam I need across the top. Any help is appreciated.
    Been hashed out several times here, but more importantly "Why ?"
    Steal the design from Wallace, everyone else does.

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    First find the 7 ton chain fall, go to the scrap yard and find the beams, and the hard part the wheels...Phil

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    Quote Originally Posted by digger doug View Post
    Been hashed out several times here, but more importantly "Why ?"
    Steal the design from Wallace, everyone else does.
    I did a search on here, went thru 7 pages of results, but didn’t find anything I could use. Maybe you can point me to some threads that would be helpful. Who’s Wallace?

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    Did a search for what’s laying around here, got some 12” I beams for uprights, but wondering if the 14” beam is strong enough for the top piece. The more I think about it, I think I will make it 12 to 14’ inside, so it would work over equipment. Haven’t found wheels, so I think I’ll leave it on skids for the time being.

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    Quote Originally Posted by gmark1 View Post
    I did a search on here, went thru 7 pages of results, but didn’t find anything I could use. Maybe you can point me to some threads that would be helpful. Who’s Wallace?
    Let me Google that for you.

    Portable Gantry Cranes | Wallace Cranes

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    I don't see wrecking yards using those kind of cranes anymore. Forklifts are cheap enough and much more manuverable.
    Bill D

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    Not wrecking yards,but machinery repair shops certainly use them.....if youve ever used a forklift with the shop idiot (apprentice) driving it,then the value of a gantry crane is very obvious.....On we had was so old ,it was rivetted together ,used to bend down alarmingly ,but always spring back after.....beam was something like 8" not 14,and the upright A frame 2" tube,with four big cast wheels ,not swivelling ,but very stable......No use making these things massively heavy ,unless in fixed position.

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    I did not realize he meant a gantry crane. I thought an A frame crane was like an overgrown tow truck boom. Used to see them welded to the inside of the trunk of a cadillac at wrecking yards. very homemade looking. Not sure what kind of winch they used for lifting. I think the entire boom lifted up not just the hook.
    Bill D

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    more than 20 years ago, I built one based on copying the Wallace designs. Mine was a lower tonnage, but it has worked well for a long time. For 15' wide, 7 tons, Wallace uses a 15" Beam.

    Help design an A frame hoist

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    You can substantially reduce the beam size with tie rods and struts.....With turnbuckles in the rods ,bend in the beam is easily corrected too.......on the subject of bend,its not a structural problem ,but the monkey will tend to run down to the lowest point ,which can be a nuisance at times.


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