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Thread: Gantry crane in WOOD?

  1. #1
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    Question Gantry crane in WOOD?

    I am dedicating my entire cellar to shop use and I need to get my milling machine down into it by craning it down through a hole in the floor before I fill it up with a staircase....

    Since I have no real need for a dedicated gantry-crane I find that shelling out the money to make one out of steel is a bit of a waste of money.

    Soooooooooooo............. I was thinking about making one out of wood(pine or spruce) so I was wondering????

    How much load can one put on a single 2"x4" 5 feet long supported at the ends on the 2" side????

    Will an A-frame gantry-crane made from 2x4's be strong enough(bearing in mind it will only be used a few times)???????????

    Oooops
    Forgot to mention that its a rf30 clone (chesterE30) and only weighs 280-300kg
    Last edited by MasterMaker; 04-24-2010 at 03:17 PM.

  2. #2
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    Quote Originally Posted by MasterMaker

    Soooooooooooo............. I was thinking about making one out of wood(pine or spruce) so I was wondering????

    How much load can one put on a single 2"x4" 5 feet long supported at the ends on the 2" side????

    Will an A-frame gantry-crane made from 2x4's be strong enough(bearing in mind it will only be used a few times)???????????
    No! a 2X4 with a 5' span is definitely not strong enough to support a mill.
    Just off the top of My head, I would say that the minimum be a 4X6 and that might be on the light side.
    Having said that, I'm sure that a gently placed load on a pristine 2X4 may support the weight of a mill, but I don't want to hang one from a strap or chain and then start bouncing it up and down with a chain fall or come a long to see if I was right or wrong .

    Steve

  3. #3
    Too_Many_Tools Guest

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    I have been thinking about this approach for an use I might have.

    I would go to someone who does wooden trusses for homes and ask see what they have to offer.

    TMT

  4. #4
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    Can't you hire one for the day ? If not please be careful. Alistair
    Please excuse my typing as I have a form of parkinsons disease

  5. #5
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    I could always double up on the 2x4 and of course I will bolt it together---

    I do have an innate dis-trust for the stuff, hence the question here.

  6. #6
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    2x4's only seem strong untill you snap one in half like a toothpick using it as a lever to push a 4' ball of snow around the yard (to make it bigger!)

    for 300kg, you have a good way to test this...
    get 4 friends, hang off the center of an even longer 2x4, and then ask them to all try and bounce up and down on the beam. :P

    Or maybe just support it 6" off the ground and ask them to jump on it.
    I bet even on its side it snaps before the 3rd person gets on.

    Remember that you WILL have sudden starts/stops that will cause LARGE shock loads on your structure. Something as simple as a chain link moving slightly can drop a load enough to cause a several fold shock load.

    Also, all 2x4's are not made from the same wood, or even dryed the same.
    I only buy kiln dryed 2x4's because I HATE WARPAGE in wood. I won't even use a visabley crooked 2x4 in a cosmetic wall thats to be sealed. Likey a waste of good wood but oh well, im OCD.

  7. #7
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    I once made a wooden gantry support for a chain block to lift around half a ton. I used a good quality 8"x2" on edge, around 8ft long - no problems, but that was 25+ years ago when timber seemed a lot heavier and stronger !

    Whatever you build, make sure you test it thoroughly with at least 150% of the anticipated load first, don't ever stand under it, and there shouldn't be a problem.

    You can always take the mill apart to make life easier - I carried mine up the garden path in pieces... Head just slides up and off, 4 bolts at the base to separate the column, remove the table if you need to...

    Cheers

    .

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    While I'm not against getting wood to do the job, testing with people won't cut any ice. Soft bendy people can't even approach the shock loading that a moving mill will transfer to the crane by way of a chain, unless it's hanging on a bungy rubber. Now there's an idea !

    Hanging the mill from the apex of an A-frame, with a well designed trunnion at the joint, will handle it, because you're using wood in tension and compression only, which is what it's good at. Wood is no good in bending, unless it's 8x2 teak, or something else exotic - oak at a pinch. Trouble with the A-frame is you really need a full triangular based derrick. Your base has to have a hole in the middle, so you're now designing a tetrahedral shape, and the joints are all three-way.

    The exotic route is an idea though - can you find a future use for an 8x3 beam of teak ? Are you building an old fireplace any time soon ?

    I hang my mill head from a hole halfway up an 8 ft span of a 8x2 floor joist, but that's only the head for a Centec, and I can just lift that by hand, anyway.
    Richard

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    Bah humbug!

    300Kgs is not all that much.

    I would suggest that rather than planning to use your 4x2 horizontally you should instead make a tri pod over the opening, shear leg style.

  10. #10
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    Hmmm, it is possible that you are misunderstanding..
    When I say an A frame I mean along the lines of 2 Aframes with a beam supported in each end by the top's of the A.

    Maybe two 2x6 on end for the beam and 2x4's for the rest...

    Part of the reason I need an A frame gantry rather than just using an engine-hoist(which would be twice the money of the wood) is that the mill is on a meter wide base of stacked 2x4's so the legs of an engine hoist wont be far enough apart to fit

    I wish I could rent a steel gantry but there is no longer any available locally.

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