Gantry crane legs
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  1. #1
    Join Date
    Jun 2017
    Location
    Lower Michigan
    Posts
    9

    Gantry crane legs

    Hey Folks,

    I’m building a gantry crane for my shop and I want it to be height adjustable. The beam on top that I’m using has a 4” flange so I’m thinking about a 4” square tube that slides into something larger. My dilemma is the welded seam on the inside of hot rolled square tube.

    Anybody have any advice on what wall thickness or tube type I should look at?

    I don’t want a lot of slop in the system just to accommodate the seam but I understand it can’t be too tight or you’ll never get it to move if it gets cockeyed.
    Should I be thinking about a cold rolled square tube for the outside piece?

    What have you folks done for extending legs? (Be it on a gantry or other.)

    -Dave

    P.S. I should note that I’m only interested in talking about the legs here. I’m not asking for advice about how to connect the legs to the beam, load ratings for the beam or casters, etc. just trying to get the adjustability end of things worked out. I’ve worked with plenty of square tubing. Just never with larger sizes that had to slide in and out of each other.


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    Last edited by Super Dad; 07-13-2019 at 10:16 PM.

  2. #2
    Join Date
    Mar 2015
    Posts
    207

    Re: Gantry crane legs

    I haven't tried this so you be the judge. Hypothetical sizes for demomstration only. Your 4" sliding into 5" with 0.125 wall and 0.25" high interior seam weld equal's 4.5" interior. 1.5"x1.5"x0.1875 (3/16) cold rolled angle tacked to four corners of 4" tube leave's 0.125 (1/8) clearance between interior and exterior tubes. If my math is right.

  3. #3
    Join Date
    Mar 2004
    Location
    hueytown, ala
    Posts
    78

    Re: Gantry crane legs

    don't know about larger tube but have done it with smaller stuff. on the interior tube surface, grind a notch along the tube that will clear the inside weld protrusion. sorta like a keyway

    john

  4. #4
    Join Date
    Oct 2006
    Location
    Illinois
    Posts
    8,771

    Re: Gantry crane legs


  5. #5
    Join Date
    Jun 2017
    Location
    Lower Michigan
    Posts
    9

    Gantry crane legs

    Now THAT’S exactly the kind of stuff I was looking for!! Those are great ideas! Shimming the interior tube with angle iron, grinding a key way for the weld seam and seeing how Wallace put their model together. (Looks like maybe some channel around the interior tube.

    Thanks folks! Much appreciated!

    I’m thinking that the outer tube is going to be somewhat short so I don’t have a long amount of leg to worry about. Here’s a pic I found that speaks towards what I’m thinking.





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    Last edited by Super Dad; 07-14-2019 at 11:49 AM.

  6. #6
    Join Date
    Sep 2013
    Posts
    148

    Re: Gantry crane legs

    My gantry has extendable legs like you’re describing. I used 4x4 inside of 5x5. On the bottom of the 4x4 I welded a 1/2” plate that is profile cut to match the inside of the 5x5, with a notch where the seam is. Then on the top of the 5x5 I welded a bolt flange, to which I bolted another piece of 1/2” plate with a square hole about 4.05” square.



    The concept is similar to this:




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  7. #7
    Join Date
    Apr 2012
    Location
    NW OR
    Posts
    103

    Re: Gantry crane legs

    The square cap plates are slick.

    You don't want the tubes as tight together as you think. If it's ever sitting on remotely uneven ground, you'll have a hell of a time getting it down to a lower setting. The legs on mine are commercially made by Spanco. They are just plain 3/8 wall box tube sliding together. There's like a 1/4"+ gap all around between the 8" outside box tube and the telescopic portion. Any slop gets bound up as soon as you have a load on. The guy I bought this one from showed me a picture of him lifting a 9 ton ship's propeller when it was his only shop crane before he installed a bridge crane. A little rattle in the joint causes no issues.




  8. #8
    Join Date
    Feb 2010
    Location
    anoka co mn
    Posts
    520

    Re: Gantry crane legs

    I used 5x5 3/16 for the outside and 4x4 3/16 for the inside tube. Shimmed the difference with UHMW bearing plates.

  9. #9
    Join Date
    Sep 2005
    Location
    Cave Creek AZ
    Posts
    2,782

    Re: Gantry crane legs

    Quote Originally Posted by djd775 View Post
    My gantry has extendable legs like you’re describing. I used 4x4 inside of 5x5. On the bottom of the 4x4 I welded a 1/2” plate that is profile cut to match the inside of the 5x5, with a notch where the seam is. Then on the top of the 5x5 I welded a bolt flange, to which I bolted another piece of 1/2” plate with a square hole about 4.05” square.



    The concept is similar to this:




    Sent from my iPhone using Tapatalk
    That is a darn fine method of doing that. I hope I rememberit next time I need it.

  10. #10
    Join Date
    Jun 2017
    Location
    Lower Michigan
    Posts
    9

    Re: Gantry crane legs

    Man! I really like that idea djd775. Fitted plates on the ends. I hear what others are saying about binding up but what’s your experience been when adjusting the height of your gantry. Seeing how the cheap HF models adjust (crank one side a little, then the other a little, repeat.) makes me want to ask you how you raise and lower your beam? I thought about making a fixed point on my shop ceiling that I could attach the beam to with a winch/come along/chain fall/etc. and adjust the beam height with that while hanging from the ceiling. I don’t expect to have to adjust it often and I’m not planning on having it outside the shop. (Mr. Murphy will likely make me regret saying that . . .)

    Thanks for the pics everyone. It’s really helpful to see what others have done.


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  11. #11
    Join Date
    Dec 2018
    Posts
    1,380

    Re: Gantry crane legs

    Like in the earlier post...……...a diaphragm works fine. No need to monkey around with weld flash on the inside of the tubing.

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    Size the diaphragm to the OD on the slip fit, weld 'er up. Fixture the two exterior pieces of tubing so's they're aligned.

    Kind of a throw-it-together build sometime back around 2011, when I had to put a new suspension under the trailer.

    I get into this kinda weird stuff...…………………..Holy crap, need a new suspension, need something to hold the whole mess up while I'm under it working

  12. #12
    Join Date
    Dec 2012
    Location
    Valley City, Ohio
    Posts
    410

    Re: Gantry crane legs

    Your throw it together is a under statement! You show pictures of your work and you are a true craftsman and then i look at your background pics and your working in a field and in some rough conditions not in a cozy shop with a concrete floor. I sure enjoy your post.

  13. #13
    Join Date
    Sep 2013
    Posts
    148

    Re: Gantry crane legs

    Quote Originally Posted by Super Dad View Post
    Man! I really like that idea djd775. Fitted plates on the ends. I hear what others are saying about binding up but what’s your experience been when adjusting the height of your gantry. Seeing how the cheap HF models adjust (crank one side a little, then the other a little, repeat.) makes me want to ask you how you raise and lower your beam? I thought about making a fixed point on my shop ceiling that I could attach the beam to with a winch/come along/chain fall/etc. and adjust the beam height with that while hanging from the ceiling. I don’t expect to have to adjust it often and I’m not planning on having it outside the shop. (Mr. Murphy will likely make me regret saying that . . .)

    Thanks for the pics everyone. It’s really helpful to see what others have done.


    Sent from my iPhone using Tapatalk
    I can’t really speak to the binding issue...I raise/lower it with my forklift and it moves without much issue. A fixed point on the ceiling sounds like it could work well if you can winch right at the balance point.


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  14. #14
    Join Date
    Jun 2017
    Location
    Lower Michigan
    Posts
    9

    Re: Gantry crane legs

    A fork lift!!! That’s what I need!!! One of those would solve all kinds of problems.

    It’ll be a while before I have something like that, although a skid steer is in the plans at some point for clearing land.

    Glad to hear you don’t have binding problems.

    As for finding the center of the beam for balance, I might just weld a bucket hook to each end of the top of the beam and run a chain or lift strap between them and grab that with whatever I’ll be hoisting the beam up with. It’ll still need to be centered but won’t be as sensitive to being off center a little. Or maybe just find the center and weld a D ring . . .

    I’m gettin’ off topic.

    Even if I had a somewhat looser fit, I still like the end plates with a notch for the seam for two main reasons: 1) I don’t have to get any DOM tubing to avoid the seam. Saves money. 2) A loose enough fit to simply allow for the seam would immediately scratch whatever paint I put on there all to heck.

    A plate with a notch . . . I like it.

    -Dave




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