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  1. #31
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    Oct 2011
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    Adelaide
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    59
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    Quote Originally Posted by Bryan View Post
    I think I like the A frames instead of the usual inverted T with bracing. But if I wanted height adjustment I would need the verticals.
    We have one of these at work - GHE Lifting Specialist
    Not cheap but Kennards hire them too. As you can see, they do a Y frame that allows some vertical adjustment of the beam position. Most of the structure is Al. I once hired the smallest version of these and managed to pack it all into a 323 hatchback with the beam on the roof.

    Michael

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  3. #32
    Join Date
    Aug 2009
    Location
    Quindanning, WA
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    175

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    Quote Originally Posted by Bryan View Post
    Gallegos, what are the height and span of your design? Have you ever found these dimensions limiting? My current thinking is minimum span would be to clear a trailer, so say 2.4m, and clearance under the roller door is about 2.65 so under beam height would be 2.5 at best. Which sounds pretty skinny for a mill, even on a trailer. And no good for a truck. Sounds like you weren't interested in vehicle loading.

    I was going to ask about the beam but I think I get it. Once I zoomed in I could see the bolts. You've doubled the centre section and bolted the ends to the braces. Looks real sturdy.

    And I think I like the A frames instead of the usual inverted T with bracing. But if I wanted height adjustment I would need the verticals.
    Mines about 2.8m high, which was as high as I could go while still clearing the lowest point inside the shed. Its about 1.8m wide, which was just the length of the offcuts of steel I had at the time and was about right to suit my lathe. The plan has been to make another wider beam so it will fit over a car for pulling engines but the problem with making it wider will be it taking up more room when not being used and being harder to move around. Even at the moment it hard to move in one direction because the end frames are just far enough apart to be difficult to push on both at the same time. I've also used it for moving lengths of steel around and this is another situation where being to big would be an issue.... swings and roundabouts.

    I'm lucky enough to have an excavator for unloading so this is only for moving stuff around inside the shed.

    The inverted T with bracing would be fine and you could extend the bracing up as high as possible to suit the minimum height you need to get in and out of the shed and maintain most of the strength anyway. Should be pretty easy to make telescoping columns that would be strong enough using 90mm SHS nested inside 100mm SHS.

    Have a look at richmond wheel and castor company for castors, from memory mine were about $200 for the 4. There are a massive number of options but I got 200mm cast iron ones just with the bushed axles as they were the cheapest option that would support 500kg. They are also available with bearings so I keep meaning to pull one apart to see what would be involved to retrofit bearings on mine.

  4. #33
    Join Date
    Feb 2013
    Location
    Laidley, SE Qld
    Posts
    368

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    Quote Originally Posted by Oldneweng View Post
    This is not the ideal design for a truss............
    The square frame truss is fine just so long as the verticals are fully welded to the horizontals, ie they are moment resisting joints rather than pinned joints. Consider it as a fabricated beam. I like them from a fabrication point of view because all the members are square cut.


    Vierendeel bridge - Wikipedia, the free encyclopedia

  5. #34
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    Jan 2011
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    Far West Wimmera
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    63
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    2,765

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    Quote Originally Posted by bob ward View Post
    The square frame truss is fine just so long as the verticals are fully welded to the horizontals, ie they are moment resisting joints rather than pinned joints. Consider it as a fabricated beam. I like them from a fabrication point of view because all the members are square cut.


    Vierendeel bridge - Wikipedia, the free encyclopedia
    Yes they are easier to make. The bridge shown in the link relies on the bulk of the vertical beams to provide the triangulation strength. Triangulation is still there but contained within each single vertical beam.

    I am not suggesting that your beam is not capable of doing what you want, but if a truss is to be made a triangulated beam is the strongest type using the least amount of material. A beam could be made using this method which is equal to yours in capacity using much smaller cross section material. Angled cuts are required but it is the cheapest and lightest method. Virtually all building of structures uses triangulation of some type.

    Your beam could be improved by adding angle placed reo. The strength then is dependant on the tension of the reo and the welds and has nothing to do with the bending strength of the material. An I beam because of its height uses a form of triangulation.

    Cheers Dean

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