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MEWP's* on raked floors?

Discussion in 'Safety' started by JohnD, Oct 3, 2018.

  1. JohnD

    JohnD Well-Known Member Fight Leukemia

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    *First off, MEWP seems to be a British acronym (for Mobile Elevated Work Platform) but I'm using it since it's so descriptive.

    In another thread HERE there is a picture of a scissor lift on a raked floor. I was wondering if there was any standard for using them (and even ladders and scaffold) on a surface that isn't level?

    Yes there are ladders that have extendable legs for leveling**. There the threaded bases for scaffold leveling**

    ** I guess leveling isn't the correct word, I suppose it should be plumb instead.
    The Genie AWP and similar do have outriggers with screws for uneven floors, but that doesn't change plumb. There is the Super-Straddle of course which does.
     
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  2. soundman

    soundman Well-Known Member

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    I have seen people build counter rakes for a raked stage that will 'flatten' an area for a lift. so if your stage has a 5 degree slope you build a deck or two with a 5 degree slope the other way so when the counter rake is put on the normal stage deck you have a level surface to use the lift on.
     
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  3. Ben Stiegler

    Ben Stiegler Active Member

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    And it stays put how? Just by weight and friction, or ?
     
  4. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @soundman From experience, a counter-rake works well and two work better for 'flip-flopping' your way across a system pipe so long as a helpful co-hort doesn't try to rotate your counter-rakes to better accommodate your personnel lift. I've survived someone's attempt at rotating the counter-rakes as well but rapidly learned to keep an eye for such "helpful" behavior.
    Toodleoo!
    Ron Hebbard
     
  5. Ben Stiegler

    Ben Stiegler Active Member

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    One can imagine taking a tranquilizer dart gun up the MEWP to forestall such assistance ... or sandbags to drop.
     
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  6. soundman

    soundman Well-Known Member

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    Friction would be my guess. I don't recall ever having done a show with a raked stage. Just reporting what I have seen in the wild while visiting others. with an steep angle I would feel better with some screws or another locking trick.
     
  7. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @Ben Stiegler @soundman Full-bore productions of "Les Miz" (Broadway, Toronto and Vancouver) were routinely done not only on a rake but a rake including a 40' diameter automated raked revolve. They employed an interesting application of counter-rakes for 'flip-flopping' across stage when focusing. Even national and international tours included the rake and raked revolve.
    During my days in Stratford, their Avon proscenium space was raked and at least one season several productions from the Avon toured with the rake going along for the tour. In my memory, the counter-rakes were fitted with rubber feet glued and pneumatically stapled in place which provided adequate grip. The counter-rakes were ONLY used for work calls, it's not as if they were in use for performances and subject to dance and / or constant foot traffic.
    Toodleoo!
    Ron Hebbard
     
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  8. Quillons

    Quillons Active Member

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    Basically!

    *Physics warning!*
    Generally speaking, the weight of things points straight down. On an incline, this straight-down force can be thought of as two forces added together and corresponding to "along" the angle (the rake of the stage) plus "normal to" the angle (perpendicular to "along"). The force of friction is basically dependent on two things: how much weight is on the angled floor, and how slippery the surfaces are (things slide easier on ice vs on sandpaper, for example). As long as the "along" portion of the weight (fairly easy to calculate) is equal to the friction force (also not hard if you know the slipperiness), then the lift will not slide down the rake.

    It'll be a bit different if you want to consider that the wheels on the lift may roll down the stage (instead of skid along), but I'm pretty sure it's still a similar concept.

    What I would worry about would be tipping the lift when someone's in it and working up high. That's a different calculation though.

    Weight and friction for inclined lift.jpg
     
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  9. bobgaggle

    bobgaggle Well-Known Member

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    They make self leveling excavators for work on mountains and such, but I guess the demand for man lifts with the same capability isn't high enough to justify making them.

    Capture.JPG
     
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  10. FMEng

    FMEng Well-Known Member Fight Leukemia

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    I don't know about scissor lifts, but boom lifts have tilt sensors. If the wheels are too far out of level, the machine simply refuses to raise the boom. Knowing how careful the manufacturers are to prevent misuse of their products, I wouldn't be surprised if scissor lifts do the same.
     
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  11. Dover

    Dover Active Member

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  12. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    It would need to be a strong raked deck.
     
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  13. mbrown3039

    mbrown3039 Member

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    Here in Vegas there at least two places where you can rent one of those -- not so much because of raked decks, but because those lifts give you pretty good reach but still fit through standard doorways...m
     
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