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Thread: Workbench Safety

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    Should Get Out More maccecht's Avatar
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    Default Workbench Safety


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    I made a workbench for my man shed many moons ago from some scrap metal. Tis a simple affair and operates much like a deckchair. Initially it was raised via a trailer winch and then I went lazy and added an electric winch with 2000lbs capability. Over time only the last 2m or so of rope gets used and it had suffered a bit as it got flattened and misshapen. This inevitably caused it to fail the other night when I was raising a bike and it almost took my head off
    Bike was only about a foot off the ground so no damage done. I will renew the SWL but need a safety device that can work going up and down should a rope failure happen again. Going up not an issue can make a stay that drops into serrated teeth or pins on the lower frame but going down mmmm!!! any good ideas chaps? Sorry about the links but they are safe. When it is down it is the floor. Fair bit of strain on the initial lift as it pulls up and back but no room to install a jack as the floor is a raised affair.
    https://www.dropbox.com/s/umg43btxon...embly.jpg?dl=0
    https://www.dropbox.com/s/zdh3pxqch2...aised.jpg?dl=0
    https://www.dropbox.com/s/9p33ux9rn9...wnpos.jpg?dl=0

    https://www.dropbox.com/s/y83yb2qmxg...inuse.jpg?dl=0

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    Default Re: Workbench Safety

    This might be a complete non-starter, but for lowering the ramp could you use something like a hydraulic support strut (as fitted to car tailgates) to slow the movement?

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    Default Re: Workbench Safety

    Quote Originally Posted by Lutin View Post
    This might be a complete non-starter, but for lowering the ramp could you use something like a hydraulic support strut (as fitted to car tailgates) to slow the movement?
    My poor design would make this difficult it is just one square frame on top of another with legs that fold down when the frame is lowered. I would change SWL to a strap as it is less likely to fray but there is no way of mounting the strap onto the winch

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    Default Re: Workbench Safety

    Most lifts seem to have a jack working at an angle....that does up and down. Are you sure there is no room to install a ram/jack at an angle?

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    Default Re: Workbench Safety

    Quote Originally Posted by davidat19 View Post
    Most lifts seem to have a jack working at an angle....that does up and down. Are you sure there is no room to install a ram/jack at an angle?
    Nope the bench is set withing wooden joists which are raised a foot above the ground so no support for a jack and the way I have a hinged section to accommodate the bench lifting on the end preludes any use of a jack. Left hand end in the photos. I have resolved the going up by welding a load of 16mm pins on the bottom frame which a leg drops into as the bench goes up. The leg houses into the top frame when the bench is down and as it goes up it drops in behind each pin in succession so it can only ever drop an inch if it fails on the way up. Yet to resolve the going down bit.

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    Default Re: Workbench Safety

    Not really a solution, but inspect &/or change the rope at regular intervals? PITA, but AFAIK what the professionals to with lifting gear.

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    Default Re: Workbench Safety

    an airbag would do the job, and would likely fit in the space between the frames, might be spendy tho. The other option is a fall arrest type rig, which could be home built. The simplest is a second cable that runs to a drum/ratchet setup. The ratchet pawls are rigged so they can fly outward if the drum rotates too quickly and lock up, under a controlled descent the drum doesn't spin fast enough to lock. A more sophisticated version puts a paddle wheel in a closed drum of oil, at high speed the the oil offers a lot of resistance, at low speed it's barely noticeable. The safety cable attached to either device generally lasts pretty well as it isn't subjected to any significant load, but they will still eventually wear out due to the strands breaking from bending fatigue.

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    Default Re: Workbench Safety

    Quote Originally Posted by Cousin Jack View Post
    Not really a solution, but inspect &/or change the rope at regular intervals? PITA, but AFAIK what the professionals to with lifting gear.
    And along with BP's post immediately after yours, something which can fail is, sooner or later, likely to do so. The recovery industry (i.e. the 'AA relay' type trucks that winch cars up) suffer from the cables breaking. Inspection isn't sufficient as they often go from the inside first. The AA, IIRC, use a 'fall arrest' type link in parallel with the cable.

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    Default Re: Workbench Safety

    Most fall arest systems have minimum angles they work to. The SWL looked fine until it failed. Might just put the climbing rope I have to use and have it rigged as a safety line. Going up is sorted with my add on support leg.

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    Default Re: Workbench Safety

    Quote Originally Posted by Horse View Post
    And along with BP's post immediately after yours, something which can fail is, sooner or later, likely to do so. The recovery industry (i.e. the 'AA relay' type trucks that winch cars up) suffer from the cables breaking. Inspection isn't sufficient as they often go from the inside first. The AA, IIRC, use a 'fall arrest' type link in parallel with the cable.
    Which is why I said "inspect &/or change". I would be treating a wire rope like that as a life-limited part, after x years (probably 1 or 2 but I have no real idea) I would change it anyway. The inspection bit would be every 3 or 6 months, if it looked iffy (eg badly flattened) it would get changed early. A separate safety system would be better.

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    Default Re: Workbench Safety

    cables aren't generally time limited, unless you are in something like the nuke industry. They generally fail through bending fatigue and/or erosion, and unless they are subject to massive overloads, the outside strands go first, as they are subject to the greatest amount of bending. FWIW, the british standard for cables uses the following recommendation for inspecting wire ropes: put on a heavy leather glove, lightly grasp the cable and then run your hand along its length, in both directions. You then inspect anything that snags , because it's most likely a broken strand. Rust or erosion is unlikely to be a problem in this application.

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