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Thread: Ratchet type chain or rope and pulley system

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    Ratchet type chain or rope and pulley system

    Every so often, we build a rope bridge. We own two three way pulleys which we use to tension the bottom rope which the YP walk on. However, I have been wondering if there is a better way (and making the tension stronger) than having lots of YP pulling it tight, although that is great for teamwork!

    I was wondering about using some sort of wire or chain based system with a ratchet, but all the googling I can do has shown me solutions for lifting rather than for tensioning. It may be I'm looking for the wrong thing. Does anyone have any idea what I am talking about and may be able to offer some guidance or help?

    Thanks in advance

    Bert

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    Senior Member Bushfella's Avatar
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    You could use ratchet straps such as used in slack-lines.
    Ewan Scott

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    Quote Originally Posted by Bert View Post
    Every so often, we build a rope bridge. We own two three way pulleys which we use to tension the bottom rope which the YP walk on. However, I have been wondering if there is a better way (and making the tension stronger) than having lots of YP pulling it tight, although that is great for teamwork!
    So bearing in mind that your purpose is not to build a better bridge, it's to build people who can work in teams, what exactly is your problem here?

    You could use a two-pole winch: requires teamwork and gets it tighter, and not very dangerous.
    John Russell
    ex-CSL now ACSL 1st Pinhoe Exeter Devon
    Cubs don't care how much you know, but they need to know how much you care.

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    I am not recommending them as I do not have the enough knowledge of their capabilities; but have you looked at Tirfor winches, they are designed for heavy duty pulling using steel rope, e.g. removing tree stumps.
    A week of camp life is worth six months of theoretical teaching in the meeting room. Baden-Powell

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    Senior Member Bushfella's Avatar
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    Quote Originally Posted by Bert View Post
    Every so often, we build a rope bridge. We own two three way pulleys which we use to tension the bottom rope which the YP walk on. However, I have been wondering if there is a better way (and making the tension stronger) than having lots of YP pulling it tight, although that is great for teamwork!

    I was wondering about using some sort of wire or chain based system with a ratchet, but all the googling I can do has shown me solutions for lifting rather than for tensioning. It may be I'm looking for the wrong thing. Does anyone have any idea what I am talking about and may be able to offer some guidance or help?

    Thanks in advance

    Bert
    A bit more time on this...

    There isn't really a better way.

    "lots" of yp pulling on the rope... has a real impact on the tension. The average adult will exert 75kgs pull, a teenager putting effort in will probably be around 40kgs ( a guesstimate), so 10 teenagers could put around 400kg pull on the line. The old AR code had a 2:1 leverage element, so 800kgs tension. However, not everyone had suitable pulleys and many used a double and triple, or two triples, so multiplying the pull by roughly 6 times - close to 2.4 tons of tension, more than enough to keep the main hawser taught. And way more than a slack line ratchet strap.

    I've seen 10 adults hauling on the line, putting close to 4.5 tons of tension on the hawser - or thereabouts. The problem is that the rating of rigging on the smaller malleable block pulleys is nowhere near that sort of load, steel plate and sheave type have an even lower rating. Neither the ropes, nor the sheaves of the pulleys.

    The above is of, course, theoretical and open to variation, but nonetheless gives a rough idea of the loads involved.

    As John says, the whole idea is teamwork, so a ratchet style approach completely misses the point. I have always found that kids love the idea of building bridges and runways as a team. Why do away with that?

    I have, in the past, anchored a Land Rover, chocked the wheels and used a winch to tension a hawser... It dragged the Land Rover despite it being chocked, and the rope tension was lower than when the kids did the job properly.
    Ewan Scott

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    I was thinking tirfor jack. However, googling tirfor jack brought up this https://www.toolstation.com/pull-winch/p98107

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    Quote Originally Posted by Kev View Post
    I was thinking tirfor jack. However, googling tirfor jack brought up this https://www.toolstation.com/pull-winch/p98107

    Used to have one of these till it collapsed at a critical point and it was nowhere near 4000kg. Wire ropes need very careful handling. I'd never let kids anywhere near them ( or most adults).
    Ewan Scott

    It seems that there are a lot of Nawyecka Comanch around....





    Nawyecka Comanch'": "Means roundabout--man says he's going one way, means to go t'other" Ethan Edwards - The Searchers



    www.upperdearnevalleynavigators.org.uk

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