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Thread: Winch on a winch!

  1. #21
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    Quote Originally Posted by Didge View Post
    If your mate is hanging over a cliff and you have to rescue him/ her and you're both hanging on by one arm each, you are feeling the full weight (force) of the person who is dangling through that one arm. Right so far? So, as we've all seen in the movies and would, no doubt, do ourselves we would employ our other idle arm and grab the dangling person's idle arm. There, we've halved the load on the first arm we used. So the load would be halved but the rescue, retraction speed would not.
    Not if you were using that arm to hang onto something to stop yourself going over the cliff.

    OK, I know you said the other idle arm.

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  2. #22
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    there are 2 scenarios possible here.

    I'll use perfect world examples and at no point will i consider miscellaneous factors Just maximum numbers.

    In black,
    I'll assume that both winches will pull a steady 9000lb for the whole pull and not take into account the dropping of the line pull as the winch drum diameter increases as cable is wound on nor the increase in line speed as that occurs. Naturally both winches wind at the same speed.

    In blue I'll give a simple rundown on what tends to happen in a basic real life example

    IF you set up to recover hook to hook both winches experience 9000LB of pull once winching commences. Both winches will wind in at the same speed so with one vehicle anchored its line will wind in its hook at a set speed If the second vehicle starts to winch then it will winch towards its hook at the same speed. As the hook is moving towards the anchored vehicle at Xm/min and the second vehicle is moving towards the hook at the same Xm/min then the overall speed of the second vehicle is 2Xm/min.

    In reality it doesnt quite work that way, one winch will hold at its stall point as the second winch winds in then as the load comes off the first winch will begin to wind in. As the second winch is winding in more quickly it will wind on more cable and thus reduce its pulling power, at this point the first winch will do more winding untill the balance point is reached, both winches will wind in untill one or the other overloads and stalls before the load comes off and it begins winding in again. the vehicles overall speed goes up and down but usually averages out at something like 1.6-1/7X single winching speed if both winches are near enough to identical and wind on evenly. Typically winching this way, youd wind one winch in for 30 seconds and then the other, once you were out of the really properly stuck bit youd wind one winch in all the way (it takes more juice and makes more heat starting the winch under load compared to continuous light winching) then winch the other one in.


    The main advantage of this kind of winching is that you get double the recovery range.

    The second method is hooking the winch of each vehicle to and anchor point on the other.

    This method double your pulling effort but not range or speed.

    Vehicle A is winching its hook at Xm/min and YKg of tension
    Vehicle B is winching its hook at Xm/min and the Same YKg of tension.
    the winches are winding at the same speed but as the winch of Vehicle A is stationary and the hook of vehicle B is attached to the vehicle the line speed does not increase however the amount of pull is increased X2 as you have 2 seperate winch configutations working. Xm/min and 2YKg of pull.


    In real life one winch will work faster than the other pick up more load and slow down untill the second winch begins to take up some of the load. In the case of electric winches once both cables are taut they will stay that way untill some one runs out of batteries or stops winching. The biggest advantage of doing this is it doubles your pull, In reality you wouldnt do it as you would be unlikely to be able to anchor the anchoring vehcile well enough to prevent it from pulling free and if you had enough ability to anchor it well enough you would usually setup a second anchor and winch directly from that with a snatch block or the recoveree's winch.



    Yes, I have been that bored and messed about with this...
    Dave

    "In a Landrover the other vehicle is your crumple zone."

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  3. #23
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    I thought this would get everyone brains going
    Our Land Rover does not leak oil! it just marks its territory.......




  4. #24
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    phil needed winching!
    looking forward to those pics...

  5. #25
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    Quote Originally Posted by dullbird View Post
    I thought this would get everyone brains going
    Trouble maker, ask a hard question then disappear

  6. #26
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    Ok, here is the definative answer! (unless I'm wrong)

    Hook to hook:
    Line speed doubled
    Pull force maintained

    Hooks to bars
    Line speed maintained
    Pull force doubled.

    Much like using a lever (such as a gearbox or pully), we see the power doubled over single winch from the additional winch, and the additional power is seen as either increased line speed or increased pulling force.

    This said, the assumption here is that load vs winch speed has a linear correlation... which it does not.
    Cheers
    Slunnie


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  7. #27
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    the real answer is, both winches will crap out, break shear pins, cook motors and kill batteries.......

  8. #28
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    Homestar is offline Super Moderator & CA manager Subscriber
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    Just to add to the confusion a bit - there is some talk here of a double line pull. Did the result of this conversation yield any result from previous discussion? I thought that running a cable through a snatch block back to the rig halved the speed, but didn't provide and mechanical advantage - what was the result of all that...?
    If you need to contact me please email homestarrunnerau@gmail.com - thanks - Gav.

  9. #29
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    Quote Originally Posted by bacicat2000 View Post
    Just to add to the confusion a bit - there is some talk here of a double line pull. Did the result of this conversation yield any result from previous discussion? I thought that running a cable through a snatch block back to the rig halved the speed, but didn't provide and mechanical advantage - what was the result of all that...?
    Please explain, your argument does not agree with school boy physics. By using a double line pull you have effectively done a reduction gear job by taking twice the time to move the same distance. In an ideal world 1/2 the load on the winch.

  10. #30
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    Homestar is offline Super Moderator & CA manager Subscriber
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    I think you are right, but there is a huge thread on this and I ended up with a headache reading it all. Just wanted to know what the final outcome was - I've just been back to re read some of it, and I think you are right, but there was a lot of back and forth on all of this.
    If you need to contact me please email homestarrunnerau@gmail.com - thanks - Gav.

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