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  1. #21
    Senior Member lvleph's Avatar
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    I am not sure. That is why I need to study.

  2. #22
    Senior Member blackbishop351's Avatar
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    Quote Originally Posted by Just Jeff View Post
    Is there another static equation that fits better? What's left to study up on? (Seriously asking...not being sarcastic)
    Quote Originally Posted by lvleph
    I am not sure. That is why I need to study.
    There isn't. It's a pretty simple force diagram analysis - but if you're like me you don't take someone else's word for it!
    "Physics is the only true science. All else is stamp collecting." - J. J. Thompson

  3. #23
    Senior Member Just Jeff's Avatar
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    That's what I thought...but I'm not the trig teacher!

    Let us know if you find another way to diagram it, though...always interested in geekdom when it comes to hammocks! (We're like that here. )
    “Republics are created by the virtue, public spirit, and intelligence of the citizens. They fall when the wise are banished from the public councils because they dare to be honest, and the profligate are rewarded because they flatter the people, in order to betray them.” ~Judge Joseph Story

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  4. #24
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    What would really be interesting is if she can connect a hammock support to a gauge and get actual force reading. Then we can compair those with the calcuations everyone uses that Jeff posted. I would be very interested to see how accurate they are.

    I realize we are arguing the finer points of something that we already can guess pretty close on using basic physics.
    Is that too much to ask? Girls with frikkin' lasers on their heads?
    The hanger formly known as "hammock engineer".

  5. #25
    Senior Member Just Jeff's Avatar
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    Yeah - I might be able to scrounge up something at work for that, too. I'll ask around if I get some free time.
    “Republics are created by the virtue, public spirit, and intelligence of the citizens. They fall when the wise are banished from the public councils because they dare to be honest, and the profligate are rewarded because they flatter the people, in order to betray them.” ~Judge Joseph Story

    - My site: http://www.tothewoods.net/
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    IMPOSSIBLE JUST TAKES LONGER

  6. #26
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    Quote Originally Posted by Just Jeff View Post
    Yeah - I might be able to scrounge up something at work for that, too. I'll ask around if I get some free time.
    I have been thinking about this. It actually would not be that hard. All you need is a scale that measures weight by hanging something on it. Like the fish scales or the ones you see people hanging their pack on to weigh.

    With that we could attach it inline with the hammock support. We know the weight of the hammock, so we can figure that in. We can add a 20 lbs weight to it and see what the resulting pull on the scale is. Than scale it up to whatever the user weights.

    It should be a linear system. The only thing that I can see making it non-linear and skewing the scaled down experiment, is if the ropes or hammock body perform different with different loads on them. If they did, it should be small enough to approximate out.

    Kind of a back of the napkin way of doing things, but should work.
    Is that too much to ask? Girls with frikkin' lasers on their heads?
    The hanger formly known as "hammock engineer".

  7. #27
    Senior Member blackbishop351's Avatar
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    Quote Originally Posted by hammock engineer View Post
    I have been thinking about this. It actually would not be that hard. All you need is a scale that measures weight by hanging something on it. Like the fish scales or the ones you see people hanging their pack on to weigh.

    With that we could attach it inline with the hammock support. We know the weight of the hammock, so we can figure that in. We can add a 20 lbs weight to it and see what the resulting pull on the scale is. Than scale it up to whatever the user weights.

    It should be a linear system. The only thing that I can see making it non-linear and skewing the scaled down experiment, is if the ropes or hammock body perform different with different loads on them. If they did, it should be small enough to approximate out.

    Kind of a back of the napkin way of doing things, but should work.
    If you're going to do it at all, why not go all out? Get a bunch of 2L soda bottles, fill them with water, and weigh each one as it goes in the hammock. As the weight gets up there, just use a bag of dog food or something to reduce bulk. I'd go all the way to around 200 lbs. - that way you'd KNOW if the function was linear or not.

    One issue - as the weight increases the support angle will change, which WILL make the data nonlinear. You could use a plumb bob and a protractor to measure the angle each time, but there would be a lot of room for error there. I'm not sure how else you'd account for it though.
    "Physics is the only true science. All else is stamp collecting." - J. J. Thompson

  8. #28
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    Quote Originally Posted by blackbishop351 View Post
    If you're going to do it at all, why not go all out? Get a bunch of 2L soda bottles, fill them with water, and weigh each one as it goes in the hammock. As the weight gets up there, just use a bag of dog food or something to reduce bulk. I'd go all the way to around 200 lbs. - that way you'd KNOW if the function was linear or not.

    One issue - as the weight increases the support angle will change, which WILL make the data nonlinear. You could use a plumb bob and a protractor to measure the angle each time, but there would be a lot of room for error there. I'm not sure how else you'd account for it though.

    Good point on the angle of the support. I forgot about that saging as weight is added. I think I would account for that by measuring the angle of the hammock when I am in it, then using that angle for my scaled down weight.

    The reason I am thinking about the scaled weight, is just finding a scale that will read 700 lbs. Much easier to find one that goes up to 50 lbs or so.

    I was also thinking of putting the scale in 2 different locations. L1 being from the hammock body to the rings (of other point in different setups), and L2 being on the strap to the tree. Both places are using line with load ratings. I think the angle for L1 is usually over 20 deg, so I am not too worried about it. But than again that is the rope rated to 1400 lbs. I am not sure of the strap rating off the top of my head, but it should be higher.
    Is that too much to ask? Girls with frikkin' lasers on their heads?
    The hanger formly known as "hammock engineer".

  9. #29
    Senior Member blackbishop351's Avatar
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    Quote Originally Posted by hammock engineer View Post
    Good point on the angle of the support. I forgot about that saging as weight is added. I think I would account for that by measuring the angle of the hammock when I am in it, then using that angle for my scaled down weight.

    The reason I am thinking about the scaled weight, is just finding a scale that will read 700 lbs. Much easier to find one that goes up to 50 lbs or so.

    I was also thinking of putting the scale in 2 different locations. L1 being from the hammock body to the rings (of other point in different setups), and L2 being on the strap to the tree. Both places are using line with load ratings. I think the angle for L1 is usually over 20 deg, so I am not too worried about it. But than again that is the rope rated to 1400 lbs. I am not sure of the strap rating off the top of my head, but it should be higher.
    You can find gauges that are designed for use on high-tension cables - that might work pretty well. It would definitely work for that load range. I tried to find a link to one, but no luck so far. Then again I didn't look that long :P
    "Physics is the only true science. All else is stamp collecting." - J. J. Thompson

  10. #30
    slowhike's Avatar
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    if someone lived near the cost, they could probably find some one that would be willing to let them use the scales that they hang the big ones from (sharks, marlins, etc) for a few hours to record stress & angles & such.
    don`t leave the CREATOR out of the creation!

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