Thread: MA Calculation

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    Default MA Calculation

    I recently found this drawing explaining Mechanical Advantage in a text I was reading.

    I believe it to be mislabeled in the text. Tell what's your opinion on the MA.
    3:1 or 4:1.

    I'll share my opinion in a few days with my reasoning.

    Steve
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    Well, we got 1T+1T =2T at the first load, 1T+1T at second load which makes 4T

    That's my guess.

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    3:1. Only 3 ropes pulling the load. The 4th pulley is merely a change of direction.
    Shawn M. Cecula
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    I agree with Shawn....it's a 3:1 with a redirect.
    "Training Prepares You...For Moments That Define You

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    3:1

    What was is labeled as? The picture doesn't say.
    ~Drew
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    Darn, I never was good at math. Back to reading the T-method in my book.

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    3:1, if the end of the rope is attached to the load end then the MA should be and odd number, if the end of the rope is attached to the anchor end it's an even MA

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    Quote Originally Posted by MichaelXYZ View Post
    Well, we got 1T+1T =2T at the first load, 1T+1T at second load which makes 4T

    That's my guess.
    Michael, you did your T-Method wrong.

    1T enters the system at the haul.
    Goes around the change of direction, comes out 1T.
    Enters the traveling pully, becomes a 2T.
    Enters the second change of direction, still 2T.
    Pulls on the load at the knot +1T added to the 2T = 3T.

    Let me know if you have any questions.
    ~Drew
    Firefighter/EMT/Technical Rescue
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    Not much of a challenge there... it's clearly a 3:1 with a change of direction (aka redirect).
    Dave

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    Sorry, meant to port a followup yesterday.
    My initial thought was a 3:1 with a COD.
    However, the text identified it as a 4:1. Which is against almost 20 years of experience.
    An email to the author revealed a typo. It was suppose to be inverted with the load where the anchor is, in which case, it would be a 4:1.

    Thanks for everyone's input

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    Quote Originally Posted by schase1967 View Post
    Sorry, meant to port a followup yesterday.
    My initial thought was a 3:1 with a COD.
    However, the text identified it as a 4:1. Which is against almost 20 years of experience.
    An email to the author revealed a typo. It was suppose to be inverted with the load where the anchor is, in which case, it would be a 4:1.

    Thanks for everyone's input
    You mean 3:1 right?

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    Quote Originally Posted by MichaelXYZ View Post
    You mean 3:1 right?
    Image depicts a 3:1.

    It was evidently labeled as a 4:1 in the book.

    Chase is saying that the author wanted the load and anchor reversed which would make it a 4:1.

    Tracking?
    Last edited by FiremanLyman; 02-16-2012 at 09:42 AM. Reason: which witch
    ~Drew
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    Exactly what I meant. My apologies if I didn't explain that well.

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