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Sprockets+Roller chain+Rotation >Linear oscillation; how?

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  1. Apr 28, 2015 #1
    Hello there!

    I am a high school student, and I am really interested in Physics, esp. electronics and mechanics; I am not an expert or something, so please don't take it hard on me.

    Yesterday, I was bored and I messed around and successfully made a catapult (http://www.algodoo.com/algobox/details.php?id=100119). Of course, not IRL, but on my PC.

    I am not advertising or something, but I am just saying, you should check the free software named "Algodoo"; it is a 2D physics sim, worth a shot, and totally free. If you can get it, it is easier for you guys to help me because I am using that program.

    Anyways, to the point, I am very keen on replicating Mythbusters' "Arrow Machinegun"(), which is a very simple mechanism, basically containing two sprockets, one roll chain, some handles, a slider, bow, string, release mechanism and other miscs.

    The problem is, how in the bloody universe, do you have two sprockets and a chain to reciprocate? I heard Jamie saying "the sprocket engaging the slider", but how?

    I would really like it if you guys can draw me a model of how I can do it. It'd be even more awesome if you can use Algodoo and draw it for me!

    Thanks a lot! :D
     
  2. jcsd
  3. Apr 29, 2015 #2
    Hello? Anyone?

    Guess not. :/
     
  4. Apr 29, 2015 #3

    jack action

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    I'm not sure how the presented mechanism work, but you can convert rotational motion into a reciprocating motion with many mechanisms:

    The crank and slider:

    p.gif

    The Hoeckens linkage:

    Hoeckens_linkage_Animated.gif

    Any 4-bar linkage of the crank-rocker type:

    650px-Linkage_four_bar.svg.png
     
    Last edited by a moderator: Apr 18, 2017
  5. Apr 30, 2015 #4
    @jack action

    First off, thanks a lot for the reply!

    The linkage systems, cranks and basic rotary/linear converters won't work for me, because the mechanism I am using is attached to the roll chain, which consists of both rotary and linear motions, so it won't cut it for me.

    HOWEVER, I worked it out with a very simple solution this morning; I fused it with a scotch yoke! I attached it with a red pin on the roll chain, and it works just fine; eureka!

    Check out the pictures I attached.

    Red: Slotted link mechanism
    White: Frictionless sliders
    Green: Body
    Gray: Roll chain
    Yellow: Sprockets (gears, wutevz)

    Anyways, thanks a lot for your help! :D

    https://flic.kr/p/sm8Sb5
    https://flic.kr/p/sogoSW
    https://flic.kr/p/sogp2U
     
  6. Apr 30, 2015 #5

    jack action

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    I forgot about that one. Good catch, as I couldn't wrap my head around why they use a chain with 2 sprockets of the same size. It makes perfect sense now.
     
  7. Apr 30, 2015 #6
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