ballistic pendulum speed tests

Discussion in 'General Slingshot Discussions' started by onnod, Nov 22, 2012.

  1. onnod

    onnod Im from Holland, isnt that weird?

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    hey guys,<br>after i heard Barnabas Malchus talking about a ballistic pendulum i wanted to test this, so i made a setup with some wire, a can and some clay and started testing.<br>i did 10 shots all with 14 mm steel and removing the steel ball after every shot(if you don't do that you will get a different result every time)<br>the steel ball made the can witch weighted 353 grams swing and this resulted in a 9,3 cm height difference.<br>I then put these results in to <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/balpen.html" class="postlink" target="_blank" rel="nofollow">THIS</a> table.<br>this gave 43.8 m / 143 ft per second.<br>this gives you 10.75 joules.<br>well this was enough physics for this week.<br>bye<br>onnod<br>
     
  2. slingpit

    slingpit Slingshot addicted

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    Thats interesting.<br>Thanks for the Link.
     

  3. zwillie

    zwillie New Member

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    hehe, same with me.<br>Very cool invention.
     
  4. FIAAO

    FIAAO Failureisalwaysanoption

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    Ah, very interesting! I think I have to try this myself. Thanks for the link! <img src="http://illiweb.com/fa/i/smiles/icon_smile.gif" alt="Smile" longdesc="2">
     
  5. tokSick

    tokSick Senior Member

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    So no chrony needed? Nice. I already watch that on you tube but i didn' t get it good. Gonna try to understand the physics later but i have to find a second hand brain for cheap first <img src="http://illiweb.com/fa/i/smiles/icon_wink.gif" alt="Wink" longdesc="15"> .
     
  6. Arturo Borquez

    Arturo Borquez Administrator

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    Very interesting Onnod ... how did you measured the "lifting" of the pendulum ... a camera with a ruler?
     
  7. onnod

    onnod Im from Holland, isnt that weird?

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    i used a cutting mat as background and my camera(mobile phone) to see the distance, so basicly a camera and a ruler
     
  8. FIAAO

    FIAAO Failureisalwaysanoption

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    What about the weight for the swingarm of the pendulum?
     
  9. Arturo Borquez

    Arturo Borquez Administrator

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    Yeah ... I also has a cutting mat in cms !!! (didn't tought was that simple !!! <img src="http://illiweb.com/fa/i/smiles/icon_scratch.png" alt="scratch" longdesc="33">) you are a smart young man Onnod ... thanks ...
     
  10. zwillie

    zwillie New Member

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    @ onnod <img src="http://illiweb.com/fa/i/smiles/icon_cheers.png" alt="cheers" longdesc="28">
     
  11. FIAAO

    FIAAO Failureisalwaysanoption

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    Interesting fact: Using the same bullet as you use, and a pendulum with the same weight as yours, the amount of joule is about the same as the height of the swing + 10% of the swing, using the calculator you linked to! <img src="http://illiweb.com/fa/i/smiles/icon_razz.gif" alt="Razz" longdesc="9">
     
  12. JoergS

    JoergS Administrator

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    A pendulum should use a non deforming plate, otherwise the deforming will falsify the data.<br><br>Also a pendulum shows the momentum of the shot rather than the energy. Means, the formula is <br><br>mass x speed<br><br>rather than<br><br>0,5 mass x speed x speed = (energy)<br><br>Here is where slingshots shine - a solid hit from a 20 mm steel ball, flying at 75 m/s, will let the pendulum swing out more far than a high velocity .22 hit, and about as far as a hit from a 9mm Luger. <br><br><a href="http://slingshotchannel.blogspot.de/search?q=momentum" target="_blank" rel="nofollow">http://slingshotchannel.blogspot.de/search?q=momentum</a>
     
  13. CEZ

    CEZ New Member

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    Hi Joerg, does it still make sense to use it as a cheap speed indication device for us non-chrony owners?
     
  14. FIAAO

    FIAAO Failureisalwaysanoption

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    <table width="90%" cellspacing="1" cellpadding="0" border="0" align="center">
    <tr><td><span class="genmed"><b>JoergS wrote:</b></span></td></tr>
    <tr><td class="quote">A pendulum should use a non deforming plate, otherwise the deforming will falsify the data.<br><br>Also a pendulum shows the momentum of the shot rather than the energy. Means, the formula is <br><br>mass x speed<br><br>rather than<br><br>0,5 mass x speed x speed = (energy)<br><br>Here is where slingshots shine - a solid hit from a 20 mm steel ball, flying at 75 m/s, will let the pendulum swing out more far than a high velocity .22 hit, and about as far as a hit from a 9mm Luger. <br><br><a href="http://slingshotchannel.blogspot.de/search?q=momentum" target="_blank" rel="nofollow">http://slingshotchannel.blogspot.de/search?q=momentum</a>
    </td></tr>
    </table>
    <span class="postbody"><br><br>As far as I get it, you can by using this calculator calculate what speed the projectile is moving at. From that, you can then calculate the joule by knowing the speed and the momentum. It may sound weird but I think Im right...</span>
     
  15. CEZ

    CEZ New Member

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    Cool, how accurate is it?
     
  16. JoergS

    JoergS Administrator

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    I think for accurate speed tests, it is way easier touse the laptop method. <br><br><a href="http://www.airgunforum.co.uk/forums/showthread.php/100758-Simple-Accurate-DIY-Chronograph" target="_blank" rel="nofollow">http://www.airgunforum.co.uk/forums/showthread.php/100758-Simple-Accurate-DIY-Chronograph</a>
     
  17. tokSick

    tokSick Senior Member

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    Hello Joerg,<br>I already saw something similar <a href="http://www.france-airsoft.fr/forum/index.php?showtopic=111787" class="postlink" target="_blank" rel="nofollow">HERE</a> ( french). But the link you gave is much easier.<br>Thanks.
     
  18. onnod

    onnod Im from Holland, isnt that weird?

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    thanks for the link joerg, i will try that one day too
     
  19. CEZ

    CEZ New Member

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    Even better, thanks Joerg! <br>Is the second mic necessary? Am I right in thinking that it's there just so that you don't have to deduct the time it takes the sound of the ammo hitting the target to come back to the first microphone?
     
  20. tokSick

    tokSick Senior Member

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    Hey CEZ,<br>I was thinking about the same too.<br>I ask myself: does it work if you put the computer half way of the target and the slingshot?