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New user, New idea (Read 9066 times)
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Matthew 11:25-30

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Re: New user, New idea
Reply #15 - Apr 9th, 2004 at 1:47pm
 
It is rather like a robust, lightly constructed Trebuchet at the end of a sling.   I will draw a sketch for you to consider until I get time to get one on the board.   It is a fun curiosity that never really found favor with me as the Pro/Con list balanced out with no real advantage to be gained in the end.   But a nice curio it is.....
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WildAtHeart
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Re: New user, New idea
Reply #16 - Apr 9th, 2004 at 1:51pm
 
like a stick with a sling on the end? I made one of those once with a hockey stick. It was really clumsy, but it allowed me to throw big stones FAR.
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WildAtHeart
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woo hoo

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Re: New user, New idea
Reply #17 - Apr 9th, 2004 at 2:12pm
 
here's my idea on the physics of a sling with an elastic portion:

In an overhand throw, the stone is swinging from in front of you to behind you, with the strings taut the whole time. Then, when the stone is at about 6 o'clock or before, you twist your torso and throw your arm and shoulder forward, thusly pulling the stone with you and accelerating it. When the stone is at 3 or maybe 2 o'clock is when the greatest tension is on it. If there was a piece of elastic in the cord, then at that point the band would stretch due to the tension. From there I'm not sure what the result would be. It seems like it might propel the rock faster - imagine pulling a loaded trailer with a truck. If its connected with a chain, that's like a conventional sling. However, if the connection was a stretchy cable, the trailer would *snap* forward when the tension in the elastic cable becomes too great. I think the same effect would happen with the sling.
What do you think?
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Matthew 11:25-30

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Re: New user, New idea
Reply #18 - Apr 9th, 2004 at 2:40pm
 
Ok,  here is an oversimplified sketch.   My original was of somewhat different construction and materials.  This sketch in no way conveys the deceptively complex dynamics of such a system.  One must work out the desired angle of departure of the leverage weight as well as the ammo.  It requires tweaking to find the sweet spots!   (This would of course be eliminated in a solid production model).   After several throws with a 'captive leverage weight' model and the resultant recoil....I found that releasing the leverage weight at the correct moment provided satisfaction.
(Oh the depths of fanatical obsession one can reach in any endeavor!) .......suffice it to say,  I have much stranger devices than this.   Yes indeedy......


http://www.ezimagecenter.us/image.cfmImageID=3608
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Matthew 11:25-30

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Re: New user, New idea
Reply #19 - Apr 9th, 2004 at 4:07pm
 
I almost forgot.....welcome to the forum WildAtHeart.   To quote you:

"I wish I knew some physics equations to help me figure this out. I have the worst physics teacher ever".


I wish you did too, WildAtHeart.    I wish you did too..... Undecided  Wink   I have always been a bit 'reversed' when it comes to equations.....
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woo hoo

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Re: New user, New idea
Reply #20 - Apr 9th, 2004 at 5:04pm
 
I'll try my best though. I bet I can dig out some equations about centripedal force and stuff. I slept through that class though  8)
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Re: New user, New idea
Reply #21 - Apr 9th, 2004 at 5:06pm
 
Techstuff:  All I can say is "Wow."  That's quite the device.  Do both missiles go forward? 

Wildatheart:  Welcome!  I think, with elastic cords, they wouldn't so much snap forward as they would continue to extend and then snap back into shape after the release.  If you accelerate your swing at a constant rate, centripetal (O.K., centrifugal, although my high-school physics teacher says there's no such thing) force will continue to increase until you release -- more force, more speed, and more extension of the cords until you let go.  Also, since the cords start off as shorter, you're robbing yourself of leverage through the initial portion of the swing.  If you could make a sling go from longer to shorter, you'd get more speed/power/distance, but with elastic cords I think you'll be going from shorter to longer, giving yourself less speed/power/distance.  I don't have any equations for you, and my last physics course was some time ago, but that's what makes sense to me.
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Matthew 11:25-30

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Re: New user, New idea
Reply #22 - Apr 9th, 2004 at 5:09pm
 
Hobb,  yes they do, albeit at different angles and velocities.  The trick is designing the device to release both at the moments desired.
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Matthias
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Re: New user, New idea
Reply #23 - Apr 9th, 2004 at 7:16pm
 
Wow indeed! That's quite the sling! I hope you can dig up an example and share it... maybe even a video?  Wink

This is at right angles to what I was thinking about, so I'll carry on this weekend (I'm out of the city with room to throw!) and let you guys know how it pans out.

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Re: New user, New idea
Reply #24 - Apr 10th, 2004 at 1:27am
 
Welcome WildAtHeart,

The problem with elastic cords is that the harder you sling, the more they stretch.  When they stretch, it doesn't go any faster.  And, as other people mentioned, all that energy you exert making it go faster is really just stretching the elastic, which is not what you want.  With "rigid" cords, all your energy goes into the speed of the projectile. 

Chris
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