Trebuchet












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Katy B's trebuchet. It's so trebu-GREAT!

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Some people just aren't meant for building trebuchets... me, for example.






Applicable Physics Principles of a Trebuchet

The two applicable physics principles are the conservation of energy and work and centripetal motion.

Conservation of energy and motion comes into play here, because the law of conservation of energy states that: energy cannot be created or destroyed, only altered in form. An example of how this is used is when the trebuchet is loaded, there is no kinetic energy. But when it is released, it is released with a velocity equal to the work done by the weight on the other end of the arm.

Centripetal motion is mentioned because centripetal means: moving or directed toward a centre or axis. When the arm of the trebuchet is released, the weight wants to go toward the ground, but since it is attached to the arm, the arm is stopping it from going to the ground. The centripetal force that is acting on the weight and arm, makes it go in a kind of circle.

 

The materials I used to make this trebuchet included:

  1. some wood...
  2. several screws
  3. 3 door hinges (for weight)
  4. 2 marker lids
  5. a piece of cloth
  6. lots and lots of tape
  7. string
  8. 2 eye screws

          I started off with the base for the trebuchet. It's pretty big.. I guess you could say. My design was definitely ... different from others, in a way. It was much crappier. I suppose we could say that.

          I then made the arm out of two pieces of wood stuck together with tape. I stuck a dowel between them so it could be attached to both arms and would hold the arm up. And so it could... swivel. Or whatever. The dowel was held in place by 2 marker lids I screwed into each arm. With the help of a lot of tape they stayed up. I <3 tape.

          I made the sling out of a piece of cloth and attached one eye screw into the arm, and another into the base... I'm not too sure why I put the one eye screw in the base... but I did. I attached the string to the piece of cloth, and attached the string to the eye screw in the arm. I attached a piece of a metal coat hanger to the end of the arm. The other end of the string that was attached to the piece of cloth, I attached a ring to. I then slid the ring onto the piece of the coat hanger.

          The weight on the other end of the arm was a bag of screws and about 3 door hinges. The weight was attached with a lot of tape. Again, I must emphasize how much I like tape.

          So yeah. That's basically how I built it. I think. I made adjustments as I tested it, such as making the string for the sling shorter. That was a big help. It wasn't even firing before I made the string shorter. In closing, I was happy it kind of worked. At least it fired, right? Yeah. Okay.

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          Trials:
          1. mass: 3.3kg; arm length: 94cm; distance: 106cm; Power=d/ml= 0.000342 W
          2. mass: 3.3kg; arm length: 94cm; distance: 227.5cm; Power=d/ml= 0.000733 W
          3. mass: 3.3kg; arm length: 94cm; distance: 250cm; Power=d/ml= 0.00086 W
          4. mass: 3.3kg; arm length: 94cm; distance: 90cm; Power=d/ml= 0.00029 W
          5. mass: 3.3kg; arm length: 94cm; distance: 95cm; Power=d/ml= 0.000306 W
          6. mass: 3.3kg; arm length: 94cm; distance: 106cm; Power=d/ml= 0.000342 W
          7. mass: 3.3kg; arm length: 94cm; distance: 113cm; Power=d/ml= 0.000364 W
          8. mass: 3.3kg; arm length: 94cm; distance: 150cm; Power=d/ml= 0.000484 W
          9. mass: 3.3kg; arm length: 94cm; distance: 270cm; Power=d/ml= 0.00087 W

          The average distance the ball went was 1.56m. How sad is that? Oh well.






          THE medieval war engine to have! Build yours today!








































          Thanks go out to the bell, for ringing and making people leave so they couldn't see my launch. You rock Mr. Bell! Ha.

            

          I'm amazed I actually finished this thing...