Floating arm trebuchet (dimes and pennies)

thingiverse

This human catapult employs a suspended arm as opposed to a fixed arm, enabling the weights to drop straight down rather than diagonally like in standard human catapult designs. Consequently, this system achieves a more efficient and powerful throw compared to traditional human catapults. Witness a test firing sequence at http://i.imgur.com/9QZHuB0.gif . It requires 4 toothpicks, some twine, and 64 quarters to fill the weights. Instructions Assembly is quite straightforward. You will need 2 toothpicks, and 10-15cm of twine along with the 3D printed components. It's crucial to print two of the weight holders, one stand, and one wheel. Every other component only needs a single print. Each shape should be properly aligned as I did not build them on the intended printing plane. I used a resolution of 0.025mm height with 0.05mm width for all parts, especially since some components are tiny and are precisely 1mm in width to prevent small gaps from occurring. Side1 and side2 should be pressed together until they're flush. This might be slightly difficult, but this is necessary to ensure that the components remain securely attached and won't come apart prematurely. I employed a small vice to press the pins together that I couldn't manage with my hands. The stands merely snap onto the assembled frame. The sling simply clicks together. As soon as both halves are joined, make sure they swing freely. If this doesn't occur you may need to make some slight edits to the file in order to configure it properly for your 3D printer. These small pieces can vary slightly due to their size. For the arm take one of your toothpicks and cut it into two equal parts. One portion will be utilized as your firing pin, so save that for later use. With the other half trim it down to a length of 9mm. This part goes through the hole which is second from the top on the arm (top being the thickest end of the arm). Next insert one wheel onto each end of the toothpick. The other toothpick secures the weights, arm and frame in place by passing through one vertical slit followed by the uppermost hole on the arm, then another vertical slit. Once completed you can slide the weight holders into position and fill them with quarters. You may want to enlarge the size of the weight holder if using pennies or some other denomination coin. To attach the strings, a piece must pass through the lowest hole on the arm before going through one string attachment on the sling. Another piece must be knotted at one end and secured to the other string hole on the sling. When fully loaded the sling should sit centrally in the frame with the twine taut but not excessively tight or it will lack power to swing the weights; however if it is too loose, your coins will be tossed into the ground. To avoid issues simply research human catapults and how they work, and you'll have no trouble ascertaining their proper construction.