In the modern world, many hobbyists derive joy from the use of projectile-based platforms such as the crossbow and slingshot for target shooting or from building these platforms themselves. Historically, these ranged weapons saw use over countless centuries (7th century BCE in china) and in the 700s BCE in Greek Syracuse. The invention of the crossbow itself revolutionized battle strategy alongside many variations of it. While all these platforms brought their advantages, ergonomically, crossbows were notorious were for their difficulty to reload (see image of archer conducting a reload) and thus lacked the rapid repeatability of its precursor - the bow and arrow. As such, there is room to experiment with the automation of the firing and reloading process in a closed kinematic chain as this project presents an intriguing level of complexity and challenge in its completion.
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Therefore, we propose the following:
A stationary mechanically linked auto-loading, projectile launching machine (an automated crossbow/slingshot hybrid)
that utilizes a long linear stroke of a modified walking beam mechanism to charge and pull an elastic cable back, reload a
projectile, and fire cyclically and repeatedly.
A brainstorm led to the concept of implementing a walking-beam mechanism to fulfill the firing process, and an adaptation of Lazy Susan to reload.
Walking Beam Mechanism: This 8-bar mechanism saw use in France for drilling artesian wells and is commonly used for conveyer setups. It excels for having an output that traces out a semicircular path using one degree of freedom. This rectilinear-esque path profile combined with a curvilinear portion presents an excellent basis for interfacing it with a projectile-launching system. By using this mechanism to linearly pull back a chute and curving away from the chute, a repeatable firing mechanism can be established and is mechanically similar to a person pinching back a slingshot and letting go. The image below is figure P4-9 and is retrieved from Robert L. Norton's Design of Machinery (229, 5th edition).
Lazy Susan: As defined on Wikipedia, "A Lazy Susan is a turntable (rotating tray) placed on a table or countertop to aid in distributing food."( https://en.wikipedia.org/wiki/Lazy_Susan). See the animation below for a visual understanding. This working principle is best outlined in the video below (credit to Jordan W. on YouTube)
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With this knowledge established, our goal was to fulfill the proposal statement by designing, prototyping, analyzing and constructing a mechanism.