This is a set of plans to help you build the hand-cranked full auto crossbow that I demonstrated on YouTube: https://www.youtube.com/watch?v=3bK1TJP5IkQ
It is a very unique and interesting mechanism that you can have fun building and shooting! The purchase gives you a download of a zip-file containing the plans and some photos of the example crossbow. You also may be able to produce finished versions of this to sell if you wanted (I sold one for $75 without much effort, for your reference if you want to try that).
Due to file size limit, the instruction picture for the arrows is on a small separate file.