Mini Repeating Crossbow 2.0

thingiverse

Remixed from Naus' original "Mini Repeating Crossbow" design, this new version has a couple new features and improvements! BOW: I was having trouble getting the notch to catch the rubber band while it was in its slot. In fact, I ended up breaking several rubber bands because it seems like the notch just ended up pinning the rubber band against the side of the wall where it sits and that prevented it from firing and actually started to wear away at the band until it broke. To fix this, I modified the length of the notch (and also the length of the hole on the magazine) to that the notch should have no problem lifting the band up and our of the groove to fire. New: Thick_Bow After a lot of use, the ends of the bow sometimes crack and break off. To fix this, I strengthened the bow by making it thicker which also made it more powerful. [The "Thick_Bow" design has not yet been tested . . . use at your own risk.] MAGAZINE: When I did get the machine to fire, the bolts that I was firing (Q-tips) wouldn't go anywhere because the barrel of the bow was conical-shaped in that the mouth of the crossbow was smaller than the opening at the other end. Also, I had a problem with getting the bolts to stay in the magazine when I rotated the crossbow. (Sidenote: It looks like Oliver_D also had this problem, and he made a remix that adds a top with slots to store extra bolts to the magazine! It's really cool, and is compatible with the new magazine as well – Try it out!) To fix these issues, I added a groove down the length of the barrel to help the bolts stay straight and also to prevent jamming. Also, I widened the radius of the barrel to a uniform width, and I added the aforementioned lid to the MAGAZINE.stl file. ARMS: Like a few others, I was having some trouble with getting those pins to print so I ended up assembling this whole thing with Q-Tips and hot glue, so I thought it was fitting that I make the holes on the arms go all the way through so I can add my hot glue on the outside. So now this mini crossbow can be built with Q-Tips and fire them too! TURRET STAND: I just added the design for a little turret stand for this thing. This will make you able to put it flat on a table to show off, and should make it able to fire with one hand... The fun awaits! UP NEXT: A miniature xbow target? Thoughts? Print Settings Printer: DaVinci XYZ 1.0 Pro Rafts: Doesn't Matter Supports: Yes Resolution: 0.2mm Infill: 10% Post-Printing I used Q-Tips for the axles/joints. I have heard that using extra filament also works well. Overview and Background Overview This is a great physics demonstration to help teach kinematics. The xbow and stand cold make studying projectile motion painless and fun. Print a large model for the class or a small model for each table - the choice is yours! Lesson Plan and Activity Lesson Plan Ideas There are countless ways to use this fun miniature xbow to teach physics or other related subjects, some ideas include... –> Calculating Trajectory by manipulating angle of launch. –> Experimenting with Potential and Kinetic Energy through different strength rubberbands. –> Student Discipline :) Materials Needed Materials –> A 3D Printer –> Q-Tips or Filament –> Rubber Bands