Variable Moment of Inertia Fidget Spinner

thingiverse

Assignment for my manufacturing class, a fidget spinner project that went overboard. I was tasked with designing a unique fidget spinner and its uniqueness had to be more than just aesthetic. The idea I came up with was to create a spinner with variable moment of inertia so the velocity over time behavior for its spins would change. I wanted it to mimic what I used to do as a kid on swings, twisting the ropes up and letting myself spin, then tucking my legs in to increase my angular velocity. My spinner actually worked and I proved the difference in behavior versus fixed mass spinners through spectrograms of audio recordings of spins. A brief summary is attached as a pdf if you want to read about it. To make this fidget spinner you'll need: a) [1x] The Body - 3D printed (the STL and CAD are attached) b) [2x] The Grips/Holders - 3D printed (the STL and CAD are attached) c) [1x] 608 skateboard bearing d) [1x] 3mm diameter metal tubing or rod cut to size in 3 pieces (or adjust the hole size in the body's CAD for something different, or try printing these pieces with metal on metal to ensure minimal friction) e) [30x] ¼” inner diameter, 1” outer diameter fender washers f) [2x] #9 Hillman Compression Spring, cut them in half and you'll need 3 of those halves g) [3x] ¼”O.D x ½”length, 6-32 Thread, aluminum spacers h) Bondo body filler (or any cement/bonding agent/glue) Here are some links for the specific items I used: c) https://www.amazon.com/gp/product/B07VH6XT6Z/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1 d) https://www.amazon.com/gp/product/B00S50NRLQ/ref=ppx_yo_dt_b_asin_title_o04_s06?ie=UTF8&psc=1 e) https://www.hillmangroup.com/us/en/Fastening-Solutions/Fasteners/Washers/Fender-Washers/Zinc-Fender-Washers/p/290012 f) https://www.hillmangroup.com/us/en/Home-Solutions/Home-Accessories/Springs/Compression-Springs/Hillman-Compression-Spring/p/540027 g) https://www.hillmangroup.com/us/en/Fastening-Solutions/Specialty/Spacers,Bushings,&Bearings/Spacers/Threaded-Aluminum-Spacers-Assortment,(6-32,8-32,&10-32)/p/545SC60 Note that these are just the items I used based on what I had on hand and could cheaply get through a quick run to my local ACE Hardware. I encourage you to search around, be creative and use whatever is easiest for you. To assemble the masses use a vice or clamp to hold ten washers together. Apply Bondo to the outside of an aluminum spacer and push it into the washers. Make sure it has sufficient bonding agent to stick, then wipe away excess. Let cure. Repeat for the other two masses. Video of spinner disassembly/assembly: https://youtu.be/lhV_asJLJz4 Video of it spinning: https://www.youtube.com/watch?v=ELkqryU4Dow