Magyro Ball

youmagine

Note: This design is still in alpha and the SCAD code has not been test-printed. The concept is inspired by ThinkGeek's Nanodots GYRO DUO: Magnetically Gyroscopic Balls, which can be found at http://www.thinkgeek.com/product/18ae/?pfm=homepage_BestDeals_10_18ae. This design is a modification of the original, adapted for FDM printing using magnets with the following specifications: * h = 5mm * d1 = 25mm * d2 = 15mm Possible sources for these magnets are: https://www.magnet-shop.net/neodym-magnete/scheibenmagnete/scheibenmagnet-250-x-50-mm-n50-nickel-haelt-86-kg::250.html https://www.magnet-shop.net/neodym-magnete/scheibenmagnete/scheibenmagnet-150-x-50-mm-n40-nickel-haelt-48-kg::48.html These magnets have a holding force of 86kg and 45kg on full contact. Be careful not to damage your fingers. To find the optimal magnet(s) for this design, you may need to recompile the STL files according to your specific magnet size. It is assumed that all magnets have the same thickness. The goal is to choose two magnet radii that fill a common sphere as well as possible. For feedback, the OpenSCAD code will output two "corner radius factors." If one of the magnets has a factor below 1, you may want to adjust its radius or the other magnet's radius until both factors are near 1. Tips for making the gyro-ball: * Using thinner and harder bearing pins can significantly reduce the risk of mechanism clogging. This is because the magnets will create higher lever forces. * Suitable materials for bearing pins include iron nails, copper wire, brass rod, printing filament, toothpicks, and others. * To make pins from filament, use a retractable utility knife to create a notch in a piece of 3mm diameter PLA filament. Then, use pliers to break the piece and cut off any fragments that deviate from a flat fracture. * Use thin oil to lubricate the joints. * Keep the mass of the gyro parts small (low infill) but note that this is not crucial since the magnets are heavy anyway. Additional notes: * Due to the mechanics involved, it's unavoidable that the distance between the magnets becomes significant. Therefore, big magnets with relatively thin shells are preferred. * When working with gimbals, be aware of gimbal lock (http://en.wikipedia.org/wiki/Gimbal_lock). * The OpenSCAD design is animatable. * It might be interesting to try adding excess mass to one magnet side. * There may be sources for fully transparent plastic balls. Info about some design decisions: * All sizes are dynamically generated from magnet size to maximize the amount of magnet power penetrating through the shell. * For simplicity and assembly, an irreversible assembly design was chosen that includes glueing and/or plastic welding. * The gap between the gimbal ring and the gimbal sphere is determined indirectly via the "bearflatadd"-parameter (no specific reason for this). * In the code, radii with an underscore postfix correspond to the radii of the bearing flats, while radii without an underscore postfix correspond to the majority of the gimbal surfaces. * The parameter relationships became complex because all components had to be cramped together to absolute minimal space. This design is released under the GPL license due to a lack of original idea but a significant amount of code.