Izzet Life Spinner

thingiverse

###Please read the issues and notes section before printing! This life counter for Magic: The Gathering was designed by me! I wasn't satisfied with traditional life dice, as they were too easily knocked over by accident. After a bit of tinkering, something amazing happened. This spinner uses planetary gears to keep track of life points. The inner gear rotates through the ones digit while the smaller, outer gears slowly cycle through 0-20 on one side and 30-50 on the other. I printed this design using an HP laser jet 3D color printer with nylon powder. While it may work well on a more typical printer, I'm not entirely sure. To print this life counter, you'll need only one set of files - either STLs or 3MFs. You can choose the format that suits your needs best. You can find a video showcasing this design here: https://www.reddit.com/r/magicTCG/comments/grza88/i_invented_an_izzetthemed_life_spinner_nylon_3d/?utm_source=share&utm_medium=web2x ###Issues and notes Keep in mind that you may want to scale these files as needed. I designed the outermost rings to be 3 inches in diameter. To print the life counter, simply print the outer ring twice. Unfortunately, the outer rings don't snap together cleanly on their own, so you'll need to glue them together. If this design generates enough interest, I plan to fix these issues and create an updated version. ##Possible design fixes I already have some ideas for improving this design in future versions: * The halves won't lock together. To make it worse, the reveal I included doesn't look great. + This issue wasn't present when printed as one piece, but I added a split and reveal to fix it. * It's difficult to spin the life counter. + A video showcasing this design might exaggerate the issue, but people have noted it in person. * The tens digit may not be easily visible when placed on a playmat. + One thing I wanted to achieve with this design was to make it intuitive for players to see how much life they had. However, I didn't quite hit the mark. ####How I designed this The mathematics behind planetary gears are simple yet counterintuitive. I aimed to get the red gears to turn a certain amount with each full rotation of the big gear, matching the ones digit with the tens digit. ##Prompt Assume the outermost ring (the purple/silver piece) doesn't move. If you rotate the inner gear one full rotation, how far do each of the outer gears travel around the circle? ##Hints 1 When trying to derive this, it's easier to assume the blue gear does not move. As the purple outer ring moves one rotation, how far does a red gear go around the circle? A crucial part is to figure out how many times a red gear rotates as it undergoes one full trip around the circle. ##Hints 2 In this setup, the red gears travel one third of the way around the circle when the blue gear makes a full rotation. The inner gear in this set of gears has 24 teeth, each of the six outer gears has 12 teeth, and the outermost ring has 48 teeth. ##Partial Solution If I remember correctly, the amount the red gears travel when you spin the blue gear a full rotation is directly proportional to the number of teeth the purple ring has versus the number of teeth the blue gear has. Ask me to dig up my notes if you want the full answer.