Izzet Life Spinner
Description
###Please read the issues and notes section before printing! This is a life counter I designed for Magic: the Gathering! I wasn't satisfied with life dice, as they were too easily knocked over by accident. A bit too much time later and bam! Izzet things happened. This spinner uses planetary gears. 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 on an HP laser jet 3D color printer. It uses nylon powder. I'm not sure how well it would do on a more typical printer. You need only one set of files, so pick either STLs or 3MFs. Video 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 You might want to scale these files as you deem fit. I made the outermost rings 3 inches in diameter. Print the outer ring twice. The outer rings don't snap together cleanly (they don't lock together by themselves). I plan to glue the two halves of my print. I will fix these issues if this design generates enough interest. ##Possible design fixes I already have a few things in mind for the next version of this print, if I make it: - The halves don't lock together. Plus, the reveal I put in doesn't look good. - The split and reveal weren't originally in the design, but this design didn't work when printed as one piece. - It seems hard to spin. - The video exaggerates this because it isn't glued, but I've had people note this when shown the design in person. - The tens digit might not be easily visible when sitting on a playmat. - One thing I wanted to nail in this design was how intuitive it was. Other people have tried to re-invent the life dice, which is good, but when someone sat down with a literal mini-abacus it was a little absurd. While I wanted it to be immediately obvious to all players how much life I am at, I feel I didn't quite hit the mark on this one. ####How I designed this (because Thingiverse ate my formatting in the other textbox) The mathematics behind a planetary gear are simple, if counterintuitive. I wanted to get the red gears to turn a certain amount with a full rotation of the big gear, to match the ones digit with the tens digit. The following is an incomplete explanation; I do not have my notes with me and I do not want to re-derive it. Because I am a nerd at heart, I made it into a fun math problem. ##Prompt - Assume the outermost ring (the purple/silver piece) does not move. - If you rotate the inner gear one full rotation, how far do each of the outer gears travel around the circle? - What determines this ratio? If I wanted to make the red gears 0, 10, 20, and 30 on one side instead of just 0, 10, and 20, what adjustments would I have to make? ##Hints 1 - When trying to derive this, it is easier to instead 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 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. 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 teeth the blue gear has. Ask me to dig up my notes, if you want the full answer.
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