If you were a kid that grew up with Legos, then you are a lot more likely to understand the fun of the gear set. You can scale it to any size you want and it's still a 3:1 ratio :). The gears should be 100% fill though to prevent any delimitation under gear loading. I would also use a strong material like ABS/PLA/Nylon. The shaft is press fit, so use a rubber hammer and a socket over the shaft to assemble to the pinion. Hack this design and make a prototype! Have fun. Like this design? Check out my website or my shop on Etsy! http://ShookIdeas.com https://www.etsy.com/shop/ShookIdeas?ref=hdr_shop_menu Thanks!