Contra-rotating Propeller Model

thingiverse

A contra-rotating propeller system consists of two propellers rotating in opposite directions on the same axis. This setup should not be confused with counter-rotating propellers, which involve two separate propellers mounted in different locations and rotating in opposite directions, such as those found on either side of an aircraft's wing. For more information, check out https://en.wikipedia.org/wiki/Contra-rotating_propellers/. This system is designed to demonstrate how bevel gears can be used to make coaxial shafts rotate in opposite directions. In a real propulsion system, the inner shaft would be driven directly by the engine, and the outer shaft made to rotate in the opposite direction using a gear chain. As a demonstration toy, I built the handle to extend from the intermediate gear. I initially planned to design this system with bearings for smooth rotation but ultimately scrapped that idea as it complicated the system unnecessarily and required additional parts not readily available to most builders. Instead, I focused on creating something anyone can build without needing to purchase extra components. A simple locking feature is built into the handle; a piece of 1.75mm filament can be inserted into the small hole to keep the handle securely in place and prevent it from falling off. The stand is merely for display purposes and not an essential part of the system. Simply print and assemble, and you're ready to go! A build video is available on YouTube: https://www.youtube.com/watch?v=HEANtxbMmus. UPDATE September 2019: Remaining files that were initially missing have been uploaded.