Gear ratio example model for Physics study

The Multi-Ratio Gear Demo Board is an open-architecture STEM educational apparatus engineered to visualize the principles of rotational mechanics, angular velocity, and mechanical advantage. The design features a flat-lay configuration where a single 24-tooth central driving gear simultaneously engages four independent satellite gears, exposing four distinct transmission ratios: i = 2.0 (48T), i = 1.5 (36T), i = 1.0 (24T), and i = 0.5 (12T).

Optimized strictly for consumer-grade FDM 3D printing, all components are modeled using a metric module of 1.0, a 20-degree pressure angle, a 0.25 mm root fillet radius, and a structural thickness of 6 mm. To ensure smooth, friction-free rotation directly off the print bed without manual post-processing, a precise 0.2 mm backlash tolerance was integrated into the involute gear profiles, paired with a 0.2 mm center-to-center axle distance clearance on the baseplate.

Furthermore, the assembly successfully addresses a critical geometric constraint regarding the high-speed 12-tooth gear; since its root diameter is only 5 mm, piercing it with a standard 15 mm axle hole would compromise structural integrity. This was resolved by designing a solid gear core featuring a native, upward-extruded pin shaft to handle localized rotational stress. By manipulating the central driver, users receive immediate visual and tactile feedback on how variations in teeth count inversely alter angular velocity and torque, transforming abstract formulas into a tangible physical demonstration.