"Give me a lever long enough and a fulcrum on which to place it, and I shall move the world" is a quote attributed to Archimedes that perfectly illustrates the power of mechanical advantage. If we ignore pesky annoyances like friction and choose to work "in a vacuum," as the physicists like to say, Archimedes was right. One can achieve similar results through gear reductions, as well. But selecting gearboxes for your motors isn't always easy, which is why Michael Rechtin designed a 3D-printable, stackable planetary gearbox system that you can use to achieve the gear reduction you require.
A pair of gears can either reduce speed and increase torque, or increase speed and reduce torque. But if, for instance, you want a huge reduction, such as 100:1, the first gear would need 100 times as many teeth as the second gear. That would be quite large, so there are various gearbox designs that use multiple gears to achieve the same reduction in a more compact package. Planetary gearboxes are a popular example. Rechtin's design is a 4:1 planetary gearbox, but stackable. That means that stacking two of these gearboxes will result in a 16:1 reduction, stacking three of them will result in 64:1, and so on.
Rechtin designed this gearbox system to work with powerful brushless DC motors, which one can drive using standard ESCs (electronic speed controllers). Every piece of the gearbox is 3D-printable, aside from hardware like bearings and screws. Because the parts, including the gears, are 3D-printed plastic, this gearbox can't stand up to extreme forces. But in Rechtin's testing, the plastic held up well. White lithium grease helped to lubricate the gear teeth and reduce wear.
If you need a configurable, 3D-printable gearbox system, this seems like a great choice. Rechtin published all of the STL files to print the parts, so you can get started right now.