Please ensure that JavaScript is enabled in your browser to view this page.

The gear systems that most people are familiar with and that facilitate many fundamental principles of mechanical engineering rely on physical engagement. In a bicycle, for example, the chain makes physical contact with the chain rings and cassette. But there are other methods that don’t rely on physical contact and they might be more suitable for 3D-printed mechanisms, which is why YouTuber Retsetman experimented with magnetic gears

Many gearheads will already be familiar with non-physical engagement as it relates to viscous limited-slip differentials (LSDs), which rely on hydrodynamic coupling to limit the speed differential between wheels. A viscous LSD contains very thick fluid that creates hydrodynamic engagement. That engagement is also why unloaded drive wheels will spin slightly, even when the clutch is disengaged. Retsetman’s magnetic gears work in a similar way, but with the attractive force of magnets providing the engagement.

The simplest implementation of a magnetic gear system contains one input gear and one output gear, each lined with magnets (or one with magnets and the other with ferrous elements). As the input gear spins, magnetic attraction causes the output gear to spin too. But as Retsetman demonstrates, far more complicated arrangements are possible. For example, a planetary-style setup allows for greater reduction. But because magnetic fields interact, the dynamic engagement becomes difficult to intuit as one introduces additional gears.

Retsetman goes into great detail explaining these complex interactions, complete with diagrams and animations. With polarized film, one can even see the magnetic fields as they morph during operation. We recommend watching the full video if you want to learn about the math and objective engineering lessons. But the real potential here and the reason we featured these experiments is that magnetic gears would work well for 3D-printed mechanisms.

People can and do 3D-print traditional gears that make physical contact, but they tend not to last long because of the wear caused by friction. Even with generous lubrication, that friction can cause 3D-printed gears to deteriorate. But because these magnetic gears do not make physical contact, one could 3D-print them without concerns about durability. The only downside is that the magnetic engagement can’t hold up to high torque, which means that these magnetic gears are best suited to high-speed, low-torque applications.