Tom Stanton is a maker who has gained a pretty substantial following on YouTube building projects. His focus is often on 3D-printed builds, and especially things that fly. Unlike most other YouTubers who do this kind of work, Stanton goes into a lot of detail about the physics involved. He doesn’t just explain how he builds a drone, but also why it works the way it does. In his most recent video, he gives that treatment to the classic flying spinner toy.
You likely had some version of this toy as a child, as their affordability and fun ensured that they were quite popular. They come in many variations, but they all work in essentially the same way: a propeller wheel is spun at a high speed and eventually released. When it is released, the rotational inertia stored in the wheel causes the propeller to keep spinning so it can fly away. The propeller can either be spun up to speed using some kind of hand-powered mechanism or with an electric motor.
As Stanton explains, the propeller wheel acts as its own flywheel to store the energy as rotational inertia. Like all flywheels, the weight correlates to the amount of energy stored. Stanton built his using a milled aluminum ring with 3D-printed covers on the spokes that provide thrust. A special locking mount keeps the flywheel in place as it is being accelerated, and then allows it to release the propeller the moment that the motor spins at a slower speed than the propeller does. Stanton used a powerful brushless motor to spin the flywheel, and was able to get the flying disk to cover some pretty impressive distances and altitudes.