How does a coil spring work?

The coil spring can be designed for a number of rotations, generally with a lower spring constant. Look at any old windup watch or clock and most likely the energy storage mechanism is a coil spring. Some old clocks are powered by dropping weights, but these are usually not "wound" to add the energy.

How does a motor work?

In a typical motor, a component called a rotor turns inside a stationary component called a stator. One of those components contains permanent magnets that have south and north poles. The other has wire coiled around it. Putting electricity through the coils creates magnetic fields that attract and repel the poles of the permanent magnets.

Can a rotary motor store more energy?

For fast rotary motion this could work, but for slow motion, the pneumatic motor may "leak" and store little or no energy. For "many many many rotations", a permanent magnet motor /generator -> DC rectifier -> battery (or supercapacitor) may work to store considerably more energy.

What happens if you spin a motor in reverse?

Spinning the motor causes air to be forced through a tube, one-way valve, and storage tank. Opening the valve allows the compressed air in the tank (potential energy) to flow back through the tube and motor, spinning it in reverse. As the number of rotations increases, the pressure increases, acting to stop the axle for a given torque.

How does a spring store energy?

With a normal spring, you compress it using a linear force to store energy and then it decompresses and releases the energy, again in a form of linear force. Is there a mechanical mechanism that stores energy by rotating force and releases energy by rotating force?

How does a motor turn electricity into movement?

Designing a motor to turn electricity into movement is tricky. In a typical motor, a component called a rotor turns inside a stationary component called a stator. One of those components contains permanent magnets that have south and north poles. The other has wire coiled around it.