The Uncanny Gyroscope

bicycle tire gyroscope
An ordinary bicycle wheel with handles makes a great
demo on gyroscopic forces.

Level: Middle School to H.S.

Time involvement: 15-20 minutes.

From electronic game controllers to instruments guiding aircraft and spacecraft to the very universe itself, (the stabilization of the solar system), the gyroscopic principle is everywhere. Human’s fascination with the principle began centuries ago in the form of simple spinning tops that could appear to defy gravity. This mini-lesson uses the ever-popular toy gyroscope and a bicycle wheel fitted with a pair of handles at the axis.

The mini toy version is activated by a sharp pull of a string and activating the spinning wheel supported by a rigid frame and placing the affair on a table, a pencil point or a string. For as long as the spinning wheel maintains its speed, (as friction steals energy and the effect fades), the wheel will stubbornly refuse to fall over.

The much larger bicycle wheel with its supporting handles requires two persons to effectively create the demonstration. A “Lazy Susan” platform large enough to support a person is required to experience the full effect. The demonstration begins with the student standing on the platform while holding the wheel by its’ handles, at full arm’s length directly in front of themselves. The “teacher” grasps the wheel and gives it a firm spin. The student is instructed to smoothly tilt the wheel alternately to the left and right while keeping the elbows straight. Amazingly, as the wheel is tilted the person and platform will be forced to rotate to the left or right. It the person is smaller (lighter weight) the force may be strong enough to cause the person to make a full rotation back to the starting position.

Discussion: The mathematics behind the gyroscopes’ behavior is complicated using vectors and trigonometry. This oversimplification uses the well-understood concept of inertia. To accelerate or decelerate a speeding automobile will require the force of the brakes or engine. When the gyro wheel is tilted from its’ initial spinning plane certain areas of the circumference are either speeded up or slowed down. By the principle of Newton’s third law those areas that are being forced to change speed “push back”. That “push back” force acts against the central axis, thus causing a tilting effect. Scientists and engineers use the term “precession” and speak of the principle of “conservation of angular momentum”.

The practical application of all this theory is that gyroscopes provide stable platforms necessary to guide ships, aircraft and spacecraft. The Hubble Space Telescope uses nearly a dozen gyroscopes to aim its’ lens at particular areas of the sky. Modern electronics have devised ways of simulating the spinning wheel by using fiber optics in thin coiled fibers, and tiny accelerometers to track locations.

An interesting footnote to this lesson is the historical fact that Leon Foucault is the person credited with the invention of the term “gyroscope” (visualizing turning). In 1852 he was able to demonstrate the first physical proof that the Earth is turning, thus supporting the Heliocentric Theory of the Solar System. Since his gyroscope was actually a swinging pendulum he also demonstrated the connection between gyroscopes and pendulums. In his honor many larger science museums display huge Foucault Pendulums that serve as mechanical clocks driven by the turning of the Earth!

Learn more: This demonstration is often coupled with the Turn Coordinator demonstration. The Turn Coordinator is a basic aircraft instrument used to help control aircraft without outside visual reference. This demonstration uses an actual Turn Coordinator powered by a 12-volt battery. With the case removed the internal gyroscope is readily visible and the interconnecting mechanism that gives the pilot vital attitude information can be seen. Together these two demonstrations remove much of the mystery of how aircraft can fly safely into clouds. An unusual practical application of the gyroscope is in professional hand-held video cameras. With gyro stabilization of the camera a walking person can be photographed by a photographer walking nearby carrying a gyro- stabilized camera.