$15 for Three Groupons, Each Good for $9 Worth of Gyros and Sandwiches at West Side Gyros ($27 Value)

West Side Gyros Chicago

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The Deal

  • $15 for three Groupons, each good for $9 worth of gyros and sandwiches ($27 value)
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Gyroscopes: Wheels That Keep on Turning

With a lean and a dash of physics, a Segway rider can turn in any direction. Check out Groupon’s guide to gyroscopes to learn what else these spinning wheels navigate.

At its simplest, a gyroscope is a children’s toy—a spinning wheel mounted on an axle in a metal frame—but at its most complex it’s a device capable of orienting airplanes, satellites, and Segways. Imagine a simple toy top. When someone sets it spinning, it seems to defy gravity, standing on its axis and even resisting a nudge or bump. Attach that top to a frame with ball bearings on its top and bottom and you have a basic gyroscope. The interesting properties of a gyroscope go beyond resistance to a bump: with enough spin, the device is capable of balancing on a string or at a rakish angle until it slows.

This works because the wheel’s motion spreads force all around the axis, powerfully resisting change. The gyroscope’s inertia is so great that it resists even strong but slow forces such as the motion of Earth. By placing the gyroscope in a separate ring that allowed it to spin independently of its base, 19th-century French scientist Léon Foucault observed the rotation of Earth. As the planet spun, the gyroscope remained on its original spinning plane, appearing to rotate around its horizontal axis in 24 hours. It was he who named it a gyroscope, “gyros” being Greek for “revolution” and “skopein” meaning “to see.” But the principle was understood before the name came into play. In the 1740s, an English scientist noted how a toy top remained level even when the surface it was on tilted. He determined that it could serve sailors as an artificial horizon when fog, choppy seas, or an impenetrable flock of albatrosses obscured the true horizon and made their sextant navigational tools (which relied on calculating angles with the horizon) useless.

Although the navigational possibilities didn’t really take off until the 1800s, modern-day travel is dependent upon the principle of the gyroscope. Within airplanes, these devices help measure the roll of the craft, note its direction in space, and even control its autopilot. When the craft tips, the gyroscope remains in place and is brought into contact with sensors in its housing that relay information to the pilot or an automatic stabilizing system. The gyroscopes at the heart of the turn indicators of small aircraft maintain their constant motion with the help of a steady stream of air or an electrical power system that propels them around at 10,000 revolutions per minute, about the same rate as records made for mosquitoes. In many newer aeronautical applications, a quite different principle of physics has been exploited to create ring laser gyroscopes, which rely on phase disturbances between two laser beams to indicate a craft’s rotation.

The Fine Print


Promotional value expires 120 days after purchase. Amount paid never expires. Limit 1 per person. Limit 1 per visit. Merchant is solely responsible to purchasers for the care and quality of the advertised goods and services.

About West Side Gyros


By purchasing this deal you'll unlock points which can be spent on discounts and rewards. Every 5,000 points can be redeemed for $5 Off your next purchase.