Simple Machines Used in Elevators
By Andy Darnley
Elevators, like all complex machines, are made up of several simple machines working together. Unseen by most elevator users are the hidden parts needed for an elevator to work. These include the metal box or “car” a user rides in, counterweights for balance, an electric motor and braking system, pulleys with cables that run between the motors, and a safety system in case a cable breaks. All of these key parts are made from six simple machines.
Wheel and Axle
The wheel and axle is a simple machine made with a rod running through the middle of a wheel. The momentum the spinning wheel creates is used to pull heavy objects with ease. In an elevator, the wheel and axle works together with a pulley to pull the metal cars to the floors above. The gears used in the elevator’s motor are also examples of a wheel and axle.
A pulley is another simple machine that combines a rope or cable with a wheel and axle to lift large objects. Pulleys with large metal cables are used in modern elevators. The cable is wrapped around a groove in the wheel and axle. An electric motor pulls the cable, lifting the car between floors. Several pulleys can be combined to reduce the necessary work to lift a load. Flag poles, cranes, and window blinds all use pulleys.
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- The Case of the Powerful Pulleys
- Museum of Science and Industry: Simple Machines Game
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- What Is a Pulley? (video)
A lever is made of a beam and a fixed fulcrum (also known as a pivot). This simple machine trades force for distance to lift heavy loads. A seesaw is an example of a simple lever. The fulcrum is the part of the lever that the beam pushes against. If a fulcrum is close to the object being lifted, then the object can be raised with less effort than if the fulcrum was farther away. In an elevator, a lever mechanism is used to trip the braking system if the car is moving too fast. This braking system is used when the cables on pulleys break. The teeth of gears used in the electric motor that drives an elevator may also be considered levers. Gear teeth are simply levers that can rotate continuously.
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- What Are Levers?
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A wedge and an inclined plane are similar. An inclined plane is also known as a ramp. A ramp is a flat surface with one end higher than the other. Gravity makes it easier to move a heavy load up and down an inclined plane than to move that same load straight up or down without the help of a simple machine. A wedge is two inclined planes placed back to back and put into action. A knife, saw, or scissors are examples of wedges. In an elevator, the braking system drives a wedge into notches on the rail the elevator car is attached to so the car stops in case of emergencies (such as cables snapping).
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Screws and inclined planes may not seem like they have much in common, but close inspection reveals that a screw is actually an inclined plane wrapped around a rod. Screws can be used to lift or lower objects by twisting the inclined plane up and down. Screws also can be used to fasten objects together if the screw is driven into the surface of the objects. A spiral staircase is an example of a stationary screw that helps people lift themselves and objects up and down with ease. Screws are used in elevators in a variety of ways. Small screws are used to fasten the panels inside the elevator car, hiding the simple machines inside. Larger screws are also used to assemble the elevator’s electric motor.
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