How Elevators Are Made

Elevator Myths

For some of us, elevators are such a part of our daily lives that we might never stop to think about what makes them work. Despite Hollywood portrayals of people falling down elevator shafts, or cables snapping and sending elevator cars plummeting hundreds of feet, we still just trust these machines to work, and with good reason. Elevators have been around for over a hundred years, and the safety measures in place make a fatal accident nearly impossible. There are two main types of elevator in service today, piston elevators and rope elevators.

Piston Elevators

Piston elevators are pushed up from below by a hydraulic piston. Underneath the building, a motor controls the pumping of hydraulic oil into a piston. When this fluid is pumped into the piston, the increase in pressure causes the elevator to rise. When the elevator needs to lower, the fluid is allowed to drain from the piston back into the reservoir. These elevators work well for smaller buildings. However, when the elevator is on the first floor, the piston must be entirely below the building. This means that the motor and piston must be buried as deep below ground as the building is high. This limitation makes the piston elevator less than ideal for larger structures.

Rope Elevators

Rope elevators use steel cables connected to a pulley system to move the elevator up and down the shaft. At the top of the shaft, in the elevator control room, the steel cables wrap around a large pulley. Below, one end of the cables is attached to the elevator, and the other end is attached to the counterweight. The counterweight weighs as much as the elevator with an average load in it. When the car goes up, the counterweight goes down. This setup greatly reduces the amount of energy that is required to lift the elevator by allowing gravity to do most of the work, similar to the way a teeter-totter works. A motor in the control room turns the pulley. When the pulley is turned one way the elevator goes up; when it is turned the other way the elevator goes down.

Control Systems

Today’s elevators are controlled by sophisticated computer systems. Lights placed in the shaft at each level are detected by the car as it travels to tell the computer which floor the elevator is currently passing. When the car nears its destination, the computer gradually slows the motor to a stop. At one time, elevators went all the way up before returning and coming all the way down. This was the most efficient way at the time to insure that everyone got picked up in a timely manner. Modern computers, though, can route the elevators up and down depending on who wants to be picked up and where the passengers currently on the elevator are going. When multiple elevators exist in the same building, the process becomes even more efficient. The computers are even smart enough to use the weight of the car to guess how many people are on the elevator and prevent elevators which are full from stopping for more passengers until someone gets off.

Safety Mechanisms

Elevators are extremely safe, due to multiple security measures. To prevent the cars from swaying, they run inside guide tracks. These guide tracks have friction brakes which will slow the car in the event of an emergency. The pulleys in rope elevators also have brakes which will automatically engage if the the pulley begins to spin too fast. Roped elevators also have four to five ropes suspending the car even though one is enough to carry the weight.

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