Elevators and Escalators
RSMeans Engineering Staff
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Seed Newsvine |
We push a button and it comes to us. We push another button and it takes us somewhere. We step on it, and though it travels in a never ending circle, it takes us from point to point. We take them for granted, but elevators and escalators have become a part of our lives.
Elevators have made vertical transportation within a structure easier, but most of us know little about how they work. They can be primarily categorized into two types: hydraulic and electric.
Hydraulic elevators work by pumping an uncompressible liquid into a sealed container. A piston within the container is forced to move by the liquid filling in its space. The cab of the elevator is attached to the piston. Controls manipulate the quantity of liquid and the rate at which it is pumped to vary the speed and distance that the cab has to travel. During starting and stopping, the liquid is pumped or drained slowly, so the cab and its passengers transition from standing still to motion or motion to standing still in a comfortable manner. While traveling, the liquid is pumped or drained evenly to promote a smooth ride.
Some hydraulic elevators require a hole to be drilled into the ground, at least as deep as the distance the elevator must travel vertically, where the container and piston reside. Others mount the container and piston within the elevator shaft and use a series of cables and pulleys in combination with the motion of the piston to move the cab.
In general, hydraulic elevators are used on lower buildings. Skyscrapers require a different way to move the cab.
Electric elevators use a powerful electric motor, cables, pulleys and counterweights to provide motion. To describe it simply, the cab is attached to a cable. The cable is wound around a pulley that is attached to the electric motor. The motor is turned by the elevator controls to move the cab up and down. The counterweight is used to offset the weight of the cab and its passengers. As the cab moves upward in the shaft, the counterweight will move down and vice versa. The next time you are in a hotel with an atrium lobby and glass elevators, watch the elegant dance performed by the cab, cables and counterweights. It is truly a marvel of engineering.
Elevators are priced much like automobiles. There is a base model that can be adapted or modified with dozens of performance and aesthetic options.
Escalators are similar to a bridge. They span the distance from floor to floor much like a bridge will span the distance from support to support. Within the structure that crosses the span is a remarkable machine that has an endless loop of stair treads that act much like a chain. The stair treads ride on two sets of wheels that fit in two pair of tracks. The path of the two pair of tracks allows the stair treads to magically rise when they are needed and then magically fall when they are not. Escalators move people efficiently between floors and in the case of moving walkways over long distances.
Escalator pricing is highly dependent upon the distance they are required to travel, the amount of rise and the various appearance options available.
So the next time you step into it or onto it, enjoy the ride!
