Hydraulic Elevators

• In a world that is progressively looking to skyscrapers in order to increase housing and office space, the elevator has become a very important tool. They have been around for more than 150 years, and their basic designs have changed very little.
  There are two main types of elevators, the hydraulic and the cable, though the cable is used far more often. The hydraulic elevator is typically not cost effective and needs too much energy to operate. It is a simple process, though, where the elevator car sits on a platform that is connected to a piston. The piston must be long enough for it to extend and push the car to the top floor, which means engineers need to dig very deep in order to give it room to lower when the car is on the first floor.
  Hydraulic elevators have a tank of fluid, usually oil, and a pump that causes the liquid to flow up a shaft that pushes the elevator up. When the elevator car wants to go down, a valve opens that allows the liquid to flow back into the tank, and thus lower the car. This is a good system for buildings no more than a few stories high.
  
  

Cable Elevators

• The most common type of elevator is the cable elevator, which is a much better energy spender and doesn't require intense drilling to build. An elevator car is hooked up to four to eight steel cables that run over a grooved pulley at the top of the building. The cables are attached to a weight on the other side of the pulley that acts as a balancer, conserving energy so the pulley doesn't have to move much to raise or lower the elevator car. A computer system is put in place that locates where the elevator car is and keeps track of floor requests when buttons in the elevator car or on different levels are pushed. Depending on the elevator system, the computer then figures the best way to move the car as efficiently as possible to get everyone where they need to go.
  
  

Safety Measures

• Many people have a fear of elevators that is probably heightened by Hollywood. While there is a possibility of elevators failing to function, there are many security systems put in place to stop them from plummeting or hurting anyone.
  The first are the cables themselves. One is strong enough to hold the elevator car and the opposite weight on its own, and there are usually four to eight. In the pulley, there is a mechanism that hooks into the sides of the pulley when the elevator car moves too quickly and stops it from turning, which catches the elevator in the case of a fall.
  On the sides of the elevator, emergency brakes also spring into place that catch onto grooves on the side of the elevator shaft, slowing and stopping the elevator from falling should other safety measures also fail.