Then imagine a modern city without buildings over ten storiesl Along with structural steel and reinforced concrete, the elevator was essential to the development of the modern skyscraper and thus to the common form of the modern urban center.
The elevator's practical impact was almost matched by its symbolic impact. With property values skyrocketing in the cities, the middle-class families could not afford single family homes.
Apartment building owners promoted apartment living with advertisements of "high-tech" amenities: hot and cold running water, telephone systems, central gas for cooking and lighting, fully equipped bathrooms, and elevators.
Moreover, with all these modern conveniences, apartment living captured the middle-class imagination as the embodiment of a new organization of domestic duties. Buildings came with centralized heating, ventilating, and plumbing systems; some had kitchens in the basement which would prepare food for individual apartment dwellers; some even had a centralized vacuum system with nozzles in each room connected to a pump in the basement.
The elevator was even extolled as a contributor to democracy. In an elevator-equipped building, it mode little difference which floor one lived on; every floor was equally accessible.
By contrast, in Europe, wealthy families were generally found on the middle floors where they did not have to climb many flights. Poorer families were usually confined to the basement or the upper floors. Elevator hoisting cable usually consists of six or more strands, each of which consist of a number of separate steel wires. The strands may be twisted around a hemp center which serves as a cushion and also contains a lubricant.
In a lifting drum installotion, a hoist cable runs down from a drive drum attached to the hoist motor, around a large pulley on the top of the elevator, up to a second pulley honging from the roof of the elevator shoh, and down ogoin to the counterweight.
In a troction drum installotion, the cable runs from the elevotor, up and once around a drive drum attoched to the hoist motor, then bock to the counterweight.
The electric hoisting motors are specifically designed for elevator service and may drive the hoisting drum through a gearbox, both of which are purchased parts. These standards may be incorporated into local building codes, or the local codes may have their own safety standards. The state must inspect, rate, and certify each passenger elevator installation before it goes into operation and must reinspect on a regular basis thereafter.
Elevators have not changed substantially in many years and are unlikely to do so in the near future. Electronic controls will continue to improve in ways that are evolutionary and not very dramatic. Control systems are being developed that will learn from past traffic patterns and use this information to predict future needs in order to reduce waiting times. Laser controls are coming into use, both to gauge car speed and distance, as well as to scan building floors for potential passengers.
Elevator Technology. Halsted Press, Ford, Barbara. The Elevator. Walker and Company, Evans, Barrie. Richards, Kristen. Toggle navigation. When the counterweight goes up the elevator moves down and vice versa as simple as that, however, it has a great benefit. Without a counterweight, the whole load will be mainly on the pulley system and the cables.
That requires the motor to generate more energy to lift the car. In spite of just requiring to say KJ with the existence of the counterweight, now it needs to double the energy to lift the same load. The counterweight has also its own role with the safety system in case of cables and braking system, the strain on the cables will decrease making the elevators a little bit safer.
Imagine if there were no counterweight: a heavily loaded elevator car would be really hard to pull upwards. In order to control the speed of the elevator, there has to be a separate speed-regulator machine which is called the Speed Governor. It is avery complicated flywheel supported with massive mechanical arms.
So if there is a problem with the elevator that makes it move too fast, the first mechanism inside the speed governor trips one or more of the braking system. So the wait at the very top and very bottom, the areas most in need of elevators, can be a nightmare. More importantly, large buildings usually have banks of elevators, not just one. If each follows the elevator algorithm, then under heavy traffic, the elevators start leapfrogging each other a few floors at a time.
And they bunch up in the middle of the building, potentially even serving the same calls twice. To handle these larger setups, engineers developed a slew of tricks. Just having the lifts talking to each other goes a long way. If Car 1 is headed up, Car 2 can instead handle a lobby request. Furthermore, lifts can be assigned to specific clusters of floors. You also may have seen elevators hanging out in a lobby, doors wide open. This is the parking strategy, where idle elevators return to a commonly requested floor.
Thanks to traffic prediction and real-time monitoring, the elevators can switch between strategies to adapt to the morning or close-of-business rush.
The coup that really carried elevator programming up a few floors happened in the s, when reprogrammable computers came on the scene. If someone had a new elevator routing strategy, they no longer needed to sell a mogul on the idea and wait for a building to go up. Instead, they could test and fine-tune their ideas in software simulations.
A flurry of new algorithms hit the shafts. Another favorite was to always hand the most urgent call to the car predicted to create the best outcome for that passenger: minimize journey time, use the least energy, or whatever else the designers prioritized. The apex of the computerized control is destination dispatch, which you can experience if you visit skyscrapers built or modernized since the s.
In these buildings, rather than simply pressing up or down, you enter what floor you want to go to, and it tells you which elevator will come to take you there. This efficiency was estimated for a load of lb, which matches a regularly sized residential elevator, being driven at 1. There is a transfer of power throughout the elevator system.
Electrical power put into the motor is equal to:. This power is then transferred through the output of the motor shaft,. Where T is the torque and w is the rotational speed.
Once the power is transferred through the gear reducer the output speed will be reduced and the torque will be greater. Tension on the rope from the elevator pulley is equal to the weight of the elevator, W e. The tension on the rope from the counter weight is W c. The following analysis has been done for steady state no acceleration operation. The force on the driving pulley is equal to the difference of the two exerted tensions on each side.
On one side, this force is equal to W e and on the other side, it is W c. Therefore, the net force exerted on pulley 1 the drive pulley is:. In order to find the power required for elevator movement, either the rotational speed of the drive shaft attached to pulley 1 or the velocity of the elevator must be known. As explained above, the brake is held closed by a spring and released using a magnet.
The free body diagram below shows how these forces are distributed. The force exerted by the spring is much closer to the pin joint and, therefore, is easily overridden by the force of the magnetic pull because of its longer moment arm great distance from the point of rotation. Elevators can be found in many residential and business buildings.
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