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Falling Elevators: Movie Science Gone Mad

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Some action movies feature a scene where the protagonist gets inside an elevator, but the villain cuts the cables. Or for some reason the cables broke due to an explosion of some kind. The doomed elevator then plummets down the building and sometimes ends with a fiery ball of fire.

Sure, with high adrenaline and a well-built body, the action hero manages to get out of the plunging elevator and escapes with a minor scratch. But it isn’t every day that we have the adrenaline rush—to survive a falling elevator. Imagine the gripping fear of plunging into the bottom of a building when the elevator cables accidentally breaks.

Fortunately, in real life, elevators are equipped with safety features, so we don’t have to worry about these exaggerated events we see in the movies.

Credit: fastcocreate.com

Breaking Cables

Elevators are held by multiple cables (for to eight cables) made of coiled steel. Even if a cable snaps–which rarely happens—other cables will still be able to hold the card. Besides, maintenance inspectors are periodically checking the wear and tear of these cables.

Now, let’s say that in a freak accident, all the cables did break. Should we give in to free fall and just shriek in terror as we plummet to the bottom (just like in the movies)?

Either the filmmakers are ignoring the fact that all elevators have tension brakes, or they just want to create drama out of the usual elevator trick. Drama or not, an action hero’s flight up  the elevator shaft, holding on to dear life—while the elevator freely falls—is extremely unrealistic.

How do tension breaks work? It is simple. Elevators are lifted and lowered by a cabling system with pulleys. If the elevator cables break, the tension in the cabling system disappears, and so the brakes are activated and stop the elevator car from falling more than a few inches.

The braking system can stop the car from falling in two ways. One way is through the clamping action made by grabbing the steel rails running up and down the sides of the elevator shaft once the tension brakes are activated. Another is through driving a wedge into notches in the rails. Normally, these safety features are managed by what is called a mechanical speed governor, which activates the braking system when the pulley spins too fast.

Worst Case Scenario

If all else fails (all cables snapped or braking systems did not work), the elevator will surely drop rapidly but not without friction. The friction between the rails and the elevator shaft will slow down the car. Of course, the car will still end up on the bottom, but the fall will be cushioned.

Elevators have a built-in shock absorber—typically a piston in an oil-filled cylinder—at the bottom of the shaft, ready in case the braking system fails. And, as the elevator falls down, it will compress the air beneath it; the air pressure will slow down the falling car.

It will not be a freaky fall after all.


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