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Hello, we're the Treehouse Detectives, and we need to learn more about elevators.

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Well, you've come to the right place.

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I'm Edith DeFrancesco, Vice President of Product Development here at Otis Elevator Company.

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Wow, that sounds interesting.

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Do you actually build elevators?

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Here at the test tower, we test elevators for safety and efficiency, and I don't personally

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build elevators, although as a mechanical engineer, I've worked on elevator designs.

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You're an engineer?

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I'm doing a report on engineers for Career Day.

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Great, I'll show you where we design and test our elevators.

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We have lots of engineers working on elevator design.

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This is our test tower.

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After we design the elevators, we bring them here to test them, to see how they will work

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when they're installed.

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How do elevators work?

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Elevators are driven by electric motors, and on the motor shaft is a pulley called

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a shiv.

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Over the shiv hang steel cables.

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It's basically a box on a rope.

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On one end of the cable is the elevator car, which carries the people, and on the other

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end is the counterweight.

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What's a counterweight?

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A counterweight is a steel frame full of weights, and it balances the weight of the elevator

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car and the people in it, so that it takes less force to move the elevator.

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How does it reduce the amount of force needed?

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Think of it like a balance scale.

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The force needed to turn the shiv is related to the difference between the weight of the

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car, with the people in it, and the weight of the counterweight.

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The closer those two are in weight, the more balanced the system is, and the easier it

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is to turn the shiv.

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How does an elevator go up and down?

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Well, when the motor turns, the shiv rotates.

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The cables stay on the shiv in these grooves, and with the friction between the cables and

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the shiv, the cables move with the shiv when it rotates, making the elevator go up and

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down.

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Sounds like friction's a good thing to have in an elevator.

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Yes.

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We call it traction, and it's very important.

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We don't need a very big elevator for our treehouse.

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Do elevators come in different sizes?

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Yes, they can be as small as a dumbwaiter, about a half a meter by a half a meter.

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How big can an elevator be?

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Some elevators are as big as a truck.

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They're used to carry freight containers and seaports, but a typical commercial elevator

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is about a meter by two meters, and carries ten or twelve people.

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Designing an elevator seems like a lot of work.

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It sounds like a lot of fun.

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It has its ups and downs.

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Thanks, Mrs. DeFrancesco.

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We've learned a lot about elevators.

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You're welcome.

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And if you have any more questions, just give me a call.

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Bye.

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Bye.

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