How cable-free elevators move sideways using magnets

HostWe have been riding in elevators for over a hundred years, and the basic idea hasn't changed much. It's usually a box hanging from a steel rope that goes up and then comes back down. But now there's a way to get rid of that rope entirely and let the lift move in any direction it wants. How do you actually move a heavy elevator car without a cable pulling it from the top?

GuestIt really comes down to using magnets to do the heavy lifting. If you have ever held two magnets in your hands and felt them push away from each other or snap together, you have felt the force we're talking about. To make this work, we put very strong magnets on the back of the elevator car and more magnets on a track built into the wall of the shaft. By switching the power on and off in a specific pattern along that track, the wall basically pushes and pulls the car along. It's a lot like how those super-fast bullet trains work. They don't have an engine that turns wheels. They just ride on a wave of magnetic force that carries them forward. In a building, we're just doing that vertically. We call it a linear motor. Usually, a motor is a round thing that spins to turn a wheel. But if you were to cut that motor open and roll it out flat, you would've a long track. Instead of spinning, the magnets push in a straight line.

HostSo it's basically a train that goes up instead of across the ground. But a train has the ground to catch it. If the power goes out in a tall building, what keeps that elevator car from just falling down the hole?

GuestThat's a big worry for a lot of people, but the system is actually built to be very safe. The first layer of safety is the brakes. In a normal car, you have to press the pedal to make the brakes grab. In these magnet elevators, the brakes are held open by the power. If the power cuts out for any reason, the brakes automatically snap shut and grab the rail. They don't need a computer or a person to tell them to do it. It's just how the spring is built. On top of that, the magnets themselves can only move the car at a certain speed. It's like a gear that can only turn so fast. Even without the brakes, the way the magnets are set up creates a natural drag that prevents the car from just dropping like a stone. It would be a very slow, controlled slide.

HostOkay, that makes sense for going up and down. But the real magic here is that these elevators can turn a corner. How does a track that's built into a wall suddenly decide to go left or right?

GuestThink of it like a train track with a turning section. The elevator car sits on a piece of the track that's mounted on a big pivot. When the car reaches a floor where it needs to go sideways, it stops on this special joint. The whole piece of the wall behind the car rotates ninety degrees. It happens very quickly and quietly. Once that section has turned, the magnets that were pushing the car up are now facing to the side. The car just follows the new path into a horizontal hallway. To the person inside, it feels a bit like a very smooth car ride. You might feel a tiny bit of a shift when the track turns, but because there's no rubbing or heavy gears, it's much smoother than any lift you have ever been in.

HostThat sounds like it would be fun to ride, but is it really worth all that extra work just to go sideways?

GuestIt's less about the ride and more about the building itself. Right now, every elevator needs its own big empty shaft. If you want ten elevators, you have to give up a lot of space in the middle of your building for ten giant holes. That's space that could be used for offices or apartments. With magnets, you can have lots of cars in the same shaft. They can follow each other like cars on a highway. They go up one shaft, move sideways at the top, and come down a different shaft. It turns the whole thing into a loop. You could've a lift arrive at your floor every thirty seconds because there are five or six cars all moving in a circle. It also means we can build towers in shapes we never could before. You could've a building that looks like a giant ring or one that leans over, and the elevator can just follow the curves of the walls.

HostI can see why a builder would love that, but what about the power bill? Pushing a heavy box with magnets must take a lot more energy than using a rope with a weight on the other end to balance it out.

GuestThat's a good point. Old elevators use a big heavy block of metal on the other end of the rope to act as a counterweight. These magnet lifts don't have that, so they do have to work harder to move the weight. But we solve that by making the cars much lighter. We use things like carbon fiber instead of heavy steel. And because the motor is spread out along the whole track instead of being one giant machine at the very top, it's actually quite smart about how it uses power. When a car is going down, it can actually act like a little power plant and put energy back into the building for other cars to use. It's a very tight, closed loop.

GuestThe real shift is that we're no longer limited by how much a single steel rope can hold or how long it can be before it snaps under its own weight.

HostThe old steel cable kept us moving in straight lines for over a century, but these magnets are finally letting us turn the corner.