How do seat belts work?

Question

We all know that seat belts save lives when a car crashes and the seatbelt saves you from flying out the window. But how do they work?

How does it recognize that you're stopping suddenly and almost instantaneously locks itself to stop you from flying forward?

Answer 1

First, seat belts not only keep you in the car but they keep you from hitting the inside parts of the car.

To answer your question, some very expensive or advanced cars use electronic seat belt tensioners taht receive a signal from the brakes that you are stopping suddenly and so it tightens the seatbelt. But in all cars, there are two weights around a center rod inside the seat belt pulley taht will expand outward due to centrifigual force when the rod spins quickly and lock the pulley preventing more belt from expanding out. Really is it caused by how fast the belt is being pulled out so you can try it by just grabbing the seat belt with you hand and pulling it out very quickly and it should lock if you can pull it fast enough.

Answer 2

there's a sort of "toggle switch" inside the belt at the top that swings back and forth. Notice when you accelerate or stop suddenly your body moves forward or back? The toggle does the same thing. If it's not hanging straight down, it automatically "locks" the belt tight.

Answer 3

My Toyota, and most Japanese cars have a centrifugal setup that throws the locks on when it is pulled quickly.

Most American cars have a pendulum setup that swings forward, locking the reel when you put on the brakes hard or hit something.
These do not lock when you pull on them quickly.

Answer 4

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