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Asked by sciencelover123 to Dalya, Derek, Sarah, Tim, Tom on 19 Jun 2011.
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Derek McKay-Bukowski answered on 16 Jun 2011:
There is a spring inside it.
There is a cylinder with a valve. This acts as the “brake” to stop it going up and down. You have to release the valve to allow it to move. Because the air inside this cyclinder can be compressed slightly, the chair has a bit of bounce to it (which makes it comfy!).
If you are sitting on it, the spring is not enough to support the weight. If you pull the lever, the air can be released and the chair no longer has its brake. Thus the seat descends.
Without a person on it, the spring is enough to push the seat back up. That’s why you need to take some weight off the chair by partially standing, so that the spring becomes the more powerful force.
Note that with time, some air may leak through the brake cylinder. This means that if you come back to an office after a long time, the chair can sometimes be jammed up under the desk – even though you never left it like that!
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Tim Millar answered on 16 Jun 2011:
Was trying to work this out inn the office earlier. We have a “comedy” that sinks when anyone sits on it and it goes right down to the bottom. We like it because it always catches people out.
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Sarah Thomas answered on 17 Jun 2011:
My office chair does not exhibit this phenomenon!
But I can spin round on it! Weeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee!!
(Luckily it’s 8 am and nobody else is here yet) 😀
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Tom Crick answered on 19 Jun 2011:
Haha, Some great answers here! I don’t like those fancy spinning chairs, I have a bog-standard four legged chair in my office!
But usually it is some form of spring or compressed valve that returns the chair to its original position.
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