Speaker 1: Welcome to brain Stuff from how stuff works dot com,
Speaker 1: where smart happens High Marshall Brain. Next time you're filling
Speaker 1: up your tank at a gas station, ask yourself this,
Speaker 1: How does the nozzle know when the tank is full? No,
Speaker 1: there's not a miniature camera inside the nozzle hooked to
Speaker 1: a microprocessor. This mechanism has been around for decades. It's
Speaker 1: purely mechanical and ingenious. Near the tip of the nozzle
Speaker 1: is a small hole and a small pipe leads back
Speaker 1: from the hole into the handle. Suction is applied to
Speaker 1: this pipe using a ventur e. When the tank is
Speaker 1: not full, air is being drawn through the hole by
Speaker 1: the vacuum, and the air flows easily. When gasoline in
Speaker 1: the tank rises high enough to block the hole, a
Speaker 1: mechanical linkage in the handle senses the change in section
Speaker 1: and flips the nozzle off. Here's a way to think
Speaker 1: about it. You've got a small pipe with suction being
Speaker 1: applied at one end and air flowing through the pipe easily.
Speaker 1: If you dick the free end of the pipe and
Speaker 1: a glass of water, much more section is needed, so
Speaker 1: a vacuum develops in the middle of the pipe. That
Speaker 1: vacuum can be used to flip a lever that cuts
Speaker 1: off the nozzle. The next time you fill up your tank,
Speaker 1: look for this hole, either on the inside or the
Speaker 1: outside of the tip of the handle. Do you have
Speaker 1: any ideas or suggestions for this podcast? If so, please
Speaker 1: send me an email at podcast at how stuff works
Speaker 1: dot com. For more on this and thousands of other topics,
Speaker 1: go to how stuff works dot com.