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Speaker 1: Welcome to brain Stuff from house stuff works dot com

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Speaker 1: where smart happens. Hi Am Marshall Brain with today's question,

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Speaker 1: why is a table saw so quiet but a portable

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Speaker 1: circular saw is so loud? A circular saw makes a

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Speaker 1: lot more noise because of the type of motor it uses.

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Speaker 1: The circular saw has a universal motor in it, and

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Speaker 1: this type of motor is extremely noisy. Universal motors are

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Speaker 1: called universal because they are happy to run off of

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Speaker 1: either a C or D C electric power. Circular saws

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Speaker 1: use brush type universal motors. Vacuum cleaners, routers, and electric

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Speaker 1: drills also use universal motors. These motors produce so much

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Speaker 1: noise because the brushes rub on a slotted armature. In

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Speaker 1: circular saws and drills, you also have gear train noise.

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Speaker 1: Something like a radial arm saw or a table saw

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Speaker 1: that you have in your garage uses an induction motor instead.

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Speaker 1: Induction motors run only on a C power and they

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Speaker 1: do not use brushes. That's the main reason why they're

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Speaker 1: so quiet. They also run slower and usually use a

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Speaker 1: belt drive instead of a gear train. Manufacturers use universal

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Speaker 1: motors because they are smaller and much lighter than induction motors.

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Speaker 1: A three quarter horsepower induction motor might weigh twenty pounds.

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Speaker 1: A three quarter horsepower universal motor might weigh two or

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Speaker 1: three pounds. The weight difference is huge. A circular sty

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Speaker 1: would be almost unusable if it contained an induction motor.

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Speaker 1: If you have a quiet appliance, it probably has an

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Speaker 1: induction motor inside it. Ceiling fans and refrigerator compressors both

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Speaker 1: use induction motors to keep them quiet in your house.

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Speaker 1: It's always a good idea to where ear protection when

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Speaker 1: using a loud power tools. Even the quiet radial arm

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Speaker 1: SAD gets pretty noisy as soon as it starts chewing

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Speaker 1: through a piece of wood. Do you have any ideas

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Speaker 1: or suggestions for this podcast? If so, please send me

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Speaker 1: an email at podcast at how stuff works dot com.

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Speaker 1: For more on this and thousands of other topics, go

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Speaker 1: to how stuff works dot com and be sure to

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Speaker 1: check out the brain stuff blog on the how stuff

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Speaker 1: works dot com home page.