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GEARS. What is a Gear?. Gears or toothed wheels transmit rotary motion through interlocking teeth of two or more gears. Gears have “drivers” that are attached to a motor. Gear A is the driver in this animation. Gear Rotations.
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What is a Gear? • Gears or toothed wheels transmit rotary motion through interlocking teeth of two or more gears. • Gears have “drivers” that are attached to a motor. • Gear A is the driver in this animation.
Gear Rotations • With two gears, the output of the driven gear will rotate in the opposite direction of the drive gear • With more than two gears, every other gear will rotate in the same direction
Purpose of a Gear • Energy Transmission • Gears can be used to increase or decrease speed and torque. • Gears are also used to transfer rotational motion to a different axis.
Gear Terminology • Gear Ratio– also known as “speed ratio” which is determined by the number of teeth on the output-drive gear compared to those on the input shaft. • Gear Mechanical Advantage– Output advantage determined by comparing the input revolutions per minute (RPM) to the output (RPM)
Gear Teeth and Speed • When gear 'A' completes one revolution gear 'B' turns 1.5 revolutions (1½ times) • Gear ‘B’ revolves the fastest. A basic rule of gears is - if a large gear (gear ‘A’) turns a small gear (gear ‘B’) the speed increases. • On the other hand, if a small gear turns a large gear the opposite happens and the speed decreases.
Types of Gears: Spur Gear • The most common type of gear. • Found in oscillating sprinkler, washing machine, etc. • Disadvantages: really loud.
Worm Gear • Worm gears are used when large gear reductions are needed (20:1). • The worm can turn the gear, but not vice-versa. • Advantage: the locking feature can act as a brake when the motor is not turning.
Bevel Gears • Bevel gearsare useful when the direction of a shaft's rotation needs to be changed. • They are usually mounted on shafts that are 90 degrees apart, but can be designed to work at other angles as well. • The teeth on bevel gears can be straight, spiral or hypoid.
Applications Recreation (fishing) Efficient Transportation (sprocket system)
Gear Facts • The RPM of the larger gear is always slower than the RPM of the smaller gear. • Mating gears always turn in the opposite directions. • Gears locked together on the same shaft will always turn in the same direction and at the same rpm. • Mating gears always have the same size teeth (diametral pitch).