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Gears & VEX Adapted: Dec 2015 HEP
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Agenda Essential Terminology Gear Types Direction
gear testing apparatus Essential Terminology Gear Types Direction Gearing Up/Gearing Down Gear Ratios Examples
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Essential Terminology
Driver – gear attached to a motor Follower (driven) – gear doing useful work Idler – gear between the driver and follower Geared Up – the follower moves faster than the driver Geared Down – the follower moves slower than the driver
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Do you get it? B A Which gear is the driver (A or B)?
motor Which gear is the driver (A or B)? Which gear is the driven (A or B)?
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Do you get it? B A Which gear is the driver (A or B)? → A
driven B A motor Which gear is the driver (A or B)? → A Which gear is the follower (A or B)? → B
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Do you get it? A B C Which gear is the driven (A, B, or C)?
wheel motor A B C Which gear is the driven (A, B, or C)? Which gear is the driver (A, B, or C)? Which gear is the idler (A, B, or C)?
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Do you get it? A B C Which gear is the follower (A, B, or C)? → C
wheel motor A B C Which gear is the follower (A, B, or C)? → C Which gear is the driver (A, B, or C)? → A Which gear is the idler (A, B, or C)? → B
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Gear Types spur gears differential bevel gears rack & pinion worm gear
X - not used at this time
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24 tooth - only works with the worm gear
Spur Gears 12 tooth 24 tooth 84 tooth 36 tooth 60 tooth The number of teeth on each spur gear is a multiple of 12. 12 = 1 x 12, 36 = 3 x 12, = 5 x 12, 80 = 7 x 12 24 tooth - only works with the worm gear
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Rack & Pinion pinion rack
Racks and pinions are used to translate rotational motion into linear motion.
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Direction every time you add a gear the direction reverses
even number of gears: driver & follower turn in opposite directions odd number of gears: same direction driven driver driver driven driven driver
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Would the follower gear move clockwise or counterclockwise?
Did you get it? driver Would the follower gear move clockwise or counterclockwise?
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Would the follower gear move clockwise or counterclockwise?
Did you get it? driver Would the follower gear move clockwise or counterclockwise?
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Would the follower gear move clockwise or counterclockwise?
Did you get it? driver Would the follower gear move clockwise or counterclockwise?
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Would the follower gear move clockwise or counterclockwise?
Did you get it? driver Would the follower gear move clockwise or counterclockwise?
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Geared Up large driver turns small follower (driven)
less torque (turning force) more speed driven driver driver gear driven gear
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Geared Down small driver turns large follower (driven)
more torque (turning force) less speed driver follower driven gear follower gear
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Gear Analysis To analyze any gear train you need to:
Find the number of driver teeth Find the number of driven teeth
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Example 12 tooth driver 36 tooth follower Gear Analysis
follower teeth: 36 driver teeth: 12 3/1 or 3:1 read as 3 to 1 3 turns of the driver will turn the follower 1 time
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What is the gear ratio? 84 tooth driver 84 tooth driver
60 tooth follower 60 tooth follower
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What is the gear ratio? 84 tooth driver 60 tooth follower
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Your Turn What is the gear ratio of the Protobot? 60 tooth gear
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Your Turn What is the gear ratio of the Protobot? Gear Analysis
60 tooth gear 60 tooth gear Gear Analysis follower teeth: 60 driver teeth: 60
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Thanks/Resources Inventor’s Guide: 3·19 - 3·13
Teaching Gear Theory to Students CMU's Vex Curriculum: Gearbox Lesson
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