Gears & VEX Adapted: Dec 2015 HEP

Agenda Essential Terminology Gear Types Direction gear testing apparatus Essential Terminology Gear Types Direction Gearing Up/Gearing Down Gear Ratios Examples

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

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)?

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

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)?

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

Gear Types spur gears differential bevel gears rack & pinion worm gear X - not used at this time

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, 60 = 5 x 12, 80 = 7 x 12 24 tooth - only works with the worm gear

Rack & Pinion pinion rack Racks and pinions are used to translate rotational motion into linear motion.

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

Would the follower gear move clockwise or counterclockwise? Did you get it? driver Would the follower gear move clockwise or counterclockwise?

Would the follower gear move clockwise or counterclockwise? Did you get it? driver Would the follower gear move clockwise or counterclockwise?

Would the follower gear move clockwise or counterclockwise? Did you get it? driver Would the follower gear move clockwise or counterclockwise?

Would the follower gear move clockwise or counterclockwise? Did you get it? driver Would the follower gear move clockwise or counterclockwise?

Geared Up large driver turns small follower (driven) less torque (turning force) more speed driven driver driver gear driven gear

Geared Down small driver turns large follower (driven) more torque (turning force) less speed driver follower driven gear follower gear

Gear Analysis To analyze any gear train you need to: Find the number of driver teeth Find the number of driven teeth

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

What is the gear ratio? 84 tooth driver 84 tooth driver 60 tooth follower 60 tooth follower

What is the gear ratio? 84 tooth driver 60 tooth follower

Your Turn What is the gear ratio of the Protobot? 60 tooth gear

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

Thanks/Resources Inventor’s Guide: 3·19 - 3·13 Teaching Gear Theory to Students CMU's Vex Curriculum: Gearbox Lesson