Gears VEX J M Gabrielse Agenda gear testing

Gears & VEX J. M. Gabrielse

Agenda gear testing apparatus • • • Essential Terminology Gear Types Direction Gearing Up/Gearing Down Gear Ratios Examples J. M. Gabrielse

Essential Terminology • Driver – gear attached to a motor • Follower – 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 J. M. Gabrielse

Do you get it? B A motor • Which gear is the driver (A or B)? • Which gear is the follower (A or B)? J. M. Gabrielse

driver Do you get it? follower B A motor • Which gear is the driver (A or B)? → A • Which gear is the follower (A or B)? → B J. M. Gabrielse

Do you get it? wheel motor A B C • Which gear is the follower (A, B, or C)? • Which gear is the driver (A, B, or C)? • Which gear is the idler (A, B, or C)? J. M. Gabrielse

Do you get it? 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)? →J. M. B Gabrielse

Gear Types spur gears differential bevel gears rack & pinion X - not used by the Summer STEM Academy worm gear J. M. Gabrielse

Spur Gears 12 tooth 24 tooth 84 tooth 36 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 60 tooth X - only works with the worm gear J. M. Gabrielse

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

Direction • every time you add a gear the direction reverses follower driver • even number of gears: driver & follower turn in opposite directions • odd number of gears: driver & follower turn in same direction driver follower driver J. M. Gabrielse

Did you get it? driver Would the follower gear move clockwise or counterclockwise? J. M. Gabrielse

Geared Up • large driver turns small follower • less torque (turning force) • more speed follower driven gear follower gear J. M. Gabrielse

Geared Down • small driver turns large follower • more torque (turning force) • less speed driver follower driven gear follower gear J. M. Gabrielse

Gear Analysis To analyze any gear train you need to: 1. Find the number of driver teeth 2. Find the number of follower teeth 3. J. M. Gabrielse

Example 12 tooth driver 36 tooth follower Gear Analysis 1. follower teeth: 36 2. driver teeth: 12 3. – 3/1 or 3: 1 – read as 3 to 1 – 3 turns of the driver will turn the follower 1 time J. M. Gabrielse

What is the gear ratio? 84 tooth driver 60 tooth follower J. M. Gabrielse

Your Turn What is the gear ratio of the Protobot? 60 tooth gear J. M. Gabrielse

Your Turn What is the gear ratio of the Protobot? 60 tooth gear Gear Analysis 1. follower teeth: 60 2. driver teeth: 60 3. J. M. Gabrielse

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