Gears & V E X
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Transcript of Gears & V E X
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J.M. Gabrielse
Gears & VEX
J.M. Gabrielse
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J.M. Gabrielse
Agenda
• Essential Terminology• Gear Types• Direction• Gearing Up/Gearing Down• Gear Ratios• Examples
gear testing apparatus
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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
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Do you get it?
• Which gear is the driver (A or B)?
• Which gear is the follower (A or B)?
A B
motor
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J.M. Gabrielse
Do you get it?
• Which gear is the driver (A or B)? → A
• Which gear is the follower (A or B)? → B
A B
motor
driver follower
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J.M. Gabrielse
Do you get it?
• 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)?
A B C
motorwheel
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J.M. Gabrielse
Do you get it?
• 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
A B C
motorwheel
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J.M. Gabrielse
Gear Types
spur gears
differential bevel gears rack & pinion worm gear
X - not used by the Summer STEM Academy
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J.M. Gabrielse
Spur Gears
84 tooth
60 tooth
36 tooth
24 tooth
12 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
X - only works with the worm gear
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Rack & Pinion
rack
pinion
Racks and pinions are used to translate rotational motion into linear motion.
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J.M. Gabrielse
Direction
• every time you add a gear the direction reverses
• even number of gears: driver & follower turn in opposite directions
• odd number of gears:driver & follower turn in same direction
driver
driver
driver
follower
follower
follower
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Did you get it?
driver
Would the follower gear move clockwise or counterclockwise?
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J.M. Gabrielse
Did you get it?
driver
Would the follower gear move clockwise or counterclockwise?
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J.M. Gabrielse
Did you get it?
driver
Would the follower gear move clockwise or counterclockwise?
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J.M. Gabrielse
Did you get it?
driver
Would the follower gear move clockwise or counterclockwise?
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J.M. Gabrielse
Geared Up
• large driver turns small follower
• less torque (turning force)
• more speed
driven gear follower gear
follower
driver
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J.M. Gabrielse
Geared Down
• small driver turns large follower
• more torque (turning force)
• less speed
driven gear follower gear
follower
driver
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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. thdriver tee
eethfollower t ratiogear
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Example
Gear Analysis1. follower teeth: 362. 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
12 tooth driver 36 tooth follower
1
3
12
36
thdriver tee
eethfollower t ratiogear
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What is the gear ratio?
84 tooth driver
60 tooth follower
84 tooth driver
60 tooth follower
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What is the gear ratio?
7
5
teeth84
teeth60
thdriver tee
eethfollower t ratiogear
84 tooth driver
60 tooth follower
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Your Turn
What is the gear ratio of the Protobot?
60 tooth gear
60 tooth gear
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J.M. Gabrielse
Your Turn
What is the gear ratio of the Protobot?
60 tooth gear
60 tooth gear
Gear Analysis1. follower teeth: 602. driver teeth: 60
3. 1
1
60
60 ratiogear
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Thanks/Resources
• Inventor’s Guide: 3·19 - 3·13
• Teaching Gear Theory to Students
• CMU's Vex Curriculum: Gearbox Lesson