1. Forging new generations of engineers
Gears
Principles of EngineeringTM
Unit 4 - Lesson Mechanisms
Forging new generations of engineers
Project Lead The Way, Inc.
Copyright 2007

2. GEARS

3. Presentation Objectives
Gears
Principles of EngineeringTM
Unit 4 - Lesson Mechanisms
Presentation Objectives
Identify parts of the gear trainer
Identify gears
Identify gear terminology
Identify tooth terminology
Identify gear purpose
Determine RPM
Determine torque
Project Lead The Way, Inc.
Copyright 2007

4. Gear Trainer Gears Principles of EngineeringTM
Unit 4 - Lesson Mechanisms
Gear Trainer
Project Lead The Way, Inc.
Copyright 2007

5. What is a Gear? A gear is a toothed wheel Gears
Principles of EngineeringTM
Unit 4 - Lesson Mechanisms
What is a Gear?
A gear is a toothed wheel
Project Lead The Way, Inc.
Copyright 2007

6. Spur Gear

7. Worm Gear Drive

8. Bevel Gears

9. Crossed Helical Gear

10. Harmonic Gear

11. Planetary Gear Train

12. Car Differential

13. Car Differential

14. Gear Terminology Gear - A toothed wheel
Gears
Principles of EngineeringTM
Unit 4 - Lesson Mechanisms
Gear Terminology
Gear - A toothed wheel
Drive Gear - The gear which produces the input
Driven Gear - The gear which produces the output
Chain Drive - Combines the sprocket and chain that mesh together to produce a positive mechanical force
Gear Ratio - The description of the mechanical advantage obtained through the use of rotating devices
Mechanical Advantage - An output increase determined by comparing the input revolutions per minute (RPM) to the output revolutions per minute (RPM)
Project Lead The Way, Inc.
Copyright 2007

15. Gears
Principles of EngineeringTM
Unit 4 - Lesson Mechanisms
Gear Terminology
Pulley - A wheel used to transmit power by means of a band, belt, cord, or rope
Torque - The turning effort that causes something to rotate. If torque produces rotation, then work is done
Wheel - A lever that is rotated 360 degrees around an axle
Work - The ability of force to travel through a distance
Gear Train - A series of two or more meshed gears used to increase or decrease the RPM, torque, or direction of rotation of the output gear.
Project Lead The Way, Inc.
Copyright 2007

16. Gear Terminology Compound Gear Train Simple Gear Train Worm Gear
Gears
Principles of EngineeringTM
Unit 4 - Lesson Mechanisms
Gear Terminology
Compound Gear Train
Simple Gear Train
Worm Gear
Miter Gear
Project Lead The Way, Inc.
Copyright 2007

17. Spur Gear Terminology Involute Profile Gears
Principles of EngineeringTM
Unit 4 - Lesson Mechanisms
Spur Gear Terminology
Involute Profile
Project Lead The Way, Inc.
Copyright 2007

18. Spur Gear - Tooth Parts

19. Gear Tooth Size Called Diametral Pitch

20. Purpose of a Gear Energy Transmission
Gears
Principles of EngineeringTM
Unit 4 - Lesson Mechanisms
Purpose of a Gear
Energy Transmission
In the proper combination can be used to increase or decrease speed and torque
Project Lead The Way, Inc.
Copyright 2007

21. 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 (ie. Gears 1, 3, 5 will rotate clockwise and gears 2, 4 will rotate counter clockwise)

22. Determining Gear Rpm Driving Gear Teeth Driven Gear Teeth
Gears
Principles of EngineeringTM
Unit 4 - Lesson Mechanisms
Determining Gear Rpm
Driving Gear Teeth
Driven Gear Teeth
X Driving Gear RPM = RPM of Driven gear
Project Lead The Way, Inc.
Copyright 2007

23. Gears
Principles of EngineeringTM
Unit 4 - Lesson Mechanisms
What Is Torque?
The turning effort (measured in inch-pounds or foot-pounds) that causes something to rotate. When torque produces rotation, then work is done.
Project Lead The Way, Inc.
Copyright 2007

24. Determining Torque Power Out = Power In
Gears
Principles of EngineeringTM
Unit 4 - Lesson Mechanisms
Determining Torque
Power Out = Power In
1HP at 100 rpm=1/2 HP at 200 rpm
1 HP at 200 rpm = 2 HP at 100 rpm
Project Lead The Way, Inc.
Copyright 2007

25. Importance Modern Multi Speed Bicycles Automobiles
Gears
Principles of EngineeringTM
Unit 4 - Lesson Mechanisms
Importance
Modern Multi Speed Bicycles
Automobiles
Construction Equipment
Project Lead The Way, Inc.
Copyright 2007

26. Also Recreation (fishing) Timing Gears
Principles of EngineeringTM
Unit 4 - Lesson Mechanisms
Also
Recreation (fishing)
Timing Gears
Efficient Transportation (sprocket system)
Project Lead The Way, Inc.
Copyright 2007

27. Car 3 Speed Transmission

28. 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 direction.
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).
The gear ratio between mating gears is the ratio between the number of teeth, the pitch diameters and the rpms.

29. Gear Review What is a gear? Name 4 different types of gears.
What is torque and rpm?
What is diametral pitch & how is it shown?
List 10 places where gears are used.