1. Lesson 32 - Gears & More Gears
What are gears?
What do gears accomplish?

2. Big Idea!!!
If we use a gear to “reduce” the output speed of a system, we will end up “multiplying” the output force
Visa Versa
If we use a gear to “multiply” the output speed of a system, we will end up “reducing” the output force.

3. Example 4 3 2 1 R

4. Click on the hyperlinks
Listen to the Gearing!
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5. Definitions
Gear
Gears consist of two or more toothed wheels meshed together to form a gear.

6. The Driving Gear
The DRIVER GEAR is the first gear in the system and is the gear that has the energy source coupled to it
The DRIVER GEAR moves the system
DRIVER GEAR
Please draw a picture of a bike in your notes and label the “driver” and “follower” gears

7. The Follower Gear
The FOLLOWER GEAR is the second gear in the system and is the gear that receives the energy from the driving gear
The FOLLOWER GEAR is moved in the system
FOLLOWER GEAR

8. Lesson 32 - Gears & More Gears
Why is That Important?
We need to know which is the driven gear and which is the driving gear if we are to figure out if the force or speed is being reduced or multiplied
We base the terms…
MULTIPLYING or
REDUCING
gear systems based on the NUMBER of REVOLUTIONS of the FOLLOWER GEAR

9. Reducing Gears Reducing Gears
If the DRIVER GEAR is smaller than the FOLLOWER GEAR the number of revolutions in the follower gear will decrease or be “reduced”
However the force of the FOLLOWER GEAR will go up, it will be like taking the force from several turns in the driving gear and concentrating them into one turn of the follower gear

10. Reducing Diagram FOLLOWER GEAR
This gear will receive the force from the driving gear but will not spin as quickly thus reducing the speed in the system. It will concentrate the force from several spins into one
DRIVER GEAR
This gear will need to spin around several times to every one time the larger gear spins
This would be like the “1st” gear in a cars transmission because…

11. Multiplying Gears Multiplying Gears
If the DRIVER GEAR is larger than the FOLLOWING GEAR the number of revolutions in the follower gear will increase or be “multiplied”
However the force of the FOLLOWING GEAR will be “reduced”, it will be like taking the force from one turn in the driving gear and spreading it out over several turns of the following gear

12. Multiplying Diagram DRIVER GEAR
This gear will have the force applied to it first and will only have to spin once to make the other gear spin several times
FOLLOWER GEAR
This gear will spin around several times to every one time the larger gear spins, thus multiplying the speed in the system
This would be like the “Over Drive” gear in a cars transmission because…

13. Lesson 32 - Gears & More Gears
Gear Ratios
Example Ratios
1 : : : 3.5
1st Number in a Ratio
The 1st number in a gear ratio always represents the number of rotations the DRIVER gear will make compared to the other gear
2nd Number in a Ratio
The 2nd number in a gear ratio always represents the number of rotations the FOLLOWER gear will make compared to the other gear

14. Question???
What would the gear ratio be if both gears were exactly the same size?
DRIVING GEAR
FOLLOWER GEAR

15. Answer!!!
The gear ratio would be 1 : 1 because both gears would turn the exact same number of times.
DRIVING GEAR
FOLLOWER GEAR

16. Lesson 32 - Gears & More Gears
Gear Ratios
Follower Gear
LOW GEAR RATIOS
The lower the gear ratio the slower the output speed will be for that gear system
Low gear ratios are shown by having a very large number represent the driving gear (1st number in the ratio) because it is spinning many times compared to the follower gear
Examples 6 : : : 1
Driver Gear

17. Click on the hyperlinks
Reducing Video
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18. Gear Ratios HIGH GEAR RATIOS
The higher the gear ratio the faster the output speed will be for that gear system
High gear ratios are shown by having a smaller number represent the driving gear (1st number in the ratio) because it is spinning fewer times compared to the following gear
Examples 1 : : : 50
Follower Gear
Driver Gear

19. Homework !!
You are being given a short worksheet that you can use the rest of the class to complete
You may use the textbook pages shown here to help you but your notes will be your best source
We will go over this worksheet in the next class
Please use your time wisely to get this sheet completed
Pages
Pages

20. Click on the hyperlinks
Playing with Gears
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