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

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.

Example 4 3 2 1 R

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Definitions Gear Gears consist of two or more toothed wheels meshed together to form a gear.

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

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

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

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

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…

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

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…

Lesson 32 - Gears & More Gears Gear Ratios Example Ratios 1 : 15 4 : 1 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

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

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

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 20 : 1 100 : 1 Driver Gear

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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 : 2 1 : 10 1 : 50 Follower Gear Driver Gear

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 287 - 289 Pages 273 - 275

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