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Gears

Gears. Gears. They can reverse the direction of a motor or drive. They can increase or decrease the turning of a motor. The speed of a motors turning is called RPM- rotations per minute.

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Gears

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  1. Gears

  2. Gears • They can reverse the direction of a motor or drive. • They can increase or decrease the turning of a motor. The speed of a motors turning is called RPM- rotations per minute. • They can increase or decrease the power of a motor's turning. The power of a motor turning is called Torque.

  3. WHAT IS A GEAR RATIO A gear ratio defines the relationship between multiple gears. Gear Ratio= Output gear # teeth / Input gear # teeth For example, if our motor is attached to a gear with 60 teeth and this gear is then attached to a gear with 20 teeth that drives a wheel, our gear ratio is 60:20, or more accurately 3:1 If you do not want to count a gears teeth (or if they do not exist), gear ratio's can also be determined by measuring the distance between the center of each gear to the point of contact. For example, if our motor is attached to a gear with a 1" diameter and this gear is connected to a gear with a 2" diameter attached to a wheel, From the center to edge of our input gear is 0.5“ From the center to edge of our output gear is 1" Our ratio is 1/0.5 or more accurately 2:1

  4. How does a gear ratio affect speed: • The gear ratio tells us how fast one gear is rotating when compared to another. • If our input gear (10 teeth) is rotating at 5 rpms , and it is connected to our output gear (50 teeth), our output gear will rotate at 1 rpms. Why?Our gear ratio is 50:10... or 5:1 • If our small gear rotates 1x, our large gear only rotates 1/5. It takes 5 rotations of our small gear to = 1 rotation of our large gear. Thus our large gear is rotating at 1/5 the speed = 1rmp. • What if our gear ratio where 1:3?In this case our input gear is 3x larger as large as our output gear. • If our input gear were rotating at 20 rpms.... each rotation, would result in 3 rotations of our output gear. Our output would be 60rpms.

  5. Gearing Up If you use a large gear to drive a small gear, the small one will turn faster.

  6. Gearing Up • Gearing up increases speed, but decreases force. • A example of a gearing-up system in real life is a 10-speed bike - when you shift into 10th gear, you turn a large gear with the pedals, which drives a small gear attached to the rear wheel. • For this model, one turn of the 40-tooth driver produce five turns of the 8-tooth follower. This ratio of 1:5 is called the gearing up ratio

  7. Gearing Down If you use a small gear to drive a large gear, the large one will turn slower.

  8. Gearing Down • Gearing down decreases speed but increases force. Since it's easy to turn a small gear at a fast speed, we use it to move the large one. • A small driver gear makes a large follower gear turn more slowly. • For this model, five turns of the 8-tooth driver produce one turn of the 40-tooth follower. • This ratio of 5:1 is called the gearing down ratio.

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