Gears

Gears Used to transfer energy from one place to another Rotary motion and force transferred from one part of a machine to another part Gear Wheel: a wheel with matching teeth around its edge Gear Train: two or more gear wheels that mesh rotary motion from one gear is transferred to another gear

Driving Gear (Driver): supplies the driving force in a gear train Driven Gear (Follower): The gear wheel that the driving gear applies it’s force to Mesh: gears must mesh, or interlock neatly as they rotate

Gears Can Increase Rotational Speed A gear train can increase the rotational speed of a device Ex. a hand mixer, bike The driving gear is larger (has more teeth) than the driven gear so the driven gear travels faster Driving gear Driven gear

Gears Can Decrease Rotational Speed Reducing gears are drive trains that decrease the rotational speed of a device so they decrease speed Ex. bicycle, car Driving gear Driven gear

Gears can Change Direction Parallel gears are the same size, so they have the same rotation speed, but they change the direction of the rotary motion Drive wheel: clockwise; Driven wheel: counterclockwise Ex car transmission

Gears can change rotary motion into straight line motion Load

Gears can transfer a rotary motion from one shaft to another without changing direction

Mechanical Advantages of Gear Trains To calculate the increase or reduction in rotational speed calculate the ratio of the size of the driving gear to the size of the driven gear This is called the speed ratio

Multiplying Gears Driving gear = 10 teeth = 2 Driven gear = 5 teeth The speed of the gear has been changed by a factor of 2, the driven gear will move twice as fast as the driving gear 5 teeth 10 teeth

Reducing gears Driving gear = 4 teeth = 1/2 Driven gear = 8 teeth The speed of the gear has been reduced to ½ it’s original speed 8 teeth 4 teeth

Sprockets Sometimes gears are connected with a chain called a sprocket Used to gain a multiplying effect, reduce effort or a parallel effect The gears both rotate in the same direction In a 10-speed bike there are 5 gears on the rear wheel and 2 gears on the pedal crank

Wheel and Pinion A gear train that has 2 different sized gears Larger gear is called a wheel Smaller gear is called the pinion Ex. a push lawn mover: the wheels transfer power to the blades (the pinion) which move faster than the wheels