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GEARS

Presentation Objectives

• Identify parts of the gear trainer

• Identify gears• Identify gear terminology• Identify tooth terminology• Identify gear purpose• Determine RPM• Determine torque

Gear Trainer

What is a Gear?• A gear is a toothed wheel

Spur Gear

Worm Gear Drive

Bevel Gears

Crossed Helical Gear

Harmonic Gear

Planetary Gear Train

Car Differential

Car Differential

Gear TerminologyGear - 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)

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.

Gear Terminology

Spur Gear Terminology

Involute Profile

Spur Gear - Tooth Parts

Gear Tooth Size Called Diametral Pitch

Purpose of a Gear

• Energy Transmission• In the proper combination can be used to

increase or decrease speed and torque

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)

Determining Gear Rpm

Driving Gear Teeth

Driven Gear TeethX Driving Gear RPM = RPM of Driven gear

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.

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

Importance

• Modern Multi Speed Bicycles

Automobiles

Construction Equipment

Also

Timing Gears

Recreation (fishing)

Efficient Transportation (sprocket system)

Car 3 Speed Transmission

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.

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.