Automotive Drivetrains

• Connect/disconnect engines power to the drive wheel(s)

• allow for different speed ratios• provide for reverse• power control for safe turning• torque multiplication

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Purpose:

Automotive Drivetrains

• Transmission• Axle assembly • Transaxle (fwd)• Drive Shaft(s)• related components

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Components:

Automotive Drivetrains

• The turning effort of the crankshaft• measured in pounds per foot• maximum torque is produced

within a narrow RPM range (torque curve)

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Engine torque:

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Engine Torque

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Automotive Drivetrains

= work performed at the rate at which it is being done

= torque X RPM / 5252

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Horsepower

Engine Horsepower

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Automotive Drivetrains

• Used to apply torque to other rotating parts of the drivetrain• used to multiply torque in

automobiles

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Gears

Automotive Drivetrains

• Spur gear (most basic)• Helical gear (helix = form a curve)• Herringbone gear = 1 gear w/2 helical

gears w/teeth angles reversed• Bevel gear - cone w/top cutoff• hypoid gear - similar to above• planetary gear(set)

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Gear Types

Automotive Drivetrains

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Spur gear

Automotive Drivetrains

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Helical Gear

Automotive Drivetrains

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Straight Bevel Gearset

Gears must be perpendicular to each other

Automotive Drivetrains

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Spiral Bevel vs. Hypoid

Worm Gear

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Automotive Drivetrains

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Planetary Gear

Automotive Drivetrains

• Backlash - the clearance between two meshed gears–measured with a dial indicator

• end play - axial or end-to-end movement of a gear– also measured with a dial indicator

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Gear Measurements

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Torque MultiplicationTorque is calculated by

multiplying force X distanceOR

the center of the shaft times (X)

the point where the force is exerted

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Automotive Drivetrains

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Gears Continued:

Automotive Drivetrains

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Gears continued:

Automotive Drivetrains

As torque is multiplied power remains unchanged

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Automotive Drivetrains

• The mathematical relationship of one gear to another

• expresses the amount of torque multiplication between two gears

• ratio = # of teeth of DRIVEN gear / # of teeth of drive gear

- OR -

• ratio = outside diameter of DRIVEN gear/ O.D. of drive gear

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Gear Ratios:

Gear Ratio

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Automotive Drivetrains

= a reduction in the driven gears speed

= an increase in the driven gears torque

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Gear Reduction

Automotive Drivetrains

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Automotive DrivetrainsIf the DRIVING gear in the previous example is producing 250 ft.-lb. of

torque how much torque is the DRIVEN gear producing?

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4 X 250 = 1000 ft.-lb. torque

Automotive DrivetrainsBearings

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•Used to attach a shaft to a common component AND allow for movement or rotation

•friction reduction

Automotive Drivetrains

• Bushing (simplest type) also called a plain type bearing

• ball bearing - balls used for friction reduction

• roller bearing

• tapered roller

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Bearing Types

Bushing (simplest type) also called a plain type

bearing

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Ball Bearing

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Roller Bearing

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Needle Roller Bearing

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Tapered Roller Bearing

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Automotive Drivetrains

• radial or journal bearing

• thrust bearing

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Bearing Usage

Automotive Drivetrains

• Bearing preload - the amount of torque- load on a bearing–measured with a torque wrench

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Bearing Measurements

Automotive Drivetrains

CLUTCH38

The engine produces torque

Torque is transferred to the drive wheels through a series of gears and shafts

How do we disconnect engine power from the drive wheels?