Automotive Drivetrains

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Automotive Drivetrains
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Automotive Drivetrains
Purpose

• 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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Automotive Drivetrains
Components

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

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Automotive Drivetrains
Engine torque

• 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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Automotive Drivetrains
Horsepower

• work performed at the rate at which it is being
  done
• torque X RPM / 5252

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Engine Horsepower
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Automotive Drivetrains
Gears

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

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Automotive Drivetrains
Gear Types

• 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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Automotive Drivetrains
Spur gear
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Automotive Drivetrains
Helical Gear
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Automotive Drivetrains
Straight Bevel Gearset
Gears must be perpendicular to each other
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Automotive Drivetrains
Spiral Bevel vs. Hypoid
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Worm Gear
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Automotive Drivetrains
Planetary Gear
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Automotive Drivetrains
Gear Measurements

• 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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Torque Multiplication

• Torque is calculated by multiplying force X
  distance
• OR
• the center of the shaft
• times (X)
• the point where the force is exerted

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Automotive Drivetrains
Gears Continued
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Automotive Drivetrains
Gears continued
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Automotive Drivetrains

• As torque is multiplied power remains unchanged

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Automotive Drivetrains
Gear Ratios

• 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 Ratio
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Automotive Drivetrains
Gear Reduction

• a reduction in the driven gears speed
• an increase in the driven gears torque

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Automotive Drivetrains
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Automotive Drivetrains

• If the DRIVING gear in the previous example is
  producing 250 ft.-lb. of torque how much torque
  is the DRIVEN gear producing?

• 4 X 250
• 1000 ft.-lb. torque

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Automotive Drivetrains

• Bearings

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

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Automotive Drivetrains
Bearing Types

• Bushing (simplest type) also called a plain type
  bearing
• ball bearing - balls used for friction reduction
• roller bearing
• tapered roller

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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
Bearing Usage

• radial or journal bearing
• thrust bearing

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Automotive Drivetrains
Bearing Measurements

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

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Automotive Drivetrains
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?

• CLUTCH