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 2 Automotive Drivetrains Components: • Transmission • Axle assembly • Transaxle (fwd) • Drive Shaft(s) • related components 3 Automotive Drivetrains Engine torque: • The turning effort of the crankshaft • measured in foot-pounds • maximum torque is produced within a narrow RPM range (torque curve) 4 Engine Torque 5 Automotive Drivetrains Horsepower = work performed at the rate at which it is being done = torque X RPM / 5252 6 Engine Horsepower 7 Automotive Drivetrains Gears • Used to apply torque to other rotating parts of the drivetrain • used to multiply torque in automobiles 8 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) 9 Automotive Drivetrains Spur gear 10 Automotive Drivetrains Helical Gear 11 Automotive Drivetrains Straight Bevel Gearset Gears must be perpendicular to each other 12 Automotive Drivetrains Spiral Bevel vs. Hypoid 13 Automotive Drivetrains Planetary Gear 14 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 15 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 16 Automotive Drivetrains Gears Continued: 17 Automotive Drivetrains Gears continued: 18 Automotive Drivetrains As torque is multiplied power remains unchanged 19 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 20 Automotive Drivetrains Gear Reduction = a reduction in the driven gears speed = an increase in the driven gears torque 21 Automotive Drivetrains 22 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 23 Automotive Drivetrains Bearings • Used to attach a shaft to a common component AND allow for movement or rotation • friction reduction 24 Automotive Drivetrains Bearing Types • Bushing (simplest type) also called a plain type bearing • ball bearing - balls used for friction reduction • roller bearing • tapered roller 25 Bushing (simplest type) also called a plain type bearing 26 Ball Bearing 27 Roller Bearing 28 Needle Roller Bearing 29 Tapered Roller Bearing 30 Automotive Drivetrains Bearing Usage • radial or journal bearing • thrust bearing 31 Automotive Drivetrains Bearing Measurements • Bearing preload - the amount of torque- load on a bearing – measured with a torque wrench 32 Automotive Drivetrains The engine produces torque Torque is transferred to the drive wheels through a series of gears and shafts CLUTCH How do we disconnect engine power from the drive wheels? 33