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Unformatted text preview: The Pennsylvania State University Department of Civil and Environmental Engineering CE 321: Highway Engineering Class #7: Tractive Effort and Vehicle Acceleration Spring 2008 Overview Available tractive effort – How much can the engine generate? – How much can the tire/road deliver? Vehicle acceleration Maximum Tractive Effort At some point, the engine can develop additional power beyond which can be supported by the pavement / tire interface. At this point, the additional power will merely spin the wheels. – No vehicle acceleration. Available Tractive Effort 1 2 Available Tractive Effort f r mah To Calculate W r L Wh mah Wl h R W g g f a r θ sin cos ± + + = Available Tractive Effort f r mah To Calculate W f L Wh mah Wl h R W g g r a f θ sin cos ± += Looking Back and Substituting L Wh mah Wl h R W g g f a r θ sin cos ± + + = YIELDS ) sin ( g a f r W ma R L h W L l W + + + = Looking Back and Substituting g rl a R R R ma F + + + = Eq. 2.2 RECALL YIELDS g a rl R R ma R F + + =) sin ( g a f r W ma R L h W L l W θ + + + = ) ( rl f r R F L h W L l W+ = For a Rear Wheel Drive Car r W F μ = max ) ( rl f r R F L h W L l W+ = = L h L h f l W F rl f MAX 1 ) ( For a Front Wheel Drive Car + + = L h L h f l W F rl r MAX μ 1 ) ( Example Problem 1 A 2,500 lb car is at rest. It has a 120inch wheel base. The center of gravity is 40inches above the pavement and 40inches behind the front axle. What is the maximum tractive effort if: a) the car is front wheel drive, b) the car is rear wheel drive....
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 Spring '02
 Petrucha
 Environmental Engineering, Automobile, Gear ratio, tractive effort

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