Lab Manual - MAK 411E Experimental Methods in Mechanical...

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Unformatted text preview: MAK 411E Experimental Methods in Mechanical Engineering AUTOMOTIVE LABORATORY MANUAL Özgen AKALIN O. Ak ı n KUTLAR Istanbul Technical University Department of Mechanical Engineering 2 TABLE OF CONTENTS I. VEHICLE TECHNOLOGY LABORATORY: Part 1. Determination of the center of gravity location. Part 2. Determination of brake force distribution. II. INTERNAL COMBUSTION ENGINES LABORATORY: Determination of the performance and heat balance characteristics of a diesel engine. 3 I. VEHICLE TECHNOLOGY LABORATORY Part 1. Determination of the center of gravity location: The location of center of gravity (CG) is necessary for • Calculating the climbing ability (Gradability) • Acceleration performance • Designing brake systems and springing • Vibration considerations • Handling and rollover considerations • Driving stability investigations • Determining mass moment of inertia etc. Low center of gravity is always desirable, as they are associated with fewer driving dynamic problems and increased vehicle performance during cornering and braking, but in practice the design options are relatively restricted. The position of center of gravity is highly dependent on the loading; when the vehicle is loaded the CG changes in both longitudinal and vertical axis. The body lowers when it is loaded, i.e. its center of gravity drops. The center of gravity of the passengers and the luggage is usually higher than that of the body so the end results a higher overall center of gravity. The first step in calculating the individual wheel loads in steady state cornering, accelerating, or braking conditions is to determine the CG location. Therefore, in Part 1, the location of CG will be determined experimentally, and using this data, braking performance of this vehicle will be analyzed in Part 2 Instruments: A simple crane, a frame to lift the axle of the test vehicle, a load cell connected between the frame and the crane, amplifier (bridge), voltmeter, and a straight ruler. Figure 1 Location of vehicle’s center of gravity. L l 1 l 2 W r st W f W r h L l 1 l 2 W r st W f W r h 4 Mathematical observation of the measurement is as follows: Using known front and rear axle loads, location of the center of gravity along the longitudinal axis (l 1 and l 2 ) can be easily calculated. From Figure 1, total weight is r f W W W + = ( 1 ) a n d w h e r e 2 1 l l L + = ( 2 ) Taking moment at rear tire contact point: L W l W f . . 2 = Thus, L W W l f = 2 and 2 1 l L l − = (3) In Figure 2, taking moment at the center of the rear axle . . . . . . 2 = − ′ + ′ l Cos W h Sin W Cos L W f α α α (4) where L H = α s i n ( 5 ) and calculating h ′ , height of the center of gravity is st r h h + ′ = ( 6 ) where r st is the static radius of the tires....
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Lab Manual - MAK 411E Experimental Methods in Mechanical...

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