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Lecture Engineering drawing and design - Lecture 15: Mechanical elements – Shafts

Lecture 15: Mechanical elements – Shafts. The following will be discussed in this chapter: Common shaft loading mechanisms, shaft design characteristics, shaft design, how to connect elements to the shaft? Limits and fits, preferred fits in the basic-hole system,. | Design web Design web Introduction ME 1110 – Engineering Practice 1 Engineering Drawing and Design - Lecture 15 Shaft – a rotating element used to transmit power or motion. It provides axis of rotation for rotating elements and controls their motion. Axle – a non-rotating element that carries no torque and is used to support rotating elements. Spindle - a short shaft There are two aspects of shaft design: Mechanical Elements – Shafts » Deflection and rigidity (bending and torsional deflection) » Stress and strength Prof Ahmed Kovacevic To design a shaft, other elements: gears, pulleys, bearings should be located and specified. Design objective necessary to check if a shaft diameter is sufficient to sustain loads School of Engineering and Mathematical Sciences Room CG25, Phone: 8780, E-Mail: a.kovacevic@city.ac.uk www.staff.city.ac.uk/~ra600/intro.htm 1 Ahmed Kovacevic, City University London 2 Ahmed Kovacevic, City University London Design web Design web Common shaft loading mechanisms 3 Ahmed Kovacevic, City University London 4 Ahmed Kovacevic, City University London Design web Design web Shaft design Shaft design characteristics Shaft topology Shaft is usually of circular cross section Deflections are function of the geometry and load. Steps in the shaft design are: a) b) Choose a shaft configuration to support and locate the two gears + two bearings Solution uses an integral pinion, shaft with three shoulders, key, keyway and sleeve. Bearings are located in the housing Choose fan shaft configuration Solution uses sleeve bearings, a straight through shaft, locating collars, setscrews, pulley and fan c) d) • Define shaft topology Specify driving elements Free body diagram Select bearings Consider shaft deflection and stress » Specify connections » Dimensions 5 Ahmed Kovacevic, City University London Driving elements 1. » » » » » Driving elements (gears, pulleys, sprockets ) have to be selected and calculated Minimum diameter .