Lecture #9

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Lecture #9
Pulley Recitation
Course Name : DESIGN OF MACHINE ELEMENTS
Course Number: MET 214
The shaft is driven at a uniform speed by pulley C. The shaft in turn drives pulley B & D. The diameter of pulleys B, C,D
are 10 in, 12 in, 14 in respectively.
Belt tensions are shown. The diameter of the shaft is 1 1/2inches.
a) Calculate Belt tension F3.
b) draw torque diagram starting from A and preceding to E.
c) calculate max shear stress due to torsion
d) determine total bearing reactions at A & E
e) draw shear and moment diagrams in horizontal & vertical lanes.
f) sketch composite moment diagram
g) determine  due to bending.
h) Calculate  max using the 1927 shaft standard
Problem #2
Given the information below and/or the information provided on problem #2 shown in the preceding
diagram which includes pulley diameters, etc, find the quantities requested. Assume pulley D, when
viewed from the end of shaft 2 looking toward load A, is rotating clockwise.
HP of load A=5 HP
Speed of shaft 2, n2=150 rpm
a) Find torque associated with pulley D, i.e. TD=
b) Find torque associated with pulley B, i.e. TB=
c) Find speed of rotation of motor shaft, (rpm) i.e. find n1=
d) Find speed of rotation of shaft #3, i.e. n3=
Problem #2 continued:
Assuming Tc=2000 in-lb
e) Find torque associated with pulley A i.e. TA=
f) Find motor torque TM=
g) Find motor horse power HPm=
h) Identify on drawing of problem #2 the direction of rotation of each pulley in the system.
i) Given the FBD for the motor shaft and the axes for a torque diagram provided below, show all torques
applied to the shaft and draw a torque diagram for the shaft on the axes provided
Example 2-8 : The carbon – steel countershaft shown in Fig. 2-25 is 25 mm in diameter and supports two
V-belt pulleys. The countershaft runs at 1100 rpm. The belt tension on the slack side of pulley A is 15
percent of the tension on the tight side. Assume the shaft has a uniform diameter of 25mm.
Assume pulley labeled with letters C & D is a driven pulley transferring power to the shaft.
a) What amount of torque is transferred by the shaft between the pulleys?
b) draw a torque diagram
c) Compute the angle of twist of the shaft between the two pulleys as a function of G.
d) Find the maximum torsional shear stress in the shaft
e) additional questions appear on next page
f) For the system shown, determine total bearing reactions at both bearings.
g) Determine the maximum amount of bending moment existing in the shaft.

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