Suez Canal University
Production Engng & Mechanical Design Dept
Faculty of Engineering
Machine Design
Port Said
Time 1 hours
3 rd Year ( Power Dept )
Mid Term, April 2008
Answer All the questions and assume any missing data you find it necessary to complete your design
Question No 1 25 Marks
Its required to design a suitable coupling to transmit a torque of 250 N-m between two coaxial shafts. The shaft is made of alloy steel, flanges made out of cast iron and bolts out of steel. Four bolts are used to couple the flanges. The shafts are keyed to the flange hub. The permissible stresses are given below:
Shear stress on shaft = 100 MPa
Bearing or crushing stress on shaft = 250 MPa
Shear stress on keys = 100 MPa
Bearing stress on keys = 250 MPa
Shearing stress on cast iron = 200 MPa
Shear stress on bolts = 100 MPa
Present a neat sketch of the assembly indicating the important dimensions. The stresses developed in the various members have to be checked before finalizing the design. ( The Final neat Drawing of the coupling has a direct effect on the evaluation of the total marks )
Question No. 2 5 Marks
( solve either of the following 2 questions )
A - Calculate the length of a Cross Belt Drive , consider in your answer the following notations
r1 and r2 = Radii of the larger and smaller pulleys,
x = Distance between the centers of two pulleys (i.e. O1, O2), and ,
L = Total length of the belt.
OR : 5 Marks
B -Prove that the ratio of the driving tensions on the two sides of a pulley is
T1 / T2 = e μθ
where T1 = Tension in the tight side of the belt,
T2 = Tension in the slack side of the belt,
μ = Coefficient of friction between the belt and the pulley, and θ = Angle of contact in radians.
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