Question 1
The motor shown in Fig. 1 supplies power to Gear C through solid steel motor shaft GF (having a diameter
of 200 mm) and Gear F. The torque delivered to Gear C is 200 kNm. Gears A, B, D and E supply powers to
three machines. The torques delivered by gear A, gear B and gear E to the machines are 60 kNm, 30 kNm
and 40 kNm, respectively. Shaft ABCDE is also made of steel (G = 75 GPa). The shaft part ABC is solid
having a diameter of 200 mm while shaft part CDE is hollow (with an outside diameter of 200 mm and a
thickness of 30 mm). The diameters of gears F and C are 1200 mm and 300 mm, respectively.
. Determine the power of the motor with 120 rpm. Determine also the frictional force between Gear C
and Gear F.
(4 Marks)
Determine the maximum torsional shearing stresses in shaft GF and ABCDE. Also determine the
rotation of gear E relative to G and the rotation of gear E relative to gear A. What would be the length
of the shaft DE if the rotation of gear E relative to Gear A is limited to 0.012 radian?
(10 Marks)
If the shaft ABC is transformed into solid rectangular section (Depth = 1.5 times of width) having the
same cross-sectional area, calculate the rotation of gear A relative to gear C and also the maximum
shear stress in the shaft ABC. If the allowable shear stress for steel in shaft ABC is 300 MPa, find the
factor of safety.
(5 Marks)
Determine the torsional stress in shaft FG, if it is transformed into hollow circular section with 1 mm
thick wall (having the same outer diameter of 200 mm). If the allowable shear stress for steel is 350
MPa, will it be safe?
(3 Marks)
A semicircular groove of radius 5 mm is made in shaft FG, find the torque that can be resisted by the
shaft if the allowable shear stress is 350 MPa. How this groove affects the capacity of the whole
system?
(3 Marks)
