Design1 Sheets

MACHINE CONSTRUCTION
Sheet1
Revision
1. For the shown figures, calculate:

a. Area.
b. Center of gravity.
c. Moment of inertia about vertical and horizontal axes, which passes through the center of gravity.
2. If these sections experience a. Tension Normal force of 100N, b. Bending moment of 20000 N.mm
about horizontal axis c. Bending moment of 10000 N.mm about vertical axis d. Shear force of 300
N in the vertical direction.
Calculate
a. Normal stress.
b. Bending stresses due to bending moment about vertical and horizontal axes.
c. Average shear stress d. Maximum shear stress for figures 1, 2, 3.
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3. Find the reactions at the supports and plot the shear-force and bending moment diagrams for the
beam shown in the figures. For the shown beam section, calculate the principle stress at critical
section or sections.
Sheet 2
Shaft design
1. The rotating solid steel shaft is simply supported by bearings at points B and C and is driven by a
gear (not shown) which meshes with the spur gear at D, which has a 150mm pitch diameter. The
force F from the drive gear acts at a pressure angle of 20º. The shaft transmits a torque to point A of
TA = 300 Nm. = 250 MPa. Determine the minimum allowable diameter of the 250 mm section of
the shaft based on Static yield analysis.
2. A shaft is supported by two bearings placed 1 m apart. A 600 mm diameter pulley is mounted at a
distance of 300 mm to the right of left hand bearing and this drives a pulley directly below it with
the help of belt having tight side of 2.25 kN & loose side of 1.058 KN. Another pulley 400 mm
diameter is placed 200 mm to the left of right hand bearing and is driven with the help of electric
motor and belt (Driver), which is placed horizontally to the right as shown below. Determine the
suitable diameter for a solid shaft, allowing working stress of 63 MPa in tension and 42 MPa in
shear for the material of shaft. Assume that the torque on one pulley is equal to that on the other
pulley.
4. The figure is a schematic drawing of a countershaft that supports two V-belt pulleys. The
countershaft runs at 1200 rev/min. The belt tension on the loose side of pulley A is 15percent of the
tension on the tight side. Consider bearing at O & E are simple support and calculate shaft diameter
& power transmitted in shaft.
Knowing that ( Ϭ = 120MPa & ꚍ = 70 MPa )
5. Design a shaft to transmit power from an electric motor to a lathe head stock through a pulley by
means of a belt drive. The pulley weighs 200 N and is located at 300 mm from the center of the
bearing. The diameter of the pulley is 200 mm and the maximum power transmitted is 1 kW at 120
r.p.m.
Knowing that (Ϭ = 120MPa & ꚍ = 70MPa)
Sheet 3
Key design
1. A pulley keyed to a 24-mm steel shaft with a 6 x 20 square Key. If the hub length is 20 mm and the
allowable shearing stress for the key material is 100 MPa, how much torque can be transmitted?
2. A key 24 mm wide, 21 deep and 300 mm long is to be used on a 115 kW, 1160 rpm squirrelcage
induction motor. The shaft diameter is 100 mm. Determine the maximum shearing and compressive
stresses on the key and the maximum torsional shear stress on the shaft, considering v effect of the
keyway.
3. A belt pulley is fastened to a 75-mm shaft running at 200 rpm, by means of a key 18 mm wide by
125 mm long. The permissible stresses of the key material are 55 MPa in shear and 90 MPa in
compression. a- determine the power can be transmitted. b- What is the required key depth?
Sheet 4
Power screw
1. A power screw with square thread has diameter of 25 mm and pitch of 5 mm. a) Find the thread
depth, the thread width, the mean and root diameters, and the lead, provided square threads are
used. b) Repeat part (a) for Acme threads. c) Repeat part (a) for metric V threads.
2. A power screw with single square thread is 25 mm in diameter with a pitch of 5 mm. An axial load
on the screw reaches a maximum of 6 kN. The coefficients of friction are 0.05 for the collar and
0.08 for the threads. The frictional diameter of the collar is 40 mm. Find the overall torque to "raise"
and "lower" the load and thread efficiency in both cases.
3. The press shown ion the figure has a rated load of 22.5 kN. The twin screws have Acme threads, a
diameter of 75 mm, and a pitch of 12 mm. Coefficients of friction are 0.05 for the threads and 0.06
for the collar bearings. Collar diameters are 125 mm. The gears have an efficiency of 95% and a
speed ratio of 75:1. A slip clutch, on the motor shaft, prevents overloading. The full-load motor
speed is 1720 rpm. a) When the motor is turned on, how fast will the press head move? b) What
should be the power rating of the motor?
4. A square-thread power screw has a major diameter of 32 mm and a pitch of 4mm with double
thread (2 starts), and it is to be used in an application shown in the figure. The given data include f =
fc = 0.08, dc == 40 mm, and F = 6.4 kN per screw. a) Find the thread depth, thread width, pitch
diameter, minor diameter and lead b) Find the torque required to raise and lower the load. c) Find
the efficiency during lifting the load. d) Find the body stresses, tensional and compressive. e) Find
the bearing stress. f) Find the thread stresses bending at the root, shear at the root, and principle
stress and maximum shear stress at the same location.
5. A single square-thread power screw has an input power of 3 kW at a speed of 60 rpm. The screw
has a diameter of 36 mm and a pitch of 6 mm. The frictional coefficients are 0.14 for the threads
and 0.09 for the collar, with a collar friction radius of 45 mm. Find the axial resisting load F and the
combined efficiency of the screw and collar.
Sheet 5
Bolt design
1. In the shown hydraulic cylinder, the maximum oil pressure is 6 MPa. The inner diameter A is 120
mm. the flanges width are D=12mm and E=15mm. The dead end flange is fixed by 10 bolts M14x2.
Calculate the minimum allowable tightening torque of these bolts. If the bolt material normal yield
strength is 300 MPa, check the bolt for failure under various stresses.
2. In the shown connection, the coefficient of friction is 0.05. Calculate the minimum allowable
tightening torque to carry the load F=1000N. If high tensile bolt 9.8, calculate the design factor of
safety.

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MACHINE CONSTRUCTION

1. For the shown figures, calculate:

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