Exam. 2-C

Machine Elements Design

Student Name:

Student No.


1) A- Define the following:


a- Spring stiffness (rat):


b- Area second moment of inertia:

c- Double shear:

d- Helical spring active coil number:




B- Write the type of car suspension springs:


Type of spring

Type of car










C- If k1 = 900 N/mm, k2 = 300 N/mm

i- Which one of the two springs is the softer spring?




ii- Find the equivalent spring rate in case:

a- the two springs are in parallel


b- the two springs are in seires







iii- What is the deflection of the springs in parallel under a load of  1000 N



2) A) Find the shear stress of the coil spring due to

i-                   Torsion only

ii-                 Torsion + direct shear

iii-               Torsion + direct shear + wire curvature


          P = 6000 N

          D = 150 mm

          d =  15 mm

          n = 17

          Type of ends (Squared and ground)













B) Find the spring deflection in that case (G = 91,400 N/mm2)





C) Check the nomogram for case B and C



3) A force of 50,000 N is applied to the clevis pin with a required safety factor of 3. If the pin diameter is 18 mm, determine a suitable material for the pin.