Question

A spring is to be designed to fit over a valve rod of 15 mm diameter as shown in figure Q2. The forces acting on the spring while closing and opening of the valve are F1 and F2 respectively. Using the data given table Q2 and assuming that spring has squared and ground ends,

Determine:

(i) Wire diameter of spring

(ii) Outside diameter of spring   

(iii) Number of turns   

(iv) Stiffness of spring

(v) Free length   

(vi) Pitch   

(vii) If this spring is cut into two springs having equal number of turns, determine the spring stiffness of each resulting springs   

(viii) Discuss the load carrying capacity of the resulting two springs when used in parallel compared with that of the original spring

40 N Length of spring when valve is open:

30 N Length of spring when valve is closed :

15 mm Diameter of valve rod:

6 Spring index :

1400N/mm2 Ultimate tensile strength :

82000 MPa Modulus of rigidity:

30% ultimate tensile strength Shear Stress :

200 N Force (F1) when the valve closes :

300 N Force (F2) when the valve open :

Answer 1