An engine valve spring having 12 coils has the ends squared and ground. The outside diameter of the coil is 110 mm and the wire diameter is 11 mm. It has a free length of 180 mm.
A. Determine the length of the wire to which this spring must be initially compressed to hold a bolt pressure of 1.01 MPa on the valve seat of 4 cm diameter. Modulus of rigidity is taken as G = GN/m².
(A) 100 mm
(B) 98.5 mm
(C) 97.9 mm
(D) 96 mm
B. Find the spring stress if it is compressed to its solid length.
(A) 160 MPa
(B) 165.5 MPa
(C) 168.2 MPa
(D) 163.3 MPa