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Q1. An engine fuel injector is operated by fuel oil pressure acting on the underside of a needle valve. Movement of the needle valve is opposed by a spring with 14 coils of outside diameter 22 mm and wire diameter 6 mm. Fuel oil pressure acts on an effective area of 34 mm² on the underside of the needle valve. Fuel injection should not commence until the fuel pressure has risen to 26 MN/m². Valve lift is limited to 0.8 m. Calculate EACH of the following:

(a) The required initial axial compression of the spring;

(b) The maximum force on the spring;

(c) The maximum torsional stress in the spring.

Note: Modulus of Rigidity for spring material = 80 GN/m²