A helical compression spring is required to provide a minimum force of 80N at installation and have a working deflection of 25mm. The spring rate is 35N/mm. The coil must fit inside a 50mm diameter hole with 2.5 mm clearance. The spring has squared and ground ends and is made from ASTM A227 4.0mm wire, without presenting. Using a 15% clash allowance find
1. The number of coils required
2. The free length of the spring