An elevator moving at a constant speed of 1.75 m/s is brought to rest by a spring buffer (as shown in Fig 2) consisting of Four helical spring arranged in parallel. The mass of the elevator is 1020 kg. The springs are compressed by 80 mm in bringing the elevator to rest. The spring index can be taken as 8. The springs are made of steel wire with ultimate tensile strength of 1250 N/mm2 and modulus of rigidity of 81370 N/mm2. The permissible shear stress for the spring wire can be taken as 40% of the ultimate tensile strength. Design the spring and calculate: