Design a concentric (nested) spring system for equal load sharing and simultaneous bottoming.

For two concentric springs sharing load equally, each carries P/2. For simultaneous bottoming, deflections must be equal: delta_1 = delta_2. Using k = Gd^4/(8D^3N), this gives (d1^4.N2.D2^3)/(d2^4.N1.D1^3) = 1. To avoid interference, D1_inner > D2_outer + clearance. For opposite hand winding, clearance should exceed wire diameter to prevent tangling. Stress in each spring: tau = 8PD.K/(pi.d^3). Check buckling: free length/D < 4 for stable operation. Total rate k_total = k1 + k2. Often used in valve springs for surge prevention.