This article presents an optimization approach for the design of an inspection robot that can move inside variable diameter pipelines having bends and junctions. The inspection robot uses a mechanical design that mimics the locomotion of a caterpillar. The existing prototype developed at LS2N, France is a rigid model that makes it feasible for working only inside straight pipelines. By the addition of a tensegrity mechanism between motor units, the robot is made reconfigurable. However, the motor units used in the prototype are oversized to pass through pipe bends or junctions. An optimization approach is employed to determine the dimensions of motors and their associated leg mechanisms that can overcome such bends. Two optimization problems are defined and solved in this article. The first problem deals with the determination of motor sizing without leg mechanisms. The second problem deals with the determination of sizing of the leg mechanism with respect to the dimensions of motor units obtained from the first problem. A 3D model of the optimized robot design is then realized using CAD software.