Aircraft warning spheres are installed on overhead power transmission lines to improve conductor visibility for low-flying aircraft and helicopters, thereby reducing the risk of aerial collisions. Conventional installation and replacement operations are generally carried out using helicopters, cranes, or scheduled transmission-line outages, resulting in high operational costs, increased safety risks, and interruptions to power delivery. To address these limitations, this study presents the design, development, and experimental validation of a mobile robotic platform capable of autonomously installing and removing aircraft warning spheres while travelling directly on overhead transmission-line conductors. The proposed robot combines a compact conductor-traversing mechanism with a dedicated quick-release clamping device and a suspended capsule-shaped battery module that improves stability under inclined operating conditions and wind-induced disturbances. Mechanical analyses were conducted to determine the required characteristics of the clamping system, and numerical simulations were performed to evaluate the robot's mobility, stability, and mechanical performance. The results demonstrated that the robot could reliably travel along the conductor, transport the warning sphere to the target location, complete the installation process, and safely return to its initial position. The experimental results agreed well with the numerical predictions, confirming the effectiveness of the proposed mechanical design and its practical applicability. The proposed robotic platform provides a safer, more efficient, and cost-effective alternative to conventional maintenance methods while reducing operator exposure to hazardous high-voltage working environments.