In this paper, a robot design suitable for swarm based security system is presented. First, a possible layout for swarm based security system is conceptualized and literatures related to mobile robot design are reviewed. Second, a set of conceptual designs for the swarm robot are evolved and discussed. Third, expressions are arrived for weight, rolling resistance, obstacle crossing ability and amount of slip based on robot geometric parameters. Fourth, the obstacle crossing ability for rear wheel driven and rear wheel driven robots are investigated. Fifth, a prototype is made and the analytical expressions arrived are verified experimentally. Sixth, the drive power required for the direct drive robot is determined. Finally, based on weight, number of actuators, type of drive, type of wheels used, rolling resistance, and obstacle crossing ability an appropriate robot design is selected.