This paper discusses the design of a mechanical structure of a miniature pipe inspection robot capable of moving through very small pipes (down to 41 mm inner diameter). The requirement to negotiate bends, T-joints and steep inclinations pose another set of strict design constraints. The proposed robot consists of a modular design (7 modules) with a relatively low number of active degrees of freedom. The system is using a novel clamping mechanism with a series-elastic drive. The design of this mechanism has resulted in a high spreading factor allowing the system to operate in a wide diameter range (63 mm to 125 mm outer diameter). In this paper the mechanical design requirements and control system will be discussed. Preliminary test results will be given.