Science educators advocate hands on experiences and the use of manipulatives as important for children's conceptual development. Consequently, the utilisation of "Lego" robotic technologies in teaching and learning has become more prevalent in school science classrooms. It is important to investigate their value as educational tools, particularly their role in helping children develop conceptual understanding of scientific principles. The purpose of this study was to explore the effectiveness of robotic technology with elementary age children, specifically focusing on the children's conceptual development concerning gear function and mechanical advantage. Our results indicate the robot sessions helped develop the students' understanding of gear function in relation to direction of turning, relative speed, and number of revolutions. However, when we examine the children's understanding around the concept of mechanical advantage, we still see the majority of children unable to provide an accurate explanation. The children had difficulty explaining the reasons underpinning their gear arrangement choices for making their robots fast or powerful. The results suggest that providing students with physical experiences is not enough for students to "discover" the relationship of gears to a vehicle's power and speed. A guided inquiry instructional approach is important during the early stages of developing a conceptual understanding of mechanical advantage. (Contains 6 figures.)