The topic of this paper is the design and implementation of an interacting Lego digger and dumper truck through the use of Petri nets. The focus of this is primarily on the use of Petri nets in the developing of dependable systems, an area of particular concern in the full-size equivalent of our experiment. The content of this paper will discuss the progression of the Petri net model of these two Lego robots, from design to implementation, and finally evaluation. The paper also features an extension to the Petri net, intended to allow the dumper to authenticate the digger for added security.