About the design of float-ram, a manually operated press to produce compressed earth blocks for building construction

The right to adequate and sustainable housing remains an unresolved challenge worldwide. Self-construction techniques based on stabilized rammed earth represent an economically accessible, ecological, and efficient alternative to traditional wood-fired burnt bricks. This paper presents the mechanical design, experimental characterization, and socio-economic impact assessment of the Float-Ram manual press conceived for manufacturing the "Blocco Mattone", an interlocking stabilized compressed earth block. To overcome the constructive complexity, high cost, and ergonomic shortcomings of existing commercial bidirectional presses, Float-Ram features an innovative architecture based on a central cylindrical joint, a floating mold to achieve bidirectional compression and two cam-follower transmissions for the compression phase and the ejection of the block. The compression cam profile is designed to convert a constant input force into high compression forces with compression profiles that match experimental data on the compression of the soil mixture. Experimental laboratory testing conducted on a fully sensorized prototype validates the theoretical performance. Field deployment in Tanzania, including the construction of housing in Njombe, the Mkiu kindergarten, and the nursing school and hospital in Ikelu, demonstrates the technology’s significant social impact.