Hydraulic fracturing is currently used to extract natural gas from shale formations in the U.S, but there are major concerns regarding the environmental impact. As an alternative method of well stimulation, a mechanical device driven by explosive loading was developed. The goal of the device is to control the orientation of crack growth, in an unfavorable in situ stress field. Small scale model testing was conducted in PMMA, simulating an unconventional reservoir. A hydraulic press was used to simulate the in situ stress and high speed cameras were used to capture images of detonation, device function, and crack development. Variations were made to device geometry and the resulting crack growth is visually compared. Optimal device dimensions for fracture initiation are determined, and the effect of borehole characteristics on crack formation is discussed. Scaling recommendations for testing the device at full scale are provided.