Texas was the last US coastal state to implement Cultivated Oyster Mariculture (COM). Several implementation issues hamper COM in the very shallow Lower Laguna Madre (LLM) of South Texas where much of the state’s seagrass beds are located. Along South Padre Island’s west coast exists an extensive area of shallow sandy bottom waters that is mostly devoid of seagrass and bordered by extensive tidal flats approximately 1 km wide closer to the island. Shallow water oyster grow-out trials are being conducted in th is area at UTRGV’s Experimental Field Station to minimize seagrass impact . The aim of this engineering project was to develop a device that would assist in equipment transport to the LLM field site across the periodically submerged tidal flats. The terrain is challenging where vehicles may get stuck or damage the sensitive tidal flat ecosystem . S tandard beach wagons are not suitable as their tires sink into the sediment . Currently equipment is carried on foot, which is physically demanding and inefficient. The proposed amphibious wagon device must be practical and efficient for the research team. It must also utilize accessible materials and be affordable for other potential users such as economically disadvantaged oyster farmers and local fishermen.
The team investigated similar products on the market , and established design specifications. A morphological chart was used to compare many solutions for integral device components and were mixed and matched to find the most optimized solution. M aterial selection wa s important due to the corrosive salt-water sandy environment , having to be lightweight but strong enough to withstand the load capacity of the research equipment and possibly an average person’s weight for an eme rgency to be carried out of the field. A finite element analysis (FEA) was conducted to analyze the frame’s high stress and deformation points. Stress calculations were done by hand to verify the simulations. Archimedes’ Principle was used to calculate the buoyancy force needed to float the combined weight of the load and device.
Figure 1 shows a CAD model created on SolidWorks. The device is composed of several major components: Frame (F), floats (L), wheels (W), handle-steering mechanism (H), and base plate (B). The frame holds all the components together and takes the bulk stress of the load.