Xiangzhi‘s Portfolio
Objective
Design a lightweight skateboard deck for users weighting up to 180 lbs and shoe sizes up to US 12. The deformation of the platform under the static load exerted by the weight of the user should produce a vertical displacement of no more than 0.375 in across the span of the board. Assume that the board is supported by pin joints above the front and back truck axles.
Mission
In my design, I choose to make a slalom skateboard. The tip of slalom skateboard is normally sharp with a lifted tail. This may produce a good turning ability. In order to reduce the stress at the lifting edge, the transition between the lifted edge and the board is designed as a curvature shape in order to reduce the stress that accumulates at the edge. The blue curve is drawn with the center at the blue point and the radius is equal to the thickness of the board. The upper curve is parallel to the lower curve. In my design, I choose to make a slalom skateboard. The tip of slalom skateboard is normally sharp with a lifted tail. This may produce a good turning ability. In order to reduce the stress at the lifting edge, the transition between the lifted edge and the board is designed as a curvature shape in order to reduce the stress that accumulates at the edge. The blue curve is drawn with the center at the blue point and the radius is equal to the thickness of the board. The upper curve is parallel to the lower curve.
To choose the proper material, I search up in the Granta app. I limited my ideal material in carbon fiber is relatively much stronger than other materials such as bamboo. My goal is to reduce the weight but choose the one with a good yield stress. Therefore from the graph, an ideal material should be at the top left corner of the graph since this is the position with minimum density and maximum young's modulus.
To model the most extreme case, I designed two rectangles representing the feet of size US 12, acknowledging the variation in foot dimensions among individuals despite having the same shoe size. The dimensions of these rectangles—width and length—are based on the average measurements for a US size 12. To replicate the scenario exerting the maximum shear force on the board, I positioned the rectangles adjacent to each other, mimicking a person standing at the board's midpoint.
The rear box is positioned 5 cm from the board's edge, while the front box is located at the midpoint of the line connecting the two side joints. These boxes denote the locations for the trucks.
I conducted a design study aimed at identifying the lightest possible mass. In this simulation, the choice of material served as the variable, while stress, strain, and displacement were the parameters kept under control. The objective was to minimize mass. The stresses observed were significantly lower than one-third of the yield stresses for each material. Additionally, all measured displacements were below 0.375 inches, indicating that all considered materials meet the required standards. Based on the mass data, both high-modulus carbon fibers and high-strength carbon fibers emerged as promising options due to their relatively lower weights compared to the other materials evaluated.