SKATEBOARD ANALYSIS
Goal of the Project:
We have been assigned the task of creating a skateboard design to model the characteristics of a long board. Through intense research and analysis of dimensions, shape, material selection, stress/strain deformations per material, and optimizations, the goal is to give enough information for manufacturer replication.
Constraints:
When trying to break down what a skateboard is supposed to do, and how a skateboard is supposed to do it, there are many limitations that come to mind. Of course, we need the skateboard to be able to move. We also need to make sure that a user can control their board with ease. After all, safety is a key part when trying to make something. We cannot pitch or sell a product that is not designed with the upmost consideration of user protection.
An important constraint worth noting is the weight of the skateboard. When a business creates a product, a goal that is aimed for is convenience. A product should not bring any problems to a user. With that said, we need the skateboard to be lightweight so that a user can carry when not riding. Nonetheless, the material must also be durable and stiff enough for long term use, even if it a lightweight material. It must be able to carry the weight of a user (for the sake of precision and accuracy, the user weight between 150 lbs – 180 lbs).
Summary of information that is relevant to your project
When considering the design and material selection of a skateboard, there are many questions that come to mind. Firstly, what is the most efficient way of manufacturing a skateboard? Although there are many ways of making a skateboard that can take someone from point A to point B, some can be less cost-effective than others. Even though we could use steel on the deck to make sure it is durable, it becomes more unideal to use when considering the replication of a skateboard by the thousands. The cost per unit grows at an exponential rate if we were to use steel. This is why we must think of many alternatives that can complete the task at hand. Additionally, we must also keep in mind how a skateboard should act in all environments, not just one. Will our skateboard still be intact if it comes across a crack or rocks along the road, or is it only designed to work on smooth surfaces? These are some considerations worth noting when selecting how we want to go about this manufacturing process.
Design decisions:
The design of a skateboard is basically the same across all types of age groups. Generally, the skateboard deck has a popsicle shape. Is symmetrical across both sides so that a user can switch sides on the board. Generally, each side curves upwards on the board. This is so that a user can apply more pressure without losing mobility of the board. The dimensions are about the only thing that change in a skateboard design. With age, a user grows in size. With that said, there are different sizes so that both kids and adults can have a suitable board. For this report, a full size skateboard will be used with 32.25 inch length by 8.75 inch width by .5 inches thick. Above the deck, a grip tape made of sandpaper will be applied so that a user can remain stable on the deck while he is in motion. The friction of the sandpaper is how a user will remain stable.
Material Selection:
There are three main parts of a skateboard. Firstly, we have the deck, which will be the main platform for the user. There are several different types of wood that are used for decks. Some of the more popular ones include bamboo, maple wood, and plywood. It is not rare for skateboards to be hybrid, meaning that several types of wood and metal alloys are laminated together using glue. Although this is commonly used in order to get the best qualities from all of the materials, this does have a higher environmental cost on the world as opposed to using one type of wood.
Attached are important properties that relate to these woods
With this research, it is seen that there are not huge discrepancies across the types of wood, so ideally, any of these options can work for a skateboard deck design. However, Bamboo is more environmentally friendly than the other types of wood, and it does edge them out in the GPa and MPa estimates above, so for our skateboard design, bamboo will be the most reasonable type of material.
As for the wheels, rubber, specifically polyurethane rubber, is the most ideal decision for material selection. The wheels must be durable enough to last a couple thousand uses, and since polyurethane has a high tear resistance (175.1 kN/m) and high flexibility, it can meet the standards that we want.
Lastly, the trucks and bearings can be made by different types of metal (steel, brass, etc.). Ultimately, we should steer clear of plastic, as plastic can easily deform under so much weight and tension. Stainless steel will be the most viable option for the trucks and bearings
For clarification purposes, the skateboard model shown below represents a skateboard made of Balsa, since there is no option for Bamboo as a material. Many relevant properties of Balsa are displayed in the table as well.
​​Material Index:
We are using a single joint on one end and a roller joint on the other. Keeping this in mind, these equations are derived and calculated as follows.
Going from this, we find these numbers from our FEA in SolidWorks
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Finite Element Analysis and Results
Stress -
Displacement -
Strain -
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Conclusion -
After running motion study and FEA, we find that these numbers do in fact, have a sort of similarity. It is seen that most of the stress is along the center of the board, and reasonable so. There is support along the ends that resists the weight of the user along with the acceleration due to gravity. Along with that, the thickness of a board is critical in resisting these forces. If the board were to be thinner, the stresses would be far greater. However, when we consider the thickness, we must also consider how it has an effect on its weight. A fair balance must be made for the skateboard to be effective.
References -
Board Materials | Science Behind the Sport | West Virginia University (wvu.edu)
The physical and mechanical properties of treated and untreated Gigantochloa Scortechinii bamboo (scitation.org)
How skateboard is made - material, manufacture, making, history, used, parts, components, dimensions, steps (madehow.com)