Design a Bicycle Helmet
4 Students are introduced to the biomechanical characteristics of helmets, and are challenged to incorporate them into designs for helmets used for various applications. By doing this, they come to understand the role of enginering associated with saftey products. The use of bicycle helmets helps to protect the brain and neck in the event of a crash. To do this effectively, helmets must have some sort of crushable material to absorb the collision forces and a strap system to make sure the protection stays in place. The exact design of a helmet depends on the needs and specifications of the user. Safety engineers design products with a specific user in mind. It is important that engineers fully understand the needs and specifications of the user to produce a functional product. If the product is interacts with the body, the engineers must have an understanding of biomechanics, which is the application of the principles of physics to the body. biomechanics engineering design materials safety After this activity, students should be able to: Analyze a product to determine the need it was designed to meet and the customer it was meant to attract. Produce, use, and evaluate a prototype of the design solution. Describe the personal impact of the designed product. Communicate the solution to a problem and justify decisions. oak tag or poster board (approx. 20 x 30 in) markers, colored pencils, etc. 2 or more example helmets EPS (expanded polystyrene) or Styrofoam (approx. 10 in2) PET (polyester terephthalate, such as cutting the plastic from a 2-liter soda bottle to lay flat) 5-pound weight scissors masking tape Engineers use scientific principles and other background information to design and create useful things that we use and depend upon every day. In designing and creating, the engineer goes through a problem solving process in which math and science are important components. (As necessary, review the steps of the engineering design process, an approach all engineers have in common as work to create great design solutions.) Each year, nearly 1,000 people die from injuries sustained in bicycle crashes, with head injuries accounting for more than 60% of these deaths. In addition, many more people survive non-fatal head injuries resulting from bicycle crashes. While some of these survivors may experience only minor headaches or dizziness, others may suffer profound and disabling neurological difficulties. One effective way to prevent head injury from these accidents is to use bicycle helmets. What do you think would be important characteristics for a helmet to have? (Listen to student ideas.) Helmets generally consist of two parts: an impact protection system to absorb the force and a strap system to keep the protective layer in place. Often three layers are used together to provide impact protection. The outer layer is generally a hard shell or a micro-shell made of fiberglass, Lexan or ABS plastic. This shell serves many purposes: it distributes the force of the collision over a large area; it allows the helmet to slide, thereby causing a slower deceleration; it provides a shield against penetration; and it holds the middle layer together. The middle layer is usually a crushable liner that absorbs the shock of collision. This layer is often made of expanded polystyrene, also known as EPS. The inner layer, which may be more segmented, helps to ensure proper fit and comfort. How do you think engineers might be involved in safety helmets? (Listen to student ideas.) Well engineers are involved in all aspects of helmet design and manufacturing. That includes, design, development, research, production and sales. A rigid, famed plastic that can be used for its insulating or protective properties. A hard, thin plastic with high strength and rigidity. Refers to the study of the human body from the mechanical engineering perspective. Able to compress rather than shatter or crack when a force is applied. Gather materials and make copies of the worksheets and score sheets. Prepare to show students the attached Bicycle Helmet Design Slides, either via overhead transparencies or a PowerPoint presentation. Part 1 Review slides 1-7: People who design and manufacture bicycle helmets must know how to make a helmet protective, functional and marketable at the same time. In groups, consider the following: all helmets contain the same basic parts to protect the head in an accident. However, helmets are not all alike. They may differ depending on who will use them and for what purpose. Determine the purpose of a bicycle helmet. Pass around the bicycle helmets so that the students can identify the parts. Have students note the sticker from the CPSC (Consumer Product Safety Commission) that shows that the helmet meets a safety standard, or the blue SNELL sticker indicating that the helmet has passed more stringent tests. Describe the parts of the helmet and discuss the purpose of each part. hard and slick shell crushable liner padding layer strap system vents To reinforce the purpose of the hard shell, conduct the following experiment: From shoulder height, drop the 5-pound weight onto a piece of EPS. Pass the EPS around the class and have students note the deformation. Tape the flat plastic piece onto the EPS. Drop the weight from shoulder height onto the combination of EPS and PET. Pass the combination around the class and have the students note the deformation. Think about the helmet characteristics that are designed for a certain application. By adding these characteristics to the basic helmet, the proper design can be determined for an application. Review slides 8-11. Pass out Worksheet A: Helmet Design Project (2 pages) and assign each group one of the design challenges. Have students brainstorm ideas and complete the worksheet. Part 2 Have students prepare a two-minute poster presentation on their designs. Require the posters to include the helmet designs and that students be prepared to discuss the choices they made. Finish with a discussion about how students approached the problem like engineers. At each stage of the project, what engineering role were they performing? Bicycle Helmet Design Slides (pdf) Score Sheet (doc) Score Sheet (pdf) Worksheet A: Helmet Design Project (doc) Worksheet A: Helmet Design Project (pdf) Make sure the presenters are careful when dropping weights onto the test materials. How would you test bicycle helmets to make sure that they are safe? After an accident would you need a new helmet? How can a consumer tell if a helmet is safe? Evaluation: Use the attached score sheet to evaluate each group, judging on criteria such as problem statement, group needs, design changes, marketing techniques, illustration and overall presentation. Have students research other types of foam that have been used in helmets, such as expanded polyurethane and expanded polypropylene. Have students research helmets that are designed for specific applications. Decide if the classroom designs are similar to the commercial product. Check websites on bicycle safety to see if specially made helmets exist for these applications. Some people feel that wearing helmets makes riders more reckless and more prone to injury. Have students poll other students to see if this is the case. Collect enough data to be able to see if gender plays a part in the findings. For upper grades, have students design their own experiments to test bicycle helmets for impact resistance and strap strength. Obtain used or low-priced helmets for this activity. Bicycle Helmet Safety Institute Snell/Harborview Studies Bell Helmets