College of Engineering and Science CAD Challenge - Brake Pedal Design PREAMBLE • This activity is designed to be undertaken in groups (max. 3 students). • Each group, with equal contribution from each member, is to submit a design summary before 4.00 pm on the specified due date. Marks will be distributed equally between the students. • The summary must be presented in a professional engineering format. • Your final documentation must contain professional computer aided drawings of your final design as well as a clear list of specifications and design loads • See the attached marking scheme for a holistic marking rubric. Problem Statement: Your team has been put in charge of preforming the preliminary design and topology optimisation for a new brake pedal for the Victoria University Motorsport (VUM) F-SAE open-wheeled race car. A pedal box arrangement has been designed; however, an optimised pedal is required. The existing pedal box design makes use of front mounted push type master cylinders and this configuration must be maintained. Your task is to design and carry-out the topology optimisation of the brake pedal and to develop a 3D model ready for further analysis using sophisticated Finite-Element-Analysis software. The 3D model you develop must fit the existing pedal box design without alteration. All parts on the race car will be subject to a design judging competition; therefore all design decisions must be defendable. Key design considerations include ease of manufacture, cost and mass. Existing Parts list 1 x AP Racing CP5623 master cylinder 1” (for rear brakes) 1 x AP Racing CP5623 master cylinder 5/8” (for front brakes) 1 x Bias bar 1 x Brake pedal box 1 x Brake pedal shaft College of Engineering and Science Bias bar details The bias bar allows the percentage of total force applied to the front and rear brake master cylinders to be adjusted by altering the position of the centre pivot point (see Figure 1). The centre pivot has a width of 3/8” and an outside diameter of 1”. The pedal design must allow for at least 10 mm bias adjustment in both directions. Figure 1: Bias bar arrangement (http://www.racereadyproducts.com/) Figure 2 shows an example use of a bias bar in a pedal box design using rear mount push type master cylinders. Figure 2: Use of a bias bar for rear mount push type master cylinders (http://seniordesign.engr.uidaho.edu/fsae/car08.html) Rear mount push type master cylinders Centre Pivot Bias bar College of Engineering and Science Pedal box design A pedal box has been designed for the VUM F-SAE car. Your pedal must fit the existing design. See Figure 3 for details. There is 35 mm between the centre of the pivot and the pedal box; however, the pedal will have 15-20 mm of travel at the driver’s foot when braking so remember to allow for this. Pedal shaft design A brake pedal shaft has been designed for the VUM F-SAE car. Your pedal must fit the existing design. See Figure 4 for details. Performance requirements The brake pedal must be designed to allow for a maximum brake fluid pressure of 27.28 MPa in the front brake lines and 9.08 MPa in the rear lines at a safety factor of 1. The pedal ratio (combined master cylinder force to foot force) is required to be 5:1 (at 50:50 bias). The pedal design must allow for an adjustable pad position. Note: The set bias will not be 50:50 to achieve the above pressures (what will it be?) College of Engineering and Science Figure 3: Existing Pedal box 40 70 35 Pedal shaft location College of Engineering and Science Figure 4: Existing Pedal Shaft College of Engineering and Science SUMMISSION REQUIREMTNS You are required to submit your work in a professional format which requires you to take the following steps (minimum): 1. Develop a brief overall summary of your design including selected material, method of manufacture and final mass 2. Create solid models (include an isometric view in your final submission) and orthogonal drawings of your pedal design based on your topology optimisation 3. Create a specifications table including (but not limited to) all design loads (e.g. foot force), overall length, pedal ratio, pedal mass 4. Compile steps 1-3 as a preliminary design submission 5. Document and justify the methodology (positioning of design loads, constraint type, symmetry, shape controls etc.) followed during the topology optimisation 6. Capture key images related to the topology optimisation and solid modelling processes and describe using brief discussions 7. Compile steps 5-6 in one document as supporting information for the design summary Notes: 1) The submission must be concise but include all relevant information (i.e. do not pad. Tell me only what is needed) 2) All figures and tables must be described and referred to in text College of Engineering and Science Holistic Marking Rubric Level Description HD Devises well thought-out analysis approach which is easily understood. Considers design alternatives. The selection of materials and methods of manufacture are made using well considered analysis methods. Drawings and report are of professional quality. D Creates a report which is carefully considered, demonstrates an understanding of the analysis and results. Drawings, including associated dimensioning, are well planned and meet the requirements according to the drawing standards. C Is able to write as an engineer. Report is presented in a logical, easy to follow sequence. Makes correct use of engineering software. Presents drawings which take into consideration the drawing standards listed. P Shows some ability to write as an engineer and to apply the suitable engineering tools. Has made a genuine attempt to meet each step listed in the submission requirements. Able to correctly determine design loads with only minor errors and shows an understanding of how to apply them in the software. Presents neat orthogonal and isometric drawings. N Develops a basic report. Is able to determine correct loads and generate basic results but does not show an understanding of the correct use of the software. Poor drawings. N1 Poor understanding of the concepts and techniques used. Tendency to recite provided information or to list information without analysis or supporting logic.