1 School of Computing, Engineering and Mathematics 301018 Mechanical System Design Mechanical System Design Project Redesign of Da Vinci Automovile A/Prof Richard Yang Mechanical, Robotic and Mechatronic Engineering School of Computing, Engineering and Mathematics Western Sydney University February 20172 Background Leonardo da Vinci was yesterday credited with anticipating the car when a model of one of his drawings was hailed as the first self-propelling vehicle conceived. The wooden 5 ft by 5 ft by 6 in model, featured in an exhibition at Florence's Science History Museum, is driven by springs. It is also the first projected vehicle with programmable steering. Designed to operate as a robot, the car, which can travel a few yards at a time, has an unusual optional extra: a steering column. The coiled springs concealed in drums beneath the car are most likely source of power. While the drawings of the car (see Figure 1), made in 1478, have long been known to scholars, understanding how it worked has been an enduring mystery. An example of the deep historical context implied by “Dream”, Da Vinci’s “car” is one of many models on the show floor that fascinates the mind and goes beyond the general notion that creative transportation philosophy began with Henry Ford. Figure 1 Leonardo Da Vinci’s original drawings for a car (Source: http://www.3wheelers.com) A working model of Leonardo da Vinci’s 1478 3-wheeler was completed in 2004 and took technicians 7 years to make as shown in Figure 2. This extraordinary invention of 1478 could have paved the way for Mars rovers (see Figure 3).3 Figure 2 A working model of Leonardo da Vinci’s 1478 3-wheeler. (Source: http://www.scottgrundfor.com/) Figure 3 From Sojourner to Curiosity: A Mars Rover Family Portrait. (Source: http://www.theatlantic.com /)4 Learning goals To greatly narrow down the gap between theory and practice of engineering via synergistically applying fundamentals of machine element design and mechanical system design based on the theory of systems engineering constructed in 301018 Mechanical System Design to design a typical mechanical system – a modern version of Leonardo da Vinci’s 1478 car to perform a design practice and finish design loops. Design Problem A working model of Leonardo da Vinci’s 1478 3-wheeler has been shown in Figure 2. Each team needs to design its own version of this car which can have three wheels or four wheels. Design Requirements For this design project, we assume a toy manufacturer planned to develop a new product of a toy car based Leonardo da Vinci’s 1478. Functions The functions of this product are listed as follows: 1. To receive power from two coiled springs through a series of power transmission drives, including gears, belts, and/or chain drive, etc. 2. To transmit the power through these machine elements to gradually release the energy stored in the springs to make the car run at a certain distance in a smooth surface. Working conditions  The toy car is running 2 hr/day, 7 days per week, with a design life of 3 years. This is approximately 10,000 hours of operation and its operation is generally smooth.  The highest speed of the toy car can be 10 m/s, which is permitted to vary  5%.  The car can reach a maximum distance of 30 m in a smooth concrete surface.  To reload the toy car can be easily done by a kid at 4-8 years.  A mechanical efficiency of greater than 95% is desirable.  The speed ratio at each drive should be in a reasonable range. Selection Criteria 1. Safety: The toy car should operate safely and provide a safe environment for people near it, especially for kids. 2. Cost: Low cost is desirable so that the car appeals to a large set of customers. 3. Small size. 4. High reliability. 5. Low maintenance. 6. Smooth operation; low noise; low vibration. Methodology You will be allocated to teams of 2-3 to achieve the design goal with creative ideas together and for equity, a peer-review report to evaluate each team member’s contribution is employed5 with the group slides and design report for submission at the end of the semester as required in the learning guide. In your team you should have a unified and clear target to design the toy car as required. Your design will involve in the following commonly-used machine elements:  Gear drives  Belt and Chain Drives  Keys, Couplings and Seals  Housing  Shafts  Bearings  Fasteners and Springs The design will be focused on both machine part design of gear drives, belts, chain drives, springs and couplings and the adoption of design philosophy and system development process of Systems Engineering including requirement analysis, stakeholder analysis, risk management, etc., according to the unit contents of 301018 Mechanical System Design (Mott, 2006; and Kossiakoff, 2011). Format for submission of Design Project The mini design project report should be submitted electronically by uploading the necessary files into the appropriate assignment area in the vUWS site. The following important notes are highlighted: 1. All reports will be assessed by “Turnitin” in the vUWS site. “Turnitin” ensures the originality of your reports by comparing against a repository of previously submitted reports, current and archived internet contents, periodicals, journals and publications. 2. Submit all files for marking. In Solidworks, all part files used in the creation of an assembly must be submitted or else, the assembly cannot be opened. It is a good practice to keep all files for an assignment in a separate directory so that you do not miss any important files during the submission process. 3. Drawings can be submitted in e-Drawings format with all drawings in ONE file. Use the following checklist before you submit any drawings:  All drawings must use 3rd angle projection. 1st angle will not be accepted  All line types, arrow styles, dimensioning, sectioning, auxiliary views etc. must conform to the Australian Standards.  Use the UWS title block and sheet format for all drawings. 4. Make sure you retain a copy of all of your assignment files and create a back-up somewhere. If an assignment gets lost in the system this will help you to demonstrate that the assignment was completed by the due date and allow you to easily re-submit the files for marking. 5. Due date: 17:00pm, Friday 26th May 2017, Week 14 (Online Submission only).6 Marking Criteria for Design Project Designers, according to Nigel Cross, Professor of Design at the Open University, produce novel, unexpected solutions, tolerate uncertainty, work with incomplete information, apply imagination and constructive forethought to practical problems, use drawings and other modelling mediums as a means of problem solving. The highest grades will be given to submissions that:  make clear statements about the design problem in terms of needs and goals;  show a high standard of analysis of the design problem;  show clear evidence of literature research, and evaluation of products already on the market by paying considerable attention to their benefits and shortcomings;  clearly document the design's development and show consideration of alternative approaches, methods or material considerations; and  provide a high-standard evaluation that demonstrates an understanding of the strengths and weaknesses in the final design through detailed analysis. The qualities described above are critical features central to good design practice. Consider the methodologies you devise in order to communicate the extent of your personal achievements of the above criteria as your first design challenge. A particular problem with design assignments is in how far to go with the final design. Students might be either afraid to do anything to an old design, or produce something that is impossible to manufacture or redefines the product so much that it cannot be considered to perform anywhere near the level of the original. Therefore, you must be careful not to fall for any of these problems. Essential Elements of the Project  Each Project has to have a clear, broad objective (task) to achieve: e.g. lift a man in a wheel chair on to a theatre stage; place caps on bottles on a conveyer belt; lift a heavy object and transfer it from one end of a warehouse to another; etc. Common to all these is a general intent or purpose the needs of which have to be met (engineered).  Given the task needing to be accomplished, it is necessary to provide specifications involving performance characteristics: 90kg man, 2m lift, 30 seconds, a 10 tone object, 60m long warehouse, 15 minutes, 3 cm diameter, etc  There is usually a number of ways to accomplish a given task. These should be identified and described.  One design should be chosen as the optimum – and this selection justified. This is an important part of the Design Process and great care should be paid as to the reasons for choosing a particular design – against all others that had been identified as possible solutions to the set problem.  A sketch of the chosen device/machine should then be made.  Main components should then be designed involving choice of material and application of analytical procedures, justification of sizes, types of member cross sections, types of loading, drives, gears, controls etc. This is the most important part of the project as it shows application of design principles to sizing of machine components, selection of drives and machine components which when all put together perform the desired task – a7 trademark of an engineer. You do have to be good at it – it is not a chore, it is what Engineering Professionals are made of.  Having sized all the machine components and selected any commercial items, the next task is to draw up an Assembly Drawing. It shows – usually in cross section – the whole machine with each part labelled (numbered). A parts list is given in the drawing (according to the Standard) – stating the part ID, material and the number needed (“number off” – or “no. off”). This is necessary for costing purposes, material purchase, manufacturing (machining) – and assembly. The drawing should be done in any CAD you are familiar with. CAD proficiency is also expected of you in Industry – especially in your early years of employment. You should be practicing with the School’s Solid Works in any “free” time you may have – using given on-line tutorial guides. Individual machine parts should have an indicator of the surface finish required and each dimension should have a tolerance associated with it.  If there is any time left, produce a complete set of machine drawings “workshop ready”. All of the above items should be presented in its detailed form in the report, and in “highlights only” format in Power Point Slides presentation. Design report A design report would most likely contain the following items (separated by headings and subheadings): 1. Title page 2. Table of Contents page 3. Executive Summary 4. Introduction 5. Main body - The contents of this section (divided into suitably headed subsections) is subject to change, and it depends upon what is being examined. Typical contents would be analysis of initial object, redesign of object, assumptions made and analysis of redesign (discussion of why concept may or may not fail). No design is foolproof. In most cases, design is the art of compromise/trade-off. Typically, by making a change to an object, you will improve one characteristic of that object, but decrease another. These trade-offs should be recognised and discussed.  Aim and objectives  Performance criteria and design constraints  Conceptual design  Design analysis and decision making (Force, motion and stress analyses and CAD modelling, etc.)  Detailed design 6. Summary 7. Acknowledgments 8. References 9. Appendices – Peripheral information, including catalogues, technical drawings and calculations may be placed here or in the main body of the report depending upon its relevance (e.g. repetitive calculations should be left in the appendices, but you may wish to include a sample calculation within the body) ‘standard’ calculations would also be8 better in this section, rough sketches of rejected designs (including descriptions as to why they were rejected). Outcomes of mini design project In either case, each student or a design team has to produce a  Power Point Presentation of the highlights of the Design Project – particularly the aim and steps towards realising it, as well as how much in effect was accomplished in the time available for the exercise. The actual presentation should be made by each student involved in the project – and take no longer than 5 minutes.  You are also required to produce a written design report: one per team. References 1. Mott LR, 2006, Machine Elements in Mechanical Design (4th Edition) Pearson/Prentice Hall. 2. Kossiakoff A, Sweet, WN, Seymour S, Biemer SM, 2011, Systems Engineering: Principles and Practice, Wiley.