Develop skills, knowledge and abilities in systematic design processes to create practical solutions to mechanical problems Develop skills and understanding of Manufacturing Processes and their suitability to specific applications Research, model, document, employ and select the best professional practices, processes, techniques, and tools for Engineering Design to fulfil an users requirements Investigate and select engineering materials based on performance cost and sustainability 5. Design, specify and communicate design concepts for creating mechanical systems using fundamental machine elements and components 6. Use Machine elements in the correct context to design mechanical systems The aim of this assignment is to develop your design skills by the full, detailed design of a relatively simple mechanism – to include the manufacturing details of individual components. This is a group assignment; you will be working in groups of 2.You can split the work how you wish but you need to identify who is responsible for each section. There is a choice of problems – see following sheets for the details. Develop and submit the following: 1. Research into existing designs and any relevant national and international standards, Develop a Product Design Specification, Include the design brief in your write up. (10%) 2. A layout diagram showing the chosen solution, to scale, in various positions, to demonstrate and/or analyse the movement (a drawing using lines and points rather than actual parts – this can be done by CAD, but equally well on a (large) piece of paper); (10%) 3. Calculations – Identification of force requirements, hydraulic system design and size of key functional components to withstand applied loads. (25%) 4. An assembly drawing of the detailed components of the mechanism, showing the extreme positions of movement and showing all the parts designed. Two or more views will be necessary, using a cross-section and enlarged scrap views if appropriate). Add a numbered parts list of all components ("balloon" referenced on the drawing), giving materials chosen and suitable manufacturing processes.(25%) 5. Costed process plans for key components given for each project. This should include determining key manufacturing processes, appropriate process plans and the hourly or unit rate / cost for manufacturing processes used. (25%) 6. A brief report on the design, identify the inputs of each group member. (see details for each problem) (5%) Do not submit copies of standards or other background work; refer to them in the calculations or include them in an appendix. Drawings should be on A3 sheets, folded to A4 with the title block showing. Please put your name on each item of work you complete. This assignment forms 50% of the coursework for the module. Mechanisms assignment – Option A: Car Front Suspension Design You are involved in the development of a lightweight two seat kit car. The car has a custom-built space frame chassis but uses commercial engine and transmission parts. For the front suspension, a double wishbone design with a 'coil over' configuration of the spring and shock absorber/damper has been specified. A commercial upright, hub and wheel have been sourced. Your job is to design the wishbones, upper pick up point of the spring/damper, the custom spring and also select a suitable adjustable shock absorber. The drawing below shows some initial dimensions of the proposed design. 1. Four pivot locations are shown: two on the chassis (A, B) and two on the upright/hub (C, D). Because you are using a commercial upright, the relative position and orientation of points C and D in the design cannot be changed. If necessary, you can make reasonable changes to the position of the suspension pick-up points on the chassis, A and B. 2. For good handling, the camber angle[*] will ideally remain negative as the car rolls or goes over bumps. The front roll centre[†] of the car should be as close to the centre of gravity of the car as possible. Your report should discuss the camber and roll behaviour of the suspension and highlight features of your design that will give good performance. 3. The position of the upper spring/damper mount has not been determined, but should be as close to point B if possible. The lower point of attachment of the spring/damper is onto the lower wishbone at a suitable point between A and D. A custom coil spring design must be specified. A shock absorber that will fit inside the spring and operate over the required range of movement must be found. 4. The car's total weight is 600kg excluding driver and passenger. In the maximum rebound position there is very little force in the spring. Detail designs, for the wishbones including inboard pivoting attachments to the chassis and attachment of the lower end of the spring/damper, must be carried out. The upper mount for the spring damper will bolt to the chassis, and this also must be designed. Two alternative manufacturing processes must be considered for the wishbones and spring mount; one for a manufacturing volume of 10 units per year, and one for a volume of 5,000 units per year. Figure 1 - Typical Suspension Layout 650 (nts) Mechanisms assignment – Option B: Hydraulic Jack Design You are involved in the design of a vehicle trolley jack for home use. The lifting capacity of the jack has been specified as 1.5 tonne and the desired lift 265mm. An initial concept design has been developed and is shown below. No analysis of competitor designs has been carried out, so these design criteria can be modified if this can be justified. Your job is to design a jack that has comparable performance to commercially available jacks. This will include design of the main linkages, hydraulics, a suitable base and the lifting pad. The drawing below shows some initial dimensions of the proposed design. The four pivots have been defined, two on the jack frame (A, B) and two on the lifting pad (C, D). The lifting pad must remain parallel to the floor. A suitable hydraulic actuation system should be designed so that the jack can be used by most adults; male and female. Safety is very important and relevant design standards related to lifting equipment must be referred to. Detail designs, for the main linkages, hydraulic actuation system, a suitable base and the lifting pad must be carried out. Standard bought-in components must be specified. Two alternative manufacturing processes must be considered for the upper link and lifting pad; one for a manufacturing volume of 500 units per year, and one for a volume of 50,000 units per year. Figure 2 - Typical Pivot locations 650 (nts) Mechanisms assignment – Option C: Aircraft Undercarriage Design You are required to design a simple retractable undercarriage mechanism for a twin engine light aircraft. The drawing below shows one possible design of a similar undercarriage. The design must lock the wheels in "landing " position using the principle of 'over-centre' locking. The design must clearly have a suitable range of movement to fully retract the wheels into the wheel well. 1. You will need to research existing product designs and any applicable standards and design codes necessary to inform your work. (Search look for JAR-23 / CS-23) 2. The design must cope with typical loads which the mechanism will be exposed to in order to select suitable materials and dimensions for components. Detail designs, for the main linkages, hydraulic actuation system and upper mounting point of the undercarriage must be carried out. Standard bought-in components must be specified. Two alternative manufacturing processes must be considered for the 'triangular link' (or equivalent in your design) and upper mounting point of the main undercarriage upright; one for a manufacturing volume of 4 units per year, and one for a volume of 400 units per year. [*] Camber is the angle between the ground and a vertical fore-and-aft plane through the wheel - if the top of the wheel leans out, this is positive camber. When the car rolls, poor suspension geometry can generate positive camber on the outer wheel which gives bad handling and loss of tyre grip. So the upper wishbone is usually shorter. [†] The car roll centre height is also determined by the angle of the wishbones to the horizontal and should not be too low. The car C of G is 450mm above the ground. See Car Suspension and Handling by Donald Bastow (1993) or Race car vehicle dynamics by Milliken and Milliken(1994) and similar sources. Car manufacturers may also be useful for information and examples.