Bicycle brake caliper computer aided design and manufacture materials - 2200 Words

Bicycle brake caliper computer aided design and manufacture materials (Coursework Sample) Content: BICYCLE BRAKE CALIPER COMPUTER AIDED DESIGN AND MANUFACTURE MATERIALS by (Name) The Name of the Class (Course) Professor (Tutor) The Name of the School/University/Institution The City and State where it is located The Date Introduction While it may look simple in motion, designing an entire bicycle is no joke and requires a lot of engineering design concepts. The concepts have to be applied properly to ensure that the bicycle is built properly and that is performance is not only efficient but also safe. The design process is a long one and entails three key stages. These include concept generation, embodiment and detail. The inputs to concept generation include identification of market need requirements and various constraints governing design. During design, key design tools that one needs include function modelling, feasibility studies, approximate analysis, geometric modelling, cost modelling, simulations method, finite element modelling and analysis and component modelling among others. The outcome of the design process is a product specification. In light of modern day requirements for mechanical components, in terms of aerodynamic performance and other considerations, it is required that a bicycle caliper be redesigned. In the following discussion, the outcome of the design process and the product specification achieved is presented. Problem Definition A bicycle manufacturing firm has identified a market opportunity, requiring the provision of high quality, low weight bicycle. The conditions of the identified opportunity are such that the current bicycle calipers cannot meet both the conditions of high quality and low weight due to its material compositions and dimensional related constraints. Furthermore, in line with current trends worldwide, the bicycle designed is required to meet sustainability aspect. This means that a total overhaul of the material making up the bicycle caliper is required, as well as a redesign to ensure a compact design which is both efficient in motion and safe, with the latter condition being critical due to the fact that the target market comprises of children aged 6 to 8 years. Objectives The objectives to be met are as outlined in Table 1: Objective Benchmark Unit of Measurement Rigid Deflection under load Millimeters Lightweight Weight Grams Low cost Cost US Dollars Aerodynamic Drag Newtons Table SEQ Table \* ARABIC 1: Objectives for new bicycle part Constraints The requirements for the new braking system are that: the systems developed must be independent and the ability for the systems to be engaged simultaneously. The new calipers developed should be designed for recessed mounting in order to save on weight. The reach dimensions should be limited to between 40 and 50mm (Brandt, 2005). Concepts Generation and Selection Appraisal of the Current Brake Caliper The current caliper is made of aluminium alloy AA6061 T6. The material has a density of 2.7 g/cc. Its hardness (Brinell) is 95g/cc, ultimate tensile strength of 310Mpa, tensile yield strength of 276Mpa, elongation at break of 12%, modulus of elasticity of 68.9Gpa, notched tensile strength of 324Mpa, Ultimate bearing strength of 607 Mpa, Poisson's ratio of 0.33 and fracture toughness of 29Mpa-m1/2. The material's machinability is 50%, its shear strength is 207Mpa and its shear modulus 26GPa (Kutz, 2002). The caliper has a reach of between 57 and 67 mm (reach refers to the effective length of the arms of a caliper brake and is measured from the centerline of the center bolt, diagonally to the middle of the brake shoe). The brake shoes are adjustable, typically between ten and fifteen millimeters, hence the expression of reach in terms of a range (Morris, 2013). From the preceding discussion, it is clear that the current caliper does not meet the requirements for the new bicycles the company is supposed to manufacture. The caliper is heavy (vis a vis proposed materials) and its dimensions do not meet the requirements. Furthermore, its vibration damping is poor and its stomp on the pedals and go responsiveness is poor. Design Considerations Cost is defined in terms of US $ and will include the amount of money required to design and build the entire braking system, including the materials costs. Cost determination is important as it will influence the ultimate pricing for the bicycle. Efficiency is defined in terms braking time. In this case, the most efficient design will be that which brings a bike traveling at a high speed to a halt while requiring the least energy. The design will also consider the lifecycle of the designed part and ensure that it is in line with the requirements of the company and that it can help the firm reinforce its reputation is providing high quality and highly durable bicycle parts. By definition, weight refers to the amount of force that an object has due to gravity. The overall weight of the caliper is important as it contributes to the entire weight of the bike. The current braking system is caliper brakes. The new design will retain this braking system, but will be redesigned to incorporate new materials and new dimensional constraints. Common types of caliper brakes are the single-pivot side pulls, dual-pivot side pulls and the center pulls. In the single pivot side pulls, both brake arms pivot around the center bolt that attaches the brake to the frame or fork. In this type of caliper brake, the cable housing attaches to one brake and the inner wire to the other. The disadvantage with this type of caliper brakes is that centering can be a major issued due to the fact that each brake arm is retracted independently by a spring. Contrary to the single-pivot one, the dual-pivot side pulls has its brake cable housing being attached to one brake arm and the inner wire to the other. The resulting mechanism is asymmetrical, with one brake arm rotating around the center bolt and the other around a pivot above the wheel. A dual-pivot side pull has been considered for the current design due to the fact that it centers well compared to the single pivot one. (Brandt, 2005) Functional Requirements The requirements for the new brakes is that they should have a high hand lever ratio (mechanical advantage) (preferably above 5:1). This will help striking a convenience compromise between the brake strength, reach of the hand and brake pad clearance to the rim. Adopting a dual-pivot side pull design will help in the achievement of this requirements as its greater leverage and the ability to work with smaller pad-to-rim clearance helps in reducing the pad-to-rim clearance that is required for having a high mechanical advantage. The caliper must also have a light feel considering that the main target market is children. Having a dual-pivot side pull will help in this regard due to the lower (reverse) ratio of the caliper as their springs to not exert a strong return force. The new caliper must also have a high strength to weight ratio and this requires the designer to move away from the traditional design materials. Strength-to-weight ratio refers to the material's strength divided by its density. The light weight nature of the materials makes them ideal for application in industries where low weight without compromising on strength governs design, such as in aerospace. However, machining such materials is a difficult task, in addition to the difficulties that come with designing for stress concentrations in the materials. Materials and Manufacturing Processes Materials Selection Since the current task is a redesign, the focus is on materials substitution. In engineering, substitution may be perceived as referring to an activity through which a material, a process or a product is replace in favor of a more suitable alternative (Ashby Johnson, 2014). When making a substitution decision, key considerations for the designer is the relative value, which includes price ratio, substitution costs, and the client's propensity to substitute. In general the common reason for substitution include achieving higher reliability, improvement of performance, taking advantage of new processes, longer life, making the product more competitive, and reduction of costs. A simple substitution of materials does not guarantee that the resulting design will be an optimum one, hence the need to redesign the entire part. The reason for this is that it is impossible for one to realize the full potential of a new material, unless one redesigns the component to take advantage of its stro ng points as well as its manufacturing characteristics (Pecas et al., 2014). There are several methods that one can use for selection of materials. One of the methods is Pugh decision matrix, which helps one compare various materials on the basis of their properties. Figure SEQ Figure \* ARABIC 1: The use of Pugh Decision Matrix for Material Selection One should also perform a cost-benefit analysis to ensure that the material chosen offers the best value for money. A common method employed for material selection is the Ashby method. The method requires the use of charts for the quantitative selection of a material. There are variations in this method, one of them being the Esawi and Ashby method, which compares the approximate cost of resources of materials, capital, energy, time and information needed for the production of components. As per this method, a material is evaluated on the basis of its material costs, tooling costs and overhead costs (Kumar Jagadish, 2014). A polymeric material was chosen on the basis of the Ashby plot. The material options available included P-75 fiber with polystyrene matrix and 35% fiber, P-75 fiber with polystyrene matrix and 30% fiber and P-100 fiber with Polystyrene and 30% fiber. The thre...