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ET 494 Senior Design Proposal DocumentAdvisor: Dr. MitraFebruary 9, 2018Team:Thomas BallingerSamuel CampoEvan VasalechJeremy PassaroAbstractThis semester our group was tasked with designing an effective, low cost, low profile bicycle assist system that would be compatible to most bicycles. There has been an expanding market for power assisted/hybrid bicycles; however, the costs for many models are too high. Some innovative ideas are also uncomfortably heavy, which may dull the cyclist’s comfort and feel of the bike and the ride. There are also range issues for some of the options. Our goal is to combat the cons of many assistive powered bicycle systems and deliver an effective concept that meets our criteria.Purpose of This SystemIt may seem counter intuitive to implement a system that makes a tool that functions as exercise equipment easier to use, however there are several reasons why systems like these are often needed and growing in popularity. Many people are forced to use bicycles as daily commuters because of gridlock city traffic, strong views on maintaining and improving air quality in the environment, and even lack of ability to afford a car. In these conditions, riders are not primarily riding bicycles for the health benefits, as much as getting from one place to another. Additionally, many active outdoor adventurers who enjoy the exercising aspects of biking or enjoy looking at nature sceneries are unable to do so or unable to do this as often due to a variety of injuries. In each of these scenarios there is a demand for assistive powered bicycles, as well as a respectable supply and variety of assistive powered options. Costs however can be over $1000. We believe we can design and fabricate our own system for a relatively low cost while delivering the safety, quality, and performance of the more expensive models. Restrictions, Research, and DesignUpon receiving our assignment, we were also given some criteria for our design. The design must be safe, cost effective, small, lightweight, and capable of fitting most bikes. With these restraints in mind as well as any related legal restraints we researched preexisting solutions, analyzed them and compared them to each other. Our selection for this design is the most intuitive and simple: simply designing a one size fits all mount and placing an electric motor and battery on the mount. We believe this design will work best because it will be easiest for a customer to assemble, easy to manufacture, and compatible with most bicycle designs. These factors help keep theoretical production costs down and revenue up.Our first task was determining how much power we required. To do this we had to find the approximate values of the forces at work on a moving bicycle. It was determined that the resistive forces to overcome were rolling friction (rolling resistance) and air resistance. Rolling friction is given asFR=CNR where C is the coefficient of rolling friction (found in our ET 381 textbook: ), N is the normal force (determined using a 200 lb rider and 40 lb bike) and R is the radius of the wheel (using 13”). Air resistance is given as the product of the drag coefficient, air density, cross-sectional area, and velocity, all divided by 2.AR=12*cd*ρ*A*v Our desired velocity is set to be 20 mph; the other values were determined from an online resource. The approximate force to be overcome is about 110 N, which when multiplied by velocity, gives a required power of 990 W (1.3 hp). Due to the high required power, a 48V system was chosen.With the power sorted out (and by definition the voltage and amperage for the circuit), the circuit was the next issue. The system will require a high amperage of 21 A, meaning we will be using 10-gauge copper wire for the application. We are also implementing a safety factor on the battery to increase longevity. We will be searching for a 48V lithium-ion battery which is rated for about 26 Ah (will run at 80% capacity for approximately one hour). The circuit will include a fuse, a rocker on/off switch, a snap action switch in line with the bike’s mechanical brakes, a speed control, and the motor itself.Figure SEQ Figure \* ARABIC 1 Circuit layoutThe mount was designed in solidworks. It has been designed to attach to the rear seat via clamp and to attach to the rear part of the bike frame. As of right now we plan on providing motion to the rear wheel via belt/chain from the motor mounted on the mount to the rear wheel hub.Figure SEQ Figure \* ARABIC 2 Mount design 2017Figure SEQ Figure \* ARABIC 3 Clamp to rear wheelDeliverablesOur goals for this semester are as follows:Improve the mount design; which includes material selection and drawing of the mountFabrication of the mountOrder components and materials based on the previous semester’s specificationsSafety considerations on circuitry and electrical componentsWeatherproofing electrical circuitAssemble and test the system to ensure it meets our specificationsDevelop solutions to any problems after testingPrepare finished product to presentTask Organization Our team of mechanical engineering technology majors each play key roles in reaching our deliverables. Research and safety will be every group member’s responsibility; each group member will have the freedom to give design input based on new research as well as the authority to bring any and all safety concerns to the team’s attention. Independent of these responsibilities, the tasks have been divided between two teams as seen below:Evan and Sam will work as a team to finalize and refine the drawings of the mount and the Axle C-Clamp. Once completed, they will determine what materials would be required for their design and organize fabrication of the mount and clamp. Another task to be completed will be the process of designing the protective casing for the battery and motor. Some of the design requirements include weather proof material that will provide proper ventilation. Jeremy and Tommy will work as a team in selecting and ordering parts for both electrical and mechanical designs. Additional tasks to be completed include finalization of selected dimensions, to ensure compatibility with design, and assemble the full circuit. This team will also conduct the testing phase, using the heaviest, lightest and closest to weighing team members to see how well our system performs.TimelineDuring February, the process of refining the circuit and mount design will be completed, as well as the material we will be using to fabricate the mount.In March, we will select a feasible method to create the mount and begin the mount making process. We also plan to obtain all electrical components by the end of the month.By the middle of April, the product’s field testing should begin and will finish in late April/ early May. During this time, all kinks will be worked out. Our budget will be finished once the final product is ready, after which, the final report will be drafted.Sources??, Robert L.(2010) Statics and Strengh of Materials.Upper Saddle River, New Jersey: Pearson Education, Inc. ................
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