Creating Web Pages in your Account – Computer Action Team
Portland Pedalounge - Mechanical______________________________________________________________________________ME 493 Final Report - 2015Team Members:Matt BachmanMatt BellEdgard MusafiriTim Roberson-HamlinEdson SixtosBrandon SwartoutFaculty Advisor:Sung Yi, Ph.D.Pedalounge Sponsor:John BoblettExecutive SummaryThe Portland Pedalounge is a party bike tourism business operating in Portland, Oregon. The owner of the Pedalounge, John Boblett, has proposed a design project with the Mechanical Engineering department at Portland State University. The purpose of the project is to design and implement a system that allows riders to change the active gear ratio of the Pedalounge to create a more enjoyable pedaling experience.A party bike is a multi-passenger pedal powered vehicle where the passengers provide the power and a driver controls the steering and braking. The Pedalounge, like all party bikes, is a single speed vehicle that travels at a maximum of ten miles per hour. Currently no multi-speed system is being produced for implementation on party bikes. Over his four years of operation, the sponsor has gathered feedback from riders and has determined that the single speed nature of the Pedalounge does not optimize his customer’s experience on the bike.The Portland Pedalounge – Speed Selection System capstone team has developed product design specifications and completed extensive research and analysis on design solutions. A derailleur design was selected based primarily on budgetary reasons. This design will allow each individual rider to select their speed and will feature one higher gear ratio and one lower gear ratio while maintaining the current ratio. After redesigning the initial solution, the team is currently implementing and testing the latest design on one seat to ensure it meets the product design specifications. Table of ContentsExecutive Summary …………………………………………………………………………………………..……………………….iIntroduction ……..…………………………………………………………………………………………………………………….. 1Mission Statement..…………………………………………………………………………………………………………………. 1Project Timeline ………………………………………………………………………………………………………………………. 1Product Design Specification …………………………………………………………………………………………………… 1Top-Level Design Evaluation and Selection ………………………………………………………………………..….… 2Design Process .……………………………………………………………………………………………………………………….. 4Initial Design ….……………………………………………………………………………………………………………………….. 6Implemented Design .………….………………………………………………………………………………………………….. 7Product Design Specification Results .….………………………………………………………………………………….. 8Conclusion ……………………………………….…………………………………………………………………………………..... 8Appendices .………………………………………………………………………………………………………………………...… 10IntroductionThe Portland Pedalounge is geared in a low single speed and operates mainly in flat neighborhoods of Portland. Weighing in around 2,000 lbs, the low gear ratio is great for getting the bike moving; however, once the Pedalounge is up to normal operating speed, passengers will typically find themselves working very hard to keep the pedals turning fast enough to have any beneficial effect on the bike’s speed. This leads to a situation where users wear themselves out attempting to contribute even a small amount. The sponsor views this as a problem as it decreases the customer’s positive experience since they are either contributing and becoming rapidly exhausted or they are unable to keep up with the rest of the group.These issues can be resolved by adding higher gear ratio selections that can be engaged once the riders have topped out at a particular speed. A higher gear ratio means that the pedals can be turned slower while achieving the same or better output speed at the wheels.Mission StatementThe Pedalounge – Speed Selection System capstone team will be designing and installing a new speed selection system to improve the performance of the Pedalounge. The goal is to provide a solution that uses correct engineering methods to ensure that safety, performance, and minimal expenses are the top priority. Ultimately, the final design must increase customer satisfaction. A fully functional product will be provided by May 31st, 2015.Project TimelineIn order to ensure the timely completion of the project, a timeline was developed and weekly meetings were being held to keep the group on track to complete the project on time. As some of the project constraints have changed, so have some of the deadlines. The complete timeline can be found in Appendix A1.Product Design SpecificationThe product design specification summarizes the sponsor’s expectations for the project. The highest priority design requirements are as follows: the Pedalounge must be able to travel up to 10 mph and climb hills with a 4% grade without the passengers over exerting themselves. The proposed design must remain within the budget of $1000 for all ten seats. The required maintenance shall be no more than one hour every six months per seat. The PDS is fully detailed and up-to-date in Appendix Level Design Evaluation and Selection The first of three design concepts consists of a derailleur setup similar as to what’s seen in a standard street bicycle. The orientation of the derailleurs would need to be altered and custom mounting would need to be designed. A three chainring crankset would also need to be installed as the current crankset is only one chainring. The gear ratios must be calculated and the drive sprocket leading into the differential will need to be changed to maximize performance based on the gear ratio calculations. Figure 1 shows a sketch of the proposed model.Figure 1. Two-dimensional drawing of the derailleur setup proposed by the team.The second concept option is an internal crankset. This approach is an “off the shelf” solution. There are numerous companies that fabricate internal cranksets, which means that there are a lot of sources to find useful information. Figure 3 below shows an exploded three-dimensional model of a HammerSchmidt internal crankset. An internal crankset would offer a more compact and efficient solution. However, this biggest issues with this are the cost and complexity of this equipment. The project would be $2000 over budget if this option was chosen. As seen in Figure 2, there are a large number of small and complex parts in an internal crankset. This would cause maintenance to be very frequent andright0 32016702383790Figure 2. Three-dimensional exploded view of a HammerSchmidt internal crankset.00Figure 2. Three-dimensional exploded view of a HammerSchmidt internal crankset.more time consuming than it already has been for the sponsor. The final design option is an expanding chainring which can be seen in Figure 3. The pegs in the six slotted holes expand inward and outward as if the chain were being put onto another gear like a traditional bicycle. This option, like the internal crankset, is very compact. However this is a relatively new technology so there is not much information for the team to reference. There is also a lot of assumed risk if this were to be designed from scratch.32613602600960Figure 3. Example of an expanding chainring.00Figure 3. Example of an expanding chainring.282321012065All of the design concepts were analyzed and compared against one another in order to select the design that best solves the sponsor’s dilemma. Table 1 compares the seven most important design criteria which include: cost, manufacturability/purchasability, user experience, performance, reliability, maintenance cost, and time. This was created to make the design selection easier by quantifying each design criteria to make it apparent which design is the best choice. Each concept was given a value ranging from 1-5 for ranking the importance of each design option, with 1 being the least desirable of the choices and 5 being the most desirable. A final total was taken by adding all of the criteria values together, thus resulting in the ideal solution. This method shows that the derailleur option is the design that best meets the PDS requirements. It has low initial implementation costs, a low cost of maintenance and replacement parts are readily available. Table SEQ Table \* ARABIC 1. Concept screening matrix that rates each design concept by design criteria on a scale of 1-5. A rating of 1 denotes the least desirable option, while a rating of 5 denotes the most favorable.Design ProcessThe team began by identifying several intermediate steps that needed to be completed to properly analyze and complete the detailed design. These steps are outlined in the following sections.Derailleur Gear RatioThe current gear ratio of the Pedalounge and ideal selectable gear ratios needed to be determined to ensure that once the project is complete, the Pedalounge will be able to achieve between 10 and 15 mph during normal operation and maintain its current low speed torque advantage.Once the current gear ratio was calculated, ideal gear ratios for a derailleur system were selected. The results of the calculations and gear selections are summarized in Table 2.Table SEQ Table \* ARABIC 2. Pedalounge gear train calculation matrix.During this phase of the detailed design it was discovered that the current crank chainring, at 44 teeth, is almost as large as any standard offering. This means that the size of the chainring cannot be increased to obtain a higher gear ratio. However, the situation can be remedied by increasing the size of the drive sprocket from 18 teeth to 28 teeth to modify the gear ratio of the overall system. With the new drive sprocket in place, it was determined that a three speed crankset that has a 28-38-48 tooth count offers a set of gear ratios that meet the product design specifications. When the 28 tooth gear is engaged, the Pedalounge will maintain its current hill climbing and take-off advantage. When the 48 tooth gear is engaged, the Pedalounge will reach ground speeds of approximately 12 mph which is within the desired speed range. These critical conditions are highlighted red in Table 2 and are calculated based on the standard operating pedal input conditions highlighted in blue.Derailleur IntegrationIn order to ensure the derailleur system will be properly integrated to the Pedalounge, a complete and accurate dimensional analysis of the Pedalounge was conducted. Figure 4 shows the model of the chassis and the gear system. 7124702059305Figure 4. Screenshot of a to-scale three-dimensional model of the Pedalounge Chassis.00Figure 4. Screenshot of a to-scale three-dimensional model of the Pedalounge Chassis.center-161925This model was used to ensure all space limitations were met, to design mounting brackets for the derailleurs, to modify the existing chain guards to sleeve over the derailleur set-up, and to provide prints and manufacturing information for any components designed and fabricated by the team.Initial Design3973830238315529908501975485Figure 5. Initial design of the front derailleur bracket.00Figure 5. Initial design of the front derailleur bracket.2983230621030The initial design of the front derailleur was to bend a 5” x 0.75” x 0.125” piece of steel into a U shape with an inner wall to inner wall dimension of 1.75”. The U bracket was then welded to a 1.25” diameter tube that is 4.5” long. The assembled bracket then gets bolted onto the cross member which is supporting the seat. The front derailleur will fit onto the tube and can be adjusted up or down to accommodate for the position of the chain. Figure 5 shows the CAD model of the front derailleur bracket on the cross member.39814501356360Figure 6. Initial design of the rear derailleur bracket.00Figure 6. Initial design of the rear derailleur bracket.The rear derailleur design was to create two bends in a 0.125” piece of steel that will bolt onto the bearing housing and wrap under the chain so that the rear derailleur can be threaded onto the top side of the bracket. Figure 6 shows the initial rear derailleur bracket design.Implemented DesignThe design has not yet been fully integrated onto the Pedalounge. After the first round of manufacturing was completed, an installation attempt of the brackets, crankset, and derailleur’s showed that the brackets needed to be redesigned. The rear derailleur bracket was interfering with the chain which was easily fixed by designing the bracket to wrap around the back side of the bearing housing as opposed to the front. The front derailleur bracket was redesigned to create a 15° angle between the mounting tube and the cross member of the bike frame. This was necessary because the chain was not running through derailleur properly. 43148253337560Figure 8. Final design of the rear derailleur bracket.00Figure 8. Final design of the rear derailleur bracket.431482518211804267200-56959542576751299210Figure 7. Final design of the front derailleur bracket.00Figure 7. Final design of the front derailleur bracket.Upon completing the redesign, the team hit a wall during the second stage of manufacturing. The burn table that was being used to cut the steel for the brackets malfunctioned three weeks ago and is still down currently. The team requested quotes for laser cutting and water jet cutting from companies in the area but the quotes were too high for the sponsor’s budget. At this point, the team is confident that the redesigned brackets will work based on information gathered from the first installation. Appendix D shows production drawings of the redesigned mounting brackets and Figure’s 7 and 8 show the final design of the front and rear derailleur’s respectively. Once the final product is installed, each rider will have a shifter near their hands that can be used to switch between the three different gear ratios on their crankset. This allows for each individual to choose how hard they want to work as opposed to the driver changing the active gear ratio for every rider at once. The implemented design will operate mechanically in the same way a bicycle does, however, the only responsibility the users have is shifting.Product Design Specification ResultsAlthough the final design has not yet been integrated, most of the product design specifications can be verified with the model and calculations. The requirement that the Pedalounge must travel up to 10 mph is satisfied based on the gear ratio calculations discussed above. The ability to climb hills that have a grade of 4% is achieved based on research that shows that a 4% grade causes users to have to double their effort to achieve the same speed. By selecting the lowest gear on the Pedalounge, the team calculates that the max speed able to attain while climbing a 4% grade is 5.5 mph. All space and interference requirements are met since the existing chain guard is able to be used and rest of the hardware is underneath the bike. Installing each unit in less than two hours was achieved. This was tested during the first install with the installation time being an hour and a half. Once the process becomes familiar, this time should be cut in half. The maintenance requirement is unknown and only time will tell whether or not that requirement is met. Lastly, the final budget was $1200 which is $200 over the budget of $1000. However, compared to the cost of the other two designs, the sponsor is still happy with this result. ConclusionThe top three designs were analyzed and compared to one another using a criteria matrix that was created based on the product design specifications. Upon completion of the analysis, the derailleur concept stood out as the best design to implement on the Portland Pedalounge. The determining factors in choosing this concept were that it is the most cost effective, easiest to maintain, and that it fits well in the project timeline. In order to satisfy the sponsor’s needs, the team has committed to finishing the installation of one seat once the new brackets are cut. Before this installation, a work instruction will be created on how to install the new components, and the team will guide the sponsor through the procedure to ensure he can reproduce the results. The work instruction will contain images, purchased part numbers, production drawings, and a step by step procedure of how to complete the install on each seat.Overall, the design and gear selection system to be implemented is an inexpensive and low maintenance upgrade that is marketable to party bike owners who are interested in enhancing their customer’s experience. It allows users to go at their own pace while still working to move the entire bike together. The Portland Pedalounge will soon be the very first party bike worldwide to have a gear selection system for each individual rider, and should satisfy many of the customer’s previous complaints. Appendix A: Project TimelineThe project timeline is provided below in Figure A1. The legend is included in the image to show when the tasks were started (light purple with stripes), the date when the tasks should be complete (purple), the tasks completed (tan), the tasks currently in progress (light blue), and the tasks that are incomplete (green).-63817520319847725253365Figure A1. Project timeline showing the necessary tasks to complete the project on time.00Figure A1. Project timeline showing the necessary tasks to complete the project on time.Appendix B: Detailed Product Design SpecificationThe final product design specification table is listed below in Figure B1. The outcome of each PDS requirement is highlighted as “Pass”, “Fail”, or “NA”. NA signifies that the task was completed but the proper testing has not yet been conducted.6096007179945Figure B1. Final product design specification table listing whether the requirement resulted in a pass, fail, or cannot be determined at this time.00Figure B1. Final product design specification table listing whether the requirement resulted in a pass, fail, or cannot be determined at this time.Appendix C: Pedalounge Sprocket Reference LayoutFigure C1 shows the reference layout of all the sprockets on the Pedalounge. The input sprocket to the differential (D) is the one that is being replaced to enhance the gear ratio.66675055880Figure C1. Reference layout of all sprockets on the Pedalounge to show the location of the input sprocket being replaced. 00Figure C1. Reference layout of all sprockets on the Pedalounge to show the location of the input sprocket being replaced. Appendix D: Production DrawingsThe manufacturing print of the rear derailleur is shown below in Figure D1 and the print of the front derailleur is shown in Figure D2. These will be supplied to the sponsor in the event of future use.9620255715Figure D1. Production drawing of the final rear derailleur bracket.00Figure D1. Production drawing of the final rear derailleur bracket.9620253422650Figure D2. Production drawing of the final front derailleur bracket.00Figure D2. Production drawing of the final front derailleur bracket. ................
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