Although bicycles are known as an efficient means of transportation, a considerable amount of energy is wasted every time the brakes are applied. Braking systems on traditional bicycles convert the kinetic energy of the moving bicycle and rider into heat generated by the friction between the brake pads and wheel. This heat energy cannot be captured or reused, which leads to a complete loss of energy every time the rider comes to stop. This is an especially frustrating problem for cyclists who commute through areas with a number of stopping points. Cyclists in these areas are having to exert more energy to get back up to their desired speed after frequent stops. The frustration from having to constantly rebuild momentum causes some riders to ignore stop signs and stoplights. This is an issue for the safety of riders and also one of main reasons why commuting via bicycle is unappealing to many people. Team Cycle-Path has taken on the challenge of creating a Kinetic Energy Recovery System (K.E.R.S.) to allow some of the otherwise wasted energy to be recovered and reused.
The K.E.R.S. Bicycle was Team Cycle-Path’s solution to this energy loss problem. The K.E.R.S. Bicycle will store energy that is otherwise lost during the braking process. It will do this by converting the kinetic energy of the rider and bicycle into stored potential energy in the form of compressed air. This stored energy/air is then able to be reused to help the rider accelerate back up to cruising speed. Similar electric systems exist, but have low energy return. For this reason, Team Cycle Path chose to go with compressed air with the hope that the team would be able to achieve a higher energy return than current electric systems.
The purpose of the K.E.R.S. Bicycle is to reuse otherwise wasted energy from braking while riding a bicycle. On traditional brakes, all of the energy from the moving rider is dissipated during the braking cycle. Team Cycle-Path has set out to harness that otherwise lost energy in the form of compressed air. A common application of this concept is when a car or truck is coasting downhill but is going too fast and needs to slow down. Instead of using the brake, the driver is able to downshift, creating higher RPM’s in the engine. The higher RPM means more compression happening in the pistons of the engine. The K.E.R.S. device takes advantage of that concept by using compression to slow down the bicycle and rider. When the K.E.R.S. brake is engaged, the system will begin compressing air through a custom air compressor-motor at high RPM’s, which will compress the air quick enough to be used effectively as a brake. This compressed air is stored within a pressure vessel (air tank) mounted on the bicycle. That compressed air can then be used to power the compressor-motor and accelerate the bicycle back up to speed. The success of the K.E.R.S. design hinges on three major components: a single piston compressor-motor, an experimental rotary valve, and custom valving with simplistic hand controls.
The air compressor-motor was the most intricate part that needed to be machined, as shown in the picture below. The importance of the compressor-motor is held so high because it is required to function at the highest possible efficiently while compressing air as well as accelerating the bicycle from a stopped position. Simplicity was the motto when design this part of the K.E.R.S. Bicycle, which is why the team chose to go with a single piston design. Excluding the 9 Tooth Sprocket, screws, and bolts, the entire assembly seen below was machined. The material used and machining work was donated by Concept Automation Systems (CAS).
One component that would ultimately decide the effectiveness of the K.E.R.S. Bicycle is the rotary valve. It allows the compressor-motor to run in both directions as a compressor and as a motor. One difficulty that the team encountered with this part was the amount of friction between the valve housing and the rotor itself. Friction kept the valve rotor from rotating as smoothly as expected, and the team experimented with other materials for the rotor to find the best solution to this problem. After testing the effectiveness of a few different materials, Teflon was clearly the most suitable material for this design. (Shown in the picture below)
Valves and Controls
Once the air motor has produced pressurized air, the valving system can direct, store, and release the compressed air within the K.E.R.S. device at the rider’s discretion. The valving mechanism functions by directing air with one-way check valves to the air tank once it forced from the piston chamber. This allows build up within the pressure vessel and prevents the compressed air from escaping through the motor’s inlet it just came in through. A pressure gage, safety relief valves, and adaption nozzles are used to monitor and secure the energy stored at all times within the valving system. After the user has captured enough air and desires to accelerate, the compressed air can be released through the output hose with a flick of a switch. Two hand levers were placed just behind the handlebars that will be used to control the K.E.R.S. (As seen in the picture below). The right lever activates the braking/compression phase, and the left activates the accelerating/ motor phase.
The compressor-motor was modeled off of a 50cc piston motor. It was specifically designed so that it could run as a compressor and as a motor. The compressor-motor was designed by Nick Henderson, utilizing SolidWorks. The material and labor was donated by CAS. The parts were created to have a tolerance of plus or minus 0.005 inches to ensure that the system could compress and release air with the most efficiency, while having the least possible amount of friction.
The air connections to allow the pressurized air to flow where desired was designed with the aid of Airgas. Check valves with a breaking pressure of 5 psi were used to allow one direction flow. Custom spring actuated valves were manufactured to allow control of the airflow. A spring was attached to the lever of a standard ball valve to ensure that the air is exhausted until the compression cycle is engaged by pulling the lever that is attached to the same valve. A compressor nozzle was used to allow the air from the pressure vessel to be released as quickly as possible from the pressure vessel back into the compressor-motor.
The platform on which the compressor-motor is mounted using a standard rear bicycle tire rack and a wooden platform, milled to have a secure base for the compressor-motor. The rear tire rack is bolted to the frame in six places to ensure a secure mount. The wooden platform is bolted to the rear tire rack with three large U-bolts. The compressor-motor is mounted to the platform indirectly using sliding struts, so that the tension of the chain maybe easily adjusted.
Bicycle gear shifters where modified to open and close the levers that engage the compression and acceleration cycles. Cables are run from two separate levers is each control valve. One lever controls the braking cycle, while the other lever controls the acceleration cycle.
Team Cycle-Path went through a long two semesters understanding concepts, organizing ideas, and assembling components that had never been engineered before. The elementary stages of the design process began with targeting a market. For any product, there needs to be a targeted market before it can be designed and sold. The K.E.R.S device began with a concept specifically generated for short-distance commuters who don’t want to lose all of their energy while braking. Given the difficulty and complexity of the engineering that goes into the project, the goal for the K.E.R.S. project morphed into something beyond the scope of the class. Team Cycle-Path built an entire prototype of a new type of engine within two semesters. The K.E.R.S. device will create an offset market all of its own; regenerative braking using compressed air. The climax of the previous semester was the Proof of Concept, which proved multiple overruling concepts within the project. For the K.E.R.S. device, the proof of concept was three-headed. First, it needed to prove that the piston can work as a brake. Second, it needed to be able to store a sufficient amount of energy in the form of compressed air in a pressure vessel. Third, and lastly, the objective was to show that the compressor could work as a motor, powered by the stored compressed air.
The K.E.R.S. Bicycle has hit these three important specifications that Team Cycle-Path has required since the initial design phase. The rotor valve concept proved to be an effective method of allowing the compressor-motor to operate as both compressor and a motor. The K.E.R.S. is able to work effectively as a brake while simultaneously storing compressed air to near desired pressure. Most importantly, through platform testing Team Cycle-Path has proven that the system will be able to provide a noticeable boost when activated. Some other notable achievements that the team have made include: keeping the weight of the K.E.R.S. under 20 pounds (Seen in the picture below), simplistic controls that feel natural to use, and the system was rigidly fixed to the rear tire rack excluding the pressure vessel (air tank) that sits in the water bottle holder.
This video is a representation of the braking cycle. Andy Munter begins pedaling with the K.E.R.S. system in the free riding mode. It is clear that the motor-compressor adds very little, to no friction, when in the open mode. Shortly after Andy begins to pedal, he pulls the lever to engage the braking. When the lever is pulled the valves redirect the air from being exhausted out of the system, to being directed into the pressure vessel. When the lever is engaged it is clear through the amount of effort Andy must exert to continue to pedal that there is enough force to bring the riding to a complete stop within a short amount of time. With the single braking cycle shown in the video, a pressure of 75 psi is achieved.
The pressure built by Andy in the previous video is released from the pressure vessel into the motor-compressor to accelerate the rider forward. It is clear that from the single braking cycle there is plenty of force to aid the rider in the process of regaining momentum.
A special thanks is required for Matt Moriarty, he has gone above and beyond to aide the team in tracking down all of the pressurized fittings that were required for the project. He spent countless working hours to locate the parts that we needed. He was able to get the team all of the necessary parts so that we could test the Proof of Concept.
Airgas | Matt Moriarty | 775-358-2260 | 1671 Glendale Ave, Sparks, NV 89431 | www.airgas.com
Above all, team Cycle-Path owes the most gratitude to David Midboe. David was able to convince Concept Automation Systems to donate nearly all of the raw material and countless hours of his employees’ time to ensure that our project would be machined and manufactured in time for our Proof of Concept debut. The K.E.R.S. bicycle would not be what it is today without the assistance of David Midboe and Concept Automation Systems.
Concept Automation Systems | David Midboe | 775-882-0555 | 3633 Research Way #101, Carson City, NV 89706 | www.conceptautomation.com
Tony (the Mechanical Engineering department’s Machinist) has been absolutely crucial throughout the development and manufacturing of K.E.R.S. Bicycle. He is the true definition of a mentor and a kind human being. He is always so friendly and eager to assist the team in anyway that he can. He has been the one person that always has a solution or a suggestion to what the team should do next. Team Cycle-Path owes Tony the recognition of being the reason the team has made it thus far.
Ferril Berendsen (Tony) | Development Technician III | Mechanical Engineering Machinist | 775-784-6795 | email@example.com
The employees of Kiwanis Bike Project have been a huge source of guidance as well as a the most supportive supplier for any school project. They have always been willing to take time out of their busy schedules to assist team Cycle-Path in tracking down any used parts that the team was in need of. The team owes a huge thanks for all of the support and discounts that Kiwanis has given us.
Kiwanis Bike Project | 775-337-1717 | 145 Catron Dr. Reno, NV 89512 | firstname.lastname@example.org
Meet Team Cycle-Path
Wade Cline – Team Mentor
Wade Cline, Development Technician IV, has worked at UNR nearly twenty years. He is “the person” that every physicist in the department must go to for something made from scratch that otherwise could not be found in any catalog and is unique in design. Wade received his B.S. in Mechanical Technology at Montana State University and worked for four years in vacuum technology at LLNL prior to coming to UNR.
When asked to define his job in one sentence, Wade replied, “I take the drawings and put metal to them.” Wade likes to build. After a project is done, he usually feels a sense of accomplishment and breathes a sigh of relief. He says, “It is a good feeling when the project works the way it is supposed to.” This is where Wade excels and as many faculty have told him, he is their “go to guy.” His ‘other hat’ is ‘the building maintenance person’ and everyone goes to him when something in the building is not working. He also works closely with the Nevada Terawatt Facility (NTF) technicians at Stead.
Nick Henderson is graduating with a Bachelor of Science in Mechanical Engineering and dual minors in Mathematics and Unmanned Autonomous Systems. As the inspiration for the K.E.R.S. bicycle, Nick takes a special interest in improving efficiency and energy flow within systems. Nick is a Reno local with a great respect for the environment, appreciates being outdoors, and regularly participates in activities such as mountain-biking, hiking, and skiing.
Brad Lugo – Technical Drawing Consultant
Brad Lugo is a senior mechanical engineering student at the University of Nevada, Reno. Brad is looking forward to the opportunity to get out into the engineering field and continue learning more about engineering. He is pursuing his passion for the aerospace industry after his time at the university. Brad’s hobbies include disc golf, hiking, biking, and playing and watching sports.
Justin Stewart – Veteran CADD Designer
Justin Stewart is receiving his Bachelors of Science Degree in Mechanical Engineering in the Spring of 2016. Justin’s interests are within aviation, renewable energy, & entrepreneurship. Justin’s post graduation plans will either be seeking employment within the Reno Engineering community or pursue an MBA at UNR. Justin’s hobbies are snowboarding, mountain biking, disc golfing, and playing with his doberman.
Andy Munter – Director of Research
Andy Munter is graduating with a Mechanical Engineering degree after 5 hard-earned years at UNR. He is interested in small motorized mechanisms and has recently found an interest in the UAV and micro-aircraft technology industries. He is interested in finding a job that suits his aptitudes this coming summer and eventually progressing his status to a professional engineer.
Jacob Wilson – Chief Manufacturer
Jacob Wilson is graduating in the spring of 2016 with a degree of a Bachelor of Science in Mechanical Engineering. He is currently pursuing a position as an Operations Design Engineer, at the NASA Armstrong Facility on the Edwards Air Force Base. Jacob’s skills focus on creating innovative design solutions using CADD, as well as drafting technical drawings for the parts to be manufactured. Jacob’s hobbies include reading science fiction books, fencing, exercising, and disc golf.
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