International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND ISSN 0976 – 6359(Online), Volume 6, Issue 4, April (2015), pp. 101-108© IAEME TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 6, Issue 4, April (2015), pp. 101-108 © IAEME: www.iaeme.com/IJMET.asp Journal Impact Factor (2015): 8.8293 (Calculated by GISI) www.jifactor.com IJMET ©IAEME DESIGN AND IMPLEMENTATION OF KINETIC ENERGY RECOVERY SYSTEM (KERS) IN BICYCLE Nishad Kumbhojkar1, Kunal Mohite2, Anand Kulkarni3, Sanket Patil4 1,2,3,4 Department of Mechanical Engineering, Sinhgad College of Engineering, Pune, Maharashtra, India ABSTRACT Kinetic energy recovery system (KERS) is a technology used in formula-1 cars for recovering the energy lost in braking of the car and thus providing boost to the vehicle motion. Same concept i.e. regenerative braking can be applied in bicycle which uses a flywheel which will be mounted between the frames of the bicycle, the flywheel can store the braking energy by rotating and this energy can be given back to the system which will reduce the pedaling power required to drive the bicycle. This Flywheel Energy Storage (FES) system uses flywheel with suitable clutch mechanism along with sprocket and chains. Further this project concludes about efficiency and pedaling power in flywheel bicycle. Keywords: Kinetic Energy Recovery System, Regenerative Braking, Flywheel 1. INTRODUCTION KERS (Kinetic energy recovery system) is a type of regenerative braking concept which is primarily used in formula-1 cars for the purpose of speed boosting. The energy which is applied for braking purpose of a vehicle is normally wasted; however this energy can be saved and effectively utilized as and when required. Generally when the brakes are applied, the braking energy gets converted into heat which is wasted however in this scenario when the brakes are applied the energy is passed to the motors which are mounted on the front wheels. The motors at this stage act as generator converting the mechanical energy to electrical which is then passed to motors/flywheel arrangement resulting in rotation of flywheel. This rotational energy as and when required can be restored by the means of motors to the wheels thus providing the necessary boost in speed. This principle can be successfully implemented in a passive system such as bicycle for serving the purpose of reduction in pedaling power by using a flywheel and a mechanism for engaging and disengaging the same. 101 International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 6, Issue 4, April (2015), pp. 101-108© IAEME In KERS bicycle, flywheel is used to store and restore the energy. Flywheel is mounted between frames of bicycle with aesthetic and ergonomic considerations. The flywheel is mounted on the shaft and shaft is supported by means of frames. Flywheel can be engaged with rear wheel with clutch mechanism. This mechanism consists of clutch, free wheel and sprocket with proper gear ratio for transmission. When the bicycle is down hills or with slow speed in traffic jam clutch can be engaged with flywheel to store energy and this energy can be restored when required. Now at a time when the speed reduction is required clutch is engaged and flywheel starts rotating storing energy in spite of this pedaling power can be decreased and efficiency of system can be increased. For analysis of system overdrive test is carried out and results are obtained in order to reduce pedaling power. The assembly and parts modeling is done in CATIA and Solid Works software. For simulation and analysis purpose ANSYS software is used. Fig.1 KERS Bicycle 2. WORKING The components used in the system are flywheel, clutch, chain drive, Bearing, frame. Flywheel which is mounted on the frame is driven by the rear wheel through the chain drive and clutch mechanism. When one has to apply the brakes the mechanism is such that clutch gets engaged with the flywheel and it starts rotating thus storing the braking energy. The mechanism designed is such that by manually pressing the lever (Rear brake lever of the bicycle) the clutch can engage with the flywheel this depends upon the convenience of the biker. The stored energy is utilized when the speed of bicycle decreases below the average range of speed i.e. rear wheel speed. The flywheel energy by the means of chain in this case can be restored back to the bicycle thus fulfilling its torque requirement. Consider for instance riding on a slope or in the case of mountain biking, when the speed of bicycle is more than average speed range the engagement of flywheel is facilitated and the flywheel keeps on rotating for a certain period of time mainly due to inertia this motion can be transferred back to the rear wheel thus assisting the forward motion of the bicycle.\ Objectives • Reduction in pedaling power required to drive bicycle • Increase the system efficiency • Imparting the simplest possible operation & mechanism 102 International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 6, Issue 4, April (2015), pp. 101-108© IAEME Components Designed 1) Flywheel 2) Selection of clutch mechanism 3) Shaft 4) Frame 5) Bearing Selection 3. FABRICATION PROCESS Step 1: Frame Modification In order to mount a flywheel an additional frame mounting is imperative as frame is the support structure for the flywheel. Frame mounting is the first step in manufacturing of the flywheel bicycle. Steel tubes are used as the frame structure, they are joined by welding .One end of the frame is to the front end of the bicycle (below the handle) and other end is connected near the rear sprocket. The frame is connected to the bicycle structure by spot welding. However certain considerations are made so the geometry of the frame does not hinder the riding comfort of the driver. Fig.2 Frame modification Step 2: Flywheel Manufacturing The flywheel is manufactured by performing lathe operations and certain considerations were made earlier for considering the weight of the flywheel, The weight of the flywheel should be optimum if it exceeds a particular value it will make the bicycle bulky, however even the lesser weight will not offer the required inertia to empower the rear wheel of the bicycle. Material selected for flywheel is MS (mild steel).A hole is bored centrally in the flywheel for mounting the ball bearings so that the shaft rotates with the rotation of the flywheel. Step 3: Shaft and Support Fabrication Considering the inner diameter of the ball bearing and by carrying out shaft design the diameter of shaft is decided. Thus accordingly shaft and the related shaft support structure on the frame is manufactured. 103 International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 6, Issue 4, April (2015), pp. 101-108© IAEME Fig.3 Assembly of mechanism Step 4: Miscellaneous Parts Fabrication or Procurement Another important part manufactured is the clutch plate, Clutch plate is a disc type plate of mild steel which can play a role of engaging and disengaging the flywheel from the bicycle as and when required, Helically connected discs are used for moving the clutch plates to and fro. The helically connected discs and clutch plate is a single structure, thus the movement of the discs is the movement of the plate. Sprocket of larger diameter and freewheel is procured from market which will be mounted on the rear wheel and the front assembly respectively, they are connected to each other by means of a chain. Step 5 Mounting The parts manufactured namely the flywheel with shaft and clutch plate helical disc assembly is mounted on the frame structure, which completes the manufacturing phase of the bicycle. Fig.4 Mounting 104 International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 6, Issue 4, April (2015), pp. 101-108© IAEME 4. RESULT AND ANALYSIS The flywheel bicycle increases efficiency on rides where the rider slows often. The additional weight is outweighed by the ability to recover energy normally lost during braking. Thus the addition of extra weight does not make it difficult for the rider. Also clutch provided helps in deciding the time period of activity. The overall result is that KERS system is efficient in storing the energy normally lost in braking and returns it for boosting. Weight and Performance Normally energy stored in the flywheel is directly proportional to the weight and radius. Hence increase in weight proves to improve the performance. But as we know that the maximum safe weight that can be used is limited due to frame properties and rider compatibility. And also after some extent the radius can’t be increased and the energy storage thus seems to be limited to some particular extend. This is also because of the fact that the total running speed is being reduced due to weight. Energy storage capacity increases with increase in weight but limitation seems to be the speed driving the flywheel. And performance of system is directly linked with the energy stored. Thus a graph can be plotted between performance and weight. Optimum value lies between 5 and 8 kg. Energy stored in flywheel, Ek=1/2 ω^2 Where, I‟ is the moment of inertia” ω‟ is the rotational velocity (rpm)” Moment of inertia, I = ^2 Where, k‟ is inertia constant (depends on shape)” M‟ is mass of the disc” R‟ is the radius” Thus, Ek is directly proportional to the mass of the disc. The flywheel and transmission add weight to the bicycle. The increased weight will add to the energy required to accelerate the bicycle and to ride it uphill. However, once the rider has provided the energy to reach a cruising speed, the flywheel reduces the energy cost of slowing down from this speed since it aids in subsequent acceleration. Roads are optimal environment for the flywheel bicycle because it’s flat and there are lots of reasons for the cyclist to slow down. 105 International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 6, Issue 4, April (2015), pp. 101-108© IAEME Thus as the performance versus weight graph shows maximum performance is expected at maximum weight, however considering limitations and the rider comfort optimum weight of 5 Kg is selected for the flywheel. 5. CALCULATIONS Energy is directly proportional to distance travelled, thus in case of flywheel bicycle more the distance travelled by the bicycle (flywheel engaged position) in one pedal more will be the energy saving and input energy reduction. Thus, (Difference in the distance of engaged and disengaged position/Distance in disengaged position)*100 Hence according to above method about 12% of energy reduction is obtained for the system. 6. FUTURE PROSPECTS The idea of implementing Kinetic energy recovery system (KERS) in bicycle by imparting flywheel for input energy reduction was successfully implemented, however in order to introduce it as a product certain modifications or developments need to be implemented. A number of things need to be incorporated in order to make the product more efficient; ergonomically as well as aesthetically sound, some of the modifications noticed are as follows: 1) Weight optimization (Flywheel, frame and related mechanism) by using optimization techniques or by using related soft wares such as ANSYS, HYPERMESH. 2) Improving transmission efficiency i.e. reducing energy losses mainly friction losses for improvement in performance. 3) Taking into account certain ergonomic considerations the cycle geometry can also be modified with following respect: i) Upper metallic bar of the bicycle frame can be removed. ii) Frame on the lower side which connects the triangular bar section of the bicycle with the rear wheel mounting can be removed in order to eliminate the interference of the chain with the frame, which results in friction losses as well as creation of noise. iii) Modified Frame thickness can be reduced for better ride comfort. iv) Flywheel housing can be designed to ensure that flywheel is not in contact with the environment. Double Centrifugal Clutch Concept A new concept was thought of with reference to the engagement and disengagement of the flywheel with the transmission that implies usage of centrifugal clutch. Need The implemented mechanism for the engagement and disengagement of flywheel is by using the clutch plate and the related mechanism; however this at times can be painstaking and tedious. Thus by using a centrifugal clutch which by itself is an automatic type of clutch, the power flow can be made automatic. Hence by using double centrifugal clutch concept the transmission can be made independent of the driver control. 106 International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 6, Issue 4, April (2015), pp. 101-108© IAEME Construction & Working Fig.5 Double Centrifugal Clutch The proposed mechanism consists of 2 centrifugal clutches which are mounted on the bicycle axle as shown in the above fig. Consider the bicycle has reached a particular speed, say x m/s. This speed has been set as the pre-set speed for the centrifugal clutch i.e. as this particular speed the shoe of centrifugal clutch 2 will touch the drum due to which the drum of clutch 2 will start rotating. This rotational energy will be transferred by the means of sprocket to the flywheel and flywheel will start rotating. However when the rotational energy of the flywheel is to be transferred back to the rear wheel, clutch 2 will be disengaged as rear wheel would be rotating at speed lesser than x m/s. Now centrifugal clutch 1 which is has a pre-set value of say y m/s (x>y) will be in engagement position i.e. there will be contact between drum and shoe. The clutch will rotate and energy will be transferred back to the rear wheel for pedal assist. Thus as the value of engagement is set initially engagement between rear wheel and flywheel will be fully automatic without any human intervention. 8. CONCLUSION KERS (Kinetic energy recovery system) is a system which is very efficiently used in racing cars as an energy recovery device or regenerative braking concept. Similar concept can be employed for a non polluting device such as bicycle with the intention of reducing human effort to ride the bicycle. The proposed design is a simple implementation of the same idea which uses flywheel as an energy bank or energy storing device. The idea was successfully implemented as well as validated by manufacturing and mounting the KERS system on a non geared bicycle and the results obtained were non negligible as well as encouraging. However there are certain areas that need to be looked upon, better results in terms of reduction in pedalling power can be obtained by better weight optimization. Continuously variable transmission can also be an option for better transmission efficiency. Ergonomics can also be taken into account, the idea of double centrifugal clutch if implemented successfully will make the entire transmission automatic leading to better comfort and hassle free driving experience. 107 International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 6, Issue 4, April (2015), pp. 101-108© IAEME 7. 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