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Putting a Spring into Cycling

Energy Storage for Cyclists - Dynamically-Weighted Bicycle Wheel

Flywheels are used as a method of energy storage for many different devices. This stored energy can then be released instantly or gradually over time. What if such a device could be implemented for use on a bicycle? This would allow riders to store energy from the beginning of a ride that could be called upon during drops in performance levels.

iIn 2005, Czech rider Ondrej Sosenka broke a long-standing UCI hour record, riding 49.7km (30.9 miles) in 1-hour. For this, he used a custom carbon fiber bicycle manufactured fitted with a weighted rear wheel. The wheel acted as a flywheel allowing him to maintain speed through drops in performance over the 60-minute period. Simply fitting a large heavy wheel to a bicycle would result in utilising the flywheel effect used by Sosenka. However, large amounts of energy are required to get the wheel up to speed, resulting in slow acceleration from rest.  What if these weights could be positioned at the rim upon reaching a desired speed, utilising the benefits of a flywheel and minimising the required energy input to accelerate from rest. This is what the dynamically weighted bicycle wheel is designed to do.

To find out, Heriot-Watt Masters student James Carchrie a fifth-year honours student in Mechanical Engineering set out to determine if the use of a mass sprung system would benefit cyclists and to maximise its effectiveness. The work was supervised by Heriot-Watt Mechanical Engineer, Dr. Daniil Yurchenko

You can read what James discovered by downloading his dissertation here and here. The report details the design, manufacture and testing of a dynamically weighted bicycle wheel system. Through the use of a mass-sprung system a kinetic energy storage device was developed for use on bicycles. Ultimately such a design could be utilised for any flywheel system. Following successful manufacture the weighted-sprung system was tested via human and electrical power methods. It was found that the weighted-sprung system provided a 5% increase in deceleration rate compared to an unweighted wheel. Whilst higher percentage could be achieved with a weighted rim, the weighted-sprung system allows for a much smaller initial energy input. The weighted-sprung system maintains the same properties of a weighted rim at the operating speed. Magnets situated at the wheel rim ensure kinetic energy is conserved. Future work is suggested to further enhance the concept and provide more evidence of its benefits within rotating systems.

Report Copyright: James D Carchrie April 2017. Not to be republished without permission

Want to study Mechanical Engineering at Heriot-Watt?  Mechanical Engineering offers an exciting environment where many skills are brought together to create innovative products and the infrastructure and technology for manufacture. The first two Levels provide a grounding in the core disciplines of Mechanical Engineering, which allows students to make an informed choice of the subsequent options. An individual project forms part of Year 4. Find out more here



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