Synthesis of human power and machine to achieve the fastest, most efficient vehicle on earth
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2019 record attempt

Pushing the limits

 
 

Creating such a super-bike presents unique engineering challenges. The frame must be optimised for weight and stiffness, and tailored precisely to the individual rider’s shape and strength. The drive chain and components must operate with minimal friction and rolling resistance. All of these components must fit inside the external shell of the the vehicle, which is carefully tuned to minimise aerodynamic drag. 

 

In September 2019, the team will put both rider and engineering to the test at the World Human Powered Speed Challenge, in Battle Mountain, Nevada.

 
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Key Specifications

  • Shell: Composite carbon-Kevlar / epoxy and polyurethane sandwich

  • Chassis: Integrated monocoque carbon fibre keel with roll cage

  • Tires: Ultra low rolling resistance 650c clinchers

  • Transmission: 150:14 direct drive on 8mm pitch chain and 130mm cranks


  • Wheelbase: 1330mm

  • Wheel diameter: 624mm OD on 650C wheels

  • Overall height: 849mm

  • Overall length: 2570mm

  • Overall width: 244mm

  • Custom built cranks, chainring, bottom brackets, hub, wheels, headset, stabiliser

 

Aerodynamics

 
The higher the speed of travel, the more significant is the role of aerodynamics in the consumption of the available power - specifically the aerodynamic drag that accounts about 2/3 of the overall drag. The external shape of the HPV has been carefully developed since 2015 by aerodynamicist Glen Thompson using a digital wind tunnel simulation process called Computational Fluid Dynamics (CFD). This takes into account a number of critical factors, including the speed of travel, the lower air density at 1400m altitude, and the smoothness of the polished exterior surface.

The higher the speed of travel, the more significant is the role of aerodynamics in the consumption of the available power - specifically the aerodynamic drag that accounts about 2/3 of the overall drag. The external shape of the HPV has been carefully developed since 2015 by aerodynamicist Glen Thompson using a digital wind tunnel simulation process called Computational Fluid Dynamics (CFD). This takes into account a number of critical factors, including the speed of travel, the lower air density at 1400m altitude, and the smoothness of the polished exterior surface.

The digital model used a 3mm mesh with a series of 50 much smaller “inflation” layers surrounding the surface of the vehicle, starting at less than 1/100th of a mm in thickness. The simulation used a total of nearly 12 million elements. The settings used were initially validated against published empirical data from a previous record holding HPV - the Varna.

With the model thus defined, there followed an iterative process of refining the shape and curvature of each of the key areas of the vehicle, such as the nose, the footbox, the tail, and the wheel openings, and examining the effects of these changes on the airflow. Particular focus was on the “transition zone”, the region in which the airflow changes state from laminar to turbulent; this is characterised by high velocity and low pressure, resulting in high drag forces. This zone is only detected in the simulation when the roughness of the surface is also factored into the model.

A Sand Grain Roughness Height represents the sanding and polishing treatment by generating around 3 trillion microscopic hemispheres that protrude from the surface to simulate the microscopic peaks and troughs left by sanding and polishing the surface. The effect of these adds approximately 33% onto the overall viscous drag of the vehicle.

The team are planning to work with the Boardman Performance Centre later this year, using their cycle-specific wind tunnel to measure real drag values, contrasting these with the simulations.

 
 
 

Shell and Chassis

 

Once the surface shape has been defined to optimise the aerodynamic performance, this must be manufactured into a stiff composite shell that will maintain it’s shape under the aerodynamic loads, and also protect the rider in the event of a collision.

The design was translated from CAD data to 3d physical form using the multi-axis KUKA CNC robot from the Digital Architecture Robotics lab at LSBU, which cut the foam bucks from which fibre-glass moulds were made (see this video)

The shell of the 2019 vehicle was shaped in these moulds from composite layers of carbon-Kevlar (for abrasion resistance and stiffness), sandwiched either side of a polyurethane foam core. The is stiffened by a monocoque carbon fibre chassis that provides a solid platform for mounting the transmission, steering, seat, and wheel assemblies, and a roll cage to protect the rider in the event of a collision.

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Steering and Transmission

 
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The transmission team’s goal is to optimise the steering system and the power transmission of the vehicle to ensure minimal friction and maximum efficiency.

The 2019 design builds on the core principles of Mike Burrows’ original Soup Dragon design. This incorporates a direct chain drive to the front wheel, using a gear ratio of 150:14 - carefully specified with the 93mph target in mind. Elimination of a derailleur and cassette brings significant efficiency benefits, but to enable this to work, the steering must pivot off-centre, with rotation centred on the axis of the drive sprocket. This presents further design challenges in minimising the Q-factor (the horizontal distance between the pedals) around the transmission system; aside from the biomechanical advantages of a low Q-factor, reduction in width plays a key role in the aerodynamics by reducing the frontal profile area of the vehicle.

The team are also working with project sponsor Autodesk in the use of their latest generative design technology to optimise the front chainring and crank.

 
 
 

Stabiliser

 
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Running a direct drive transmission on such a high gear ratio is optimal at high speeds, but presents significant stability issues during launch, whilst accelerating.

One of Mike Burrows’ original innovations on the Soup Dragon is a retractible stabiliser wheel, providing support during acceleration to up to self-stable speeds. For 2019, the team are working to optimise the mechanics and action of this stabiliser and the hinged panel from which it emerges.

The 2019 design incorporates an entirely new feature that enables the wheel to be stowed flat, rotating through 90 degrees on it’s axis to lock vertical as it emerges from the shell. The enables a reduction in the size of the hatch panel, reducing the impact of the split line on the aerodynamics.

The stabiliser brings the additional benefit of enabling the rider to land the HPV autonomously. Crashes and falls on landing are common, and invariably result in surface damage to the shell which impact the aerodynamic efficiency, requiring time and elbow-grease to polish out between races.

 

Rider Experience

 
 
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The Rider Experience team’s focus is on all aspects of the ergonomics, from external vision & audio comms to correct posture in the seating. The tiny space in which our riders are encased must be optimised to allow them to perform to the highest physical level so they can focus all of their attention on breaking the Human Powered land speed record!

Number one priority is the rider vision system. The recumbent riding position and the low profile shell render windscreens ineffective. The vehicle will use a camera and monitor system provide the rider with a clear, unobstructed view of the road ahead. Learning from the drone racing industry, reliable wide angle cameras with minimal latency will feed to high definition monitors inside the cockpit.

The monitors will also provide our riders with a live data feed from sensors that track power, cadence, heart rate, and speed, allowing them to tailor their performance to our predefined programme for the track.

Rider safety is of upmost importance and as such the HPV will include a 360-degree roll cage, 3-point harness and Carbon-Kevlar shell to protect them during a crash. The team are also working on a breathing system to draw in, filter, and hydrate fresh air, ensuring a constant and optimised flow of air to the rider.

The riders are working with the LSBU Human Performance Centre to develop a bespoke hypoxia training programme for them to follow over the year, conditioning the bloodstream and muscles for optimal performance in the lower-oxygen conditions of the race venue.