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Engineering the World's Fastest Bicycle

ABSTRACT: Australian track cyclists won impressive victories at the 1995, '96 and '97 World Track Championships and the 15th Commonwealth Games. The Australian team used with stunning effect a unique carbon fibre monocoque bicycle designed and built by a project team from the Royal Melbourne Institute of Technology (RMIT University) and the Australian Institute of Sport (AIS). Developed in consultation with Charlie Walsh, the national track cycling coach, this new bicycle, the 'AIS/RMIT Superbike', has allowed the Australian riders like Shane Kelly to set new records. Continued development has resulted in over twelve World Championship titles and four world records. Including the World record for the kilometre Individual Time Trial set by Shane Kelly in 1995.

The development and application of new wind tunnel testing techniques have resulted in a fifteen per cent reduction in power over the traditional diamond frame. Extensive use of a water tunnel and wind tunnel have enabled the team to optimise the frame profile for minimum aerodynamic interference from the rider's leg motion. Structural design loads were derived from track testing with strain gauged frames. Finite element analysis techniques were validated through extensive material testing. Throughout the development program extensive use was made of validated performance simulation. The simulation provided evaluation of stiffness, aerodynamics and weight. These simulations enabled rapid assessment of concepts. Track testing with power meters and strain gauged frames were used to refine design data and wind tunnel test techniques.

In order to produce the resulting bicycle new manufacturing techniques had to be developed. Unlike most equipment used by elite athletes the AIS/RMIT 'Superbike' has been designed for low cost, high volume manufacture. The hollow frame is moulded as a single unit in a one shot process suitable for automation. The frame was designed to accept standard group sets and wheels. The AIS and RMIT University has lodged patents on the unique features of the manufacturing process. Bicycle Technologies Pty Ltd (Australia) has commenced commercial manufacture of track and road variants. The New Zealand National Track Cycling Team has selected the 'Superbike' for the 1997 and 1999 seasons. It is anticipated that the technology will enable a new manufacturing industry to be developed in Australia.

The engineering development has resulted in the project winning an Engineering Excellence Award from the Institution of Engineers Australia, two Innovation Awards and the 1995 Velo News Award for "Best Technical Development for 1995 in Road or Track". This paper discuses the engineering techniques, research and project management required to create the Australian Superbike.

DESIGN CRITERIA

The stunning ride by Chris Boardman on the Lotus Bicycle(1) in the Barcelona Olympics heralded a dramatic change in Olympic track cycling. The UCI's rule change opened the door for the monocoque bicycle to show its potential. Unlike the much later Lotus Sport, Boardman's bicycle was a one-off with highly specialised components. His ride did however set the stage for a new era in competitive cycling

As Chris Boardman rode to Olympic Gold the RMIT and AIS project team set out to build a 'Superbike'. The RMIT-AIS team sought a design that optimises weight, stiffness and aerodynamics while conforming to the rules of the Union Cyclist Internationale (UCI). The University was at the time seeking a suitable project to demonstrate new low cost advanced composite manufacturing techniques. The project team included engineers, technicians and students from RMIT Aerospace Engineering, the AIS and RMIT Industrial Design.

Australian Olympic track cycling coach Charlie Walsh defined the initial design criteria with the project team in late 1992. The resulting bicycle must use a conventional group set of standard(3,6) cranks, bearings, brakes, wheels, forks, handlebars, seat, etc. Further criteria imposed by RMIT was that the design must equal or exceed the structural stiffness of a steel bicycle while offering lower aerodynamic drag and weight without compromising reliability. It was also desirable for commercial purposes that the resulting design be suitable for low cost, high volume production.

Dimensional tolerances(6) used in developing the 'Superbike'

In this project the needs of the end user were paramount to the success of the end product. Competition bicycles are made to the rider's individual specific requirements. The client specifications were defined and completely fulfilled. These specifications included critical geometry as shown below and certain subjective characteristics as ride and comfort. Stiffness, strength, reliability and use of standard components were achieved.

ENGINEERING DESIGN A systems engineering approach was adopted for the project. A requirement analysis was undertaken to establish the design criteria and project milestones. The project plan and budget were developed using the findings of this analysis. Riding position and frame geometry defined by the AIS were checked against a current AIS Olympic steel frame. This same frame was later used to define minimum stiffness criteria.

Figure 1: Gary Neiwand test rides the strain-gauged prototype

Before design could take place a mathematical performance model was written and validated. The mathematical model was validated against actual track performances using the SRM dynamometer crank system. This permitted an extensive analysis of each component in the bicycle system including the rider. The results of this investigation showed that the frame and front fork handle bars to be priority components for research. The requirement analysis also identified that aerodynamic testing techniques were not giving repeatable results of sufficient accuracy. Development of improved wind tunnel techniques was considered a high priority.

Traceability in design was maintained throughout the project by maintaining design files and technical reports on each task. Coupon testing provided material properties for the Finite Element Models(4) (FEM). Laboratory tests were used to prove structural details before progressing to track testing.

Extensive track and wind tunnel testing was used to validate design changes. Each phase of the project has required critical evaluation by both the design team and the national track cycling team. Decisions were made at project or task meetings to ensure prompt reporting of results and effective implementation of new ideas.

Every prototype was required to undergo structural testing for stiffness followed by a general inspection. Modal analysis is being developed as a tool for non-destructive inspection and quality control. This technique of vibration analysis(2) will provide a cost effective "finger print" technique for production quality control.

AERODYNAMIC DEVELOPMENT
In order to minimise aerodynamic drag new and innovative wind tunnel testing techniques were developed. This included the use of artificial legs to accurately study the airflow over the bicycle. With this unique rig the aerodynamics of the complete system could be represented.

Initial investigations showed that the rider's legs dramatically influenced the flow pattern(6) and resulting drag. To obtain accurate and repeatable wind tunnel results with live athletes was extremely difficult. The sensitive wind tunnel balance required precise knowledge of the centre of mass in order to apply corrections for induced forces due to moment couples. In the development of the 'Superbike' the rider was replaced with a pair of lightweight Styrofoam® legs. A similar lightweight torso, head and arms could also be fitted. The rear wheel was driven by an electric motor beneath the wind tunnel floor. A simple belt drive under the floor also drove the front wheel. By having the motor and drive system part of the bicycle accurate and repeatable drag measurement was possible.

By May 1993 the project team arrived at a basic conceptual design for a carbon fibre monocoque bicycle. A prototype of this design was built for initial testing. Wind tunnel testing was carried out to refine the aerodynamic shape. The instrumented prototype was evaluated on the track by world champion sprint cyclist Gary Neiwand. This testing allowed the engineers to determine handling characteristics and the loads encountered during competition. The data obtained was used to optimise the design.

Subsequent prototypes for testing and competition has resulted in the 'Superbike' meeting or exceeding all of the design criteria. Independent tests on the 1994 variant by Dr. Neil Craig of the South Australian Institute(6) of Sport at the Adelaide Superdrome showed the 'Superbike' to require 5% less power than the then current steel AIS Olympic tubular frame. Further improvement was made possible by designing a new wind tunnel balance. The use of a 'hover board' bicycle mounting eliminated balance interactions. This technique allowed further refinement and development of the 'Superbike.

Figure 2: Moving artificial legs simulates the disturbed airflow around the bicycle.

PRODUCTION DESIGN
The requirement study showed that a one-size monocoque shell could be developed to suit a wide range of rider size. One single size of the 'Superbike' can accommodate riders from 1600 mm to 1900 mm in height.

The 'Superbike' is unique in that it has been designed from the outset to be of a shape and structure that can be easily and cheaply produced in high volume(3). This manufacturing feature, a 'one size fits all concept', removes the necessity for multiple and expensive tooling. The use of a complete monocoque shell gives lower weight and greater stiffness than achieved in previous racing bicycle designs. This shell is completely hollow and requires no additional core material. Careful structural optimisation has allowed thin non-buckling skins to be used.

Refinement of the manufacturing technique has allowed Patents(7) on the process to be lodged. The Superbike is in production at Bike Technologies Pty Ltd, Melbourne Australia. Continued success in international competition has assisted the project in commercialisation(2).

Competition results for the Superbike (6,8).

STRUCTURAL DESIGN
The 'Superbike' for the 1995 World Championships has the provision for the flush mounting of instrumentation used in performance trials. This allowed for an accurate assessment of the athlete and equipment without the need to apply corrections for the aerodynamic drag of the sensors. The ability to access track test and race data for a pool of top athletes formed an integral part of the development program(6). Data from riders such as Bradley McGee, Kathryn Watt, Narelle Petersen, Garry Niewand and Shane Kelly ensured that the configuration was one that would benefit a diverse range of riders and riding positions, further developing the mathematical performance model.

Extensive use was made of Computer Aided Drawing (CAD) to input data to both Finite Element Analysis(3,4,5) (FEM) and Computer Aided Machining (CAM) of production tools. Software used in the project included Cadkey97 and STRAND6 as well as the in-house performance model.

Figure 3: STRAND6, FEM Analysis assisted lay-up optimisation.

Finite Element Modeling(3,4) was used to assist in the optimisation of the structure. This was validated against the instrumented test bicycles, which were ridden in competition conditions. Static strength and fatigue life was of importance, as an AIS track frame will average 10,000 kilometres of use per annum. The same bicycle being used in training as well as in competition. Modal analysis has been introduced as a means of ensuring that each frame is of consistent quality. Further development of this method of inspection is planned.

Figure 4: Kathryn Watt wins 'Superbike's' first ever race at 1994 UCI World Cup Colorado Springs USA.

The continued successful development(6) of the 'Superbike' is not due to any one factor being superior. Instead the credit goes to the application of a validated mathematical performance model that can rapidly evaluate structural, aerodynamic requirements and riding position.

REFERENCES

1. Hill, R. D. 'The Design and Development of the Lotus Sport Pursuit Bicycle', Proceedings of the Institution of Mechanical Engineers, pages 285 to 294, Volume 207, 1993, UK.
   
2. Lane, T. 'Push to the Limit', The Australian Way, pages 84 to 87, November 1996, Australia.
   
3. Wilson, M. 'Super Roo Sets an Olympic pace', Overseas Trading, October 1995, pages 6 to 9, Australia.
   
4. Anon. Australian Students Design Championship Racing Bicycle Frame', MSCWorld, pages 12 to 14, Volume 5, Number 3, November 1996, USA.
   
5. Priestly, D. 'Will the 'Superbike' be the Catalyst for an Aussie Made Revival?' Bicycle Industry News, page 29, September 1994.
   
6. Thompson, L. and McLean, B. 'Super Roo Bicycle', Institution of Engineers Australia, Victorian Division, Engineering Excellence Awards, Paper, September 1995, RMIT.
   
7. Thompson, L.A.'Bicycle Frame', Patent PCT/AU95/00444, September 1995.
   
8. Vaughan, R. 'Australia Dominates Worlds', Bicycling Australia, pages 44 to 45, November 1995, Australia.