ABSTRACT
This paper reports the design and construction of a prototype cycle frame intended for sprint racing. Preliminary materials selection and detailed specification of composite ply lay up sequence were based on the results of computer-aided laminate analysis and on static tests on representative coupons. The frame design was based on the overall requirements of aerodynamics (but without detailed calculation), and the need for a low sideways area concentrated close to the rear wheel. An important design consideration was that the cycle should accept standard fittings (wheels, forks, etc.).
Initially, the bicycle was conceived as a “one off’. Moreover, the work was undertaken in the context of an undergraduate student project, so that very little funding was available for tooling. It was decided, therefore, to manufacture the frame by hand lay up on a foam core. This is necessarily a laborious process requiring hand finishing, but is a low risk route, allowing continual monitoring of quality. Wet lay up (dry fabric and liquid resin) was used, and vacuum bag processing gave good laminate consolidation. Aluminium bottom bracket shell and rear drop-outs, and carbon fibre tubes for the head tube and seat tube, were bonded to the foam core and integrally laminated in the frame.
The finished frame was subjected to a series of static tests to verify its stiffness. These included vertical compliance, seat tube bending and overall torsional stiffness. The results were “benchmarked” against two commercial frames and found to be of satisfactory performance. A detailed finite element model was under development at the time of writing this paper.
A complete bicycle was assembled and raced by a member of the National Team of Greece in the 1994 World Championships. The rider succeeded in setting a new national record in the sprint event. Since then a number of bikes made for riders of national teams of Greece, Italy, Russia, Estonia and Latvia.
The paper also considers the manufacturing options for series production of cycle frames using more advanced processing technology such as resin transfer moulding (RTM). Further design studies are in progress on alternative raw materials with the aim of producing a 1 kg road racing frame.
