Composite Engineering carbon fibre component design and engineering

Grant assisted project

Recumbent cycle chassis

Project established the viability of manufacturing a recumbent cycle carbon fibre composite chassis.

Cheshire Cycle Components Ltd manufactures the Windcheetah recumbent cycle, this was originally designed by Mike Burrows, the designer behind the superbike that helped Chris Boardman win Olympic gold in 1992.

Robert Dixon's company has received a Millennium product award and a Windcheetah is currently on display at the Museum of Modern Art in New York.

The cycle is hand made resulting in a lengthy production process. The cruciform frame is currently a bonded assembly, comprising machined aluminium castings and either aluminium or carbon fibre tubes. Of particular note are the machined castings as they involve both a lengthy production process and have to be commissioned in large batches tying up working capital.

Robert contacted us as he was interested in the possibility of manufacturing the frame from carbon fibre composites as apposed to the combination of aluminium/carbon fibre tubes and aluminium castings.

Following detailed consultation with Robert it was clear that there was the potential to manufacture the frame as a single piece molding and that this presented an excellent opportunity to develop a frame for the Windcheetah that could employ advanced composite materials and manufacturing processes.

We carried out the following studies and project work on Robert's behalf.


Product and Process review

During this phase of the project we were asked by Robert to develop a concept model and to report on the manufacturing technologies that could be adopted to produce the chassis.

The report involved the following scope of work.

  • The development of a 3D CAD chassis model
  • The design and development of a baseline construction specification for the chassis
  • Manufacturing scenarios were developed and described employing the following manufacturing technologies:
    • Moulding the frame from hand laid up carbon fibre prepregs
    • Dry carbon fabric and a resin infusion process
    • Carbon fibre with a thermoplastic matrix
  • Costing's were developed to illustrate the level of investment that would be required to optimise each process
  • Additionally costs were developed for chassis produced from each manufacturing process

In conclusion the report illustrated that a chassis developed from advanced composite manufacturing technology presented a very interesting opportunity, not only did it have the potential to increase the performance of the cycle, it would considerably reduce the time to produce frames and dramatically reduce part inventory/stock levels.


Feasibility Study

Following on from the above study a manufacturing technology was chosen and we were asked to carry out a feasibility study to provide Robert with a report that enabled him to assess both the processes involved and the necessary costs of putting a carbon fibre Windcheetah chassis into low volume production.

Initially a detailed analysis of the current chassis was carried out. The main part of the existing chassis is assembled from six CNC machined LM25 heat treated aluminium castings and four tubes that are either produced from aluminium or carbon fibre depending on the particular model of Windcheetah specified, figure 1. The chassis is hand built and final assembly takes place in a bench mounted jig, this assembly is then bonded together with high performance structural adhesive.

Windcheetah components

Windcheetah aluminium chassis components

A concept chassis has been developed to enable the production of a lightweight structure, not only as a weight saving exercise as the vehicle being human powered is very sensitive to such issues, but one that also incorporates as many of the component parts of the existing chassis as possible in an effort to offset the higher costs associated with carbon fibre construction.

The features this concept will offer are summarised as follows:

  • A lighter chassis
  • One piece moulding will replace numerous components
  • Manufacturing process will provide for near identical chassis’s
  • Design and construction will reduce critical bonded joints
  • Carbon chassis will update the model line and provide current technology
  • Chassis’s could be supplied on a ‘Just in time’ basis
  • Develop further the Windcheetah brand and provide added value

A detailed step by step manufacturing process was developed together with 3D CAD models of the various components and necessary moulds and tooling. Additionally 2D CAD detailed engineering drawings were produced and these were subsequently supplied to several sub-contractors to enable detailed quotations to be received and subsequently analysed.


Conclusion

This study illustrated that it was technically feasible to produce carbon fibre chassis’s for the Windcheetah at a commercially attractive price point.

The potential to further develop the Windcheetah brand with the introduction of a carbon fibre chassis is significant and this option is currently being considered for an ultra high performance model.


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