LEAF Composite Bogie

Conventional metal bogies are the second heaviest component of a metro train (after the car body). They contribute to higher energy for operation and can limit passenger capacity or options for new technology such as onboard energy storage. Bogies are critical for the safe operation of the train providing dynamic stability, suspension, and traction and braking effort, but traditional bogies can suffer from cracking as the metal fatigues over the life of the bogie. The challenge is to design a better bogie that reduces weight and extends the bogie life by eliminating metal fatigue without compromising safety or performance.

The LEAF: Bogie uses an innovative epoxy-carbon fibre structure with high strength-to-weight ratio to reduce weight. The structure includes a transverse bolster and dual cantilever springs on either side of the bogie. Epoxy-carbon fibre has exceptional fatigue strength and has been designed so materials are not subjected to loads that would cause fatigue. The carbon fibre composite structure will not crack under normal use. Cantilevered carbon-fibre springs double up as both the structure and primary suspension system. They replace the structural arms and steel spring suspension on a conventional bogie, reducing maintainable parts and improving weight savings.

The bogie weight is reduced by over 1 tonne per bogie – equivalent to 32 passengers per car. This saving provides flexibility for the train owner to benefit from reduced energy and emissions, increase passenger capacity, and/or add new systems or technologies. The carbon fibre structure has a life of greater than 40 years, far exceeding metal bogies with typical lifetime of 25 years, providing energy savings for longer. As an added bonus, the cantilever springs reduce the unsprung mass (parts which connect to the track without any suspension) to its minimum, reducing overall wear on the wheels and track.

COMPOSITE SPRINGS: these carbon fibre springs are manufactured from over 100 layers of carbon-epoxy prepreg material, carefully layered and oriented to provide the correct strength and flexibility. Their manufacture required an innovative technique of heating and compressing in batches to achieve excellent overall consolidation of the composite material. INTEGRATED SENSING – the layered construction of the carbon fibre parts allows for the integration of strain sensors to monitor the bogie structural health and could be used detect track degradation as abnormal operating conditions. CUSTOMISATION – the bogie wheel-base, width and spring rate (flexibility) can be customised to suit the train or network conditions during design. This allows the bogie to be adapted to wide customer base. SAFETY – the bogie is designed in accordance with a diverse set of rail engineering standards from Australia, Europe, UK and US covering strength, crashworthiness, and fire performance. STABILITY –Central Queensland University’s Centre for Railway Engineering has undertaken dynamic analysis on the bogie and demonstrated that it is stable up to 160 km/h even in degraded modes of operation (e.g. with a flat airbag).