Braided frame keeps very light rail on track

A recyclable, extremely lightweight vehicle frame for Very Light Rail (VLR) has been developed in the UK.

Image: University of Warwick

The frame, which is weaved, or braided, from carbon fibre composites into a series of tubes that can be easily fitted together, has been designed by researchers at WMG at the University of Warwick, alongside composite components company Far and Stratford upon Avon-based Transport Design International.

The prototype, which can be easily assembled using adhesive and simple welding, will allow VLR services to carry more passengers, while reducing the amount of energy needed to propel the vehicle.

The design will also reduce the weight stress the vehicle places on its rails and road surface.

The demonstrator consists of an underlying tubular spaceframe chassis. If any one of the tubes, or beams, used to construct the frame is damaged through accidental impact it can simply be removed and replaced with a new one.

What’s more, the thermoplastic material used to build the beams is recyclable, according to David Goodwin, engineering manager at Far.

Image: University of Warwick

“With composites you can save a lot of weight, which is obviously appealing for the operation of the car, but with traditional composites at the end of the car’s life it is simply placed in landfill, which is not ideal,” said Goodwin. “With this [design] there is a route to recycle the car body when it eventually goes out of service, or if alternatively it suffers an impact and part of it has to be repaired and replaced,” he said.

Although each beam used to build the demonstrator has the same diameter outside, the wall thickness varies depending on where on the chassis it will be placed, in order to meet the specific performance needs of that particular section of the frame.

As well as keeping tooling costs low, this means that all of the joins can be standardised.

The braiding process used to produce the beams is highly automated, with rates of over a mile a day of braided tubing.

The process also allows a wide range of materials to be used, including fibres such as carbon, glass and aramid, and thermoplastics such as Polypropylene and Polyether ether ketone (PEEK).