Repoint: A way out of the perfect storm

Source: RTM Aug/Sept 2018

The Repoint project was originally created to examine capacity constraints at junctions. But fast-forward seven years and the radical scheme has completely changed every aspect of the track switch as we know it. Sam Bemment, senior research and development engineer at Loughborough University’s Control Systems Research Group (pictured), talks us through the latest developments as the team prepares for the first demonstration in December.

Back in March 2011, Loughborough University initiated the Repoint project in response to a call from Network Rail, RSSB and the Engineering and Physical Sciences Research Council to examine capacity constraints at junctions. The Loughborough team brought a range of expertise from rail, automotive, aviation and control systems, but were purposefully not ‘points experts’ – a conscious decision to enable fresh ideas and insight. I was subsequently recruited, having previously worked at Network Rail on the points condition monitoring aspects of the Intelligent Infrastructure project.

Whilst the initial call targeted capacity improvements, we soon began examining all aspects of existing designs. For instance, I personally sifted just under 40,000 points failure log entries to discern what was failing and when – several years of life I will never get back! We assembled a cross-disciplinary industrial panel to discuss potential improvements to the system, including maintainability and adjustment aspects.

The track switch has changed little since it was first patented in the 1830s. True, the actuation mechanism has evolved from muscle and levers to hydraulic and electromechanical, but fundamentally we are still dragging steel across cast iron and pinning it in place – and, reliability-wise, just hoping for the best. Put simply, Repoint found that many advances in engineering and technology over the previous 100 years – in signalling and other industries – had simply not been applied to points. It seemed as though the rail industry had learned to manage the status quo and its known weaknesses, paying heftily for the privilege. At the time, points were the lowest-performing fixed asset on NR infrastructure with the highest incurred performance fines. Network Rail was under pressure to increase the number of train paths, eating into traditional maintenance windows. Essentially, points failures were too common, their impact too high, and their prevention too time-consuming and costly for a railway under capacity and cost pressures. Coupled to the (then) recent memories of Potters Bar and Greyrigg, it was the perfect storm.

Eyes on the prize

Over time the project morphed from targeting capacity alone towards step changes in RAMS performance and whole-life cost, noting there is, of course, a clear relationship between asset reliability/availability and network capacity. We were chasing a much bigger prize than adding a few years to an MTBF: we wanted to get as close to ‘never fail’ and ‘never maintain’ as possible. We believed there had to be a better way.

Our answer revolved around redundancy and LRU (line-replaceable unit) maintenance. Not new concepts, of course – indeed, SSI was a key pioneer of both back in the 80s. But no-one had yet managed to apply such approaches to points. We proposed a conceptual solution which changed every aspect of the track switch as we know it – control, detection, actuation, the track elements, the motion path, rail section, maintenance, everything. ‘Repoint’ – RE-engineered and REdundantly engineered points.

Please bear in mind that our brief in that initial work was to be as radical as possible in our suggestions for change. So, extra radical we were, and I dare say when Repoint was unveiled it upset and delighted people in equal measure! One of the big changes was the proposed use of a stub switch arrangement, promptly rejected by some of the track crowd with abject terror in their eyes. Whilst we still believe the stub switch has numerous advantages over traditional long, planed-down switch rails, we later dropped this part of the concept, terming the remaining design ‘Repoint Light.’ The signalling crowd, long holding a reputation for conservatism, have embraced the concept with open arms, stating on record on numerous occasions that Repoint Light offers to eliminate the last major single point of failure in the signalling system – POE.

Key to the concept is the idea of passive locking, which enables, for the first time, the use of multiple, redundant actuators on the same point end. Unlike other machines, Repoint designs lift the switch rails out of a recess before moving them across and then dropping them in a corresponding recess for the other route. The mechanism to achieve this is remarkably simple, low-cost, and constructed from off-the-shelf components. A motor has a protruding cam wheel, which rotates through 180° in each actuation. The prototype has triplicate actuators and locks in three bearers, with any single bearer able to operate the switch alone with no loss of performance. As the rails are lifted along their length, friction is eliminated and the load instead taken by a sealed bearing in the cam wheels, much reducing energy use. Maintenance is via simple replacement and return-to-base of the sealed motor/cam units after a given number of actuations. On production models, we aim for these to be swapped out in around two minutes.

Between 2014-15 and now, we have been working on perfecting, scaling up and prototyping key parts of the design, ready for its first demonstration in-track in December 2018. Over this time the team has grown, and we have brought on board key industrial partners with expertise in areas we knew we lacked: Motion Concepts in engineering design and analysis; Progress Rail Services in manufacturing and assembling bits of steel of a size that universities don’t normally get involved in; and DEG Signal, which is ensuring our shiny new bits are able to talk to with a wide range of signalling systems safely and reliably. Great Central Railway has been very flexible in arranging a test site, and throughout this period we have relied upon great support from our funders, RSSB, and our engineering steering group, with key personnel from Network Rail, TfL and RSSB.

Beyond December 2018, the switch panel will be in the ballast at Quorn station near Loughborough and available for demonstration to any interested parties.


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