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IMechE goes Loco

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Developing young engineers is a key role of the Institution of Mechanical Engineers (IMechE). Since 1999, its Automobile Division has being doing so through the Formula Student Challenge in which teams design, construct and drive a racing car to specified criteria.

Not to be outdone, this year the Institution’s Railway Division held its first Railway Challenge which replaces the racing car with a 10 and a quarter gauge miniature locomotive. While not as outwardly sexy as a racing car, the competing teams used much ingenuity, worked hard and took great pride in their creations. These included the first locomotive built at Derby Locomotive Works for 45 years, a hydrogen powered locomotive and one with a mechanical spring drive.

Setting the Standard

The main aim of the IMechE Railway Challenge is to allow teams of engineering students studying at a UK university or apprentices working in industry to compete against each other to design and manufacture a miniature railway locomotive in accordance with a set of rules. Teams would be judged on a technical presentation and on a series of performance trials.

The Institution’s Simon Iwnicki, otherwise professor of railway engineering at Manchester Metropolitan University, first thought of the idea in 2010. Since then he has been developing the challenge’s concept and its supporting rules and technical specifications. Points are scored in five categories. Three of these are performance based: Energy Storage (250 points), Traction (150) and Ride Comfort (150). Points are also awarded for design philosophy (100) and business case (100) after the team’s presentation. The energy storage challenge requires energy stored during retardation to be available for traction power, and Simon gave this the highest weighting to drive innovation.

Tim Poole, who normally works on the sub-surface upgrade project for London Underground, produced the technical specification. This included systems assurance, performance requirements, locomotive structure and vehicle suspension. Specific requirements include refuelling in 90 seconds, 95% of materials being recyclable, remote operation from the trailing load, and the preparation of detailed drawings and maintenance manuals. Tim was impressed by the range of technologies used which he felt demonstrated that the specification has met its aim of being performance driven without constraining the team’s imagination.

In this first year, the competition would be limited to four teams. Two were from universities – Birmingham and Manchester Metropolitan, one from industry – Interfleet, and an Independent team from Derby.

The Stapleford trials

In a miniature recreation of the Rainhill trials, the competition was held on 1st July at the Stapleford Miniature Railway near Melton Mowbray. Unlike Rainhill, no one was killed although the railway did have Emma Peel tied to its tracks in a 1965 episode of The Avengers.

Stapleford was chosen because it has a 1 in 80 gradient, a central location and is not usually being open to the public. It was opened in 1958 when the Second Lord Gretton was looking for an attraction for his stately house and grounds. It proved popular and was steadily extended to its current 2 mile track layout. By the 1960s there were even 45ft long scale model liners on the adjacent lake.

After the death of its founder in 1982, the railway was mothballed. In 1992 Lady Gretton agreed to the formation of Friends of the Stapleford Miniature Railway (FSMR) to restore and operate the railway. In 1995 FSMR was able to hold its first open day, and has done so every year since then.

Innovation in miniature

Each team’s presentation of its design concept and business case provided an insight into its thinking and demonstrated how the specification had driven design. For energy storage, both Interfleet and Manchester had used supercapacitors with their rapid charge and discharge. The Manchester team had also used a coil spring which wound up at low speed when electrical regeneration is less effective. In addition, they had also designed their locomotive around the ride specification by incorporating an adjustable radial arm suspension into its frame.

All locomotives were powered by standard petrol generator sets except for one. This was Birmingham’s innovative use of a fuel cell powered by hydrogen stored in a metal hydride tank, an expensive component that stores 6,000 litres at low pressure. Although the fuel cell’s output was only 1.1 kW (compared with Interfleet’s 5kVa generator) it continually charged batteries that could deliver 4kW. Birmingham also developed a bespoke software control system with a wireless link for remote control by tablet. In a reflection of a certain real world project, it was difficult to see the screen in bright sunlight.

It was not all innovation, however, as the locomotives incorporated much conventional railway engineering with the design packs containing calculations for body frames, suspension and braking systems. To meet the business case requirement, production costs need to be minimised and in this the Independent team was successful with its entry costing £2,000, a fraction of the others.

And the winner is…

After a day of much running on the Stapleford track with a travelling judge in tow, together with presentations given to the judges. Interfleet’s graduates won the competition with a locomotive manufactured at the Roundhouse in Derby. Second, third and fourth places went respectively to Manchester Metropolitan University, Birmingham University and the Independents.

A key factor in Interfleet’s win was their locomotive being the only one tested on a miniature railway beforehand, so it was the only one that “worked out of the box” during the previous day’s testing. Other locomotives had problems with electronics and chain drives, one even required rescue by Stapleford’s “Thunderbird” locomotive.

Stephen Head, Interfleet’s team leader, felt this team had the right mix between simplicity and innovation, that energy storage was the most difficult part of the challenge and the best part was seeing the locomotive move for the first time. This comment was echoed by the Birmingham and Manchester teams, although they had different views about the most difficult aspect. For Birmingham’s Stephen Kent this was managing suppliers, deciding when to fix design and the chain tension system.

Manchester’s David Crosbee considered the hardest part to be the control system and filtering out the petrol generator spikes. This was a real issue for the independent team whose Michael Heaton wanted to show that the challenge could be met at minimal cost. His small team of four had produced the locomotive in his garage but had not tested it. Unfortunately, its diodes burnt out during the testing, following which the team spent hours installing heavier current circuitry, a job that was only just complete before their test. Sadly, after the locomotive started to haul its load, the electronics burnt out again.

Challenges for the future

Although this year’s challenge was very much a pilot, all concerned felt it was a great event. Its success was evident from the enthusiasm of everyone concerned. The general view was that everything had gone well, in no small part thanks to the Friends of the Stapleford Miniature Railway. The pilot competition did provide some lessons, one of which was the need for testing before the competition. Another concerned mass and rolling resistance not scaling down equally, so Stapleford’s 1 in 80 gradient is not as formidable as one on a full sized railway. As a result, when applied the regenerative braking stopped the miniature train instead of just retarding it.

Bridget Eickhoff, IMechE Railway Division Chairman, expects there to be a larger number of entries next year and is confident that the challenge will cope with this. She was extremely impressed by the efforts of all of the teams, with their different and innovative designs from the same specification. She wondered how long it will be before innovations in this and future challenges appear on the real railway.

In designing and building their own locomotives, the young engineers faced many real world operational, design and project management problems which provided a great learning experience. As Bridget commented, this also encouraged innovative thinking. For these reasons, future UK railways will no doubt benefit greatly from the Institution’s Railway Challenge.


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