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Imagine taking a steam locomotive design from the early 20th century and modernising it using 21st-century engineering processes and technology in a short space of time.
Sound like fun? The engineers that volunteer their time for the 5AT (Class Five Advanced Technology) project have spent the past decade designing their “second generation” steam locomotive. Now they’re set to build the first newly designed steam locomotive in the UK since the 1950s.
Engineers on the project call heritage steam locomotives, like the recent high-profile Tornado, “first generation”. John Hind, chair of 5AT’s engineering planning working party, explains how the 5AT design is different: “A second-generation design applies basic thermodynamic principles and uses modern technology. You are looking for the highest practical boiler pressure, the highest steam temperatures, and minimal losses throughout the system.”
The 5AT project says that the first demonstrator locomotive will cost £10.5 million to develop in around four years. The originator of the 5AT concept, David Wardale, completed an engineering feasibility study earlier this year, and produced a 760-page document containing calculations that define the characteristics of the locomotive. All of the work can be found online.
The 5AT takes its dimensions from the BR standard Class Five, last built in the 1950s, because at this size the designers know it will fit onto the current network. The locomotive is 85% more efficient than its 20th-century ancestor, which gives it a range of 380 miles, substantially more than its predecessor. It is designed for a continuous operating speed of 113mph, though initially it will be limited to 75mph. The performance increases are made possible by lots of improvements all over the locomotive, and by a greater attention to design detail, says Hind.
For example, the new design’s “thermodynamic heart” is a Lempor exhaust ejector to minimise cylinder backpressure. A lot of the additions on the locomotive will also be familiar to engineers with power station experience, says Hind. There is a feedwater heater, an economiser in the boiler, and a combustion air heater, which together with improved insulation raise boiler efficiency. It will have diesel-engine valve ring and liner technology on the pistons and the piston valves, air sanding to improve adhesion, and be designed for modern train control systems. “Every component is redesigned using 21st-century tools – CAD, FEA, CFD etc – which are a representation of engineering progress over the last 60 years,” says Hind. “Just as automotive and aerospace do, we can build the locomotive digitally before we commit to metal.”
The use of CAD in the 5AT design process highlights the many advantages that mechanical engineers today take for granted: modifying components quickly; simulation tools such as finite element analysis and computational fluid dynamics; rapid prototyping; the automatic calculation of weight of components and automatic section calculations – all improve the 5AT’s design beyond that of its 20th-century forebear.
Concern over where components will come from is brushed aside by Hind, who says that the loco will be built with castings and forgings of materials commonplace in the 1950s which are still used today.
But is there any point to developing a steam locomotive for the 21st century? Hind’s answer is twofold. The group believes there is an opportunity for the 5AT in the “niche” steam locomotive market. Around 300 trains a year in the UK are hauled by heritage steam locomotives. In today’s congested rail network the 5AT would have the edge over such locomotives, which have to stop for water more frequently, and would be able to reach popular destinations such as York or Bath from London without stopping. And in some industrial uses, such as hauling coal, the group estimates that it would work out cheaper to use a 5AT than a diesel locomotive.
Leaving aside any debate over the commercial merits of building a demonstrator, the more altruistic reason for the 5AT is to provide a link to past steam expertise and knowledge. Hind says: “The project trains a new generation of steam locomotive designers. The Tornado project showed to the wider public that you can manufacture it. The difference with the 5AT is that it designs and builds a second-generation steam locomotive.”
The project is now looking for investors and business partners.