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32 | the rail engineer | may 2011


rolling stock & depots


a transatlantic partnership


David Shirres writer


F


ierce competition is driving efficiency through the rail freight business. But it’s


a true success story. Between 1995 and 2007 there was a 70% increase in tonne-miles of freight traffic, with Freightliner doubling its turnover during the same period. In 2007 the company decided that, to maintain this expansion, new diesel locomotives were needed. Although its existing Class 66 fleet is reliable and cost effective, the growth in rail traffic - and associated capacity challenges - drove the conclusion that a more powerful locomotive type was needed to haul heavier trains, reducing the speed differential with passenger services. As Class 66 technology is 20 years old, a new design also offered potential improvements in fuel consumption. Freightliner’s Engineering Director, Tim Shakerley, explains that the benchmark guide for this new locomotive’s performance was a pair of Class 86s, providing more than three times the horsepower of a 66. Judged on face value, this might seem unrealistic. However achieving this benchmark does not need so much power as, at low speeds, power


is limited by adhesion and locomotives only operate at full throttle for part of their journey. Hence simulations were used to determine the tractive effort/speed curve that broadly met the benchmark. This could be delivered with a locomotive of 3,700HP with excellent adhesion control. An example simulation revealed that, from a standing start, such a locomotive hauling 1,200 tonnes up the 1:75 gradient at Shap would be a mile ahead of a Class 66 after ten minutes.


The search for compact power For its new locomotive, Freightliner needed a diesel engine 12% more powerful that its 3,300HP Class 66, compliant with the UK’s limited gauge and axle weight constraints. This proved difficult as such engines are not available off the shelf. The company’s discussions with General Electric (GE) did, however, prove fruitful. GE is the world’s largest manufacturer of diesel locomotives, at its peak producing 1,000 per annum, and was keen to expand its European market by developing suitable locos. But it needed a launch customer. This resulted in Freightliner and GE signing a partnership agreement in November 2007 for the development and production of 30 PowerHaul diesel locomotives, classified as the Class 70 in the UK. The PowerHaul locomotive was made possible by GE’s development of the compact Jenbacher engine with its high power:weight ratio. Originally a V8 engine used on Austrian Railways, it was acquired by GE Energy and converted to natural gas. Large numbers were produced for static power generation. GE’s PowerHaul engine is a


redesign, taking it from gas to diesel using proven technology from its GEVO engine - of which the company generally produces 2,000 each year for use in thousands of its Evolution locos in the USA, China, Kazakhstan, Australia and Brazil. This produced the 3,686HP PowerHaul P616 V16 engine with its twin turbochargers and very high pressure common fuel rail. A comparison table reveals how a


locomotive with the PowerHaul engine can meet UK gauge and axle weight constraints. One reason for this is its 1,500rpm speed, although this may present a maintenance penalty compared with the 900rpm of the Class 66 engine.


Engine comparison GEVO V12 PowerHaul


P616 V16


Power Weight


Power:weight ratio


Height Length


Engine speed


4,504HP (3,360kW)


19,500kg


231HP per metric tonne


3,686HP (2,750kW)


13,100kg


281HP per metric tonne


2.68 metres 2.42 metres 4.20 metres 3.84 metres 1,050 rpm 1,500 rpm


The locomotive design In addition to the power requirement,


Freightliner required a fuel efficient locomotive with low emissions, RA7 route availability, a future-proof design meeting foreseeable standards, good driver environment as well as excellent availability and reliability. The PowerHaul locomotive meets EU stage IIIa emissions standards and is fuel efficient, giving typically 10% savings compared with Freightliner’s current fleet. However these are not solely due to the P616 engine. Fuel consumption is also reduced by a blended dynamic brake that provides power for auxiliary loads and an auxiliary power unit that, when the engine is shut down, fulfils demands such as cab heating and maintains engine temperature in a state of readiness for restarting.


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