Fierce 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.
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.
The engine drives an AC alternator, which is subsequently rectified to DC, controlled and then inverted through individual inverters, to power six axle-hung AC traction motors. The use of such motors on a diesel locomotive is a UK first and provides increased torque on starting, thanks both to the characteristics of an AC motor and improved traction management with each axle having individual creep control. The locomotive can deliver full power with two motors isolated as each one is rated at 746kN (1,000HP). Auxiliary machines are not dependant on engine speed as they also have AC motors fed from individual inverters. Having been used for over five years on thousands of GE locomotives, this is proven traction equipment.
To deliver an improved driver environment, careful attention was paid to sound proofing, vibration control, heating and air conditioning for the cab – all designed using ergonomic studies to ensure correct sightlines of the interface screens that provide all the information required by the driver. There are no cab gauges. Handsets and space is provided for GSM-R equipment as well as space, cabling and power provision for ERTMS, for which the driver’s screens can be reconfigured. The locomotives are fitted with remote dial-up diagnostics to monitor performance and predict potential failures.
The crashworthiness challenge
To future-proof the design, European crashworthiness standards were used that demand double or treble the energy absorption of Railway Group Standards. Override crush boxes are therefore required, giving the locomotive its distinctive front end and adding about a metre in length. This had consequential loading gauge implications, as did the amount of on-board equipment, axle spacing to meet RA7 and the need to avoid buffer lock.
Designing the locomotive to UK loading gauge was thus a significant challenge and, in an early design, the buffer beam was 43mm foul of gauge. It had initially been considered that a gauge exception might be granted, but this proved not to be possible resulting in the locomotive being shortened by a further 300mm. Tim Shakerley considered this to be an enormous technical challenge that led to some sleepless nights. The solution included redesign of the bogie, the collision collapse area behind the buffer beam and affected the battery box design which complicated maintenance.
Production, testing and authorisation
Prior to finalising the design, Freightliner’s maintainers and drivers were flown to the USA to participate in the design integration process. Wooden mock-ups were constructed to ensure everything fitted together and help assembly line sequencing. Construction of the first two PowerHaul locomotives at GE’s Erie plant started in May 2009 and was completed two months later. Before shipping to the UK, they were subjected to over 170 tests – including ride, noise, gauge and electromagnetic compatibility – on the 4.5-mile 90mph test track adjacent to the plant. This enabled final modifications to be easily undertaken and left only dockside commissioning tests to be undertaken in the UK. Component testing was also undertaken, with the cooler group endurance-tested on a shaker rig whilst the engine was subjected to a simulated workload of seven years.
From the outset Freightliner involved industry stakeholders to secure timely authorisation for entry into service. This included discussions with the ORR, DfT and Network Rail before placing the locomotive order. The PowerHaul was the first major UK rolling stock project to negotiate the Interoperability and Safety Directives from start to finish and so required an independent Notified Body (NoBo) to confirm compliance with the relevant standards. Freightliner considered this to be a key role and, after careful selection, appointed Interfleet in September 2009. The company also provided technical support for the PowerHaul project which, to avoid compromising the independence of the NoBo, was a separate contract. As part of its NoBo role, Interfleet undertook a wheelset supplier qualification audit of GE as it had not previously supplied wheelsets to the UK market.
The effectiveness of Freightliner, GE and Interfleet’s approach to authorisation – and the support of Network Rail, ORR and the DfT – was demonstrated in December 2009 when service authorisation was secured within ten days of the technical file being submitted.
Entry into service
Although the first PowerHauls arrived at Newport docks in December 2009, Freightliner’s drivers had been driving them for some months, having been trained and certified competent in the USA as part of the strategy to ensure the fleet’s speedy introduction.
To get best use of the locomotives, they are either used to haul heavier trains or existing services over steeper but more direct routes. For example, if hauled by a Class 66, coal traffic between Avonmouth and Rugely power station would be limited to 1,054 tonnes if routed via the 1:47 gradient at Stourbridge. Consequently, 66s take a route that is 60 miles longer whereas a PowerHaul can haul 1,900 tonnes up this gradient at a balance speed of 16mph. Thus the class’ additional 400HP has almost doubled the train length as well as saving fuel and crew costs on the shorter route.
As with any new fleet there have been some teething problems. These include engine de-rating from false indication of crankcase over pressure or manifold air temperature, and high speed wheel slide. Solutions have been found to these problems with the aid of the remote diagnostic monitoring output. Tim Shakerley puts this in context by advising that the PowerHaul currently has 33% of issues that the 66 had at the same stage in its development cycle.
A triumph of partnership
With 11 locomotives in service, the PowerHaul is more than living up to its promise, with haulage performance exceeding simulation predictions. The delivery of such advanced locomotives from the drawing board in two years is an impressive achievement for the GE/Freightliner partnership, as is the effective authorisation into service for which Interfleet, Network Rail, ORR and DfT also deserve credit.
The PowerHaul partnership has proved to be a win-win for Freightliner and GE. It has given the former a locomotive that will expand its business whilst the latter has secured a firm foothold into the European locomotive market. In addition to the UK Class 70, it has signed an agreement with Turkish manufacturer Tulömas for the production of PowerHaul locos.
The PowerHaul has generated negative comment in the popular rail press for its appearance, but the last word should go to Peter Maybury, Freightliner’s CEO who, when visiting GE’s Erie plant, remarked that the locomotive has elegant solutions to the problems faced. Whatever is said about its looks, the PowerHaul’s engineering elegance is unquestionable.
This article is based on a presentation given by Tim Shakerley to the Railway Division of the Institution of Mechanical Engineers whose assistance is greatly appreciated.
For a design that has to fit in a restrictive loading gauge it seems odd that a large percentage of space is completely wasted by having two non functional walkways on either side of the locomotive. – These must account for ~20% (?) of the locomotive’s volume.
Also the three phase induction motors used are some of the least efficient types of motor (only switched reluctance are worse) – this doesn’t fit at all with the claims of increased efficiency.
Another curiosity is the bogies which appear to be identical in design (if not dimension) to the Adtranz/GE Blue Tiger locomotive from the late 1990s … it seems that GE has bolted together proven components without that much thought to making a bespoke design for the UK railways – I think the final “squeeze” to get the components in gauge, and the unexplained waste of space by employing a US style “hood unit” layout demonstrates this.
Really an uninspiring ‘make do’ design – nevertheless the attention cab comfort, and the increase power will be welcomed.
Also some of the figures quoted do not make sense – eg to haul 1900 metric tonnes up a 1:47 slope at 16mph (~7.15m/s) requires ~2833kW (ie exactly 3800HP)
This would mean a 100% efficient transmission with no energy used for any other purpose. Both GE and Powerhaul actually rate the engine at 3700HP.
Induction motor efficiency is typically in the high 80s and can as good as 95% in real world examples – but not 100%.
Thus the statement that “PowerHaul can haul 1,900 tonnes up this (1:47) gradient at a balance speed of 16mph” is based on a simplistic paper analysis and is false, and not the sort of thing one would expect from a reputable engineer. This is disappointing.
Similar overstated claims were made for the class 60 (in particular continuous tractive efforts that were impossible to achieve) – generally good engineering speaks for itself and does not require distortion of facts to state a case.
Another point of interest would be the price of these locomotives – as Freightliner has not revealed this I suspect it may be excessive, as it was for the class 60s.
Managers and engineers need to learn that there is more to locomotive design than putting a the biggest engine you can find on a frame – perhaps this time it will be different and further orders beyond those already obtained from freightliner and TCDD will be obtained – but I doubt it and am willing to take bets on it.
These ‘monsters’ generally please only their masters, and are soon consigned to history.