Articulated Diesel Electric Locomotive

The Next Locomotive Evolution
By Gerald Truswell

What could possibly inspire a former locomotive driver, close to retirement, to spend thousands of dollars of his personal income to propose and patent the next step in the evolution of the diesel-electric traction?

Introduction

When a former locomotive driver, Brian Henderson, who was once employed by The Western Australian Government Railways (Westrail) and later by the Australian Railroad Group, left the industry in 2002, he thought that would put an end to the frustrations that a life on the footplate in a changing environment can bring. However Brian, a railwayman at heart, couldn’t shake the sense of frustration brought about by the inefficient use of motive power in Western Australia.

Brian writes “The genesis behind the concept probably started while I was on holiday in the USA in 1995. I was in Chicago and obtained permission to spend the day at the Burlington Northern’s yard and Loco depot at Galesburg, Illinios. Although I was aware that railroads such as Union Pacific had used "slugs" on the main line in days gone by, it was not until I saw one working at the Galesburg hump yard, that I saw their potential. In Western Australia, my employer, Westrail had a railway system that was generally flat terrain with a few short, sharp ruling grades.

A couple of examples are as follows:
---An up grain train from Narrogin to Kwinana will encounter the ruling grade of 1 in 52.5 (1.9%) on departure from Narrogin and a short 1 in 80 grade (1.25%) is encountered near Pingelly, some 40 kilometres north. From Pingelly, it is relatively easy going with 1 in 120 grades (0.84%) encountered for the remaining 300 kilometres to Kwinana.

---An up train travelling on the Midland Railway from Marchagee to Kwinana will encounter short grades of 1 in 67.5 (1.48%) between Watheroo and Coomberdale and the 1 in 55 ruling grade (1.82%) between Mogumber and Mooliabeenie. The grade then eases to 1 in 90 (1.11%) for the remainder of the journey to Kwinana.

Most grain trains on these two lines require two locomotives working in multiple. My thinking was "What a waste!" when the second locomotive is only required for about 10 kilometres of a 280 or 340 kilometre trip (4% and 3% respectively). Why not convert some of the written off locomotives stored at Forrestfield, into slugs. The second locomotive could then be left behind. This proposal was mentioned to Westrail management at the time, but no response was forthcoming. When I considered Westrail’s Goninan/GE "P" class locomotive, which had been de-rated from 2,237 kilowatt (3,000 hp) to 1,830 kilowatt (2,500 hp) to accommodate the 17 tonne axle load limitation required for operation on Westrail’s branch lines, I thought “Why not re-rate it to its maximum horse power and connect it permanently to a slug?” The result would be increased horsepower and additional tractive effort at minimal cost. But why stop there? If a larger more powerful power assembly could be placed on the locomotive frame, the additional weight could be spread over onto the body of the slug, making it an articulated locomotive. The more I pondered the concept, and the benefits to rail operators, the more enthusiastic I became. I found that there were other areas where the "ArticuLoco" articulated diesel-electric locomotive would be advantageous, such as up the torturous 8 kilometre long, 1 in 33 grade (3%) through the now de-energised Otira tunnel in New Zealand, which restricts the number of internal combustion engines that can be used on their coal trains. The birth of the "ArticuLoco" concept had begun.

So What Is An Articulated Locomotive?

Current locomotive designs are constrained by the maximum weight that the axle can exert upon the rail, gauge outline, curvature and line side restrictions that limit the physical space available on the locomotive frame for the locomotive components (eg. diesel engine, cooling system, blowers, air compressor, fuel tank, batteries, main generator, rectifiers, inverters, etc.).
By spreading the components listed above over an additional permanently coupled platform, the axle load, gauge outline, curvature and other line side limitations are easily achieved. The complexities of separating some components dictate that they remain on the same platform, however a practical spread would be:

Power Platform
Cab, diesel engine, main generator, auxiliary generation (eg. exciter, auxiliary generator, companion alternator) radiators and cooling system, traction motor blower, equipment blower (main generator).
Auxiliary Platform
Cab, rectifier (AC to DC), inverter (DC/AC), electrical cabinet, batteries, toilet, fuel tank, air compressor (electrically driven), brake rack, main reservoirs, traction motor blower (electrically driven), dynamic brake grids and cooling fans.

How does the articulated locomotive differ from the “Slug” concept that was popular in North America in the late 70’s and early 80’s? Well, the concept does not differ all that much, however the main difference is the utilisation of a high horsepower diesel engine, which ensures there is no unreasonable trade off between traction and speed. The slug + locomotive combination is strong on tractive effort, however spreading the main generator’s output over more traction motors resulted in a loss of speed (eg. the minimum continuous speed of a Westrail L class is 22 km/h, however when mated to a 6 axle slug, the tractive effort will double, but the minimum continuous speed halved 11 km/h), which makes such an option unviable for mainline operations. However the high tractive effort at low speed makes the use of slugs ideal for low speed applications such as yard shunting situations (very popular in the USA).

To ease the cost of adapting this new technology, existing rail operators can simply utilise frames, bogies, cabs, fuel tanks, main reservoirs, etc. of existing fuel guzzling locomotives as feedstock for auxiliary platforms and simply installing the modularised components. This option would restrict new construction costs to the power platform and auxiliary platform modules.

SD39 with 6-axle slug shunting Barstow Yard (Photo by author)

The concept is not limited to a set configuration and its use is completely dependant upon the type of train that it will be deployed on (ie. timetabled kW/tonne ratio trains versus heavy bulk haul trains). The concept includes, but is not limited to the following wheel arrangements:

(concept drawings developed from locomotive information images drawn by Michael Eby, which can be viewed at http://www.trainax.net/)

So by projecting beyond the physical constraints of the current locomotive design philosophies, Brian was able to come up with a concept that would not only enable railways constrained by axle load and gauge envelope limitations access to the advantages of the latest technologies, but it would also have tangible benefits for the existing heavy haul railways/railroads around the world.

Benefits Of The Articulated Locomotive Concept

Brian set about refining his concept to incorporate the latest advancements in locomotive technology coming from the two major locomotive manufacturers in the United States of America, such as 4,474 kilowatt (6,000 hp) diesel engines and AC traction, onto the multiple platform locomotive, which provides the following benefits:

Unit Reduction
Utilising ‘off the shelf’ 4,474 kilowatt (6,000 hp) diesel engines, manufactured by both GE and EMD, powering up to twelve AC traction motors equates to two 2,237 kilowatt Co-Co locomotives. The concept is not limited to 4,474 kilowatt (6,000 hp) with the only limitation being the adhesion weight / power per axle and the size of diesel engine itself. Potentially a single 6,562 kilowatt (8,800 hp) diesel engine powering twelve AC traction motors would currently provide the same traction as two GE ES44AC or EMD SD70ACe locomotives. As the articulated locomotive concept has a cab at each end, the width of the diesel engine is only constrained by the gauge outline of the railway as full width carbodies can be utilised instead of hood type layout with a walkway on each side of the engine.

Increased Payload
The use of AC traction increases the effective adhesion weight of the locomotive from around 30% (DC traction motors with wheel slip control systems) up to 36%. This equates to approximately 15% more trailing tonnage at maximum tractive effort, which is the objective for most heavy haul railways. [1]
AC also provides the additional benefit of reduced brake block wear on the rollingstock, due to the increased effectiveness of the dynamic braking with AC traction, particularly at low speed, which is particularly attractive when negotiating the steep gradients with numerous curves.

Increased Fuel Efficiency and A Reduction Of Greenhouse Gas Emissions
The use of a single 6,000 horsepower diesel engine halves the number of parasitic auxiliary equipment that must be powered (eg. air compressors, auxiliary alternators, exciters, equipment, alternator and traction motor blowers, etc), which reduces fuel usage and greenhouse gas emissions. Current estimates suggest that 2.7 kilograms of CO2 are emitted for every litre of diesel fuel oil burnt, therefore replacing two AN / NR class locomotives with a single 4,474 kilowatt (6,000 hp) locomotive would save approximately 50% (2 x 750 lts/hour N8 [power notch 8] versus 1 x 1,000 lts/hour N8) or 1.35 tonne/hour of CO2 in N8, however when the 4,474 kilowatt (6,000 hp) locomotive is combined with AC traction, the saving of CO2 per tonne hauled would increase to approximately 70% (refer load table in appendix 1), which makes the articulated locomotive extremely environmentally friendly locomotive indeed when compared to the DC locomotive.

Reduced Maintenance
The maintenance benefits of using AC traction, the use of a single diesel engine and halving the parasitic auxiliary equipment will significantly reduce maintenance costs when compared to the maintenance costs of two comparable locomotives.

Increased Range
Placing the fuel tank on the auxiliary platform away from the heavier items (eg. diesel engine and main generator) on the power platform provides the ability to utilise a larger fuel tank as the weight limitations are removed. It would, for example, be possible to carry sufficient quantity of fuel to operate between Kalgoorlie and Port Augusta, a distance of 1,682 kilometres and thus negate the need to refuel at Cook, which is the most expensive locomotive fuel in Australia.

Technology + Articulated Locomotive = Faster Train Times

Innovative Control Systems

It is imperative that the change in locomotive design proposed in this article is matched with advances in the locomotive control system technology whereby it is to match the characteristics of the locomotive (tractive effort versus speed) to each individual circumstance encountered when hauling trains along a specific route. For example, many locomotives are deployed hauling bulk commodity trains, which are typically loaded in one direction and empty in the other.

In the loaded direction, maximum tractive effort is required (ie. utilising every available traction motor and every available kilowatt), however in the empty direction speed is more important than tractive effort as the empty consist usually operates at a higher maximum speed due to the lower mass of the wagons. Current philosophy with Co-Co type locomotives is to take units ‘off line’, shut them down or utilise fuel saving features (if available), however running time is sacrificed due to the poor acceleration characteristics of the Co-Co configuration.

By utilising the locomotive’s control system, it would be possible to reconfigure the locomotive’s traction motors to best match the load being hauled to maximise the power per axle and thus the acceleration capability of the empty consist in a similar manner to the way that USA railroads deployed high powered Bo-Bo locomotives to high speed services in the 1970’s and 80’s. In effect, isolating four traction motors on a Co-Co + Co-Co articulated locomotive and spreading the full 4,474 kilowatt (6,000 hp) over the remaining traction motors would be akin to replacing two SD40’s on a loaded bulk commodity train with two GP40’s for the empty return move maximizing acceleration and thereby reducing running times, which in turn would result in further fuel savings.

Like many contemporary fuel saving features, all traction motors on the locomotive (including those isolated) would be deployed once dynamic braking is selected to provide maximum braking capacity.

Matching capability of the locomotive to the loads and grades would be possible by the operator inputting the load and grade data at points where they alter dramatically or, for a truly ‘Smart’ locomotive, the grade data could simply be altered by the locomotive based on where it is operating by the use of GPS technology in a similar fashion to the way radio frequencies are being selected automatically now to suit the area of operation.

Other Technological Initiatives

The multiple platforms of the articulated locomotive concept also lends itself to the introduction of other new technologies being contemplated, such as:

Storing power generated by the traction motors while the locomotive is regenerative braking downhill in battery packs for use when climbing the next hill or bank. The auxiliary platform provides the ideal location for the cumbersome battery packs; and

The multiple platforms also lend themselves to alternate power sources (eg. gas turbine, hydrogen fuel, fuel cells, etc) due to the ability of the power platform to take additional weight (particularly on the standard gauge options) and the capacity of auxiliary platform to accommodate the additional weight or bulk of alternative fuel or fuel cells.

Incentives

In Australia, the federal and various state governments have funding available for fuel saving technological developments that also reduce the green house gas emissions, which will go some of the way to offset the initial development costs of the articulated locomotive concept.

Potential Utilisation Of the Articulated Locomotive

As you would have ascertained from Brian’s comments in the introduction, the initial analysis of the concept was limited to the 1,067mm narrow gauge rail system in Western Australia and, encourage by the results, the scope was broadened to encompass, in order, 1,435mm branch line activity in New South Wales and lastly heavy haul railways found in the Pilbara and the United States of America. Fuel saving, unit reduction benefits were noted across all of these applications

1,067mm In Western Australia

The following comparisons were made with locomotives utilised on various sections of the W.A 1,067mm narrow gauge network:

DA and P class locomotives hauling loaded iron ore and grain trains on the 16 tonne axle load branch line from Mullewa to Geraldton up a ruling grade of 1 in 72.5 compared to two applications of the articulated locomotive.

Currently two consists are utilised to haul 3800 tonne, one hauled by a single P class locomotive while the other is hauled by two P class locomotives. As you can appreciate from the data provided in table above, slightly more ore can be conveyed by one articulated locomotive for a 17% fuel and green house gas emission saving plus 34% reduction in maintenance costs. The Co-Co + Bo-Bo is not as attractive as the Co-Co + Co-Co, but it would still deliver unit reduction and maintenance (ie. lower operating costs) savings in the event that the overall length of train consists on this line is restricted.

Another benefit immediately presented is the freeing up of one train pathway between Geraldton and Mullewa, which equates to additional capacity.

The Co-Co-Co option was not considered for this scenario due to the difficulty getting the weight inside the 16 tonne limitation on the centre bogie.

DB and S class locomotives hauling loaded coal trains from Collie to Brunswick Junction with a ruling grade of 1 in 80.

Three options are available for this scenario, which can increase the trailing load by 60%, 96% and 135% respectively coupled with both fuel, green house gas emission and maintenance savings.

All three options produce operational benefits in relation to increased trailing load while the Co-Co-Co option, with the increase in minimum continuous speed, would provide cycle time benefits.

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The following comparisons were made with locomotives utilised on various sections of the W.A 1,435mm Mainline network:

The first table compares the operation of the DL and NR locomotives operating on the inter capital mainline network across Australia against the Bo-Bo + Bo-Bo, Co-Co-Co, Co-Co + Bo-Bo and Co-Co + Co-Co articulated locomotives on the 1 in 40 grades prevalent throughout New South Wales on the north / south mainline between Brisbane, Sydney and Melbourne.

Once again, all four options provide varying levels of benefits such as increased trailing loads, fuel savings, greenhouse emissions reductions and maintenance cost reductions, however some of these come with the trade off of speed. In reality, the Bo-Bo + Bo-Bo and Co-Co-Co options would probably be the more attractive option for an intermodal application as the speed trade offs are negligible, while the Co-Co + Bo-Bo and Co-Co + Co-Co options would be more attractive to the heavy freight and bulk operators due to the significant increases in trailing loads.

The second table in New South Wales compares the operation of PN’s 90 class and QRN’s 5000 class locomotives against the Bo-Bo + Bo-Bo, Co-Co-Co, Co-Co + Bo-Bo and Co-Co + Co-Co articulated locomotives operating on loaded coal trains in New South Wales’ Hunter Valley 1 in 80 grades.

While the performance of all four articulated options exceed the 90 class in relation to trailing loads, fuel savings, greenhouse emissions reductions and maintenance cost reductions, the 5000 class does return very slightly better fuel / greenhouse gas emission figures than the Bo-Bo + Bo-Bo option, however the latter does return increased trailing load and lower maintenance costs. The trade off for the higher trailing loads is a reduction in speed, however the increased trailing loads more than compensate.

As a comparison with the current operations:

One Co-Co + Bo-Bo plus a 90 class will haul the same load as a 90/90/82 combination while delivering reduced fuel consumption, greenhouse emissions reductions and maintenance costs;
One Co-Co + Co-Co plus a 90 class will haul the same load as a 90/90/90 combination while delivering reduced fuel consumption, greenhouse emissions reductions and maintenance costs;
One Co-Co + Bo-Bo plus a 5000 class will nearly haul the same load as a 90/90/90 combination while delivering reduced fuel consumption, greenhouse emissions reductions and maintenance costs; and
One Co-Co + Co-Co will nearly haul the same load as a 5000/5000 combination while delivering significant fuel consumption, greenhouse emissions reductions and maintenance costs reductions.

Pilbara Heavy Haul Railway Between Tom Price and Dampier

When the articulated locomotive concept was first considered, it was thought that little benefit would accrue to the heavy haul railways found both in the Pilbara region of Western Australia and the United States of America, however analysis of the above data clearly demonstrates that both the Co-Co + Bo-Bo and Co-Co + Co-Co options provide both fuel consumption and greenhouse emissions reductions.

European Rail Systems

One of the major applications for the articulated locomotive would be in the European rail systems where gauge and weight restrictions have made it impossible to incorporate all of the contemporary cost saving features of the modern diesel-electric locomotive, such as dynamic brakes and AC traction. Utilising the articulated locomotive concept would enable operators throughout Europe to incorporate all of the latest technology as well as dramatically increase the hauling capacity and allow the economies of scale that are available to the rail systems in the US and Australia (ie. longer and heavier trains).

Summary
By changing the layout of the diesel-electric locomotive it is possible for locomotive technology to become more fuel efficient and environmentally friendly.

While these are attractive benefits, the main advantage of the concept is clearly unit reduction with the articulated locomotive set to revolutionise rail traction. There are a lot of older diesel-electric locomotives in the industry worldwide and many rail operators will not commit to replace their fleets unless there are real tangible benefits that have a positive return to their bottom line. As demonstrated, the articulated locomotive concept will deliver those benefits and a properly planned asset renewal program would see the older locomotives gradually replaced by the more efficient and environmentally friendly articulated locomotives.

Further Information

For further information on the articulated locomotive concept, please contact Brian or Gerry at email@articuloco.com

References

[1] AC versus DC locomotives, National Rail Corporation Ltd 2000

Articulated Diesel Electric Locomotive

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