A Swiss company has rebuilt a main line steam locomotive in an experiment to assess the viability of a marriage between the earliest and the latest traction technology

Felix Schmid MSc is Programme Director at the Advanced Railway Research Centre at the University of Sheffield, and Thomas Schmid is with ZKB in Zürich

LATER THIS YEAR, passengers on the Nostalgie Orient Express excursion train in Switzerland and Austria will be the first to experience revenue operations with a main line steam loco rebuilt to the most modern specifications. The loco is a former German Class 52 Kriegslok re-engineered by Sulzer Winpro (formerly SLM).

With most railway companies abandoning steam traction over the past 50 years for economic, environmental and image reasons, recent attempts to improve steam loco efficiency have largely gone unnoticed.

Steam traction became discredited because the availability of cheap coal reduced the economic incentive to improve thermal efficiency. But from a systems perspective there are other benefits: low first cost, limited skill requirements, and a high starting tractive effort. Whereas the output of diesel locos is limited by the amount of heat which can be dissipated by the cooling circuit, steam engines can supply high peak loads for short bursts, thanks to the ability to harness energy stored as heat.

In recent years, steam locomotives have generally only been regarded as viable for tourist railways. Yet even in this application traditional coal firing is becoming less attractive because of environmental concerns. In some cases it is proving uneconomic to maintain antique locomotives to a standard where they can perform reliably.

Rack loco pioneers

Over the past decade, SLM has successfully developed a modern steam loco for narrow gauge rack-and-pinion mountain lines in Switzerland and Austria. Three were supplied to the Brienz-Rothorn Railway, one to Glion-Rochers de Naye and four to the Schafbergbahn. All are equipped for driver-only operation and have improved steam passages, Lempor exhausts, interchangeable parts and an electric pre-heating coil. The Swiss units are of a relatively basic design, while the Schafberg engines have an acoustically-optimised chimney.

A newly-developed single burner offers significant reductions in terms of the CO, NOX and SO2 emissions compared to a diesel locomotive on a similar operating cycle. Energy efficiency is also good in mountain railway applications, because the burner can be turned off during the descent. This also minimises the potentially higher CO2 emissions from the steam engine. Other benefits include reduced staffing and maintenance costs.

Main line trials

The next step was to ascertain whether similar benefits were achievable with a main line loco. This led to the decision to convert a relatively modern high-power steam loco in the form of a Class 52 2-10-0 built in France in 1943. This had already been rebuilt in the former East Germany in 1962. Following total re-engineering by Winpro, it ran its first full-power trial on December 28 1998.

Converted to run on diesel fuel, the loco has a value-engineered Lempor exhaust. The firebox, boiler and cylinders have been insulated to increase thermal efficiency. The burner design from the rack locos has been adopted as a pilot burner, and it is now possible to maintain working pressure throughout the night using just this pilot. Even in a closed building there have been no problems with poor air quality. Good insulation has minimised thermal losses during part load, coasting and idling, which form between 20 and 80% of a typical operating cycle.

Axles, coupling and drive rods have all been converted to roller bearings. At the same time major changes have been made to the Walschaerts valve motion to reduce the reciprocating mass, with a view to increasing the service speed from 80 to 100 km/h. The motion has been enhanced by the addition of counter pressure braking.

Calculations show that the indicated power will rise to 2200 kW from the 1700 kW measured two years ago before the start of conversion. Measurements during the proving trials are expected to reveal substantial efficiency improvements.

Winpro's next project is to convert an American-designed Class 141R locomotive built for French National Railways to oil firing and driver-only operation. This will also have full insulation and the steam injector will be replaced by an electric water pump. Electronic burner controls will not be introduced, but the controls will be modified to ease the task of the driver. As with the Class 52, it will have German and Swiss inductive train control receivers.

Winpro is discussing with several potential customers a new build of between 5 and 10 rack locos at a cost of around SFr2m each. They will have some modifications to reflect experience with the first series.

  • CAPTION: At the head of a 600 tonne test train, re-engineered Class 52 pauses at Sulgen between Winterthur and Romanshorn; there is no visible smoke. The loco is due to enter commercial service this month hauling the Nostalgie Orient Express