ONCE revolutionary, the steam engine is now the epitome of old-fashioned technology. But the motors of the industrial revolution have not run out of steam just yet. This week, in Winterthur, Switzerland, the most advanced large steam locomotive ever built is being tested at the Swiss Locomotive and Machine Works (SLM)—a division of a conglomerate called Sulzer. Although it looks like a conventional steam locomotive, SLM's engine incorporates a host of technological improvements that make it cleaner and more efficient than the Puffing Billies of old. As a result, it could give diesel engines a run for their money.
The godfather of the modern steam-engine movement is Livio Dante Porta, an Argentine engineer who realised, when steam engines started to be replaced by diesels in the 1950s, that there was still plenty of room for improvement in steam-engine design. He spent his career finding new ways to refine the performance of steam engines. He and his followers, who include Roger Waller, chief designer of the SLM locomotive, have travelled the world, restoring and modernising old engines, and trying to rekindle support for steam power.
The engine now being tested by SLM was originally built in Germany in 1942. It has been upgraded according to Mr Porta's principles, which improve performance in a number of ways. For a start, unlike conventional coal-fired steam engines, the new engine burns light oil. It also has an improved draft mechanism to supply the air for combustion. With coal-fired engines as much as half the coal is carried away by the air as it passes over the fuel, so the new engine is far more fuel-efficient. In addition, there is no need for a stoker to shovel the coal, and no danger of burning embers causing track-side fires.
Another improvement is the use of modern materials to insulate the boiler and the steam pipes. One result of this is that the boiler stays warm overnight and the engine can be brought to its operating temperature within 15 minutes in the morning, compared with three hours for a conventional steam engine. Combined with other improvements, including weight reductions made possible by the use of welded rather than cast-iron components, and the replacement of oil-lubricated bearings by modern roller bearings, the result is an engine 25% lighter, 36% more powerful, and consuming 41% less fuel than old-fashioned coal-fired engines.
But as well as outperforming conventional steam engines, the new one compares favourably with diesels, both economically and environmentally. According to SLM, modern steam locomotives cost around SFr2m ($1.5m) each to build from scratch—about the same as a diesel locomotive. Although they consume slightly more fuel, they are simpler to maintain and repair, making them especially suitable for use in poor countries. They last longer, too.
And they are also less smelly. Because they rely on external combustion (the burning of fuel at a constant rate outside the engine's cylinders, rather than explosively inside them), they produce only a fifth of the noxious emissions of diesels of comparable power. That is especially desirable in such applications as shunting, when locomotives spend 70% of their time idling, often in built-up areas in which pollution is particularly unwelcome.
The current tests involve measuring the power of a modernised locomotive by pitting it against two electric engines in a tug-of-war. Once testing is complete the engine, which belongs to a German railway company, will be used on the Orient Express. But according to SLM, tourism is by no means the only market for new steam locomotives. The company also has its eye on developing countries with extensive railway networks, such as India and China. Once the figures from this week's tests are in to prove its case, SLM hopes it will be full steam ahead.
This article appeared in the Science & technology section of the print edition under the headline "A blast from the past"