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Steam Locomotion in the 21st Century

The Recent History of Steam Locomotive Development

New Steam from Switzerland
Dampflokomotiv und Maschinenfabrik AG - DLM

updated 8 February 2022

This page relates the re-entry of long-time locomotive manufacturer SLM into the steam business during the 1990's, and the subsequent formation of the new steam locomotive company DLM in 2000. DLM continues to actively pursue projects to modernize or build new steam locomotives.


Early in the 1990's, a former steam locomotive builder in Winterthur, Switzerland re-entered the business after a nearly 40 year absence. This was the Swiss Locomotive and Machine Works (SLM), at this time a division of Sulzer, a large Swiss manufacturing company and famous builder of diesel engines. SLM engineer Roger Waller was convinced at this time that there was a market for new steam locomotives, and he did research to back up his ideas. Waller had worked with Wardale in South Africa and was familiar with the work of L. D. Porta and the possibilities for truly modern steam locomotives. Several rack railways in Switzerland, the UK, and India still operated SLM-built steam locomotives and there at least appeared to be a market for spare parts. This was soon confirmed and production of some replacement parts was resumed to fill this need. Waller finally convinced Sulzer management that there was a market for new, improved steam locomotives, and he pursued this possibility. Eventually, this led to orders for new rack steam locomotives, incorporating Porta thermodynamic principles and modern construction techniques.

[New Swiss Steam]
This photo was taken by Martin Hawlisch photographed and published under the GFDL.

New Rack 0-4-2T for the Brienz Rothorn Bahn

SLM's greatest success was the construction of 8 new modernized rack steam locomotives 1990's in Switzerland for mountain tourist railways in Switzerland and Austria. While the engines replaced locos previously built in 1891 and 1933 by SLM, they were of completely new design incorporating Porta's principles, and using modern construction techniques and technology. Featuring welded boilers, roller bearings, modern drafting arrangements, light oil firing, extensive thermal insulation, and arranged for one-man operation, they have been very successful. The boilers are so well insulated that they will maintain a head of steam overnight, allowing the engine to leave its shed under its own power in the morning and attain full working temperature and pressure in only 10 to 15 minutes after lighting the fire. An interesting innovation on these engines is the provision of an electric boiler pre-heater. This is used to pre-heat the boilers after their monthly boiler wash to save fuel. The thermal efficiency of these locomotives is over 10%. The new SLM locomotives compared to the 1933 design SLM steamers as follows :
  • Service weight reduced 25 percent
  • Power increased 36 percent
  • Power-to-weight ratio increased 82 percent
  • Fuel consumption per trip reduced 41 percent
  • Fuel consumption per passenger trip reduced 61 percent
  • Maximum speed increased 56 percent

These locomotives have now been working successfully for about 30 years. 

For more information on the Brienz Rothorn Bahn, visit their website at

SLM 0-4-2RT

Rendering of 0-4-2RT by DLM


Grate Area 0.9 m2
Tubes, number 62
Tubes, dimensions 38 x 2.9 mm
Flues, number 15
Flues, dimensions 114.3 x 3.6 mm
Total evaporative surface 30 m2
Firebox 5.14 m2
Tubes 13.80 m2
Flues 10.92 m2
Superheater surface 13.23 m2
Boiler Pressure 16/18 bar
Oil firing System Sonvico/SLM-type
Fuel Extra light heating oil
(#2 heating oil)
Cylinders 2
Diameter 280 mm
Stroke 400 mm
Valve Gear Heusinger (=Walschaerts)
Gear ratio 2.3:1
Rigid wheelbase 2070 mm
Total wheelbase 2650 mm
Rack system Abt (Riggenbach)
Driving cogwheels 2 x 2 (2 x 1)
Cogs per driving wheel 15 (18)
Length over couplers 6260 mm
Maximum width 2200 mm
Service speeds on gradients  
1 in 4 12 km/h
1 in 4.55 13 km/h
1 in 5 14 km/h
Gauge 800 1000 mm
Carrying wheel diameter (worn/new) 637/649 693/705 mm
Pony wheel diameter (worn/new) 426/440 479/493 mm
Maximum height 3200 3230 mm
Weight, empty 13000 13300 kg
Water in boiler 1200 1200 kg
Water in side tanks 1300 1300 kg
Oil (545 l, 0.86 kg/l) 470 470 kg
Weight in full working order 15970 16270 kg

Sonvico DLM
                                Oil Burner System

Sonvico/DLM Oil Firing System Viewed from Above

This interesting photo, from a DLM brochure, shows the oil firing system first used on the new build rack steam locomotives built by SLM in the 1990's, and recently fitted by DLM to a 2-6-2T on the Puffing Billy Railway in Australia. This arrangement allows very efficient combustion of light oil (no. 2 or similar) under standing, part load, and full load conditions. The center burner is a pilot burner which stays lit at all times. The small piece of tubing above the burner is the steam feed to the pilot burner, used to atomize the fuel oil as it is injected into the firebox. This tube superheats the steam, allowing less steam to be used and more thoroughly vaporizing the oil for efficient combustion. The surrounding burners admit fuel oil to the firebox during operation and are also supplied with superheated steam from the larger tube above the pilot burner.

Porta with
                                DLM 52 8055

NG ("Next Generation") 52 8055
as modified for the Orient Express

Roger Waller in the cab and world-renowned steam designer L. D. Porta inspecting the motion work
Above photo courtesy Andreas Schwander

After the success of the new rack steam locomotives, Waller continued to research possibilities for building new or modernizing existing steam locomotives. A good candidate for an extensive rebuild was found on the Eisenbahnfreunde Zollernbahn EFZ. In late 1998, SLM completed the extensive modernization of 52 series German Kriegslokomotive 2-10-0 no. 8055 for use on the Orient Express in Europe. The locomotive was extensively tested prior to being modified so that the benefit of the modifications could be documented. Over 70 percent of the parts of the locomotive were replaced or modified. As a result of these modifications, the top speed of the engine was raised from 70 km/hr to 100 km/hr and the horsepower was increased from 1600 to 3000. The engine now burns light oil and features sealed roller bearings, a central lubrication system, light weight motion-work, and extensive thermal insulation. A side benefit of light oil firing in an external combustion engine (i.e.- steam) is very low exhaust emissions. This engine emits about 80 percent less toxic exhaust gases per kW than a state-of-the-art diesel. The modifications were performed to provide a steam locomotive which could keep tight schedules and "time windows" to be allowed to run on the main lines without causing interference with normal trains. Testing of the modified locomotive began in March 1999 and the locomotive pulled its first passenger trains in April 1999.

The locomotive suffered from some teething problems, but these difficulties were gradually solved. Unfortunately, after delivery to the EFZ, German railway inspectors disapproved certain features of axles on the modified engine (features which were allowed in Swtizerland) and it never operated as intended in Germany. During this time, SLM sold off its locomotive business and the steam department formed a new company called DLM (see below). After 2 years of sitting idle, 8055 was sold to DLM in late 2003 and returned to Switzerland. Since then, minor repairs were performed on the engine followed by test runs. In December 2003, the locomotive was placed on display together with the Orient Express in Zürich Hauptbahnhof. Test runs were successful and the locomotive pulled the train on mainlines at 80 km/h between express trains and fast electric commuter trains. Since then, the locomotive operated on the Swiss Orient Express trains (Nostalgie Istanbul Orient Express) which was re-introduced under the new management in 2004.  8055 has operated on many excursions since 2004 and is available for hire from DLM.

More information on NG 8055 is available at DLM's website:

Photos of the modernization of 52 8055 can be found here:

Specifications for 52 8055 (in German) can be found here:

Another likely customer for modern steam locomotives was the Nilgiri Mountain Railway in India. For several years in the late 1990's and early 2000's, Indian Railways indicated interest in purchasing new steam locomotives for both Nilgiri and the Darjeeling Himalaya Railway, and SLM pursued both these orders. Calculations showed new steam locomotives to be the most economically viable solution to the Nilgiri's motive power requirements, but an order proved illusive. Since then, news from India indicates that some of the Nilgiri locomotives were heavily rebuilt and some were converted to oil firing. Evenually, India's Golden Rock workshops built new locomotives (to the original SLM design) for the Nilgiri as well as new locomotives for the DHR. Unfortunately, neither of these designs appeared to include any modern features apart from all-welded boilers. hardly "modern steam".

About 10 to 15 steam projects total were under consideration at SLM during the 1990's. Calculations for steam in Russia, for example, showed that a natural gas fired steam locomotive would save an estimated 60 percent in fuel costs compared to diesels and 80 percent compared to electric locomotives. Air pollution would also be considerably reduced. Examination of the conditions in different countries show diverse reasons for considering new steam locomotives: low cost of fuel, local availability of fuel, low pollution, and simplicity of construction resulting in long service life and making long-term local maintenance practical.  Also of interest, SLM built new marine steam engines for Lake Geneva ships, actually converting them back to steam from diesel propulsion.

DLM's Formation

In 2000, Sulzer Winpro (formerly SLM) in Winterthur sold its steam business to Hug Engineering, a company which makes ceramic catalysers for diesel engines. Hug also owns a machine building company which works partly for its catalyser business, but also as a supplier for the rolling stock industry.

The steam business formed a new company called Dampflokomotiv und Maschinenfabrik AG DLM (Steam Locomotive and Machine Works Ltd..) DLM is headed by Dipl. Ing. Roger Waller and its aim is to develop and to market modern steam locomotives and steam engines for naval purposes.

DLM secured its first order, the modernization of the rack steam locomotive "Breithorn", owned by Brig-Visp-Zermatt-Bahn (BVZ), which operates a highly profitable line to the mountain resort Zermatt with its famous mountain "Matterhorn", of which a little copy can be found in Disneyland in California. DLM also further wants to market its rack steam technology and will develop a new narrow gauge adhesion steam locomotive. It also intends to take part in tenders for other new steam locomotives, especially for Nilgiri Mountain Railways in India.

More recent steam proposals by DLM include a narrow gauge 0-4-0T for general service (including a variant styled for the Darjeeling Himalaya Railway in India), 4-8-4T's for service in the Netherlands, and 2-8-2T's which would be suitable for the narrow gauge railways of former East Germany as well as other services. DLM has performed extensive modernizations of several steam locomotives, and continues to build new steam engines and integrate them into existing ships in Switzerland.

DLM has also done considerable research on fireless steam locomotives and owns several relatively modern units which were built in Germany. F

The establishment of DLM was very good news for the continuation of steam locomotive production. It is particularly interesting that an established, successful Swiss company (Hug Engineering) was sufficiently confident in the market for new steam that they would invest substantial money to acquire the engineering expertise and infrastructure to support it.

In August 2020 DLM celebrated its 20th anniversary, and the company continues to advance steam power.

See DLM's webpage for up-to-date information on new steam locomotive proposals.

many thanks to Andreas Schwander for much of this information

Complete information on DLM appears on their corporate website at:


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