Key takeaways
- The Class 42 is a war locomotive of type KDL 3: deliberately simplified in construction, built for rapid production rather than long service life.
- 1,061 examples were built between 1943 and 1949 – far fewer than originally planned.
- Fastest way to identify it: five coupled axles, one leading axle in front, none behind – the 1'E wheel arrangement.
- The bigger sibling is the Class 52, which was built lighter and produced in far greater numbers.
- No longer in scheduled service: surviving locomotives stand in museums, with a few kept operational.
Contents
Fact file
| Vehicle type | heavy freight tender locomotive, war locomotive of type KDL 3 |
|---|---|
| Wheel arrangement | 1'E – one leading axle, five coupled driving axles |
| Motion | two-cylinder superheated steam engine in simplified wartime construction |
| Years built | 1943 to 1949 |
| Number built | 1,061 locomotives |
| Maximum speed | 80 km/h |
| Designation abroad | ran in Poland as Ty43, further examples went to Bulgaria, Hungary, Romania and Luxembourg |
| Current status | no scheduled service, a few examples preserved in museums |
Identifying features
Is this really the class in front of you?
- Five coupled driving axles with a single leading axle in front, no trailing axle behind
- Deliberately plain, angular construction with no decorative trim – typical of war locomotives
- Tender locomotive, often with a welded trough-shaped tender in simplified form
- Running number begins with 42; vehicles abroad carry different class designations
- Two outside cylinders, no third cylinder between the frame plates
- Today found exclusively in museums, never in scheduled freight service
Updated: August 2026 – Five coupled axles, one leading axle at the front, none behind, and a construction that dispenses with every unnecessary detail: the Class 42 is a war locomotive of type KDL 3. 1,061 examples were built between 1943 and 1949. This page explains how to recognise it, why it looks the way it does, and where surviving vehicles stand today.
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What is the Class 42?
The Class 42 is a heavy freight tender locomotive with a 1’E wheel arrangement, built between 1943 and 1949 in 1,061 examples. It carries the type designation KDL 3 and therefore belongs to the war locomotives: vehicles whose design was consistently geared towards rapid production using scarce materials. Its maximum speed was 80 km/h.
After 1945 the locomotives were scattered across half of Europe. In Poland they ran with the Polskie Koleje Państwowe (PKP) as the Ty43, while further locomotives went under other class designations to Bulgaria, Hungary, Romania and Luxembourg. In Germany there is today no scheduled service at all – surviving locomotives are museum vehicles, of which only some are operational.
What “war locomotive” means technically
The term isn’t a historical label but a concrete design brief. Once you know it, you can see a locomotive’s origin story in front of you.
Replace materials
Alloy steels and non-ferrous metals were scarce. Where possible, they were replaced with simple materials – with consequences for durability and wear.
Replace castings with welded constructions
Welded frames and tenders could be built faster and with less specialist tooling than elaborate castings.
Drop anything that doesn't move the train
Cladding, decorative parts and comfort features were dropped. The result is the characteristically angular, bare appearance of these classes.
Plan for a short service life
The locomotives were designed for only a few years of service. That many of them then ran for decades afterwards was never intended – and required extensive rework.
The best-known war locomotive is the Class 52 with the type designation KDL 1. The smaller wartime types such as the KDL 8 follow the same principle, just in a different size class. How to identify such vehicles in general is explained in the guide to identifying locomotive classes.
Build quality as a recognition feature
War locomotives look unfinished compared with pre-war standard designs: straight plating, visible weld seams, few rounded shapes. If a steam locomotive looks "rough", that's often not decay but design intent.
Context in rail operations: tractive effort versus route availability
Five coupled axles mean a lot of adhesive weight and therefore tractive effort. The price for that is axle load: the heavier a locomotive, the fewer routes it may run on. This is exactly where the war-built classes differ from one another.
| Feature | Class 42 | Class 52 |
|---|---|---|
| Type designation | KDL 3 | KDL 1 |
| Wheel arrangement | 1’E | 1’E |
| Design intent | heavier, higher tractive effort | lighter, lower axle load |
| Route availability | more restricted | usable on a very wide range of routes |
| Number built | 1,061 | several thousand |
| Current status | museum only | museum only, many rebuilt examples survive |
The practical consequence: the 52 became the ubiquitous war locomotive, while the 42 remained the specialist for heavy trains on routes that could bear its weight. At the Deutsche Reichsbahn, the 52 later gave rise to the fundamentally reworked Class 52.80, which still hauls many heritage trains today – no comparable rebuild series was ever produced for the 42.
Keep an eye on rare classes
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Spotting: research routes instead of a timetable
There are no diagrams, no home routes and no fixed depot allocation for the Class 42 in regular service. Anyone who wants to see one has to work through the operators:
- Vehicle lists of railway museums in Germany and neighbouring countries. Because many locomotives went abroad after 1945, it’s especially worth looking across the border.
- Society websites and operator documentation. These state whether a locomotive is operational, undergoing overhaul, or has been set up as a static monument.
- Historical sections of railway forums. How to find reliable information there is covered in the overview on researching heritage railways.
- Special working calendars. The guide on special trains and special workings explains which sources list dates first.
- Your own archiving. Because encounters are rare, it’s worth keeping your own photos properly organised – structure and metadata are covered in the article on building a photo archive for spotters.
The owner's house rules apply on museum sites
Engine sheds, turntables, track fields and workshop areas are operational railway land. Entering them is not permitted; barriers and staff instructions apply without exception. Photograph from designated viewpoints or publicly accessible areas – the basic rules are summarised in the article on safety distance at the track.
Photo tips for a 1’E steam locomotive
A five-coupled freight locomotive is a different subject from an express passenger locomotive. It’s long, low, and works mainly through its motion gear – not through an elegant silhouette. Four points that make the difference:
- Side view at a slight angle. About 30 to 45 degrees to the vehicle axis shows the front and the motion gear at the same time. On a 1’E locomotive, the row of five coupled axles is the real subject of the shot – shot head-on, it’s lost.
- Leave enough room ahead in the frame. With its tender, the locomotive is considerably longer than a modern main-line locomotive. Crop too tightly and you cut off the tender, losing the proportions that define a steam locomotive.
- Choose the background before the subject. Steam and smoke need a calm, dark surface to stay visible. Wooded slopes, cuttings or building fronts work for you; a bright sky works against you.
- Make use of cold air. At low temperatures, steam condenses more strongly and lingers longer. Winter running days therefore regularly produce the more striking shots – with a correspondingly shorter window of good light.
A second, often underrated point is the tone of the shot. War locomotives have a documentary quality thanks to their plain construction; a photo showing the weld seams, the straight plating and the missing cladding tells you more about the vehicle than a perfectly lit glamour shot. These very details are what make the class historically interesting.
Common mix-ups
It points to the 42 if …
- you count five coupled driving axles with a single leading axle in front
- no further trailing axle follows behind the driving wheels
- the construction looks strikingly plain and angular
- the running number begins with 42
Look more closely if …
- you see a 1'E war locomotive but can't read the number – the 42 and 52 look similar at a distance
- the vehicle is abroad and carries a foreign class designation
- a trough-shaped tender is attached, which also occurs on other classes
It's not a 42 if …
- you count four coupled axles and see a trailing axle at the rear – that points to the Class 41
- three cylinders are present, meaning one also works between the frame plates
- the vehicle isn't a tender locomotive but a tank locomotive with side water tanks
Verdict
The Class 42 is a vehicle you can only understand by keeping its origins in mind. Five coupled axles for tractive effort, radically simplified construction for rapid production, a planned service life of only a few years – and yet decades in service. Today it’s a purely museum vehicle, found through heritage societies and event calendars, not through the timetable.
In short
1'E, angular wartime construction, number beginning with 42: that's the KDL 3. It's rarer than the related Class 52 and can practically only be seen at museum railways and special events.
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Summary
- The Class 42 was built under wartime conditions and is a vehicle whose design is fully explained by material shortages and production pressure.
- Its five coupled axles gave it tractive effort, while its simplified construction cost it ride quality and service life.
- After 1945 the locomotives were scattered across half of Europe and continued running there under their own class designations.
- Sightings today are museum events and can only be planned via heritage societies and event calendars.
Frequently asked questions
What is a war locomotive?
A steam locomotive deliberately simplified under wartime conditions. Components made from scarce materials were replaced, elaborate castings were swapped for welded constructions, and anything not serving the basic function was dropped. The Class 42 carries the type designation KDL 3, the Class 52 the designation KDL 1.
How do I recognise the Class 42 in the field?
By its 1'E wheel arrangement: a single leading axle at the front, five coupled driving axles behind it, and no trailing axle. Add to that the strikingly plain, angular construction with no cladding or decorative parts. The running number begins with 42.
How many Class 42 locomotives were built?
A total of 1,061 examples were built between 1943 and 1949. The original plans called for many times that number, but were never reached. After 1945, many locomotives passed to foreign railway administrations and in some cases ran there for decades more.
What is the difference between the Class 42 and the Class 52?
Both are war locomotives with five coupled axles, but the 42 is the heavier type with a higher axle load and greater tractive effort. The Class 52 was lighter, could therefore be used on more routes, and was built in far greater numbers. When in doubt, the running number settles it.
Why is the 42 in the number range 40 to 59?
Because the classification scheme of the Deutsche Reichsbahn-Gesellschaft is sorted by purpose. The range 40 to 59 is reserved for freight tender locomotives, 01 to 19 for express passenger locomotives, and 20 to 39 for ordinary passenger locomotives. From 60 onwards come the tank locomotives without a separate tender.
Does the Class 42 still run today?
Not in scheduled service. Surviving locomotives stand in railway museums and with heritage societies in several European countries, with a few kept operational for special workings. Whether a given locomotive is currently serviceable depends on boiler certificate deadlines and workshop schedules, and changes constantly.
What does the Polish designation Ty43 mean?
This is how the Polish State Railways designated the Class 42 locomotives taken over after 1945. The Polish scheme encodes purpose and wheel arrangement in the letters: T stands for freight locomotive, y for five coupled axles. The same locomotive therefore carries a completely different designation depending on the railway administration.
Where can I find information on surviving locomotives?
Through the vehicle lists of railway museums, the websites of operating societies, and the historical sections of major railway forums. Holdings change through sales and overhauls, so checking with the operator directly is always more reliable than an older overview list found online.
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Related classes
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