ÖBB Class 77

Updated: August 2026 – A compact steam locomotive with no tender, water tanks on either side of the boiler, and a leading axle at the front and a trailing axle at the rear: that’s the Class 77, one of the classic Austrian passenger tank locomotives. This page explains its design, its dual designation, and how to tell it apart from other steam classes.

What is the ÖBB Class 77?

The Class 77 is a passenger tank locomotive with the wheel arrangement 1’C1’: three coupled driving axles, with a single leading axle in front and a single trailing axle behind. Its roots lie with the k.k. Austrian State Railways, where the design was carried as Class 629; the ÖBB later took it over under the short number 77.

What defines this locomotive is its build. As a tank locomotive it carries water and coal on the vehicle itself – in side tanks on the boiler and in a bunker behind the cab. There is no separate tender. That makes it short, agile, and able to run in both directions without turning. That was exactly what was needed on branch lines and suburban services, where the terminus often had neither a turntable nor time for a run-round move.

Why the wheel arrangement tells you so much

For steam locomotives, the wheel arrangement is the single most informative piece of shorthand there is. It tells you what a locomotive was built for before you know a single technical figure.

For the Class 77, the C denotes three coupled driving axles. Three axles mean moderate tractive effort – enough for a passenger train, too little for heavy freight. The 1’ figures before and after the C each denote a single pivoting leading or trailing axle. They carry no driving force but guide the locomotive through curves and allow smooth running in both directions.

Compare that with a freight locomotive like the ÖBB Class 52 and the difference becomes tangible: there, five coupled axles sit under the boiler, with only a single leading axle at the front and a coupled tender. Plenty of adhesive weight, little cornering comfort, built for load rather than agility.

Identifying it in three steps

The general sequence for identifying rolling stock is explained in the guide to identifying classes.

Classification in the Austrian class scheme

Designation	Meaning	Examples
Two-digit class	Standard-gauge steam locomotive	Class 52, Class 77
Three-digit class	Narrow-gauge steam locomotive	Class 298, Class 399
Class 1xxx	Electric locomotive	Class 1042, Class 1142
Class 2xxx	Diesel locomotive	Class 2016, Class 2143
Class 4xxx	Electric multiple unit	Class 4020, Class 4024
Class 5xxx	Diesel multiple unit	Class 5022, Class 5047

Then there’s the European vehicle number: for steam locomotives it starts with 90 for the traction type and 81 for Austria. If you’re looking at a narrow-gauge machine rather than a standard-gauge one, you’ll land on classes such as the Class 298 (U). And if the vehicle keeper marking doesn’t name a state railway, it may be a private-railway locomotive – for example from the fleet of the GKB Class 29.

What tank locomotives were needed for in service

To understand why a locomotive like the Class 77 existed at all, it helps to look at everyday operations of its time. Passenger trains on branch and suburban lines covered short distances, stopped frequently, and reversed at the terminus. It’s in exactly this pattern that the tank locomotive shows its strengths.

A tender locomotive has to be turned or run round at the terminus, otherwise it makes the return trip tender-first – with poor visibility and limited speed. That requires a turntable, a run-round loop or a triangular junction: infrastructure that costs space and money. The tank locomotive sidesteps the problem: it’s designed for both directions of travel, the cab offers views forward and backward, and the wheel arrangement with leading/trailing axles at both ends ensures smooth running whichever way it goes.

The price for that is the supply capacity. Water and coal fit onto the locomotive itself only in limited quantity, which makes such machines unsuitable for long distances. For a diagram between two termini with regular water stops, though, it was more than enough.

For observers this has a practical consequence: where a tank locomotive stands in front of a heritage train today, there’s usually no turning at the termini. The locomotive stays at the same end of the train and returns the way it came. Anyone wanting to photograph both directions of travel gets two very different pictures of the same train as a result – once with the smokebox leading, once with the coal bunker leading. Austrian steam locomotives are preserved, among other places, at the Eisenbahnmuseum Strasshof east of Vienna. Operational locomotives are also maintained by the ÖGEG.

Observing and photographing it

Tank locomotives are rewarding subjects because they’re compact and work in both directions. A few points make the difference:

• Look for sidelight. The water tanks are large, smooth surfaces. Lit from the front they look flat; in raking light the locomotive gains texture.
• Photograph reverse running too. Unlike with tender locomotives, running in reverse is the normal case here and a subject in its own right.
• Make use of platform scenes. While stopped, details like the valve gear, motion and cab can be photographed calmly from the platform without disrupting operations.
• Prefer cold days. Steam and exhaust become visible at low temperatures; in high summer they often disappear before they reach the frame.

The basics of the technique are covered in the guide to taking good photos of trains; how to actually find event dates is shown by the heritage railway guide.

Common mix-ups

Verdict

The Class 77 is a fine example of how much a wheel arrangement tells you about a vehicle. Three coupled axles between two leading/trailing axles, plus the tank-locomotive build with no separate tender, add up to a machine for passenger trains on routes with frequent changes of direction. Anyone who has properly learned this combination once will classify other steam classes noticeably faster too.