Gölsdorf axle

The Gölsdorf axle system is used on railway locomotives to achieve quiet running and low wear-and-tear when negotiating curves. It comprises a combination of fixed axles and axles that can slide transversely, all within a single, rigid locomotive frame. The system was invented by a young Austrian locomotive builder, Karl Gölsdorf, around the end of the 19th century. The first locomotive to use this principle entered service in 1897.

In the early days of the railway, locomotives were built with more and more axles in order the meet the increasingly heavy loads of goods trains. In order not to overstress the tracks, axle loads were often restricted, initially to 16 tonnes, occasionally to 18 tonnes and later usually to 20 tonnes. A ten-coupled locomotive had to weigh no more than 100 tonnes plus whatever tonnage the leading and trailing wheels could support. The heavier a locomotive is, the more surface pressure it places on the wheels and the more it can haul. But as more and more axles are added, curve running becomes increasingly difficult. So early on, work began to develop multi-part frames and bogies which linked sets of axles to their own drive. However driving wheels within bogies using steam was a difficult task due to the moving seals that were required. As a result, a different avenue of development was pursued, whereby a degree of smooth curve running could be achieved using a long, rigid frame through the use, for example, of axles that had sufficient sideways play. The Gölsdorf axle system avoided the need for complicated construction methods like that of Mallet locomotives. It was in effect an artifice enabling locomotives to retain a long, rigid frame (without articulation or bogies), yet whose individual axles could be better aligned when curve running.

Gölsdorf axles work in this way. Two of the five axles cannot move sideways relative to the frame because their axle boxes fix them rigidly to the frame. The other axles, however, are fitted into their bearings and attached to their drives in such a way that they can be moved sideways during curve running, depending on the sideways forces acting on them. In addition the connecting and coupling rods, through which the steam pressure and linear forces from the steam pistons are translated into the rotation of the wheels via the crank pins, also have to be able to move sideways.

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Wikipedia