The IX was an express locomotive of the Crampton type, which was originally to be built as a freight locomotive and underwent a number of modifications before it was delivered to the Grand Duchy of Baden State Railways. Also due to the very rapid development at that time, the locomotives differed depending on the year of construction.

The characteristics of a Crampton locomotive were immediately apparent. These included a low-lying boiler mounted approximately midway above the two leading axles and a single driving axle with very large wheels located behind the boiler. This design offered great smoothness at high speeds, but only a low friction weight.

Since a broad gauge of 1,600 mm was initially used in Baden, the class IX was also designed for this gauge during its development phase. However, because between 1854 and 1855 all lines were changed to the standard gauge of 1,435 mm, later locomotives were also built with this gauge. 

Another change before commissioning was the installation of a normal smoke box with the chimney at the front end of the boiler. The first two engines “Adler” and “Falke” had received a return flue from the factory, which means that the chimney was located in the middle of the boiler and thanks to the shorter steam tubes, the back pressure from the cylinders was reduced. However, this arrangement was not convincing due to the flue clogging with soot and ash and quickly disappeared from the scene.

The locomotives had an outside frame, whereby the power was transmitted to the driving axle via Hall cranks. In the second series, the leading axles were in a bogie, but in the rest they were stored in the frame again.

In addition to the two pre-series models, three other series of eight locomotives each were produced. Due to the increasing train weights, the first examples were retired in 1875. The others were first pushed into service with normal passenger trains and later only used for shunting. Today only the “Phoenix” locomotive still exists. It was refurbished in 1960 and has been in the Nuremberg Transport Museum ever since.

After the Nord had already had 100 km/h fast Crampton machines built with a driving wheel diameter of 2,100 mm from 1849, the Est procured similar ones with a diameter of 2,300 mm three years later. The engines of the Est could then even reach 120 km/h, which was beneficial to the Cramptons' reputation as “greyhounds of the rails”. To do this, the maximum speed allowed on the French railway lines had to be increased by decree of Napoleon III.

After the twelve examples numbered 79 to 90 had been delivered by Cail in 1852, another 15 by Schneider-Creusot with numbers 174 to 188 followed in 1855. The first carrying axle had a larger diameter than the second and carried a significantly higher weight. The locomotives could pull up to 15 of the passenger cars of their time and usually reached an average speed of 55 to 75 km/h with nine to ten cars.

Since the adhesive weight of just over ten tonnes later turned out to be insufficient, as with most Cramptons, a rebuild took place from 1881. In order to shift the weight further to the rear, particularly massive and heavy wheel hubs and a smaller boiler were installed. To compensate, the boiler was now operated at a higher pressure. Together with other additions, such as the Westinghouse air brake, the adhesive weight could be increased by about 3.5 tonnes.

It was not until just before the turn of the century that other express locomotives were able to overtake the Cramptons. Number 80 “Le Continent” is the only example that has survived to this day. It was restored to its original condition in 1925 and initially exhibited at the Gare de l'Est in Paris. In 1946 it was made operational again, but has been standing since 1970. Today you can find the theoretically operational machine in the Cité du train in Mulhouse, but no renewed refurbishment is currently planned.

The Cramptons of the Nord comprised a total of 58 locomotives, which, like almost all French Cramptons, were built by Cail. They had outside cylinders that were raised and inclined. The bearings were generously sized to reduce wear at high speeds. The wheels on the first leading axle were visibly larger than those on the second and also had to carry a significantly higher load.

As a rule, they pulled twelve coaches and sometimes up to 16, each of which only weighed eight tons. Four batches were delivered between 1849 and 1859, most of which had a driving wheel diameter of 2,100 mm (6 ft 10 11/16 in). Only numbers 134 to 145 from 1853 had wheels of 2,300 mm (7 ft 6 9/16 in) and a higher boiler pressure to compensate. Numbers 165 to 170 from the last batch were the first locomotives in France to have Walschaerts valve gear.

The locomotives of the Pfalzbahn with the numbers 26 to 63 were express locomotives, 17 of which have been produced since 1853 by the Esslingen and Maffei machine works. With the Crampton design, smoother running was achieved and speeds could be reached that were actually said to be unrealistic up to this point. Despite the fact that the drive wheels were only 1,830 mm in size, this type is said to have reached speeds of up to 120 km/h. The French Crampton locomotives, which were also designed for 120 km/h, had a wheel diameter of more than 2,100 mm.

However, this advantage was paid for by the fact that the large driving wheels behind the boiler could only provide a small adhesive weight and therefore little traction was available. The adhesive weight was 9.2 tonnes for the first engines and reached 9.7 tonnes for the last ones, what at that time was sufficient for an express locomotive. The locomotives were not only used on flat lines, but also had to cope with gradients of up to 0.7 percent in the Palatinate Forest.

The Pfalzbahn began scrapping the first engines in 1891. The last one disappeared in 1896, when the considerably more modern P 2.I with the wheel arrangement 2-4-2 were already available. In 1925, a replica of the locomotive with the name “Die Pfalz” was built and ten years later it took place in the centenary of the German railways in Nuremberg.