To replace the class IX a rack locomotives, which were no longer up to date in terms of power, the Grand Duchy of Baden State Railways had the IX b developed from 1908. It also had only three coupled axles, but in order to achieve a higher weight it was necessary to add a trailing axle, mainly because of the limited loads of the Ravenna Viaduct. The requirements for the IX b consisted of transporting 150-tonne trains on sections with a gradient of 2.5 percent in adhesion mode at 23 km/h and still achieving 10 km/h on the steepest section at 5.48 percent using the rack and pinion. In order to achieve the required power, the machines were designed with a steam dryer, but this was later removed due to the lack of cost-effectiveness.

As with other rack locomotives, the engine was designed as a four-cylinder compound engine, with the high-pressure cylinders driving the wheels and the low-pressure cylinders driving the rack axle. In adhesion mode, the engine worked like a conventional simple twin locomotive. The chassis could be built without any radial bogies by making the second driving axle laterally shiftable by 24 mm and the trailing axle by 40 mm. The latter also had flange lubrication on the first engines.

Since good braking performance was required on the steep sections of the route despite the relatively low train masses, the locomotives were equipped with three independent braking systems. In addition to the obligatory Westinghouse air brakes on the wheels of the locomotive and the train, a counter-pressure brake was used, which also acted on the rack axle and, for safety, a counterweight brake for the coupled wheels. 

After four engines which were built in 1910, another three were procured in 1921. They were classified by the Reichsbahn as class 97² and given the serial numbers 201 to 204 and 251 to 253. However, the service life of the locomotives ended after the conversion of the Ravenna Viaduct, which had begun in 1926, was completed. The old construction from 1885 had been replaced by a brick structure with round arches, on which heavier engines could now also drive. From then on, the class 85, which was specially developed for this route, drove here, which got along with the wheel arrangement 2-10-2 and three cylinders without a rack. Thus, the last example of the former IX b was retired in 1933, only shortly after the last 85 had been put into service.

During the construction of the Bernese Oberland Railway (BOB), it was planned to purchase one type of adhesion locomotive for the less steep section and one type of purely rack locomotive for the steeper section. By the time the line opened in 1890, the decision was made to purchase only one type with a combined adhesion and reck drive. The first three HG 3 were delivered in 1890 and three more in 1893. They later became HG 3/3 according to the Swiss system.

These were 0-6-0RT tank locomotives and had outside frames. The rack drive was mounted on the driving axles to avoid problems with the suspension. Of the two rack gears under the locomotive, one was used for driving and one for braking. The boiler was inclined by five percent compared to the frame.

After the BOB was electrified in 1914, these locomotives were no longer needed in daily operations and five of them were sold. Three were converted from the gauge of 1,000 mm to 950 mm and sold to the Italian Mediterranea-Calabro-Lucane. Two went to the Arosa Railway, but were sold to industry after a short time. The sixth locomotive remained with the BOB as a reserve.

When the Bosnian-Herzegovinian State Railways put the route over the Komar Pass into operation as the next 2 ft 6 in rack railway after the Narenta railway in 1894, more powerful rack locomotives based on the Abt system were needed. The basis for the development was the class IIIb4, which had three coupled axles and a single-axle Klose supporting tender and was already in use on the Narenta railway. Adding a second axle under the supporting tender allowed not only to increase the supplies, but also to carry the load of a heavier boiler.

Technically, the locomotives shared many similarities with their predecessors. Due to the small gauge, an outer frame was still used, and the cylinders of the rack drive were still on the inside. In adhesion mode, still the the third coupled axle was powered. There were minor differences between the individual production series, for example the grate surface was initially reduced from 1.66 to 1.58 square meters. Also, some engines were oil-fired to improve visibility in tunnels. Compared to the 60 tonnes of the IIIb4, it was now possible to tow 80 to 90 tonnes on the six percent gradient, since the power was now 300 hp instead of 250 hp. With two pusher locomotives, train weights of 240 tonnes were even possible.

Sectional drawing with dimensions

Die Lokomotive, August 1940

They replaced the IIIb4 on the Narenta railway, so that these were relocated to the route over the Komar Pass. But the IIIc5 was soon used there too. Since the two Mallet locomotives IIIb5 Nos. 751 and 752 had not proven themselves, additional engines with Klose supporting tenders were purchased in the years 1911 to 1919. This brought the number to 38, making it the most built rack locomotive. At the Yugoslav State Railways they were listed as class 97. The use of these locomotives ended there with the gauge change on the Narenta railway. The route over the Komar Pass was finally closed in 1975, which meant the end of the service life of the IIIc5. Four pieces are still existing today.

The Brig-Furka-Disentis railway ordered ten rack locomotives from SLM while under construction, the first three of which were delivered directly to the construction sites. They were based on the HG 2/3 of the Visp-Zermatt Bahn, but had a significantly higher power thanks to superheated steam. The four cylinders worked in compound operation, with the gearwheels driven by the low-pressure cylinders and always operated together with the adhesion drive. With the electrification of the railway, the locomotives were retired there in 1940. One was sold to France and four to French Indochina (Vietnam). The latter four came back to Switzerland in 1990 and two of them are now running on the Furka mountain line after being refurbished.

The Manitou & Pikes Peak Cog Railway, opened in 1891, provides an access to the famous mountain in Colorado. It starts in Manitou Springs at an elevation of 6,320 ft (1,930 m) and reaches the top at 14,115 ft (4,302 m). While its steepest section has a gradient of 25 percent, the average is twelve percent. All of its steam locomotives were built by Baldwin, with No. 6 being delivered in 1906.

No. 6 was the first one to be fired with oil. After its older sisters were rebuilt as four-cylinder Vauclain compounds, it was built this way and had its axles turned by levers instead of direct connecting rods. The boiler and the cab were inclined by 16 percent to compensate for the gradient. As opposed to most of its sisters, it is not preserved today since it was scrapped in 1955.

In order to be able to increase the weight of the ore trains on the Erzbergbahn, two heavy rack locomotives with a 2-12-2RT wheel arrangement were put into service in 1942. They were initially planned as class 369 of the BBÖ, but were now incorporated directly into the Reichsbahn as class 97⁴. At that time they were the most powerful rack locomotives in the world, but due to the lack of reinforcement of the rack rail on the north ramp of the Erzbergbahn they could only be used on the south ramp. The 97 402 was put out of service in 1949. The 97 401 became the 297.401 at the BBÖ in 1953. It received a Giesl ejector in 1958 and was retired in 1968.

The T 26 was a rack tank locomotive that was used in various regions of Prussia. It was intended for routes such as those found on the slopes of the Rhine or in the Thuringian Forest. The gradients of sometimes more than 6 percent could only be overcome with the help of a rack. The first three pieces came from the Esslingen machine factory, but the remaining 32 were built by Borsig on their own territory.

No. 9003, Borsig works number 6000

Locomotive Magazine, February 1907

The Abt rack system was used on these routes, which used two racks with offset teeth for better guidance and smooth running. Thus, the locomotives also had gears with two rows that were toothed alternately. This ensured that a tooth was engaged in the rack at all times.

Schematic drawing of the Borsig type with dimensions

Die Lokomotive, October 1907

In adhesion operation, the T 26 had three coupled axles and a trailing axle and could thus reach 45 km/h. When operating on the rack, two gear axles were used, the drive of which was separate from the coupled axles. The wheels were driven by two outer cylinders and the gears by two inner cylinders. Due to the reduced speed in rack operation to 15 or 20 km/h, the inner drive could be designed differently in order to achieve more traction.

Production of the T 26 ran until 1921 and two years later the locomotives were classified as class 97⁰ when they were taken over by the Reichsbahn. During this time, however, the T 16.1 (class 94^5-17) and T 20 (class 95) were already being procured. Due to the cheaper operation of these two new locomotives, the last 97⁰ were retired from the Reichsbahn in 1932. Seven pieces were sold to private and works railways and remained in service until the 1960s, but with the cogwheel drive removed.