The name “Old Maude” refers to a mule in a comic, but also the first large Mallet in the USA built for standard gauge. Its job was as a helper for heavy trains on inclines, what didn't require high speeds. This meant that she did not require any carrying axles, meaning that all six axles were available for traction. The top speed of 21 mph or 34 km/h was completely sufficient for her tasks. Although the locomotive, which was initially designated class O and later renamed DD1, did not have any sisters, it remained in service until 1938.

The Gts 2x3/3 was a heavy narrow-gauge locomotive for a gauge of 1,000 mm in Mallet construction and with six coupled axles. In fact, only one of the 20 locomotives that Henschel built for the Heeresfeldbahn during the First World War carried this designation. This one locomotive was bought by the Bavarian State Railways after the end of the war and used on the Eichstätt-Kinding route.

In addition to the high weight of more than 50 tonnes, the locomotives were characterized by the fact that, in contrast to many narrow-gauge locomotives of the time, they already had a superheated steam engine. With the relatively large reserves of 1.5 tonnes of coal and 4.5 cubic meters of water, it was possible to run for longer periods without refilling. In order to further improve the curve running characteristics of the chassis, the middle axle of each of the two chassis groups could be shifted 15 mm to the sides.

The use of the 20 built locomotives at the Heeresfeldbahn explains the fact that they were scattered over several countries after the end of the war. Some were also used on the Hijaz railway from Damascus to Medina. In the post-war period, the example taken over by Bavaria was used on the aforementioned route and was designated 99 201 by the Reichsbahn from 1925. After the line was converted to standard gauge in 1934, the locomotive became superfluous and was scrapped. In the years 1925 and 1928, a locomotives was built for two narrow-gauge railways in Baden. These were only designed as saturated engines and remained in use until 1957 and 1967 respectively. One of these was later used in Switzerland and can now be seen in the museum there.

Shortly after the opening of the Bernina line, they decided to operate it year-round, what required two snow blowers. They were built by SLM, were numbered R 1051 and R 1052 and differed from other snow blowers in that they had their own propulsion. Since it was not possible at this time to draw enough current from the overhead line for propulsion and the blower at the same time, they were built with steam power. This also had the advantage that they did not suffer from power outages after severe weather or when the overhead lines were frozen.

These vehicles were built like Meyer locomotives with two three-axle bogies with cylinders on the inside. This chassis was able to run through curves with a radius of 45 m. Two additional cylinders were mounted above the other four which only propelled the snow blower. All six cylinders had the same dimensions and worked with simple expansion. The first vehicle was built with a boiler pressure of 13 bars and a cylinder diameter of 310 mm, while the second one had 14 bars and 320 mm. Rated power was 500 hp for the blower and 300 hp for propulsion.

These snow blowers were able to remove up to three metres of snow. Although they could run on their own, they were mostly pushed by another locomotive to free up more power for the blower wheel. When the Bernina Railway became part of the RhB in 1944, they were renumbered to R 13 and R 14. In 1940 they received the designation X^{rot d} and were renumbered again to 9213 and 9214. They were replaced by more modern models in 1967, but were kept in working order in case they were still needed. Today 9213 is freshly overhauled, stationed at Pontresina and operated from time to time. 9214 is part of the Blonay-Chamby Museum Railway since 1996.

Originally built for Larson Lumber in November 1927, this 2-6-6-2 Mallet went to Bloedel Donovan Lumber Mills in Washington instead. Although being standard gauge, it was fairly small for a 2-6-6-2, optimized for logging service. Nevertheless it was much more powerful than the Mallet tanks of the same wheel arrangement then in use by this company. It had drivers of 51 inches and cylinders with diameters of 20 and 31 inches, at a stroke of 28 inches. Later it came to Rayonier, Inc. and still carried the number 14. It was retired in 1964 and scrapped four years later.

The class N of the Burma Railways designated 17 Mallets built by North British in four batches between 1911 and 1921. With an 0-6-6-0 wheel arrangement, they had all weight available for traction. Nevertheless, they were not only intended for freight service, but also for passenger service.

Their service area was the Lashio branch and the Southern Shan states. Even though they had a huge pulling power, they had to be assisted by 2-6-2T locomotives on steeper sections. In 1924 Beardmore built five superheated Ns class locomotives and the 17 others were rebuilt in the same form. It didn't take long until they were superseded by the Garratts starting with the GA.I.

In 1919, the Central of Georgia got ten 2-6-6-2 Mallets from ALCO-Richmond which were used as pushers on the Sylacauga grade in Alabama. They had 57-inch drivers and cylinders with diameters of 24 and 38 inches, with a stroke of 32 inches. Apparently, they were not very popular among the footplate and maintenance crews and had steam leaks in many places. As it turned out that these locomotives were too large for the small railroad, they were given to the Illinois Central that was a shareholder of the Central of Georgia in 1926. In exchange, they received some 2-10-2 locomotives. The Mallets got the numbers 6000 to 6009 from the IC and were used as switchers for about ten years.

In 1911, ALCO-Richmond built 24 2-6-6-2 Mallets for the Chesapeake & Ohio which were designated class H-2. They had 56-inch drivers and were able to reach speeds of 45 mph. The firebox had a grate of 72.2 square feet and a long combustion chamber. Compared to the previous Consolidations, they hauled trains which were 75 percent heavier at the same average speed, but consumed only a bit more coal. A single, virtually identical locomotive had been built in 1910 for the Chicago & Alton. This was sold to the C&O after a short time and became class H-1. Actually it can be seen as the prototype for the H-2.

Between 1912 and 1918, Richmond and Schenectady built 150 more of a slightly modified design which were designated class H-4. 25 nearly identical locomotives which had been built for the Hocking Valley Railway in 1917 and 1918 became class H-3. In 1927, H-4 No. 1470 was simpled and became the only member of sub class H-4a. It now had a much larger superheater and an Elesco feed water heater, while the boiler pressure had been increased by 10 psi. It was the only one that was rebuilt in this way and was retired in 1947. The last H-4 was retired in 1955.

Numbers 200 to 209 were built by Schenectady in 1909 and 1910 as 0-6-6-0 all-adhesion Mallets. Their special task was to haul rotary snow plows at speeds as low as 4 mph without stalling. Railway Gazette once wrote that this task had previously been taken over by up to five Consolidations and now one of these Mallets was supposed to accomplish this task alone. For the rest of the year, they were mainly used in regular pusher service. As early as 1912, they received a leading axle and a mechanical stoker to improve their usability in freight service. Now they were perfect to haul heavy trains through the mountains with 20 mph, with a top speed of 35 mph. 

In 1913, the railroad became the Denver & Salt Lake. In the same year they ordered numbers 210 to 216 which had a leading axle and a stoker from the start, and additionally were superheated. 210 was lost in a wreck in 1924, but the rest of the class was rebuilt in 1926. The first batch got superheaters of 1,249 square feet, but the second one retained their superheaters of 1,046 square feet. Additionally, thermic syphons and Sellers exhaust injectors were installed. In 1931 the railroad was taken over by the D&RGW and these locomotive became class L-77. They were retired between 1947 and 1952.

The challenges for locomotives on the Gotthard railway were not only the incline of 2.7 percent, but also the spiral tunnels with a radius of 300 meters. This required a high tractive force and at the same time made the adhesion conditions more difficult. In order to be able to dispense with the previously necessary one or two helper locomotives per train, eight-coupled locomotives or those with articulated chassis should be procured. In 1890 Maffei of Munich delivered locomotive number 151 to test the Mallet design.

The tank locomotive had six coupled axles and no carrying axles and was therefore given the type designation Ed 2x3/3. All cylinders acted on the third coupled axle of each group. Due to the short distance between the wheels, only the first and last axle of each running gear group could be braked from the outside, otherwise there would have been no space for the brake pads between the wheels. Since enough space had to be planned for the water tanks on the sides of the boiler, the boiler turned out to be relatively small for a locomotive with a service weight of 87 tonnes.

Since a high steaming capacity was required for the long, continuous incline, the Ed 2x3/3 quickly reached its limits. Although the locomotive offered sufficient traction and was able to convert a lot of power, the boiler was too small in comparison. Calling up full power for a short time was also difficult because the maximum coupler force could be exceeded. Thus the maximum train weight of the Ed 2x3/3 on the Gotthard railway was only 200 tonnes, while the existing D 4/4 could pull 175 tonnes. The Mallet thus remained a one-off while further, reinforced batches of the D 4/4 were purchased.

The first Mallet with the 2-6-6-2 wheel arrangement was the L-1 class of the Great Northern. They were created in 1906 by adding a leading and a trailing axle to the 0-6-6-0 in order to improve running in curves. They were used as helpers in the Cascades. After the first five, 20 more followed in 1908 after the L-2, which had been delivered in the meantime, turned out to be too light. The class Z of the Northern Pacific was identical to these.

Although they had a Belpaire firebox, its heating surface was very small compared to the total heating surface. At least two L-1s received a superheater around 1915, and they also received significantly larger high-pressure cylinders. However, as early as 1925 and 1926, all L-1s were rebuilt to class O-6 Mikados, which remained in use until the mid-1950s.