The Dundee and Newtyle Railway was built in the Scottish gauge of four foot six inches and operated three locomotives of an unusual design. They were among the first British locomotives to have a bogie, which in this case was located behind the driving axle. The cylinders were arranged vertically and transmitted the power to the connecting rods via L-shaped levers.

Two locomotives of this type were built by J. and C. Carmichael in Dundee. The “Lord Wharncliffe” differed from the first locomotive in that the cylinder diameter was 11.25 inches instead of 11 inches. A third, named “Trotter” with different dimensions came from James Stirling & Co.

After the Dundee and Perth Railway had taken over the Dundee and Newtyle, the locos were also converted to standard gauge in 1849 after the line was regauged. Both locomotives were in use until 1854. The “Earl of Airlie” was restored and photographed in 1863 but not preserved for posterity.

After Dugald Drummond became chief engineer of the Caledonian, he introduced a new class of 0-6-0 goods locomotives. As a basis he used the class D, which he had built a few years earlier during his appointment at North British. Compared to this, the new locomotives were slightly heavier with a larger boiler and larger cylinders. They were nicknamed “Jumbos” or simply “Standard Goods”.

After Drummond left the Caledonian, his successors Smellie, Lambie and McIntosh continued to build these locomotives. While the 161 locomotives built from 1883 were known as class 294, the 83 locomotives built from 1890 by Hugh Smellie and his successors are known as class 711. The latter received a Westinghouse brake so that they could also be used in front of passenger trains. All 244 came to the LMS and the first was not decommissioned until 1946. A total of 238 were taken over by British Railways and decommissioned by 1962.

For the 1886 World's Fair in Edinburgh, the Caledonian Railway had a single locomotive built with seven-foot wheels that would be able to travel at a very high average speed. The 4-4-0 of the class 66 by Dugald Drummond was used as the basis, in which the rear coupled axle was replaced by a trailing axle and the remaining driving axle was equipped with larger wheels. In order to be able to compensate for the low adhesion mass, a modern sanding system was used. Although a steam-powered system was just being introduced at the time, a different approach was being pursued here. Because Caledonian used Westinghouse air brakes instead of the vacuum brakes common in Britain, the compressed air was used to power the sand.

No. 123 in the Glasgow Transportation Museum

Hugh Llewelyn

After the World's Fair, locomotive number 123 was used in express service on the West Coast Main Line in Scotland. In the years 1888 and 1889 it got caught in the middle of the “Race to the North”, in which various railway companies on the east and west coasts unofficially tried to find the fastest journey time from London to Edinburgh. With often only two or three passenger cars, the locomotive did very well despite the inclines. On the 100 miles long section from Carlisle, average speeds of over 50 mph were regularly reached, on one occasion even 59. In addition to being used in front of heavier trains in combination with another locomotive, it was also used for special tasks. These included passenger trains for the Caledonian's inspectors and directors, and also repeatedly used as the lead locomotive for the royal family's train when they were en route to Balmoral Castle. The locomotive was taken over by the LMS in 1923 and was not withdrawn until 1935, making it the last British express locomotive with only one driving axle. From 1958 it ran again in front of special trains and is now in the Transport Museum in Glasgow.

The increasing weight of the express trains in the 1980s and 1990s also presented the Caledonian Railway with the problem that inefficient double-headings had to be used more and more frequently. John F. McIntosh, who was chief engineer from 1895, increased the performance of the 4-4-0 locomotives to the maximum that was possible within the limits of physics and engineering. Key to this was the use of a larger boiler that just fit into the gauge of the Scottish routes and was operated at 160psi. The resulting locomotive was named the Dunalastair class after a well-known Scottish clan. It also formed the basis for Belgian tender locomotives with a 4-4-0 wheel arrangement and tank locomotives with a 4-4-2T wheel arrangement, of which 424 were built.

In 1896 15 examples of the actual Class 721 were built, numbered 721 to 735 and later named Dunalastair I. This was followed in 1897 by the numbers 766 to 780 as Dunalastair II and in 1899/1900 by 887 to 902 as Dunalastair III. The latter two series received four-axle tenders in order to be able to cope better with the longer distances in the Scottish expanses. Records of the Dunalastair III show a 32 mile run with a 250 ton ton at an average speed of 58 mph. Between 1904 and 1910, another 19 units followed as Dunalastair IV. From 1910, a total of 21 engines of classes 139 and 43 were built, which had a superheater ex works and, depending on the author, are either also classified in the Dunalastair class or regarded as a separate class.

No. 769 Dunalastair II

Locomotive Magazine, June 1898

During development, the boiler pressure was increased first to 175 and then 180 psi. Beginning in 1914, when some Series II, III and IV locomotives were retrofitted with superheaters, the boiler pressure was lowered back to 170 psi and larger cylinders were installed. At the LMS they were numbered between 14311 and 14439. While all Dunalastairs in the original version were retired by 1935, the superheated engines survived longer. Of a total of four engines that were taken over by British Railways, the last Dunalastair IV survived until 1958.

The Caledonian Railway had a large number of 0-4-4T tank locomotives built between 1884 and 1925, which were intended for local passenger traffic in Edinburgh and Glasgow. One of four chief engineers who procured these locomotives was John F. McIntosh. During his service, which lasted from 1895 to 1914, twelve members of class 92, twelve of class 104, ten of class 879 and 68 of class 439 were created.

Depending on where the individual classes were to be used, the driving wheel diameter differed significantly with 54 or 69 inches. For the sections laid underground, some locomotives had a condensation device, but this apparently could not always retain all of the steam. Pickersgill introduced the class 431 in 1922, which was based directly on the 439 and was used as a banker locomotive. The LMS also had its own version of the 439 built from 1925 onwards. A large number of McIntosh's 0-4-4Ts also survived into the British Railways era.

The Caledonian Railway's class 812 comprised 79 0-6-0 freight locomotives, which McIntosh had developed as a successor to his “Jumbos”. They differed primarily in their larger boiler and longer wheelbase. The boiler was the same as that of the Class 721 “Dunalastair”. After the class 812 had been built by three commercial manufacturers in 1899 and 1900, the CR built 15 identical locomotives as class 652 in 1908 and 1909 in its own St. Rollox workshops in Glasgow.

They could reach a speed of up to 55 mph or 89 km/h and were therefore also used in passenger service. For this 17 had got a continuous Westinghouse brake. A necessary improvement concerned the frames, which had to be reinforced due to cracks.

After the founding of the LMS, these locomotives were put into the power class 3F and distributed across most of Scotland. When British Railways were founded in 1948, almost all of them were still in use. It took until 1963 for all to disappear. Only number 828 remained and is now operational and owned by the Strathspey Railway. The Belgian State Railways purchased a total of 891 locomotives in three types that were directly derived from these.

The Caledonian Railway had to operate many express trains with two 4-4-0 locomotives and also needed a helper locomotive at Beattock Summit. To improve this, McIntosh developed a 4-6-0 in 1903. Initially these were just two locomotives, numbers 49 and 50, which were based on the Dunalastair and had inside cylinders. Although these became the flagship of the CR, their performance was not outstanding and there were no sufficiently long turntables.

After longer turntables were built, McIntosh had five improved locomotives built, numbers 903 to 907. The 903 was the only one in the new series to be given the name “Cardean” and thus gave rise to the nickname of the class. All of them received a superheater in 1911, but due to the reduced boiler pressure they hardly had any noticeable increase in output.

However, since this reduced coal consumption, all of them were taken over by the LMS in 1923. There they were soon eclipsed by the LMS Compound and Royal Scot. They were retired between 1927 and 1933, with the exception of the 907, which was written off in 1915 after Britain's worst rail disaster.

In 1916, William Pickersgill had 16 class 72 4-4-0 express locomotives built. From 1920, 32 more class 113 locomotives followed, which had a slightly smaller boiler and slightly larger cylinders. Technically, they could be considered the successors to McIntosh's Dunalastair range, which is why they were unofficially called “Dunalastair V”. Like their predecessors, they had the cylinders and valve gear on the inside of the frame, but a superheater straight from the factory. They reportedly performed well, which increased their lifespans. So all members of the class came to the LMS in 1923 and to the British Railways in 1948. One was scrapped in 1953 after an accident and the rest were only retired between 1959 and 1962.