The first 19 locomotives that Brunel had procured in 1938 were partly adventurous designs to reach high speeds. On the one hand there were the “Snake” and “Viper” locomotives from the Haigh foundry, which were brought to higher speeds with a gearbox with a ratio of 2:3 and had the wheel arrangement 2-2-2. Less conventional were the two Hawthorn locomotives developed by Thomas Elliot Harrison, which used two cars to split the boiler and engine.

The first of these was the “Thunderer”, where the boiler and driver's stand were on a three-axle chassis. The cylinders were housed on another, two-axle chassis together with a gearbox with a ratio of 10:27. Here both axles with six feet wheels were driven. The live steam was routed to the engine chassis and the exhaust steam back to the smoke box via elastic pipes.

“Thunderer”

Locomotive Magazine, April 1901

The “Hurricane” got rid of the gearbox by increasing the size of the driven wheels to exactly ten feet. For reasons of space, only one axle was driven, which is why two carrying axles were added and the engine unit was thus given the wheel arrangement 2-2-2. Both “Thunderer” and “Hurricane” were only used until December 1939 and their boilers were then used as stationary steam generators and for a freight locomotive. Thanks to the experience with the locomotives, gearboxes and equally divided locomotives were dispensed with in the future and high speeds were achieved in other ways.

Daniel Gooch used the Star class, more precisely the “North Star” locomotive developed by Robert Stephenson, as a basis for developing a new broad-gauge express locomotive. He stayed with the 2-2-2 wheel arrangement and a driving wheel diameter of seven feet, but installed a larger boiler.

In the years 1840 to 1842, seven manufacturers made a total of 62 locomotives. The names of the locomotives did not follow a uniform scheme. In addition to names that began with “Fire”, there were also those that came from Greek mythology or from animals. From 1865 they were counted to the Priam class.

The “Fire Fly” is said to have traveled the almost 31 miles from Twyford to London Paddington in 1840 at an average of 50 mph, which was a record at the time. Later, the locomotives were fitted with new cylinders that were 16 by 20 inches instead of 15 by 18 inches. The decommissioning took place between 1864 and 1879. A working replica of “Fire Fly” was completed in 2005.

Based on the success of the Firefly class, Daniel Gooch wanted to build an even more powerful and faster express locomotive. The driving wheels were increased from seven to eight feet and the largest possible boiler was installed in order to be able to take full advantage of the broad gauge. The wheel arrangement was still 2-2-2 and all wheels were mounted between the inner and outer frames. The cylinders were mounted between the inner frames.

“Great Western” in its original condition

Die Lokomotive, September 1937

The “Great Western” was completed in 1846 as the forerunner of the series. After just a short trial, the leading axle broke, which was attributed to the fact that the locomotive was too heavy to distribute the load over just three axles. The solution was to replace the leading axle with two axles that were also mounted in the frame. Although this made the locomotive heavier overall, the load on the driving axle fell. A further 29 series pieces were built in this form. The class was named “Iron Duke” after the first newly built machine and is said to have reached a top speed of 78 mph. The five-car express between London and Bristol is said to have averaged 68 mph on the 53 miles long section to Didcot.

“Great Western” with fixed leading axles

Die Lokomotive, September 1937

In 1871 the “Great Britain”, “Prometheus” and “Estaffete” locomotives were converted to the Rover class. They received a larger boiler with higher pressure and a flat, elevated firebox instead of the previous haystack-shaped firebox. While the Iron Duke class locomotives were gradually phased out, their names were reused for 19 newly built Rover class examples, produced up to 1888.

The last engines of the Rover class did not have long lives, as broad gauge operations ceased in 1892. All pieces were then scrapped. It was not until 1985 that a working replica of the Iron Duke was built using parts from two Hunslet Austerity tank locos. It was not restored to service after her boiler life expired and now stands at the Didcot Railway Centre.

In 1849 the GWR manufactured the “Corsair” and “Brigand” saddle tank locomotives for passenger services on the steep and winding South Devon Railway in their own workshops in Swindon. Since the bogie could not be moved sideways, the first coupled axle was not given wheel flanges. The “Corsair” still had a sledge brake, the “Brigand” received a shoe brake on one wheel.

“Ovid”

Locomotive Magazine, June 1902

As the operation of the South Devon Railway was finally handed over from the GWR to a specially founded company, the two locomotives were used on other lines. A further 13 locomotives were ordered, but the production of these was handed over to Hawthorns'. In these, the diameter of the driving wheels had been reduced by three inches.

The class 1076 tank locomotives were actually built for the GWR standard-gauge routes and had a double frame, i.e. they had both outside and inside frames and the wheels were between them. The first six had simple side water tanks, but all others were built with a saddle tank. In the first batch, the cab was only protected by a weather board, in the later batches there was a cab that was open at the back. Later, completely closed driver's cabs were retrofitted, since tank locomotives often ran backwards.

In 1876, ten locomotives were built for the seven feet broad gauge, with the wheels outside the outer frame. Five more followed two years later and from 1884 a total of 35 of the standard-gauge engines were rebuilt in the same way. When operations on the broad-gauge lines were discontinued, the locomotives were restored to standard gauge and thus joined the remaining 216. Most of the surviving machines were even modernized from 1911 and got Pannier water tanks. The latter got their name from the panniers carried by pack animals and were popular with the GWR. The previous saddle tanks could no longer be accommodated in the engines that had been retrofitted with a Belpaire firebox with an angular external profile.

Today, more than 100 GWR broad gauge freight locomotives, which originally belonged to different classes, are called the Caesar class. They all had the 0-6-0 wheel arrangement and were designed by Daniel Gooch and built in Swindon. In contrast to their predecessors, they did not have a haystack firebox, but one with a round top.

Using the possibilities of the broad gauge, they were significantly more powerful than other locomotives with this wheel arrangement. Due to the gentle curves of the broad-gauge tracks, the wheelbase could be made very long in order to obtain sufficient running smoothness despite the lack of carrying axles. At five feet in diameter, the wheels were smaller than the boiler diameter.

Schematic drawing of “Cato”

Locomotive Magazine, April 1902

The actual Caesar class consisted of eight saddle tank locomotives built in 1851 and 1852. Their service life ended between 1871 and 1880. A restructuring of the class names in 1865 resulted in the Pyracmon, Ariadne and Caliph class tender locomotives being included in the Caesar class.

The seven Pyracmon class locomotives were based on the Premier class, which were the first locomotives built in Swindon and were to be phased out between 1871 and 1873. The Ariadne and Caliph classes were also referred to as “Gooch Standard Goods” and were delivered in seven lots between 1852 and 1863.

Most locomotives were named after gods or well-known figures from ancient Greece, but some were named after British rivers or given other names altogether. This resulted in 102 locomotives that were retired between 1871 and 1883. An exception was the “Europa”, which was extensively rebuilt in 1869 and remained in service until 1892, when traffic on the broad gauge was discontinued.

The broad gauge Bristol & Exeter Railway took over the “Flying Dutchman”, which started from London-Paddington, on the last section between Bristol and Exeter. To accommodate this fastest train in the world, eight tank locomotives with a driving wheel diameter of nine feet or 2,743 mm were ordered from Rothwell & Co. These were the largest wheels ever found on a commercially used locomotive.

There was a bogie at each end of the locomotives, while the driving wheels had no flanges. The load on the bogies was lower than that on the driving axle. Another feature was the outside frame, which ran from front to back and in which the driving axle was also mounted. They often reached speeds of around 80 mph (129 km/h), with the highest recorded speed on a slight decent reaching 81.8 mph. 

After the rebuild to 8 ft 10 in

Locomotive Magazine, October 1898

After a derailment in 1876, the remaining seven locomotives were rebuilt. They received driving wheels with a diameter of only eight feet and ten inches, which now had flanges. In addition, the outside frame was eliminated and there was now a longer overall wheelbase. Furthermore, the cylinders were now larger and, the larger boiler above all had a larger grate because it now burned coal instead of coke. Three were even converted into tender locomotives with a 4-2-2 wheel arrangement.