The “Blue Tiger” demonstrator was created by Adtranz as the first representative of a planned family of locomotives. The engine and three-phase traction motors are from General Electric. Ten production locomotives were delivered in Germany, which are only used by private railways. In addition, 30 units were built for Pakistan and 20 for Malaysia in different gauges. After Bombardier bought Adtranz, the marketing of the DE-AC33C was discontinued because diesel variants of the TRAXX had also been developed.

The class 56 originated in the need of British Railways for a new power class 5 diesel locomotive in the seventies. It was specified that the bodyshell and many mechanical parts would be from the class 47. The engine was a Ruston-Paxman 16RK3CT, that was a development of the English Electric diesels. It was rated at 3,520 hp, but set at 3,250 hp. Instead of the main DC generator of earlier diesel-electrics, now an AC alternator powered the DC traction motors via a rectifier.

Since the British builders didn't have capacities at the time due to years of cost savings, the manufacturing was transferred to Electroputere in Romania. They called the type LDE 3500 and delivered the first 30 in 1977 to Britain. It didn't take long until it was found out that they were of poor build quality and had to be withdrawn after only a few years. They only entered service again after extensive rebuilds. So a low-rate production of a revised design was started at BREL. Until 1984, they built 85 at Doncaster and 20 at Crewe with sub-assemblies coming from other works.

56026 with a coal train near Poolsbrook

Phil Sangwell

All in all, they delivered valuable services. Although maintenance wasn't as easy as for the modular class 58, they were less prone to wheelslip than this. In 1995, all remaining locomotives came to the English Welsh & Scottish (EWS). Withdrawals started soon, with the last ones being withdrawn in 2004. After some years of storage, many were sold to a multitude of new owners. So some were soon used in construction trains, some were used by private operators for freight traffic and three even came to Hungary.

Due to the poor reliability of the class 56, British Railways tendered a new diesel locomotive for heavy block trains. The winner of the tender was Brush Traction and the engine was from Mirrlees. This draws 3,100 hp from just eight cylinders and was one of the most economical on the market at the time. After a few teething problems, the first locomotives were put into service in 1990. After privatization, they all came to the EWS, which at times put 75 percent of the locomotives out of service. They later came to DB Cargo UK where some were modernized from 2010 onwards. Others were soon resold and in 2020 the first one was scrapped.

The class designation HXN5 of China Railway stands for a heavy freight diesel locomotive designed by General Electric. A total of 700 of the model called ES59ACi were ordered in 2005. They have only a cab at one end and are powered by the 16-cylinder GEVO engine only used in export locomotives. At 6,250 hp, they are among the most powerful single-engined diesel locomotives in the world.

Only the first two were built by GE in Erie, Pennsylvania and all other locomotives were built in China by CSR Qishuyan. Unlike the original plans, production was halted after a total of 300. Two other types which are related to the HXN5 are the Indian WDG-6G, called ES57ACi and the ES58ACi of the Brazilian Carajás Railway.

Due to the need for diesel locomotives for heavy shunting and freight service, China Railway had the HXN5B developed by CSR Qishuyan. It was designed after the same principles as the American Road Switchers. It is powered by a twelve-cylinder with 3,530 kW (4,800 hp) and three-phase traction motors. 

For the “Belt and Road” project, additional locomotives were needed for the Chinese-Russian border area whose bogies could be adapted to the Russian and standard gauge. For this purpose, the HXN5B was selected after the DF7C and adapted to use the SA3 central buffer coupling.