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British Rail Class 73
The British Rail Class 73 is a British electro-diesel locomotive. This type is unusual in that it can operate on the Southern Region's 650 / 750 V DC third rail power supply, or an onboard diesel engine to allow it to be used on non-electrified routes. This makes it very versatile, although the diesel engine produces less power than is available from the third-rail power supply, so the locomotives are rarely used outside of the former Southern Region of British Rail. It is one of the first bi-mode locomotives ever built. Following the withdrawal and scrapping of the more powerful Class 74 bi-mode locomotives in 1977, the Class 73 was unique on the British railway network until the introduction of the Class 88 bi-mode locomotives in 2017. Ten locomotives have been scrapped.
The Southern Railway's expanding third rail electric passenger network (which had begun as far back as 1915) was until 1941 a purely passenger electric multiple unit (EMU) system. This was because it was necessary to have gaps in the third rail for level crossings, etc., which effectively prevented the use of electric locomotives on either passenger or freight. The problem was solved when Oliver Bulleid became Chief Mechanical Engineer in 1937 and began work with Chief Electrical Engineer Alfred Raworth. To overcome the problem of gaps in the third rail three experimental locomotives were built (which later became the British Rail Class 70) which were fitted with large flywheels that maintained momentum long enough to avoid stalling in gaps. The second problem for freight train operation by electric locomotives was the serious hazard that would result if the 750 V DC third rail was laid in goods yards, as this would be a danger to personnel on the ground and also present some complex issues loading and unloading many types of freight wagons. The initial solution was to install simple tramway-type overhead wires to carry the 750 V supply in certain yards and add a pantograph on the locomotive roofs.
As a continuation of the Southern Railway's policy of electrification, British Railways then began electrifying the main lines to the Kent Coast as part of the 1955 Modernisation Plan. In addition to the few hundred new EMUs required, a small fleet of 25 Bo-Bo electric locomotives of 2,552 hp (1,903 kW) classed type "HA" (later Class 71) were built to deal with freight, parcels, and the few remaining locomotive-hauled passenger trains in Kent, such as the "Night Ferry" and "Golden Arrow" services. These locomotives also had a flywheel and pantograph, and were able to work in the more important freight yards across Kent that were fitted with the simple 750 V overhead wire system. This system was brought into use across Kent between 1959 and 1961.
Although successful this system did require considerable extra cost, and maintenance, and still limited freight operations with the new locomotives to those goods yards fitted with the catenary. Something more versatile was needed. Development and advances in both electric locomotive and diesel engine design in the early 1960s resulted in the Southern Region engineers beginning to consider the possibility of a combined electric and diesel locomotive. The requirement was for an electric locomotive with a similar power when using the electrified third rail to the already successful Type 3 Birmingham Railway Carriage and Wagon (BRCW) built diesel locomotives (later Class 33) then entering service on the Southern. This would be supported by adding a small diesel engine powerful enough to move reasonable freight loads at slow speed within goods yards. The new locomotive design would also need retractable third rail pick up shoes. This was for two reasons: the first was safety in connection with track relaying jobs, avoiding the problem of bridging a gap and energising a dead section of third rail, and electrocuting track workers who might be in contact with the dead third rail section. The second was to allow locomotives under diesel power to move off and back onto third rail areas without risk of damaging "fixed" third rail pick up shoes.
The Southern Region engineers, having done all the initial design work, set about building a prototype batch of six new "electro-diesel" locomotives at Eastleigh Carriage and Wagon Works during 1961–1962. The new locomotives had a respectable 1,600 hp (1,200 kW) on electric power, and an English Electric 600 hp (450 kW) diesel engine similar to those used in the Southern Region's diesel electric multiple Unit (DEMU) fleet. To improve versatility yet further, the locomotives were designed so that they could work in multiple with most of the Southern's electric and diesel multiple unit fleets as well as normal carriages and wagons. This meant the locomotives had to also be fitted with drop buckeye couplings and therefore the Pullman rubbing bar, and retractable buffers. The success of these prototype locomotives resulted in British Railways ordering a production batch of a further 43 locomotives from English Electric at the Vulcan Foundry in Newton-le-Willows. However minor technical differences prevented the prototypes (classified type "JA") working in multiple with the production examples (classified type "JB"). In all other respects, the new "electro-diesels" proved extremely versatile, to the point where many are still in service after a life of over 63 years.
This class of 49 locomotives were built in two batches using English Electric components. The first six locomotives were built by BR at Eastleigh Carriage and Wagon Works and introduced to service during 1962; they were built to the Hastings Line gauge, numbered E6001-E6006 and classified as type JA. With the introduction of TOPS in 1968 they were to have been classified as Class 72, to differentiate from the later built units. However, instead they became Class 73/0. In the early 1970s the locomotives were renumbered 73001-73006.
Following successful trials of the initial locomotives, a production run of 43 locomotives were ordered as part of the Bournemouth Electrification and built by English Electric at their Vulcan Foundry between 1965 and 1967. They were initially classified as Class JB and numbered E6007-E6049. They differed slightly from the six earlier machines, most notably having an increased tractive effort as well as a higher maximum speed (90 mph as opposed to 80). Following the introduction of TOPS, they became Class 73/1 and were renumbered 73101-73142. One locomotive, E6027, had already been withdrawn following accident damage and so was not renumbered. Further changes were the use of large round Oleo buffers with a pneumatic withdrawal mechanism rather than the traditional coach style (oval) saddle buffer which relied on a pin and spring mechanism. As the JA examples came in for overhaul over the years, the saddle buffers were also replaced making visual identification of the differing machines almost impossible from a distance.
From new, all members of the class were fitted with the Pullman style rubbing plate between the buffers allowing them to close couple with Southern Region electro-pneumatically controlled electric multiple units and diesel electric multiple units for push-pull train operation – the reason for retractable buffers.
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British Rail Class 73 AI simulator
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British Rail Class 73
The British Rail Class 73 is a British electro-diesel locomotive. This type is unusual in that it can operate on the Southern Region's 650 / 750 V DC third rail power supply, or an onboard diesel engine to allow it to be used on non-electrified routes. This makes it very versatile, although the diesel engine produces less power than is available from the third-rail power supply, so the locomotives are rarely used outside of the former Southern Region of British Rail. It is one of the first bi-mode locomotives ever built. Following the withdrawal and scrapping of the more powerful Class 74 bi-mode locomotives in 1977, the Class 73 was unique on the British railway network until the introduction of the Class 88 bi-mode locomotives in 2017. Ten locomotives have been scrapped.
The Southern Railway's expanding third rail electric passenger network (which had begun as far back as 1915) was until 1941 a purely passenger electric multiple unit (EMU) system. This was because it was necessary to have gaps in the third rail for level crossings, etc., which effectively prevented the use of electric locomotives on either passenger or freight. The problem was solved when Oliver Bulleid became Chief Mechanical Engineer in 1937 and began work with Chief Electrical Engineer Alfred Raworth. To overcome the problem of gaps in the third rail three experimental locomotives were built (which later became the British Rail Class 70) which were fitted with large flywheels that maintained momentum long enough to avoid stalling in gaps. The second problem for freight train operation by electric locomotives was the serious hazard that would result if the 750 V DC third rail was laid in goods yards, as this would be a danger to personnel on the ground and also present some complex issues loading and unloading many types of freight wagons. The initial solution was to install simple tramway-type overhead wires to carry the 750 V supply in certain yards and add a pantograph on the locomotive roofs.
As a continuation of the Southern Railway's policy of electrification, British Railways then began electrifying the main lines to the Kent Coast as part of the 1955 Modernisation Plan. In addition to the few hundred new EMUs required, a small fleet of 25 Bo-Bo electric locomotives of 2,552 hp (1,903 kW) classed type "HA" (later Class 71) were built to deal with freight, parcels, and the few remaining locomotive-hauled passenger trains in Kent, such as the "Night Ferry" and "Golden Arrow" services. These locomotives also had a flywheel and pantograph, and were able to work in the more important freight yards across Kent that were fitted with the simple 750 V overhead wire system. This system was brought into use across Kent between 1959 and 1961.
Although successful this system did require considerable extra cost, and maintenance, and still limited freight operations with the new locomotives to those goods yards fitted with the catenary. Something more versatile was needed. Development and advances in both electric locomotive and diesel engine design in the early 1960s resulted in the Southern Region engineers beginning to consider the possibility of a combined electric and diesel locomotive. The requirement was for an electric locomotive with a similar power when using the electrified third rail to the already successful Type 3 Birmingham Railway Carriage and Wagon (BRCW) built diesel locomotives (later Class 33) then entering service on the Southern. This would be supported by adding a small diesel engine powerful enough to move reasonable freight loads at slow speed within goods yards. The new locomotive design would also need retractable third rail pick up shoes. This was for two reasons: the first was safety in connection with track relaying jobs, avoiding the problem of bridging a gap and energising a dead section of third rail, and electrocuting track workers who might be in contact with the dead third rail section. The second was to allow locomotives under diesel power to move off and back onto third rail areas without risk of damaging "fixed" third rail pick up shoes.
The Southern Region engineers, having done all the initial design work, set about building a prototype batch of six new "electro-diesel" locomotives at Eastleigh Carriage and Wagon Works during 1961–1962. The new locomotives had a respectable 1,600 hp (1,200 kW) on electric power, and an English Electric 600 hp (450 kW) diesel engine similar to those used in the Southern Region's diesel electric multiple Unit (DEMU) fleet. To improve versatility yet further, the locomotives were designed so that they could work in multiple with most of the Southern's electric and diesel multiple unit fleets as well as normal carriages and wagons. This meant the locomotives had to also be fitted with drop buckeye couplings and therefore the Pullman rubbing bar, and retractable buffers. The success of these prototype locomotives resulted in British Railways ordering a production batch of a further 43 locomotives from English Electric at the Vulcan Foundry in Newton-le-Willows. However minor technical differences prevented the prototypes (classified type "JA") working in multiple with the production examples (classified type "JB"). In all other respects, the new "electro-diesels" proved extremely versatile, to the point where many are still in service after a life of over 63 years.
This class of 49 locomotives were built in two batches using English Electric components. The first six locomotives were built by BR at Eastleigh Carriage and Wagon Works and introduced to service during 1962; they were built to the Hastings Line gauge, numbered E6001-E6006 and classified as type JA. With the introduction of TOPS in 1968 they were to have been classified as Class 72, to differentiate from the later built units. However, instead they became Class 73/0. In the early 1970s the locomotives were renumbered 73001-73006.
Following successful trials of the initial locomotives, a production run of 43 locomotives were ordered as part of the Bournemouth Electrification and built by English Electric at their Vulcan Foundry between 1965 and 1967. They were initially classified as Class JB and numbered E6007-E6049. They differed slightly from the six earlier machines, most notably having an increased tractive effort as well as a higher maximum speed (90 mph as opposed to 80). Following the introduction of TOPS, they became Class 73/1 and were renumbered 73101-73142. One locomotive, E6027, had already been withdrawn following accident damage and so was not renumbered. Further changes were the use of large round Oleo buffers with a pneumatic withdrawal mechanism rather than the traditional coach style (oval) saddle buffer which relied on a pin and spring mechanism. As the JA examples came in for overhaul over the years, the saddle buffers were also replaced making visual identification of the differing machines almost impossible from a distance.
From new, all members of the class were fitted with the Pullman style rubbing plate between the buffers allowing them to close couple with Southern Region electro-pneumatically controlled electric multiple units and diesel electric multiple units for push-pull train operation – the reason for retractable buffers.