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British Rail Class 25
The British Rail Class 25, also known as the Sulzer Type 2, is a class of 327 diesel locomotives built between 1961 and 1967 for British Rail. They were numbered in two series, D5151–D5299 and D7500–D7677.
The first 25 locos became known as Class 25/0 and were built at BR Darlington Works. The Class 25/1 locomotives were built at Darlington and BR Derby Works. The Class 25/2 locomotives were built at Derby with some built at Darlington. The final batch of locomotives were designated Class 25/3 and built by Derby Works and Beyer, Peacock and Company of Manchester.
The Class 24 locomotives were the precursor of the Class 25 design but after the delivery of their first few units it became apparent that the speed ceiling of 75 mph (121 km/h) was unduly restrictive and the provision of additional power would be advantageous. In the course of normal development the power output of the Sulzer six-cylinder engine had been increased by 90 hp (67 kW) to give a continuous traction output of 1,250 bhp (930 kW) at 750 rpm by the introduction of charge air cooling and the first locomotives to use this became known as Class 25 locomotives.
The Class 25s were primarily designed for freight work, but a significant number were fitted with boilers for heating passenger trains. Throughout the 1970s they could be found at work across the whole of the British Rail network although the Eastern and Southern Regions never had a long-term allocation. Though regular performers into the early 1980s on Crewe–Cardiff passenger trains, they are best known in that respect for their use on the summer Saturday trains to Aberystwyth, a task they relinquished in 1984. The final Class 25 locomotive was withdrawn from operational service in March 1987 although it continued to be used on enthusiast specials until March 1991.
The first 25 locos became known as Class 25/0 and were built at the BR Darlington works using the newer 1,250 hp (930 kW) "B" engine, modified generator assembly and traction motors. This increase in power was obtained from an air/water free flow intercooler fitted between a higher capacity pressure charger and inlet manifold, included within the normal cooling circuit to maintain simplicity. The cylinder head was also modified and strengthened.
The BTH generator, type RTB 15656, was rated as 817.5 kW (1,096.3 hp), 750/545 V, 1090/1500 A at 750 rpm, only slightly different from that used in the earlier Class 24s (Note that all Class 25 locomotives used a generator designated as BTH RTB 15656, but its rating and characteristics changed over time). The generator supplied four BTH 137BX traction motors connected in parallel and rated 245 hp (183 kW), 545 V, 375 A at 560 rpm with a gear ratio of 18:79 (to give a 90 mph (140 km/h) maximum speed). Maximum tractive effort was 39,000 lbf (170 kN) and continuous tractive effort was 20,800 lbf (93,000 N) at 17.1 mph (27.5 km/h), the latter standard for all Class 25s. Power at rail was 949 hp (708 kW), now available between 9.3 and 77.6 mph (124.9 km/h). For the first fifteen locomotives fuel capacity was 520 imp gal (2,400 L; 620 US gal) (design type 25 AV) and the final ten had larger 620-imperial-gallon (2,800 L; 740 US gal) fuel tanks installed (design type 25 BV).
The Class 25/1 locomotives were built at BR Darlington and Derby locomotive works. They featured the new AEI 253AY traction motor, a result of the collaboration between BTH, MV and American builder Alco. This smaller, lighter motor was an attempt to market a traction motor to a worldwide audience, especially to the 1,000 mm (3 ft 3+3⁄8 in) metre gauge lines. For Class 25 locomotives these lighter motors meant the discontinuance of other weight saving measures being built into the design. They were highly rated in an attempt to overcome the loss of tractive effort normally found on starting. The field divert system was also modified to allow increased capability throughout all the speed ranges.
The main generator was a 12-pole machine with the rating changed to 819 kW (1,098 hp), 780/545V, 1050/1500A at 750 rpm. (The continuous rating has also been quoted as 819 kW (1,098 hp), 630V, 1300A). The four traction motors were now connected as series parallel pairs being rated at 234 hp (174 kW), 315V, 650A at 460 rpm, with a gear ratio 18:67. Pairs of motors connected in series provided a higher maximum tractive effort (usually quoted as 45,000 lbf (200 kN) although 47,000 lbf (210 kN) could be achieved) but the downside being that a series pair connected machine was more prone to slipping than one with an all parallel grouping. Full power was available between 7 and 77.5 mph (124.7 km/h), an improvement over Class 25/0 locomotives with all other ratings unchanged from the earlier series. The traction motor's continuous rating of 650 amps was not far removed from its one-hour short term or 'emergency' rating of 680 amps, and this could only be monitored manually. On heavy trains close monitoring of the ammeters was necessary to avoid motor damage. Though the body shell remained similar to D5151 there were a number of refinements. The air horns were relocated to either side of the headcode panel. The cab skirt and body fairing were discontinued, though the support lugs remained. A new driving control panel was fitted. The fuel and water tanks were also redesigned with a fuel capacity of 510 imp gal (2,300 L; 610 US gal) (also quoted in sources as being 500 or 560 imp gal (2,300 or 2,500 L; 600 or 670 US gal)).
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British Rail Class 25 AI simulator
(@British Rail Class 25_simulator)
British Rail Class 25
The British Rail Class 25, also known as the Sulzer Type 2, is a class of 327 diesel locomotives built between 1961 and 1967 for British Rail. They were numbered in two series, D5151–D5299 and D7500–D7677.
The first 25 locos became known as Class 25/0 and were built at BR Darlington Works. The Class 25/1 locomotives were built at Darlington and BR Derby Works. The Class 25/2 locomotives were built at Derby with some built at Darlington. The final batch of locomotives were designated Class 25/3 and built by Derby Works and Beyer, Peacock and Company of Manchester.
The Class 24 locomotives were the precursor of the Class 25 design but after the delivery of their first few units it became apparent that the speed ceiling of 75 mph (121 km/h) was unduly restrictive and the provision of additional power would be advantageous. In the course of normal development the power output of the Sulzer six-cylinder engine had been increased by 90 hp (67 kW) to give a continuous traction output of 1,250 bhp (930 kW) at 750 rpm by the introduction of charge air cooling and the first locomotives to use this became known as Class 25 locomotives.
The Class 25s were primarily designed for freight work, but a significant number were fitted with boilers for heating passenger trains. Throughout the 1970s they could be found at work across the whole of the British Rail network although the Eastern and Southern Regions never had a long-term allocation. Though regular performers into the early 1980s on Crewe–Cardiff passenger trains, they are best known in that respect for their use on the summer Saturday trains to Aberystwyth, a task they relinquished in 1984. The final Class 25 locomotive was withdrawn from operational service in March 1987 although it continued to be used on enthusiast specials until March 1991.
The first 25 locos became known as Class 25/0 and were built at the BR Darlington works using the newer 1,250 hp (930 kW) "B" engine, modified generator assembly and traction motors. This increase in power was obtained from an air/water free flow intercooler fitted between a higher capacity pressure charger and inlet manifold, included within the normal cooling circuit to maintain simplicity. The cylinder head was also modified and strengthened.
The BTH generator, type RTB 15656, was rated as 817.5 kW (1,096.3 hp), 750/545 V, 1090/1500 A at 750 rpm, only slightly different from that used in the earlier Class 24s (Note that all Class 25 locomotives used a generator designated as BTH RTB 15656, but its rating and characteristics changed over time). The generator supplied four BTH 137BX traction motors connected in parallel and rated 245 hp (183 kW), 545 V, 375 A at 560 rpm with a gear ratio of 18:79 (to give a 90 mph (140 km/h) maximum speed). Maximum tractive effort was 39,000 lbf (170 kN) and continuous tractive effort was 20,800 lbf (93,000 N) at 17.1 mph (27.5 km/h), the latter standard for all Class 25s. Power at rail was 949 hp (708 kW), now available between 9.3 and 77.6 mph (124.9 km/h). For the first fifteen locomotives fuel capacity was 520 imp gal (2,400 L; 620 US gal) (design type 25 AV) and the final ten had larger 620-imperial-gallon (2,800 L; 740 US gal) fuel tanks installed (design type 25 BV).
The Class 25/1 locomotives were built at BR Darlington and Derby locomotive works. They featured the new AEI 253AY traction motor, a result of the collaboration between BTH, MV and American builder Alco. This smaller, lighter motor was an attempt to market a traction motor to a worldwide audience, especially to the 1,000 mm (3 ft 3+3⁄8 in) metre gauge lines. For Class 25 locomotives these lighter motors meant the discontinuance of other weight saving measures being built into the design. They were highly rated in an attempt to overcome the loss of tractive effort normally found on starting. The field divert system was also modified to allow increased capability throughout all the speed ranges.
The main generator was a 12-pole machine with the rating changed to 819 kW (1,098 hp), 780/545V, 1050/1500A at 750 rpm. (The continuous rating has also been quoted as 819 kW (1,098 hp), 630V, 1300A). The four traction motors were now connected as series parallel pairs being rated at 234 hp (174 kW), 315V, 650A at 460 rpm, with a gear ratio 18:67. Pairs of motors connected in series provided a higher maximum tractive effort (usually quoted as 45,000 lbf (200 kN) although 47,000 lbf (210 kN) could be achieved) but the downside being that a series pair connected machine was more prone to slipping than one with an all parallel grouping. Full power was available between 7 and 77.5 mph (124.7 km/h), an improvement over Class 25/0 locomotives with all other ratings unchanged from the earlier series. The traction motor's continuous rating of 650 amps was not far removed from its one-hour short term or 'emergency' rating of 680 amps, and this could only be monitored manually. On heavy trains close monitoring of the ammeters was necessary to avoid motor damage. Though the body shell remained similar to D5151 there were a number of refinements. The air horns were relocated to either side of the headcode panel. The cab skirt and body fairing were discontinued, though the support lugs remained. A new driving control panel was fitted. The fuel and water tanks were also redesigned with a fuel capacity of 510 imp gal (2,300 L; 610 US gal) (also quoted in sources as being 500 or 560 imp gal (2,300 or 2,500 L; 600 or 670 US gal)).