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British Rail Class 141
The British Rail Class 141 is the first production model of the Pacer diesel multiple unit (DMU) railbus.
During the 1980s, British Rail (BR) was interested in replacing its first generation diesel multiple units, particularly in the use of railbuses to service its lightly used branch lines. It was decided to develop such a vehicle with a high level of commonality with the widely used Leyland National bus, leading to its modular design serving as the basis for the design. Several single and two-car prototypes were constructed and evaluated, before an order was placed with British Leyland for 20 two-car Class 141 units during 1984. During their operating lives, the units were tasked with various passenger services in Yorkshire for 13 years. Following withdrawal, a large proportion of the units were exported to Iran where they operated for a further eight years, giving the Class 141 a total lifespan of 21 years.
By the beginning of the 1980s, British Rail (BR) operated a large fleet of first generation DMUs, which had been constructed in prior decades to various designs. While formulating its long term strategy for this sector of its operations, British Rail planners recognised that there would be considerable costs incurred by undertaking refurbishment programmes necessary for the continued use of these ageing multiple units, particularly due to the necessity of handling and removing hazardous materials such as asbestos. In light of the high costs involved in retention, planners examined the prospects for the development and introduction of a new generation of DMUs to succeed the first generation.
In the concept stage, two separate approaches were devised, one involving a so-called railbus that prioritised the minimisation of both initial (procurement) and ongoing (maintenance & operational) costs, while the second was a more substantial DMU that could deliver superior performance than the existing fleet, particularly when it came to long distance services. While the more ambitious latter requirement would ultimately lead to the development of the Class 150 and the wider Sprinter family of DMUs, BR officials recognised that a cheaper unit was desirable for service on the smaller branch lines that would not be unduly impacted by lower performance specs or a high density configuration. As such, work to progress both approaches was undertaken by BR's research department during the early 1980s.
During this period, a number of prototypes were constructed to explore different designs and approaches for implementing the railbus concept. One such vehicle was a single two-car unit, designated as the Class 140, that was constructed between 1979 and 1981. This prototype was introduced with much fanfare during June 1981. Initial testing with the Class 140 uncovered several issues, such as difficulty detecting the type via track circuits, this was reliably resolved by swapping the material of the brake blocks from a composite to iron. Two less easily-addressable drawbacks were the high level of noise generated during transit, particularly on older jointed rails, which was a consequence of the railbus's direct connection between the underframe and suspension with the body that transmitted impact forces across the body. It was also observed that the inclusion of strengthening members in the mass-produced bus body added significantly to the overall production cost, which eliminated much of the cost advantage that was the primarily goal of the type.
The Class 140 was viewed to be an overall success, and thus BR issued an order for an initial production model, designated Class 141, to British Leyland during 1984 with production commencing thereafter. In subsequent years, follow-on orders would be placed, but these would be for improved derivatives of the Class 141, these being the Class 142 and Class 143 respectively. Unlike these later siblings, the Class 141 had a noticeably narrower body, having equal width to that of the standard bus; subsequent production models expanded this to maximise internal volume.
The Class 141 shared a very high degree of similarity to the design of the Class 140, a factor that enabled the latter to act as a driving instruction unit and demonstrator for the former. However, these production types also differed in numerous places. One major area of change is the separation between the underframe and the body above by a flexible mounting in contrast to the prototype's integration of these two sections; there was also a reduction in the depth of the underframe for maintenance accessibility. Furthermore, in order to maximise cost savings, the manufacturers made use of road bus-standard electrical equipment, passenger fittings, and general cab layout wherever possible.
Both the bodies and underframes were designed for interchangeability, as had been specified by BR, having been assembled upon jigs. These were designed so that the entire body could be replaced during a mid-life refurbishment/reconstruction, and that the replacement body would not be limited to the exact same dimensions either. The underframe area, in addition to its structural role, accommodated all of the propulsion apparatus along with the majority of electrical gear.
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British Rail Class 141 AI simulator
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British Rail Class 141
The British Rail Class 141 is the first production model of the Pacer diesel multiple unit (DMU) railbus.
During the 1980s, British Rail (BR) was interested in replacing its first generation diesel multiple units, particularly in the use of railbuses to service its lightly used branch lines. It was decided to develop such a vehicle with a high level of commonality with the widely used Leyland National bus, leading to its modular design serving as the basis for the design. Several single and two-car prototypes were constructed and evaluated, before an order was placed with British Leyland for 20 two-car Class 141 units during 1984. During their operating lives, the units were tasked with various passenger services in Yorkshire for 13 years. Following withdrawal, a large proportion of the units were exported to Iran where they operated for a further eight years, giving the Class 141 a total lifespan of 21 years.
By the beginning of the 1980s, British Rail (BR) operated a large fleet of first generation DMUs, which had been constructed in prior decades to various designs. While formulating its long term strategy for this sector of its operations, British Rail planners recognised that there would be considerable costs incurred by undertaking refurbishment programmes necessary for the continued use of these ageing multiple units, particularly due to the necessity of handling and removing hazardous materials such as asbestos. In light of the high costs involved in retention, planners examined the prospects for the development and introduction of a new generation of DMUs to succeed the first generation.
In the concept stage, two separate approaches were devised, one involving a so-called railbus that prioritised the minimisation of both initial (procurement) and ongoing (maintenance & operational) costs, while the second was a more substantial DMU that could deliver superior performance than the existing fleet, particularly when it came to long distance services. While the more ambitious latter requirement would ultimately lead to the development of the Class 150 and the wider Sprinter family of DMUs, BR officials recognised that a cheaper unit was desirable for service on the smaller branch lines that would not be unduly impacted by lower performance specs or a high density configuration. As such, work to progress both approaches was undertaken by BR's research department during the early 1980s.
During this period, a number of prototypes were constructed to explore different designs and approaches for implementing the railbus concept. One such vehicle was a single two-car unit, designated as the Class 140, that was constructed between 1979 and 1981. This prototype was introduced with much fanfare during June 1981. Initial testing with the Class 140 uncovered several issues, such as difficulty detecting the type via track circuits, this was reliably resolved by swapping the material of the brake blocks from a composite to iron. Two less easily-addressable drawbacks were the high level of noise generated during transit, particularly on older jointed rails, which was a consequence of the railbus's direct connection between the underframe and suspension with the body that transmitted impact forces across the body. It was also observed that the inclusion of strengthening members in the mass-produced bus body added significantly to the overall production cost, which eliminated much of the cost advantage that was the primarily goal of the type.
The Class 140 was viewed to be an overall success, and thus BR issued an order for an initial production model, designated Class 141, to British Leyland during 1984 with production commencing thereafter. In subsequent years, follow-on orders would be placed, but these would be for improved derivatives of the Class 141, these being the Class 142 and Class 143 respectively. Unlike these later siblings, the Class 141 had a noticeably narrower body, having equal width to that of the standard bus; subsequent production models expanded this to maximise internal volume.
The Class 141 shared a very high degree of similarity to the design of the Class 140, a factor that enabled the latter to act as a driving instruction unit and demonstrator for the former. However, these production types also differed in numerous places. One major area of change is the separation between the underframe and the body above by a flexible mounting in contrast to the prototype's integration of these two sections; there was also a reduction in the depth of the underframe for maintenance accessibility. Furthermore, in order to maximise cost savings, the manufacturers made use of road bus-standard electrical equipment, passenger fittings, and general cab layout wherever possible.
Both the bodies and underframes were designed for interchangeability, as had been specified by BR, having been assembled upon jigs. These were designed so that the entire body could be replaced during a mid-life refurbishment/reconstruction, and that the replacement body would not be limited to the exact same dimensions either. The underframe area, in addition to its structural role, accommodated all of the propulsion apparatus along with the majority of electrical gear.