British Rail Class 141

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.[6] 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 aging 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.[7]

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.[7] While the more ambitious latter requirement would ultimately lead to the development of the British Rail Class 151 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.[7]

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.[8] This prototype was introduced with much fanfare during June 1981.[8] 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.[7] 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.[7]

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.[7] 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.[7]

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.[7] Furthermore, in order to maximum cost savings, the manufacturers made use of road bus-standard electrical equipment, passenger fittings, and general cab layout wherever possible.[7]

Both the bodies and underframes were designed for interchangeability, as had been specified by BR, having been assembled upon jigs.[7] 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.[7]

As originally built, the traction arrangement of the Class 141 consisted of a Leyland TL11 200 HP engine, a Self-Changing Gears mechanical automatic gearbox and a Gmeinder final drive unit on each car driving only a single axle.[9] This propulsion arrangement was in part taken from the Leyland National bus, as well as shared with the earlier Class 140 prototype. The controller for the automatic transmission was observed by BR engineers to the cause of numerous operating failures and other reliability issues; this was allegedly due to defective relay logic and poor earthing; the issue was eventually resolved on the fleet by replacing the relay-based controller with an alternative that was microprocessor-based.[7]

Both axles (one driving per coach at the inner end) were fitted directly to the chassis rather than being mounted on bogies, unlike traditional DMUs. This uncommon arrangement has been attributed with resulting in the Class 141 units possessing a relatively rough ride, especially when traversing jointed track or points. Their combatively poor ride quality has been said to be a major factor in the general unpopularity amongst passengers.

• 
  141113 standing at Swanwick shed, Midland Railway - Butterley
• 
  141103 standing at Stanhope station, Weardale Railway
• 
  Driver's cab of unit 141103
• 
  141108 at the Colne Valley Railway
• 
  Unidentified class 141 unit in original West Yorkshire PTE Verona green and buttermilk livery

• "New era dawns for W. Yorks commuters". Rail Enthusiast. EMAP National Publications. May 1984. p. 15. ISSN 0262-561X. OCLC 49957965.
• "Class 141 'Pacer' DMU to become weedkilling train". RAIL. No. 332. EMAP Apex Publications. 3–16 June 1998. p. 7. ISSN 0953-4563. OCLC 49953699.

Wikimedia Commons has media related to British Rail Class 141.

• Photo gallery depicting the career of 141113 in preservation (Llangollen Railcar Group)
• YouTube footage showing cab of unit 141108 at the Colne Valley Railway
• YouTube video of a preserved class 141113 at the Midland Railway - Butterley
• A history of railbuses in UK including the Class 141