The British Rail Class 29 was a short-lived class of 20 diesel-electric locomotives rebuilt from the earlier North British-built Class 21s. The original batch of Class 21s had been fitted with licence-built MAN power units that proved unreliable in service. To address the failures, one locomotive was sent for trial re-engining in 1963, and a programme to re-engine the small fleet followed during 1964–65. After modification these machines carried a new TOPS-style identity as Class 29 and returned to traffic based chiefly in Scotland.

Design changes and technical features

The defining change for the Class 29 was the replacement of the original MAN-derived engines with Paxman Ventura V12 diesel engines, work that was begun experimentally at Colchester and completed in quantity at Polmadie Works. Alongside the new prime mover, the rebuilds received complementary alterations intended to improve reliability and crew operation.

  • New Paxman Ventura V12 engines, replacing the licence-built MAN units.
  • Revisions to ancillary systems and cooling to suit the higher-speed Paxman installation.
  • Fitting of four-character headcode displays in the nose ends to modernise visibility and operational coding.
  • Other workshop modifications carried out during re-engining at Polmadie Works.

Service history and deployment

Following completion of the conversion programme the re-engined locomotives returned to traffic from Eastfield depot in Glasgow and worked a range of mixed-traffic duties in Scotland and nearby regions. The extra power and markedly improved mechanical reliability compared with their predecessors made them useful during the mid-to-late 1960s, although they never formed a large or widespread class.

Withdrawal and legacy

Despite the improvements, the Class 29s were a small, non-standard class with a high-speed diesel engine type that did not fit easily into British Railways' move toward fleet commonality. These factors, together with broader modernisation and roster rationalisation, led to relatively early withdrawal. One example was removed from service in 1969; the remainder were taken out of use and scrapped between 1971 and 1972. No examples of Class 29 or the original Class 21 rebuilds survive in preservation.

Notable facts and distinctions

  • The Class 29s were not new builds but conversions of North British-built Class 21 locomotives, undertaken to remedy chronic engine unreliability.
  • The trial and subsequent conversions involved Paxman at Colchester and heavy refurbishment work at Polmadie Works.
  • The class illustrates mid-20th-century practice of re-engining as a cost-effective alternative to replacement when fleets were small.
  • All primary sources for further technical and historical detail can be consulted through specialist publications and archives that document British diesel locomotive development.

For additional reading and reference material on the Class 29 and related locomotive types see the rebuilt programme notes and workshop records available via specialist histories: Class 29 overview, North British locomotives, Class 21 origins, Paxman works at Colchester, Paxman Ventura engine, and Eastfield depot, Glasgow.