British Rail Class 29

The BR Class 29 was a series of twenty Bo-Bo diesel-electric locomotives rebuilt at Cowlairs Works in Glasgow between 1965 and 1967, created by re-engining the worst-performing members of the Class 21 — itself a troubled design — with Paxman Ventura engines in an attempt to salvage usable motive power from a fleet that had proved deeply unsatisfactory in its original form.

The Class 21 had been built by the North British Locomotive Company of Glasgow between 1958 and 1960, powered by MAN diesel engines that proved wholly unreliable in service. NBL, which was simultaneously struggling to produce the Class 22 diesel-hydraulics for the Western Region, found that it lacked the engineering expertise to make the MAN engine installation work properly in a traction application, and the Class 21s spent more time under repair than in revenue service. The Scottish Region, which received the bulk of the Class 21 allocation, found them a serious operational liability.

In 1965 BR authorised a programme to rebuild twenty of the least-damaged Class 21 locomotives at Cowlairs, replacing the failed MAN engines with Paxman Ventura 12YJXL units producing 1,350 hp. The rebuilt locomotives were reclassified as Class 29, with new TOPS numbers in the 29xxx series. The Paxman engine was a proven and considerably more reliable unit than the MAN, and the rebuilt locomotives performed significantly better than the originals. Allocation remained concentrated on Scottish Region depots, particularly Eastfield and Haymarket, where the 29s worked mixed freight and secondary passenger duties.

However, the Class 29s remained fundamentally compromised by the Class 21 body structure and running gear, which had been designed around the heavier MAN engine and was not ideally suited to the Paxman replacement. Maintenance costs remained higher than for purpose-built types, and the availability of the Sulzer-engined Classes 26 and 27 — which had proved far more satisfactory on the same Scottish duties — meant the Class 29 was always a stopgap rather than a long-term solution. Withdrawal of the rebuilt locomotives began in 1971 and was completed by 1973. None was preserved; the class represents one of the more obscure footnotes in BR's complicated diesel history, a rebuild programme that produced adequate but not distinguished results from fundamentally flawed starting material.