In British railway history, the British Rail Class 205 diesel-electric multiple units (DEMU) hold a distinctive place. Built by British Rail (BR) at Eastleigh from 1957 to 1962, these units served faithfully for 47 years, transitioning from the BR Southern Region to Connex South Central and finally to the Southern franchise. Their story is one of innovation, adaptation, and evolution.

The Class 205 DEMUs were born out of a unique vision to marry diesel power with electric traction motors, departing from the conventional mechanical and hydraulic drive systems prevalent at the time. This bold approach resulted in a design that positioned a diesel engine above the solebar in the leading coach, driving a generator that powered standard EMU-type axle-hung electric traction motors. The trade-off was evident: nearly half of the potential passenger space in one coach was sacrificed to accommodate the bulky English Electric diesel engine, radiator, and generator equipment. Yet, the operational benefits were significant. Despite the spatial constraints, the DEMUs boasted superior acceleration, speed, and braking compared to conventional DMUs. Moreover, the electricity generation provided enhanced heating during winter months, while sturdier construction minimized the heat and vibration issues common in lightweight mechanical drive DMUs.

Despite their operational prowess, the Class 205 DEMUs were not without their quirks. Affectionately nicknamed ‘Thumpers’ due to the distinctive noise they made while in motion, these units were as recognizable as they were reliable. Early examples of the class entered service in September 1957, and soon after, an orange “V” shape was painted on the motor coach to provide a visual indication to station staff that there was no brake van at the other end of the unit.

As the years passed, the Class 205s saw various upgrades and modifications to meet changing operational needs. However, by the turn of the 21st century, advancements in railway technology and safety standards prompted their eventual retirement. When Govia won the South Central franchise in 2001, a commitment was made to replace all Mark 1 rolling stock, including the Class 205s, by 2005.

Today, the legacy of the Class 205 DEMUs lives on in British railway history. Their innovative design, reliability, and unmistakable presence continue to inspire railway enthusiasts and historians alike, reminding us of a bygone era of diesel-powered travel on Britain’s railways.

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More Information

  • Haresnape, Brian. British Rail Fleet Survey 9: Diesel Multiple Units – The Second Generation and DEMUs. Ian Allan, 1986.
  • Robertson, Kevin, and Hugh Abbinnett. British Railway Pictorial Southern Region DEMUs. Ian Allan Publishing, 2012.
  • Steven, Simon. “Modelling a DEMU.” Update Magazine, Issue 38, PUB DATE.
  • Welch, Michael. Southern DEMUs. Capital Transport, 2005.