British Rail 10100 — the Fell experimental diesel locomotive

Design and technical characteristics

The most striking feature of 10100 was its multi-engine arrangement. The locomotive housed six medium-sized diesel engines arranged so that four provided traction power while two served as dedicated auxiliaries. The auxiliary engines powered pressure-chargers (superchargers) for the main units; this allowed the main engines to develop unusually high torque at low crankshaft speeds without relying on very large cylinders.

Rather than using a single large prime mover and traditional electric transmission, the Fell concept combined multiple engines with a complex transmission and gearing system intended to share loads and maintain torque. The design reflected contemporary interest in different approaches to boosting diesel performance and reducing wheel-slip on heavy trains. Detailed mechanical schematics and analyses are available in specialist sources; a brief technical overview can be found here.

History and development

The project was driven by industrial and engineering partners interested in demonstrating alternatives to the dominant steam and emerging diesel-electric standards. Construction took place under the auspices of the London, Midland and Scottish Railway at Derby, but by the time trials began in 1950 the railways had been nationalised and the locomotive carried British Railways markings. Trials explored reliability, fuel economy, and how the redundant-engine approach behaved under real operating conditions. Contemporary reports and trial data are summarized in retrospective accounts; further reading is available here.

Uses, assessment and legacy

10100 was experimental rather than intended for mass production. It proved the feasibility of some ideas—multiple smaller engines with forced induction could provide high starting torque—but the complexity, maintenance demands, and the rapid advance of standard diesel-electric designs meant the concept did not lead to a production family. The locomotive influenced discussions about modular power and auxiliary-driven boosting systems; modern rail and industrial designs occasionally revisit similar principles in different technical forms. A selection of analyses and historical commentary can be consulted here.

Notable facts and distinctions

• The Fell locomotive combined inputs from private industry and railway workshops in a rare collaborative experiment.
• Its six-engine layout—four traction engines plus two auxiliary supercharger drivers—was highly unusual for mainline locomotives.
• Although no follow-up production line resulted, 10100 remains a frequent subject in studies of alternative diesel transmission concepts; see dedicated resources here.