British Rail Class 112 diesel multiple unit

Characteristics

• Formation: two‑car 'power twin' sets, both vehicles fitted with engines and driving controls.
• Bodywork: standard Cravens design similar to the vehicles used on the Class 105 family.
• Powerplant: one Rolls‑Royce engine of about 238 hp per car (engine reference).
• Transmission: mechanical gearbox on the Class 112 batch; a later, separate batch used hydraulic transmission and was designated Class 113.
• Weight and performance: a fully occupied two‑car set had a gross weight around 70 tons, yielding roughly 6.8 hp per ton; empty, the ratio rose to about 8.1 hp per ton. By comparison, mixed power/trailer Cravens formations produced around 5.7 hp per ton, making the Class 112 notably better suited to hilly routes.

History and deployment

Construction was carried out in two batches of 50 vehicles each. The first 50 vehicles (25 two‑car sets) carried mechanical transmission and were allocated the Class 112 designation. The second batch of 50 vehicles had hydraulic transmission and later received a separate classification as Class 113. The Class 112 sets were introduced to strengthen local passenger services on routes where higher sustained tractive effort was required, particularly in the Lancashire & Yorkshire area.

Operationally, these units spent much of their time in the London Midland Region's Central Division and on services linking Liverpool with St Helens, an area where steep gradients and frequent stops demanded greater power per ton. Both Class 112 and the hydraulic Class 113 variants also operated for periods from depots such as Cricklewood.

Operational role and notable differences

The critical distinction that defined the Class 112 was its mechanical transmission combined with every‑car power; that configuration provided robust acceleration and hill‑climbing ability compared with power/trailer formations. Because both vehicles carried engines and controls, sets could sustain higher average speeds on undulating routes and recover more quickly from stops on gradients. Maintenance regimes and crew training reflected these differences, as mechanically transmitted power units had different servicing needs from their hydraulic counterparts.

Legacy and significance

While not as numerous as some suburban DMU families, the Class 112 exemplifies an approach to regional multiple‑unit design in which extra installed power was prioritized to meet route demands rather than relying on unpowered trailers. Their higher power‑to‑weight ratio made them a practical solution where gradients and stop‑start timetables would have limited less powerful sets. The comparison in power‑to‑weight with Cravens power/trailer formations highlights the engineering trade‑offs made for operational capability on specific lines.

For further technical details and fleet histories, see related material on the Lancashire & Yorkshire routes and contemporary Cravens designs, and consult dedicated sources for diagrams and maintenance records.