End of the line as Chiltern withdraws final slam-door DMU

Two on the buzzer. A deft twist of the right wrist to select first gear before pushing the brake off. As the brakes release, pull the power controller towards you with your left hand.

That simple sequence of actions to set a train in motion has been a part of railway operation since the mid-1950s. It finishes on May 19 when Chiltern Railways withdraws its final first generation diesel multiple unit.

These DMUs were a railway staple. In a variety of classes, formations and internal layouts, they ran across the country. Disliked by enthusiasts when they first appeared, because they displaced steam from many routes, they became as much a part of the railway as steam had been.

They were cleaner than steam and cheaper than steam. They needed just a driver and a guard for a train that could be eight vehicles long. They modernised the railway. They saved routes from closure but couldn’t rescue them all from the engulfing tide of cheap motoring.

These DMU ushered in the age of colour to British Transport Films. They’d feature in promotion films, scored with chirpy music, recording passengers swaying in sympathy with their trains as they journeyed to seaside or market town. Their large windows and view through the cab made them ideal vehicles for BTF’s efforts.

They weren’t the first diesel railcars. In the 1930s, the Great Western Railway introduced its stylish single-car units but steam reigned until the British Transport Commission authorised in 1952 the construction of diesel units for service in West Yorkshire and Cumbria. A 1954 review followed and manufacturers received orders over the next year.

The result was a plethora of types from a variety of makers, including BR’s own workshops at Derby and Swindon. Met-Camm, Cravens, Birmingham Railway Carriage and Wagon (BRCW), Pressed Steel, Gloucester Railway Carriage and Wagon, Wickham and Park Royal all turned their hands to DMUs. Some were suburban units with doors at every bay of seats, some were for secondary and cross-country routes, others were for inter-city services. Formations contained buffet cars and compartments as well as open saloons.

There were types dedicated to parcels traffic. In their early years, a box or parcels van could be tagged onto the back of a DMU such was their flexibility.

Swindon’s four-car Class 123 units were aimed at longer-distance services and had B4 bogies that gave a better ride than most DMUs with their simpler bogies equipped with leaf springs. Class 124s worked Trans-Pennine services in six-car formations packing 1,840hp to cope with the gradients they faced. Each powered coach came with 460hp in contrast to the 300hp usually available from the two engines under a more mundane DMU motor coach.

Many years later, higher power would be a feature of the Class 185 DMUs that displaced Class 158s in the mid-2000s on services over the hill between Huddersfield and Manchester and still run today. Unfortunately, ‘185s’ have just three coaches, leading to overcrowding. Meanwhile the ‘158s’ switched to the Calder Valley route via Halifax and Rochdale. This had once been the stamping ground of Class 110s built by BRCW with their 360hp per power car.

For many, Class 101s personified DMUs because they were allocated across the country but your DMU depended on where you lived. Class 107s worked in Scotland while Class 108s were familiar to travellers in BR’s London Midland Region (other classes and regions available!). Commuters into Paddington would recognise Class 117s. Whatever your local class, they’d all see drivers carrying a brake valve handle and reversing handle. Together with a control circuit key, this was the equipment you needed to drive a DMU. The brake valve handle could only be removed when in the ‘lap’ position that admitted no air into the vacuum pipes. Hence a brake valve with no handle was isolated. The reversing handle fitted into a switch in the side of the gear selector and electrically controlled air pistons that shifted a splined sliding dog within final drive gearboxes to change direction.

That it should be Chiltern operating the final mainline first generation DMUs completes a circle. It was from Marylebone that BR ran a press special to mark the first of the modern DMUs worked before these ‘Lightweight’ two-car sets built by BR in Derby started carrying passengers in 1954. As the first, they were not standard types and so were withdrawn by 1964.

Despite the many different makers, most DMUs had the same ‘blue square’ coupling code with allowed them to work with others of the same code. A train could be, and often was, composed of different classes. Indeed, even some individual units might comprise vehicles of different classes.

Despite this flexibility and the DMUs’ ubiquity, their numbers started falling in the 1980s and 1990s. BR modernised around 1,000 of its fleet of 3,000 DMU vehicles between 1975 and 1984. This bought them some time but they were still often smokey and many travellers will recognise the blue haze they’d deposit in a station as they rattled away from a stop.

Some of their work switched back to locomotives and coaches, for example, on the main trans-Pennine route. Elsewhere the introduction of second-generation units – Pacers and Sprinters – saw large numbers heading for scrap in the 1980s although there was a temporary reprieve for some as the Pacers suffered teething troubles. Network SouthEast’s Turbo DMUs then cut further into their ranks as they approached their 40th anniversary.

By the time privatisation came the ranks of first-generation DMUs in passenger service had been reduced to Classes 101, 117 and 121. The ‘101s’ were split between Corkerhill near Glasgow and Manchester’s Longsight Depot while the ‘117s’ were housed at Haymarket, Penzance and Bletchley, which was also home to four single-car ‘121s’.

It’s ‘121s’ that Chiltern Railways is about to withdraw, blue 55020 and green 55034. (The units are single cars and so carry a vehicle number, the ’55’ one, and also a unit number, 121020 and 121034 respectively.)

Not only are the pair the last surviving first generation DMUs, they are also the final UK trains running with vacuum brakes in regular service.

For many years, Chiltern’s DMUs have been an exception to rules that saw these types withdrawn in 2003. The costs of installing central door locking, and fire extinguisher regulations, saw First North Western withdrawing its Class 101s from their general use around Manchester that year but not before a farewell tour that December took a six-car formation to Buxton, Heysham and Barrow-in-Furness before returning to Manchester. In their final months FNW’s fleet was working out towards Rose Hill; a couple of years earlier they were still trusted to run Hope Valley services across the Pennines to Sheffield.

By fitting door locks and restricting them to peak services between Aylesbury and Princes Risborough, Chiltern reduced the risks associated with operating Mark 1 passenger vehicles and kept their ‘121s’ in service.

No more will passenger hear the hollow hiss of air rushing into a driver’s brake valve, notice the clunk of dogs engaging in final drives or marvel in the view forward from the cab. We are at the end of an era as we lose a direct link to the railway of the 1950s. We can allow ourselves some nostalgia but tomorrow there will still be tickets to sell and trains to run.

This article first appeared in RAIL 827 on May 24 2017.

Published by

Philip Haigh

Freelance railway writer, former deputy editor at RAIL magazine - news, views and analysis of today's railway.

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