British Rail Dieselisation - The Type 3s

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One of the most ubiquitous types of steam locomotive was the mixed traffic ‘class 5’. Charles Collett of the Great Western Railway built his Hall Class locomotive, they were medium power locomotives that were equally at home with freight and passenger trains. He also made the similar, but smaller Grange and Manor locomotives. The Hall Class was pretty much copied by the London Midland and Scottish to become the ‘Black Five’ and by the London and North Eastern to become their B1. The British Railways Standard 5 was based on the Black 5, and the was a slightly lighter Standard 4. By end of steam, there were well over a thousand of these classes of locomotive. The Type 3 diesels, being powerful, and capable of both heavy fright and express passenger workings were the internal combustion equivalent.

Class 33


With 1,550bhp, the all steel bodied Class 33s, built by the Birmingham Railway Carriage and Wagon Company only just fitted into the Type 3 classification. They were known as BRCW Type 3s or as Cromptons after the makers of their electrical equipment. Power came from a Sulzer 8 cylinder engine. They were 50ft long, weighed in between 73 and 77 tons and had a rounded front with three windows.


98 of the class were built between 1960 and 1962 and they mainly saw service in the Southern Region. The locomotives were built to work the newer electric heated passenger carriages, however most stock at the time of their introduction was steam heated. This meant that locomotives with steam boilers also had to be coupled onto the train during winter. Often this was Class 24s, which always had to be on the inside of the pair to allow their heating pipes to join, this led to complex manoeuvres at termini.


19 of the locomotives were fitted to control equipment to allow them to work in conjunction with sets of unpowered multiple units on the Weymouth Line. The Southern Region’s third rail electrification project stopped at Bournemouth, however services ran from London to Weymouth. These were formed by two sets of four-car unpowered units and one very powerful four-car set. The powered set were at the London end and provided power for the train to Bournemouth, with the unit on the front having a cab to drive the train. At Bournemouth the powered unit was taken off the back and a Class 33 added to the front to haul the remaining 8 cars to Weymouth. On the way back, the Class 33 pushed the train to Bournemouth where it was connected back to a powered unit to take it to London.


The Class 33s that were used in push-pull operations were classified as class 33/1. They also saw service on other lines including from Waterloo to Salisbury.


One of the most troublesome routes on the Southern Region for rolling stock was the Hastings Line. It featured a lot of tunnels that the original contractor had helpfully not used enough bricks in. When one of these tunnels collapsed, they all had to be relined using extra rows of bricks, this reduced the width of the tunnel meaning normal rolling stock couldn’t use it. Twelve Class 33/2s were made with a thinner body to allow them to operate on the line. It is suggested that the extra cost attributed to building such a small run hastened the demise of BRCW.


Many of the Class 33 went into locomotive hire after their generally reliable service and 24 have made it to preservation.

Class 35


The Class 35s were the medium powered locomotives introduced for the Western Region under their trial of hydraulic transmission. Its hydraulic transmission was designed a Mekydro type unit, which gave the class the nickname the Hymeks. 101 of the locomotives were built by Manchester’s Beyer, Peakcock and Company between 1961 and 1964. They used a Bristol Siddeley version of the Maybach 86 litre MD870 engine which produced 1700 bhp. At only 75 tons, the locomotives were both light and powerful, the most powerful single engine diesel-hydraulic. They had a B-B wheel arrangement.


The 51ft locomotives had a relatively simple, sleek modern design. The front had two large windows, slightly swept back at the top while the front was also slightly swept in at the bottom. For most of their working lives they carried a two-tone green livery, mostly dark green with a lighter green along the bottom of its flacks and at either end. The fronts also carried a yellow warning patch.


They were assigned to the Western Region depots in London, Bristol and Cardiff. Originally they were given the secondary passenger and semi-fast services. They then took over from the mighty King steam locomotives on the express trains from London to Wales, although they lost this duty when larger, more powerful locomotives became available. Their duties also consisted of freight and banking1


Although the Hymeks were successful in service, cost cutting meant that the diesel-hydraulics of the Western region were amongst the first locomotives to be phased out. Hymeks were replaced by Class 37 locomotives between 1971 and 1975, although a number remain in preservation. The locomotive Bear in the Thomas the Tank Engine books was a Hymek.

Class 37


The Class 37 has been one of the most familiar sights on the railways for over fifty years. 309 of these Co-Co diesel-electrics were produced between 1960 and 1965, with many still in service well into the twenty-first century. Known as Growlers or Tractors, these were built by English Electric and used a 1,750hp English Electric 12CSVT engine.


The locomotive is 61ft long, with a characteristic large snout on either end. The ends of the snouts differ throughout the class, the first 119 having a headcode boxes on either side and horns in the snout, the others having a large box in the middle and horns on the roof. The standard locomotive has a mass of around 100 tons, and is capable of 90mph.


The class 37s were used all over the network for a wide variety of tasks, both passenger and freight. Their main passenger duties started out as the Great Eastern Expresses to Norwich, but later on went to include cross country services and work on the highland lines in Scotland. These Scottish workings saw some of the Steam Heating fitted stock displace the smaller class 26 and class 27 locomotives, however eventually electric heated coaches were moved onto the line which meant the class 37s had to run with a class 25 behind it to provide the heating2.


Thanks to their reliability and sterling performance, the class 37s managed to stay in service well into the 21st century, remaining in regular use on the rail network. With the arrival of newer Diesel Multiple Units, their cross country duties have been lost and tend to only be seen on freight workings in regular service. They are often used for special excursions, both as the main train locomotive or stuck on the back of steam excursions to provide assistance if needed.


Despite their continued success, many were withdrawn from service. A lot of these found their way into preservation. As well as being cheap and powerful, the vast amount of them around means that spare parts are readily available. Many preserved railways have fleets of class 37s in a wide variety of liveries.


The class were split into a number of subclasses:

  • 37/0 - these were all the original class of 309. They stayed in this class until they were refurbished. The 37/0 were fitted with steam heating equipment for running passenger trains.
  • 37/3 - these were modified 37/0s, fitted with new bogies and having the steam heating equipment removed to increase fuel capacity.
  • 37/4 - these were refurbished and rewired in the mid 1980s and saw their steam heating equipment replaced by electric train heating. They received a new Brush generator and new bogies. It was envisioned that the 37/4s would be better able to run passenger trains all year round, but the increasing use of multiple units saw them take on more freight duties.
  • 37/5- these were refurbished in much the same way as the 37/4s but had all their train heating equipment removed. They were fitted with sanding equipment, so were primarily freight locomotives.
  • 37/6 - these were modified 37/5 locomotives owned by Eurostar for hauling night services that never materialised.
  • 37/7 - these were modified engines destined for hauling very heavy freight trains of such as coal and steel. An extra twenty tons of weight was added to improve the ability of these locomotives to cope with the trains.
  • 37/9 - these are modified to test a new engine and alternator.
1Helping heavy trains get up steep gradients like the Lickey Incline in the Midlands.2These class 25s had their traction motors isolated so couldn’t be used to pull the train, and were known as ETHELs (Electric Train Heating Ex-Locomotive).

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