67 005 "Queen’s Messenger" can now run on biodiesel produced by Green Fuels of Gloucestershire  

  67 005 "Queen’s Messenger" can now run on biodiesel produced by Green Fuels of Gloucestershire  

  In August 2007 a Class 67 Bo-Bo of English, Welsh and Scottish Railways (EWS) hauled a short train from Crewe in Cheshire to Toton in Nottinghamshire. Not a remarkable event in itself, except that the Spanish built General Motors locomotive ran on 100% biodiesel, supplied by Green Fuels of Stonehouse in Gloucestershire.

Not long afterwards HRH The Prince of Wales became the first passenger in Britain to travel on a train fuelled entirely by biodiesel. The heir to the throne’s journey from Birmingham to Scarborough behind 67 005 "Queen’s Messenger" produced 19% less carbon dioxide than if the 3 200 bhp two stroke prime mover had been supplied with mineral oil. Subsequent trials also held out the prospect of the Royal train and much of the EWS fleet running on biodiesel, not least because Britain’s largest rail freight company can use the liquid produce of Gloucestershire’s Small Business of the Year 2006 without any technical modification to its diesel electric locomotives.

Biodiesel is a clean burning fuel made from either vegetable oil – such as waste from restaurants or from oilseed crops - or animal fats by means of transesterification, in which glycerine is removed for use in soap and other manufacturing processes. The remaining fuel is biodegradable, non-toxic, carbon neutral and essentially free of sulphur and aromatics.

Subsequently, South West Trains were to trial the use of a mixture of traditional mineral oil, soya and rape seed oil to power Salisbury based diesel hydraulic multiple unit 159 007 between London Waterloo, Exeter from April to December 2008.  However, widespread adoption of railway biodiesel will depend on the pricing, taxation and overall sustainability of the new fuel.



Class 52 D1013 "Western Ranger" poses next to Class 25 D7672 at Horton Road, Gloucester in 1991


  Class 52 D1013 "Western Ranger" poses next to Class 25 D7672 at Horton Road, Gloucester in 1991  


  However, a well maintained four stroke diesel engine – be it designed to power a moped or a supertanker – should only produce a clear exhaust when running under a constant load or a momentary show of dark smoke when the load changes. Longer displays of black smoke – although often making a spectacular photograph or video recording – are indicative of problems with injection pump timings, faulty injectors, turbo chargers or engine governors. Similarly, white exhaust smoke from a diesel indicates lubricating oil burning.

Unfortunately many of the diesel locomotives introduced under British Railway’s 1955 Modernisation Plan of 1955 became synonymous with eruptions of "clag" due to poor engine design, construction and maintenance and operating procedures – some of which were the indirect fault of accountants.


  45 051heads south from Newcastle Upon Tyne once its Sulzer 12LDA28 has been started with a 96 cell battery  

  45 051 heads out of Newcastle Upon Tyne once its Sulzer 12LDA28 has been started with a 96 cell battery  


  For example, the sort of lead-acid battery generally used to turn over a British Railway’s diesel locomotive’s prime mover generally had an effective life of five years, after which its reliability deteriorated rapidly. However, due to the expense of new 48 cell ( or 96 cell in the case of Classes 44 and 45 ) heavy duty batteries, the original components were made to last ten years - often at the cost of locomotives and diesel multiple units spending hours in sidings and at station platforms with their engines running. The risk of them not starting again once switched off was too great to do otherwise!

In fact it only needed one defective cell in an aged battery to prevent an engine start and it was all too easy for such a battery to be overcharged – overheating and damaging the remaining good cells if an automatic voltage regulator was not adjusted accordingly. Similarly, because every locomotive type had its lighting changeover switches ( used select battery or external supply or to isolate the lights ) in a different place in the cab it was easy for crews departing at the end of a shift to leave the lights on and so flatten the batteries.



  Class 25 D5180 leads Fairburn Class 4 2-6-4T 42145 at Laisterdyke, Yorkshire, on 16 June 1967



Class 25 D5180 leads Fairburn Class 4 2-6-4T 42145 at Laisterdyke, Yorkshire, on 16 June 1967



  Not only did the constant idling of diesel engines waste fuel and increase air pollution but the bores of the cylinders became glazed and allowed the piston rings to pump lubricating oil into the combustion space instead of returning it to the sump – resulting in a smoky exhaust. Constant idling also promoted piston ring wear and clogged the piston ring grooves with carbon, causing them to stick. In smaller diesel engines, reduced compression on starting and increased lubricating oil consumption could be the ultimate result.

Derby locomotive works found out about cylinder bore glazing the hard way in the mid 1970s when Sulzer 6LDA28 engined Class 25s were being fitted with dual air and vacuum brakes. After the trial run to Leicester given to every locomotive that received a Classified repair it was found that there would be oil dripping from the exhaust manifolds and running down the shiny new paint on the "A" side of the locomotive. When the cylinder heads were removed it was found that the cylinder liner bores were glazed. The only cure was to fit replacements and the original liners were then honed to deglaze them and used in another engine. The cause of the glazing and subsequent oil drips was found to be the hours – or sometimes days – of engine idling while a cure was found for multiple brake faults before the engine was run in on the load bank at the Diesel Test House.


  An English Electric Class 40 idling at Bury Bolton Street on the East Lancashire Railway  


An English Electric Class 40 idling at Bury Bolton Street on the East Lancashire Railway



  Although the normally aspirated English Electric 6KT engines in British Railway’s Class 08 shunters did not seem to mind hours of constant idling between jobs their larger turbo-charged four stroke brethren certainly did.  A cold start up after servicing, too, often witnessed sticky valves and small amounts of unburned fuel and lubricating oil in the piston crowns - which in turn would make the cylinders fire up separately and produce smoke, flame and some frightening noises. Even when all the cylinders of an English Electric "lump" were firing in roughly the right order the RPM could swing wildly and the only way to restore order would be to speed up the prime mover with the power controller in "Engine Only" mode. This allowed the engine block to warm up by burning off unwanted oil and letting the governor govern. In addition, the main generator load regulators used by English Electric could only be properly set up and calibrated when running at full load on a load bank and trying to do this on the road was a hot and uncomfortable business!  

  31 160 was originally designed for a Mirrlees JVS12T but was finally powered by English Electric  

   31 160 was originally designed for a Mirrlees JVS12T but was finally powered by English Electric  


  If the diesel powerplants of Classes 20, 37, 40 and 50 did not like idling, the Mirrlees JVS12T suffered from being worked too hard. This V-12 engine first appeared - rated at 1250 bhp at 850 rpm - inside the twenty Pilot Scheme A1A-A1A locomotives numbered D5500-19, D5500 being handed over from Brush to the British Transport Commission at Loughborough on 31 October 1957. D5520 - the first of the main production batch of what would ultimately become British Railways Class 31 however – had a larger main generator and traction motors supplied by a Mirrlees JVS12T now yielding 1365 bhp at 900 rpm.

Then, as diesel locomotives in the 1500 – 1999 bhp Type 3 power band became more desirable, D5545 ( outshopped in October 1959) had the same prime mover uprated to 1600 bhp using oil-cooled pistons working at 950 rpm. D5655 to D5670 were similarly delivered from the Brush Falcon Works in Loughborough during October and November 1960 with 1600 installed bhp while in April 1962 D5835 was fitted with an intercooled Mirrlees JVS12T stretched to produce 2 000 bhp.

Trials based in Sheffield included the successful haulage of East Coast Main Line expresses from Kings Cross normally diagrammed for 3 300 bhp English Electric Deltics: although the 1 600 bhp D566x series could still misbehave - as some of the men at Derby Etches Park depot discovered. Inshopped for battery charging after a stint with the boffins at the nearby Railway Technical Centre, the Brush built A1A-A1A first refused to start. Then, after a tripped engine overspeed system was reset, it started up one cylinder at time until flames shot from the exhaust and the shed filled with so much black smoke that a fitters mate spent several weeks off work with eye trouble. The Mirrlees JVS12T then refused to stop when the engine stop button was depressed due to the control circuit breaker also having been tripped. The offending locomotive was given an "A" examination and sent back to Eastern Region.

More seriously though, after five years in service and 500 000 miles of travel, the earliest examples of the 1 365 version of the Mirrlees JVS12T began to develop metal fatigue on the fabricated engine housing and cylinder columns. Similar faults were also becoming apparent on Mirrlees powered Brush locomotives exported to Rhodesia. These problems in due course would have affected the more recent 1 600 and 2 000 bhp versions and it was evident that uprating was partly to blame because the original Pilot Scheme engines – rated at just 1 250 bhp – remained for another decade or more in service before replacement.

British Railways thus faced a locomotive availability crisis as expensive new Brush diesel-electrics lay idle for want of spare Mirrlees engines to substitute those facing repair or replacement. The solution – starting with D5677 in 1964 – was to replace the Mirrlees engines in the entire class with English Electric built 12SV prime movers, limited to 1 470 bhp to match the capacity of existing electrical generator sets. Although this output was well below the theoretical maximum of the V-12 powerplant the new engines proved long lasting and reliable. The Mirrlees JVS12Ts meanwhile were sold back to the manufacturer and reconditioned for other roles, including marine work in trawlers.


  Paxman Valenta powered 43120 awaits the signal at York to lead a GNER HST to Kings Cross in 2003  


Paxman Valenta powered 43120 awaits the signal at York to lead a GNER HST to Kings Cross in 2003



  All Paxman turbo-charged diesel engines also gained a reputation for smoking, including the 12 cylinder Ventura units fitted to the prototype High Speed Train power cars numbered 41001 and 41002. These produced so much clag on starting up that depot interiors would be blacked out by the fumes! Anyone who was familiar with Paddington, St Pancras or Kings Cross before the arrival of overhead wires would also testify that the production InterCity125s could also radically affect the air quality beneath the overall roofs when they were idling between services.

However, at least the High Speed Trains also radically improved the public perception of rail travel as the fastest diesel units in the World. Doing the complete opposite were the Class 17 "Clayton" Bo-Bos: powered by not one but two smoking 6 cylinder Paxman 6ZHXL four stroke diesel engines yielding 450 bhp apiece as they turned over at 1500 rpm.

Introduced in September 1962, the 68 ton Class 17s were a prospective Type 1 standard. Unlike the British Thomson Houston Class 15 and North British Locomotive Company Class 16 hood units ( both powered by the same smoky and unreliable 800 bhp16 cylinder 4 stroke Paxman16YHXL ) and their 1 000 bhp English Electric Class 20 counterparts, excellent all round driver vision was pivotal to the Class 17 design. This was achieved by housing the two Paxman 6ZHXL engines – originally developed for railcar use – under low bonnets at either end of a central cab. Either engine could move the locomotive on its own, making each of the GEC traction motored units a thrifty proposition when running "light engine" between jobs.

The British Railways Design Panel and Allen Barnes Bowden Ltd also gave the new freight machines a pleasant yet functional appearance. Exhausts were grouped between the windscreens which themselves extended at the outside bottom corners so that the driver could see the buffer beams while shunting. The cabs were also a distinctive feature of the class – running almost a third of the superstructure length and feeling more like the bridge of a ship than the cockpit-style footplate of a Class 35 Hymek.

A T-shaped recess was also provided under the sliding cabside windows to house tablet exchange apparatus indicating that the class was meant for single line routes in rural areas. Like the medium sized trains and local goods yards that the Class 17s were also scheduled to work with, these were under threat from Dr Beeching’s Axe in the mid 1960s. Just as Western Region’s Class 14 centre cab diesel hydraulic 0-6-0s ( powered by a single Paxman 6YJXL ) were made obsolete almost as soon as they had been outshopped from Swindon Works, so the D85xx series Class 17s found themselves under threat on Scottish Region: but not before they had been in a few scrapes of their own making!

D8500 to D8585 were built by the Clayton Equipment Company of Hatton, Derby up to February 1964 while the 13 months between March 1964 and April 1965 saw D8588 to D8616 constructed by Beyer Peacock with Crompton Parkinson electrical equipment. D8586 and D8587 meanwhile left Derby in December 1964 and February 1965 respectively powered by twin 8 cylinder Rolls Royce Type D prime movers of 450 bhp apiece.

However, these alternative diesels fared little better in service than the standard Paxman engines and the Claytons were soon so beset by oil leaks, camshaft failures and fractured crankcases that availability plummeted to 50%. When coupled in multiple ( using either Red Diamond Wiring, or Blue Star in the case of the Gorton built locomotives ) the Claytons could haul heavier trains but in doing so lost the advantage of their central cabs and were outpowered by pairs of Class 20s. Withdrawals began in 1968 and the whole class had disappeared from capital stock by 1971 despite the repainting of some members in blue livery.

D8568 was purchased by the Ribble Cement Company and has since been restored and preserved by the Diesel Traction Group as the sole example of the class but between 1969 and 1978 three Claytons became the property of British Rail’s Research Department in Derby. D8512 was used to power test trains and, following engine mounting issues, in 1972 was replaced by D8598. D8521 meanwhile became a little used mobile generator. On one occasion after a report of a faulty Number One engine D8598 had both its engines tested to maximum rpm with the result that the shower of sparks from the exhaust could be seen a quarter of a mile away while large lumps of carbon rained from the sky. As it turned out, the Number One engine problem was caused by a governor problem that was uneconomic to repair and D8598 was condemned.



North British Locomotive built MAN powered D604 "Cossack" heads west from Swindon


  North British Locomotive built MAN powered D604 "Cossack" heads west from Swindon  


  Of the German high-speed engines used on Western Region’s various diesel hydraulics the MANs not only smoked but regularly caught fire. Indeed, their incendiary tendencies also managed to write off many members of North British Locomotive’s Class 21 Bo-Bo diesel electrics even before they were reborn as Class 29s with Paxman powerplants. Apart from design flaws, those MAN engines built under licence by North British also suffered from poor workmanship, as was the case in some of the Maybach prime movers built under licence by Bristol Siddeley. The use of inferior materials also contributed to piston and cylinder head problems that were exacerbated by falling maintenance standards in the last days of the "Westerns" in 1977.  


47 105 heads a line up of Sulzer and English Electric powered locomotives at Toddington



47 105 heads a line up of Sulzer and English Electric powered locomotives at Toddington



  Arguably Sulzer was the best make of four-stroke diesel engine used in a British main line locomotive. Apart from teething troubles - rectified by a slight redesign and better welding by Vickers Armstrong at Barrow in Furness – there were only three minor issues to be overcome en route to good availability. These were the leaking water system "transition rubbers" between cylinder head and cylinder block, insecure flexible water hoses and fuel pipes located under the cylinder head rocker covers leaking into the engine sump and diluting the lubricating oil.

From the mid 1960s onward however, well maintained Sulzer 6LDA28, 8LDA28 or 12LDA28 engines produced some of the cleanest diesel exhausts on British Rail and used the least lubricating oil. In fact any Sulzer "clag" was most likely to be the result of starting up a cold engine, an irresponsible driver moving the power controller from OFF to FULL in one stroke after a long period of idling or even a case of mistaken identity. Many railway magazine pictures of Classes 24, 25, 26, 27, 44, 45, 46 or 47 producing vaporous emissions were due to defective train heating boilers rather than engine exhausts!

The flipside of this phenomenon was that any black smoke from a Sulzer engine really was a sign of trouble: although the exact cause of the problem as not always discovered.

At about 1945 one summer’s evening in the early 1970s Class 47 D1938 – at the head of a westbound Freightliner - came to a stop at the departure signal of Platform 3 of Derby station. Clouds of acrid, dirty brown smoke rolled from the exhaust accompanied by tongues of flame as loud crashing and banging noises emanated from the engine room. Fitters were summoned by the driver and on entering the rear cab – nearest to the load of aluminium ingots from Inverness and Scottish and Newcastle beer in kegs – they pressed the "engine stop" button. This seemed to have no effect at first but after a final "bang" peace reigned again – saving them the prospect of entering the engine room to manually turn off the twin bank Sulzer 12LDA28. However, two more locomotives were now required. One to take D1938 to a siding near Etches Park depot and another to take the Freightliner forward.

The next day the engine sump of D1938 – which normally held 150 gallons of lubricating oil – was found to be 25% overfull with lubricant diluted by over 45 gallons of diesel fuel. The fuel injector nozzle of Number One cylinder on "A" bank was also found to have turned blue with heat and when the "A" side crankcase door was removed the section of camshaft for Number One cylinder was further examined.

The cams were in arranged groups of three comprising inlet valve, fuel injection pump and exhaust valve. It was found that the central fuel injection pump cam was out of position by about 180 degrees, this cylinder attempting to fire at the beginning of the exhaust stroke. The fuel injection pump, valve gear push rods and cam follower guide housing were then removed. These cams were split ( secured by screwed rings ) and could be removed individually, and when the exhaust cam was removed to give access to give access to the fuel cam, the fuel cam was found to have a sheared locating key but the rest of the mechanism had suffered no further damage.

As the root cause of the failure was not discovered, a new guide housing, a new fuel cam, a new fuel injection pump and a new set of twelve injectors was ordered from Derby Locomotive Works. D1938 was then taken to Etches Park Depot a few days later, given an oil and filter change and returned to traffic.

However, within a fortnight Class 45 D61 appeared at Etches Park for an oil and filter change occasioned by fuel dilution of the lubricant supply. Such dilution was most usually caused by leaking cylinder head pipe work or defective fuel injectors: but the injector removed from "A" bank’s Number Two cylinder showed the same signs of overheating as that found on Number One cylinder on "A" bank of D1938. A fuel cam was also found to be 45 degrees displaced, making it attempt to fire too early with much of the injected fuel running down into the lubricant sump, and the camshaft keyway had a piece torn out of it. Only one part of the three-piece fuel cam needed to be replaced but until its next major overhaul D61 had a slight but detectable "chuff" from its exhaust while idling.

A few days later another Western Region based Class 47 was displaying similar symptoms on London Midland Region, but this time Crewe Power Control made sure it was dragged back home straight away!


  D5705 - seen here on the East Lancashire Railway - is the sole surviving Crossley HSTV8 powered Class 28  

  D5705 - seen here on the East Lancashire Railway - is the sole surviving Crossley HSTV8 powered Class 28  


  The cylinder wall inlet and exhaust ports of two stroke diesels tend not to open or close as fast as the poppet valves of a four stroke engines and the effect of this is most noticeable when engine speed and/or load is changed.

Unfortunately for British Railways two of their earliest production classes of two stroke diesel locomotive used Crossley prime movers that although worked well in a marine environment soon proved unsuitable for the rigours of railway use. Both the Crossley 350 bhp 6 cylinder ESNT6 – fitted to Class 08 lookalikes D3117 to D3126 – and the 1 200 bhp 8 cylinder HSTV8 - inside the Metropolitan Vickers Class 28 Co-Bos – were loop scavenged with both inlet and exhaust ports in the lower cylinder walls. D3117 to D3126 – also unusual in having Crompton Parkinson traction motors – were introduced in 1955 but had all been withdrawn by 1967. The Class 28s meanwhile lasted just a decade from 1958, finally being banished from multiple unit working on the London-Glasgow "Condor" container train to a crepuscular existence around Barrow in Furness.

Happily English Electric’s privately built "Deltic" of 1955 was to spawn the 22 strong Class 55, even if the smaller triangular sectioned two stroke engines in the Class 23 "Baby Deltics" did not prove such an inspired choice.   This was also despite the Vulcan Foundry built Type 2s featuring a turbocharger mechanically driven during startup before exhaust drive took over during sustained running.

Derived from widespread marine use – and even tracing its ancestry back to German aircraft of the 1930s – the Napier built Deltic prime movers were opposed piston uniflow types that would smoke heavily if idled for very long – ideally for less than 15 minutes. If this period was exceeded, lubricating oil would build up in each engine’s collector drum, the drains from which would inevitably clog up. Then, once the locomotive was under way, heat from the exhaust would cause this oil to burn, accompanied by large clouds of white smoke. However, once the Deltic had settled down for the lion’s share of its journey a recurrence of white smoke would indicate defective pistons or piston rings – and probably herald a loud bang in the engine room.

Bringing the two-stroke story up to date, the General Motors EMD and Detroit series of prime movers – as found in Classes 59, 66 and 67 – use a uniflow system that incorporates inlet ports in the cylinder liners and poppet valve ( usually four per cylinder ) exhaust ports in the cylinder heads, thus allowing better combustion and a cleaner exhaust than engines that rely entirely on cylinder wall ports.

Another interesting GM-EMD design feature is that cylinder head, liner and piston etc can be removed without even removing the overhead cam of an engine in situ within a locomotive body.


  English Electric DP2 at Kings Cross - a sometime victim of frozen plumbing!  


English Electric DP2 at Kings Cross - a sometime victim of frozen plumbing!



  Another misguided practice – although sanctioned by the Chief Mechanical & Electrical Engineer’s department – was to use plain water rather than water and anti-freeze in diesel engine cooling systems. This led to yet more enforced idling in cold weather – although this did not stop some of the plumbing on some of English Electric’s locomotives - DP2 included - from freezing on occasion despite the engine running!

Similarly, trying to cut corners with cheaper but less efficient lubricating oil than that specified by the engine manufacturers often led to greater long-term costs – damage repair included. Perhaps the most spectacular example of this was the use of engine oil rather than the correct heat-resistant liquids in the fluid flywheels taking the torque from British United Traction (BUT) prime movers to the mechanical transmissions of diesel multiple units. This led to flywheel bellows glands and other joints corroding, rupturing and spraying inflammable oil over hot exhaust pipes with accompanying sheets of flame. The BUT engines themselves ( built by AEC, Leyland and Albion ) also particularly suffered from the woes of long term idling. The pall of smoke from the powerplants of a Swindon built Class 120 DMU revved up to create a vacuum to release the brakes after a day of idling at Etches Park carriage sidings in Derby was enough to blot out Litchurch Lane gas works!

In addition, the DMUs of the early and mid 1950s were only fitted with batteries and electrics designed for hauled coaching stock – including dynamos that would not charge the batteries until the unit was moving at about 28 mph. Later DMUs had alternators fitted to their engines so that idling should have kept the amperes topped up. Sadly though, many of these components proved unreliable – and because the battery isolating switch (BIS) was often in a different cab location in each DMU design ( be it Gloucester RCW, Cravens or Derby for example ) many drivers could not find them. The resulting small but constant drain on the batteries even when the DMU was otherwise inert led to yet more starting issues and the long term tendency just to let the engines idle and pollute.