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Bachmann NRM Prototype Deltic
Review by David Blythman and Doug Teggin

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Photo: Peter Brumby. Doncaster 19/9/1959

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A brief history of the prototype Deltic


In October 1955 the Traction Division of English Electric unveiled the Worlds most powerful diesel locomotive at its Preston works. It was remarkable for several reasons. At 3,300hp it had almost 50% more power than other designs being considered by the nascent BR Modernisation Programme. Not only was it more powerful, it was lighter too, tipping the scales at 106 tons compared with the 140 tons of less powerful rivals.

The phenomenal power to weight ratio of this prototype was derived from changing one element of orthodox diesel locomotive design. Instead of a four stroke diesel engine with cylinders arranged in vertical banks or V formation, a two stroke design with groups of six cylinders arranged in a layout with two opposing pistons per side took its place. The triangular shape formed was reminiscent of the Greek letter Delta and so the prototype was given the name Deltic.

The Engine

The Deltic did not just spring into life in 1955 as a flash of innovation. It was in fact the logical conclusion of diesel engine development that had started in Germany in the late 1920s at the Junkers aircraft company. The simplicity and low fuel consumption of diesel engines were attractive to anyone developing long range aircraft. The challenge was to produce a design that delivered a goodpower to weight ratio. By devising the deltic layout, Junkers produced an engine that weighed 2lb per horsepower.

In 1934 the British Napier aero engine company purchased the right to manufacture engines to this design and developed two versions but neither was put into production as Napier concentrated on building petrol engines.

In 1942 Mr. George Nelson (later knighted and subsequently ennobled) was asked by the Government to reorganise the Napier works for mass production of their Sabre engine. Mr. Nelson had been Managing Director of the English Electric company since 1930. During the 1930s, English Electric became established in the diesel electric locomotive business. Shortly after Mr. Nelson arrived at the Napier works, English Electric took over Napiers and Mr. Nelson became its Managing Director.

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After the war, the Admiralty approached English Electric with a request for a high powered diesel engine to replace the petrol engines used in its fast patrol boats. English Electric passed the task of development to their subsidiary, Napiers. The result of this development was the Deltic engine, an 18 cylinder opposed piston, two stroke arranged in three banks of six cylinders with a common crankshaft at each corner of the triangle. Every effort was made to keep engine weight down through the use of light alloys. The cylinder arrangement made the unit both compact and very smooth running.

Although the Deltic engine was developed for marine use, the company looked for other ways to recoup the large investment they had made. One area which could benefit from a powerful, lightweight and compact unit was rail traction. George Nelson saw this possibility and signed off the £250,000 private venture that driven by his forceful character culminated in the unveiling of the prototype at Preston in 1955.

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The Prototype

The prototype was powered by two Deltic engines which had been derated from 2,500hp to 1,650 hp so as to extend the engine life from 1000hrs to 6000hrs. This was still considerably less than the 10,000 hrs service interval of conventional four strokes. The main reason for this was the Deltics were run at a much higher speed of 1,500 rpm rather than the conventional 850 rpm. There were concerns that the higher idle speed of Deltics might prove too intrusive in enclosed stations.


Preliminary running trials began in November 1955 on the London Midland Region between Euston and Liverpool, mainly on fast freight trains. It was withdrawn from service in early 1956 for minor modifications before returning for a series of performance tests in August and September.

The tests took place between Carlisle and Skipton covering 5,000 miles which more than adequately demonstrated the power of this locomotive. One test involved a train of 20 coaches, grossing 642 tons, being driven at full power over the 15 miles from Ormside to Ais Gill which is mostly 1 in 100.

Following the tests, the Deltic worked passenger services between Euston and Liverpool on named expresses such as the Merseyside Express and the Shamrock. In January 1957 it worked the London Carlisle route but by May it was back on Liverpool duties once more. In June the schedule was cranked up so that the locomotive was doing 700 miles a day, six days a week.

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Deltics and the Eastern Region

At Eastern Region, Assistant Superintendent Gerry Fiennes and Head of Passenger Section Stuart Ward had calculated that in order to be competitive with road passenger transport, an average speed of 75mph was needed for rail journeys. They estimated that this in turn required a locomotive with power in excess of 3000hp, considerably more than was on offer from normal diesel sources. The intense rivalry between the BR regions meant that it was difficult for them to get information on the new Goliath the LMR were trialling, but what they heard was enough to convince them they wanted one.

Their persistence paid off and in early 1959 the Deltic arrived on the Eastern Region. After some early problems adapting to the smaller dimensions of the ER, the Deltic soon settled down to working out of Kings Cross on the East Coast Main Line.


In 1961 when the first production units were nearing completion, the prototype Deltic was returned to English Electrics Vulcan works with over 400,000 miles on the clock. On Sunday 28th April 1963 the prototype was delivered by road to the Science Museum in London. It was subsequently moved to the National Railway Museum in York and is presently on view at the NRMs Locomotion exhibition at Shildon.

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Photo: NRM. Outside the NRM.


When it was introduced, the Deltic was the most powerful diesel locomotive in the world with a ground breaking power to weight ratio. Whilst it compared favourably to the diesels of its day, how does it stack up against todays machines?





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BHP / ton









































52 (Hydraulic)

















* 2 (HST)



* 2





* 2


























The table makes interesting reading and shows that the power to weight ratio of the Deltic engine has barely been surpassed. Raw numbers do not tell the whole story. Todays engines must meet ever stricter emissions controls and have vastly longer service intervals but even so the Deltic was clearly well ahead of its time for rail traction.

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Photo: David Blythman. Deltic at the NRM.


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The Bachmann NRM Model

Photos: Doug Teggin

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Limited Edition Deltic

On the 25 October 2007, the National Railway Museum (NRM) and Bachmann announced the imminent release of a special edition Prototype Deltic model. There were to be two versions of the model:

  • The first 500 models being a special limited edition in commemorative packaging with distinctive extras, that sold for £140.00.
  • The NRM would subsequently release a further 2500 standard limited edition prototype Deltic models that sold for £95.00
  • Update - August 2008: The NRM has made another 1000 standard models available for sale at a price of £110.00. The model now comes with an enamel badge (shown below, exclusively designed for the NRM by R.E.V Gomm; the high quality die-stamped with a silver finish and safety brooch fitting).
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  • Update - November 2008: A special run (limited to 300 models) of the Deltic Prototype at a price of £215.00 complete with:
    • Wooden presentation box (shown below) made by POLMAC UK Ltd based in High Wycombe.
    • Deltic Pin badge (shown above and also below placed on box hinge) by Rev Gom part of the Shaw Munster group based in Birmingham.
    • Pewter Deltic prototype English Electric builders plate (shown below placed on box hinge) by PROCAST based in Cleck Heaton, Yorkshire.
    • Certificate

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Bachmann said:

"Visitors to the National Railway Museum (NRM) this festive season will be in with a chance of getting their hands on one of the first 500 working models of a historic locomotive owned by the museum the perfect modellers gift. Bachmann Europe Plc, who have been making model railways since 1952, have produced a 00 gauge model of the Deltic for the NRM and it is hoped the colourful locomotive will be the first of a series of limited edition models based on well-known engines from the national collection."
Graham Hubbard, Managing Director of Bachmann Europe Plc said at the time:

"This project proved challenging. The works drawings no longer existed so we had to use laser scanning equipment for the first time. A special gantry also had to be erected at Shildon to enable the scanner, provided by a specialist contractor, to pass over the whole length of the locomotive but the results proved well worth it. Each sale will support the NRM in its vital work in preserving Britains railway heritage, and providing public access to the national collections."
Unsurprisingly the NRM switchboard was overloaded and the models sold out in 9 days.

Judith Whittaker, Head of Commercial Development at the National Railway Museum (NRM), said:

"The NRMs partnership with Bachmann to produce the Limited Edition Deltic Prototype model has been greeted really positively by the modelling community.

"The Special Limited Edition commemorative set is due to hit the shelves in December and has already had an amazing response, while the Standard Limited edition model is also proving a popular choice, with many collectors ordering one of each!

"We feel that the support of Model Rail Forum has definitely been a factor in the popularity of the Deltic prototype. Each purchase supports the work of the NRM and we hope that if this project proves a success we will be adding more to the National Collection in miniature."
So internet sites like this helped promote and sell the model in just a couple of weeks. So much for selling it to visitors to the museum. Anyway the NRM have raised some money for their preservation work so good for them. Lets look forward to more models from the NRM collection.

Opening the box

We have a box that is described as "commemorative packaging". It is similar to the US Bachmann Spectrum boxes, slightly thinner card and less solid than the American boxes though. There is a this clear plastic window on the side. Good to see the loco, but offering no lateral protection to the loco on the front. There is about a centimetre of foam behind the loco protecting the other side.

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Inside we see the protective foam. It does a good job and the loco is easy to remove and insert. There is evidence of scuffing from the air-horns and buffers. No damage to the model though.

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With the Limited 500 edition, we find an Acrylic stand with grooves to accommodate the wheels of the loco. This is quite a substantial stand and it does help present the loco well if you decide to put it on display.

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Detail parts

The buffer beam parts are included: coupling striker plates, scale coupling, steam and vacuum brake pipes and sand pipes. Unfortunately you can't use the coupling striker plate and the sand pipes on a working model. The bogie will just knock them off. If your model is static, then you can fit them.

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What does it look like?

Well, How can we tell if it has the right shape and form? When Bachmann developed this, the original working drawings were not available and as there was only one of these locos produced, the best option for Bachmann was to take measurements from original locomotive at the NRM museum in York. Bachmann used a 3D laser scanning device that fed data into their CAD system. So don't complain that the slope of the nose is wrong or the loco is too narrow ;-) Hopefully we can trust Bachmann to faithfully reproduce those measurements in the model. There is quite a bit of space inside the body and all the working seem to fit without a problem. This 3D scanning should be used in the manufacture of all models.

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There are one or two little issues that perhaps could have been done better. The windscreen wipers are a little too thick and the air-horns seem a little too thin. But as we know, the fineness of detail parts is inversely related to the potential to break off. The exception being air-horns, the bigger they are, the more chance you'll find them loose in the packaging.

DCC & DCC Sound

We have two options. Option 1 is to install a standard DCC decoder, Option 2 is to install a DCC sound decoder and speaker.

Option 1 (Standard DCC Decoder)
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Here I am installing a Bachmann 21-Pin DCC Decoder with Back EMF and 3 Function Outputs (36-554). This is until the sound decoder arrives. See 'DCC Sound' below.

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The Bachmann 36-554 decoder is designed for use with the 21-pin connectors fitted to many of the most recent models this three function decoder offers several advanced features including configurable back EMF high-frequency pulse width motor speed control. A shunting speed function control is provided, allowing finer control for slow speed operations.

Decoder measures 24mm long, 15mm wide with socket at one end. The decoder is reasonably priced at around £10 in most shops. I found a couple at £8.99.

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Decoder installation couldn't be easier. Remover the body, remove the blanking plug that is required for normal DC operation. Insert the decoder and check on the programming track. No problems encountered. Simple and sweet.

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Option 2 (DCC Sound Decoder)

For a review on the installation of a sound decoder, click here.

Kadee couplings

I have replaced the supplied narrow tension-lock coupler with a #19 Kadee coupler. The standard height is just about right, but there is a little vertical play in the NEM socket. I solve this by inserting a little strip of 0.3mm plasti-card under the Kadee coupler. This raises it up to correct height and eliminates the play.

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How does it run?

I followed the advice from Bachmann and ran the model on DC for about half an hour in each direction. I did this on my rolling roads and I don't have a DC layout. Rolling roads are great for this purpose as you can listen carefully to the model and determine which is the better direction of travel. This can thenbe your default forward direction set via CV29 once the DCC decoder is installed.

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Low speed

Function 3 controls 'shunting speed', basically reducing the speed of the loco. Out of the box the decoder is a little 'perky' and needs to be toned down a bit. A slower acceleration and perhaps a slower top speed and definitely turn on the inertia option (Function 4). The speed, once set is very manageable and is perfect for delicate manoeuvring.


This I haven't tested yet. I'll report back and update the review after the German Toy Fair.


A great model. Good looking right out the box. Bachmann do this iconic locomotive proud indeed. It runs well and is heavy and strong. It should pull anything that is assigned to it.

I'm sure there will be many people who never run their locos - Each to his own, but this is a great runner and you're missing something special.

The NRM hit upon a winner with this idea and I just hope that they are happy with the sales of the model. Lets hope that we see more NRM specials.

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- February 2008
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