The steam locomotive is dead (or almost so). Long live the steam locomotive.

A contradiction? No. Steam traction in what may be termed normal commercial service has passed into history nearly everywhere, and where it has not yet gone, it is in the process of going.

Any exceptions to this trend, such as steam's use on newly built provincial railways in China, will almost certainly be short-lived. Yet the steam locomotive remains an object of fascination, and despite its almost total disappearance from regular service, it has found a place in the expanding leisure industry, hauling trains on preserved and tourist railways and heading specials on normal commercial systems. But this can continue only so long as certain conditions are met, that is, the steam locomotive must:

1. Remain an object of fascination;
2. Comply with, or be exempt from regulations and standards which are becoming ever stricter; and
3. Be economically viable to operate.

Can these be taken for granted in the future?

We do tend to be nostalgic about the past - especially for something which has been lost - but we also become bored by the familiar and repetitious, and attracted to what is new and different.

It says a lot for the steam locomotive's aesthetic appeal that we are still so attracted to it despite all the new shapes on the rails. Yet I write as one of the generation that knew the magic of the steam era at first hand, which explains our devotion to it. Those who follow us will know only the relatively artificial nature of preserved steam operations using locomotives they have never seen in normal service. Will that be enough to hold their interest in the face of all the other attractions competing for their attention (and money)?

Concerning standards, there are a number of areas where they will become stricter. Obvious ones are engineering design and construction practices, safety (both of the public and workforce), insurance requirements and environmental protection. It will become increasingly difficult for the steam of a bygone era to comply with future standards, and its exemption from them cannot be taken for granted.

Problems are already being experienced; witness the summertime mainline steam ban because of the alleged fire risk from the same locomotives that were working in large numbers during all weathers in steam times. And in what might be a foretaste of official attitudes towards steam as environmental issues become more pressing, the German Green Party has apparently opposed the use of new steam locomotives on the Harzquerbahn.

The third condition, namely the economic viability of operating elderly locomotives, must also be considered. True, much of the labour involved in keeping these machines operable is provided free, which is just as well for they need a lot of attention to keep them going.

Their detail design is poor, leading amongst other things to component unreliability and high wear rates, which in turn result in a high consumption of spare parts (relative to the distances travelled), which tend to be expensive because they have to be specially made. And what about the cost of fuel and water for locomotives whose overall thermal efficiency is best not spoken about?

To sum up, even though steam locomotives have found a market they can operate in at the moment, they will surely be off the rails and confined to static exhibits at some time in the future if they do not adapt to changing conditions. Stillness is death, and the era of normal commercial steam operations has finished precisely because steam traction did not develop at the pace necessary to match its rivals. So in order to secure a future for steam as an attraction in the leisure industry, it must develop. One way forward is as follows.

I will start with an unpalatable statement of fact. The steam locomotives built in this country (and indeed the vast majority of them world-wide) were mediocre to poor, even by the engineering standards of their day. They could have been a lot better, and if they had been they would not have gone out so quickly.

Let us examine the typical latter-day British steam locomotive. It doesn't matter whether we take the products of any of the 'Big Four' railways or the BR Standards - the negative features were to a greater or lesser degree common to them all. Starting with the true heart of a steam locomotive, the exhaust system, they were simply not good enough - and this includes the Kylchaps, Lemaîtres and even the Giesls.

'Internal streamlining', the lack of which only shows up when locomotives are worked really hard relative to their size (a rare occurrence indeed in this country) was poor, this shortcoming being magnified by boiler pressures that were generally too low. Both the superheat and the feedwater temperatures were too low and no attempt was made to preheat the combustion air.

Engine design was far from ideal - for example piston valves were too small in diameter, had too short a lap, poor flow coefficients at short cut-offs, and were too heavy and probably not adequately steam--tight when mileage was high. Typical cylinder insulation can be likened to wearing an overcoat in Siberia with the buttons undone. The rapid onset of wear, looseness and vibration as a result of the prevailing mechanical construction made locomotives run down before they had accumulated a reasonable mileage, including those with the apparent panacea of manganese steel horn block liners. Hand firing restricted the amount of steam which the boilers of the larger locomotives could be expected to produce in everyday traffic, so that even the quite modest power capacity built into these locomotives could not be sustained in normal service. This was the reason why Class 5 4-6-0s could and did substitute for Class 8 locomotives and keep the schedules - why, then, build such large machines in the first place?

They were too heavy for the cylinder power they produced, guaranteeing low drawbar power and efficiency at the kind of operating speeds expected of them. And so on, for we can examine almost every component design on steam locomotives and find that it could and should have been better. Instead the whole ensemble was considered to be 'good enough' - but when challenged by diesel and electric traction it wasn't, was it?

If the 'good enough' mentality was fatal to steam then, it will ultimately prove so in the future as well, albeit in quite different circumstances. However the steam preservation movement has proved itself capable of amazing feats, culminating in the present construction of a brand new replica of an 'AI' class 4-6-2. To make this locomotive a reality is indeed incredible, yet the label of mediocrity can be applied just as much to the 'Al' design as to any other. So once the ability to build a mainline locomotive has been established, why confine it to reproducing the (mediocre) past, when a new design giving an undreamed of level of performance can be produced?

Such as? Well, such as a locomotive of Class 5 4-6-0 format - call it a Class 5GT - that would outperform any British 'Pacific'. For whilst it was rare for 2,000 hp to be reached - let alone sustained - at the drawbar of British 4-6-2s in normal service (even when it should have been for regaining lost time), our Class 5GT would be capable of over 2,500 drawbar hp at around 80mph, a speed at which the drawbar outputs of the Pacifics were already well below their respective peaks and falling fast, essentially because of the locomotives' poor power to weight ratio.

And consider that arguably the most celebrated British steam haulage feat of all time in regular service, A4 Capercaillie's wartime run between Darlington and York when 75mph was averaged over 24.9 miles pulling 730 tons, required only some 2,200 drawbar hp, not more than 85% of the power that the much smaller Class 5GT would be able to sustain at the same speed.

You don't believe me? Well, the power speed curve for the South African Railways Class 26 4-8-4 peaked at some 42 indicated hp per ton of engine weight (not counting the tender weight). For a Class 5 engine weighing 76 tons this gives some 3,200 indicated hp or about 2,500 drawbar hp at 80 mph with ? supplies in the tender. Yet because of structural limitations imposed by the original '25NG' class from which it was rebuilt, the '26' class had plenty of weaknesses, and there was hardly any facet of its performance that could not have been significantly better.

So starting with the proverbial clean sheet of paper and allowing for the (still) better quality of coal here than was burned in SAR locomotives - a factor of great importance to performance - the ability of the Class 5GT to sustain a drawbar output at least 10% higher than the above figure (i.e. 2,750 drawbar hp) is well within reach when hauling suitably heavy trains.

So how would it be done? Essentially by doing the simple things well, with no frills, correcting all the weaknesses found in the steam of the past.

Let's take one example - superheat temperature. Thermodynamics text books tell us that the inlet steam temperature should be as high as possible (the old argument that this 'wastes heat' at the-exhaust is wrong), and maximising the superheat gives a number of advantages for steam locomotives that won't be found in thermodynamics books, such as reducing the required size of tenders.

All this was known when steam was at its zenith, but most latter-day British locomotives did not exceed about 700^oF (370^oC). German locomotives managed some 750^oF (400^oC) and the best French ones 800^oF (425^oC), which was better but still not as high as the superheat temperature could and should have been - and these were maximum figures, so the average temperature at which steam was, being delivered to the cylinders will have been a good deal lower.

In contrast to this, the Argentinian engineer L. D. Porta has shown how better component design can enable a higher steam temperature to be generated and used without any of the lubrication difficulties which previous generations of engineers believed placed an insurmountable barrier against higher superheat. For example piston valves can be much lighter, valve head and liner materials can be better (but need not be exotic), valve ring design can be improved valve heads and liners can be cooled by exhaust and saturated steam respectively.

All this was well within the realm of engineering knowledge in, say, the 1930s, indeed techniques of this nature were already common practice in internal combustion engines, which is one reason they are with us now and steam is not. Used together they would have allowed steam temperatures of around 840^oF (450^oC) with the cylinder oils then in use, and one can imagine perhaps 930^oF (500^oC) with today's synthetic oils.

The emphasis on better detail design, a basic teaching of Porta, is of fundamental importance, and is why a locomotive of traditional format can demonstrate such improvement in all-round performance - in power, fuel and water consumption, and reliability - without resorting to shapes that destroy the aesthetic appeal (remember the abominable 'Leader' class).

Thus our Class 5GT would look like a steam locomotive ought to look like, for who wants a steam locomotive that looks like a diesel? But although in traditional mould it would still be a new shape, and is that not what is required to generate renewed interest in steam traction?

If a moderately-sized 4-6-0 were to demonstrate its ability to haul more coaches faster up to the likes of Ais Gill than any 'Pacific', would this not attract some attention, and fill the trains concerned? And don't forget that what can travel on British rails can operate anywhere in the world on standard gauge tracks, due to our restricted moving structure gauge.

A 'universal' steam locomotive for hauling the kind of trains for which steam traction is in demand can be envisaged, and should it not be designed and built here, the birthplace of railways?

All that is needed to realise it is vision, engineering understanding, and hard work: given the vision, the money will follow.

The design is not as difficult as might be thought - it doesn't need a super computer - but if it is not done here then someone more far-sighted may well do it elsewhere.

Are we going to import our own invention again?

A modern world steam engineer
Steam Railway's Footnote on David Wardale

David Wardale graduated in 1971 with a BSc degree in mechanical engineering with first class honours after four years of study at Portsmouth Polytechnic and industrial training with British Rail.

His first employment was as a senior technical officer with Southern Region's mechanical and electrical engineer's department at Croydon, where he worked on a project to improve the reliability of railway traction motors.

After a year in the works and equipment section with responsibility for wheel lathes and improvements to rolling stock maintenance depots amongst other tasks, he undertook a private study tour of South America. This visit lasted four months and allowed him to visit railways in Argentina, Bolivia, Brazil, Chile, Ecuador, Paraguay, Peru and Uruguay.

In March 1974 David became assistant engineer (traction) with South African Railways & Harbours, based at the chief mechanical engineer's department in Pretoria. Here, he undertook steam locomotive repair planning and analysed steam locomotive maintenance costs for use in formulating traction policy. He also undertook research on improvements to steam locomotive performance and efficiency. During this time he wrote a paper, A Comparison of the Costs of Steam, Diesel and Electric Traction, and was awarded the Diploma of Honour at the XIII Pan American Railway Congress in 1976.

He later produced papers entitled "The Steam Locomotive - Motive Power for the Future" and "Third Generation Steam - Facing the Energy Crisis".

From May 1978, he worked as assistant mechanical engineer (locomotives) at Pretoria, in charge of ten staff, and was involved in all aspects of steam locomotive development work.

Early 1984 saw David undertake another private study tour, this time of the Indian railways.

He was subsequently appointed to branches of an American company which was founded to develop steam locomotives for use both in the United States and abroad, but the venture did not raise the capital to get off the ground.

For three years beginning in 1986, David was employed as a technical consultant at the Datong Locomotive Factory in the People's Republic of China, where he had responsibility for the design and comprehensive thermal and mechanical modifications to upgrade the performance of the Chinese Railways' 'QJ' type locomotives.

He has written and published several books on overseas steam. His latest work, "The Red Devil and Other Tales from the Age of Steam" outlines his work in South Africa, the United States and China, and discusses in detail many of the issues raised in this article. It is scheduled to be published this summer.