Well, if it was my own money I might just buy 850 000 pints of Black Douglas Ale and live merrily ever after. But if it was someone else's, then why not a new locomotive (I'm good at spending other people's money on locomotives, as the SAR found out when I did the Red Devil). And if a new locomotive, then what locomotive? Another replica of one of yesterday's machines which lost the battle against diesel and electric traction (a battle they did not have to lose world-wide)? Or a high-tech challenger like the ACE 3000? Or something in between, an engineering "middle way"?
I have covered this ground before in an article entitled 'Whither Steam Now?' (Steam Railway magazine, April 1998), to which the interested reader is referred. In that article I tried to make the point that nothing survives by standing still, rather it has to move with the times - if we were to discover a better way of making things roll than wheels, then for sure one day wheels would also be history. Failure to comply with this law was the essential reason for steam's demise, and it still applies, so even 'heritage' steam operations are not exempt from it. Given this, the following points can be made:
What would the main requirements of a locomotive for mainline excursion and luxury train service be?
Firstly, it would have to be aesthetically attractive - after all, that would be its raison d'être. We are attracted to the form of the Stephensonian locomotive, and this form must be retained - no cab-ahead, no turbine propulsion, no condensing, etc. In short, it must look and sound and (preferably) smell like a proper steam locomotive. Unfortunately satisfying stricter operating and environmental rules will diminish the 'experience' of steam compared to former times - no towering columns of smoke as of old - but this will have to be accepted.
Secondly, it would have to be extremely reliable. This has always been a characteristic highly valued by practical locomotive men, and would remain so because (i) in-service failures which disrupt other services will be increasingly less tolerated, (ii) the intensive servicing and maintenance which steam received in the past (and which is still required on today's heritage locomotives) will become too costly, and (iii) spare parts will be expensive as they will tend to be special items manufacture in small quantities. It is my belief that even at the present state of the art reliability and simplicity do go together, so the simplest "no-frills" design which would give the required performance is required, which would also minimize the locomotives' design and construction cost, an important consideration. Reliability is very much a matter of good detail design, and given this an extremely reliable steam locomotive can be constructed, requiring minimal attention between periodic overhauls dictated by tyre wear at, say, 250 000 km intervals.
Thirdly, its thermal performance would have to guarantee the required power output with the minimum of fuel and water consumption. Obtaining good thermal performance also depends on good detail design, and despite the proposed doctrine of simplicity there should be no doubt that a performance level far surpassing that associated with the steam traction of the past would be achieved - indeed a rated cylinder power, at "diameter speed" and above, of at least 45 horsepower per ton of engine weight (tender excluded) would be aimed for. A factor of vital importance to high speed running is power: weight ratio, and whilst the engine itself can be designed with this in mind the tender would have to be large enough to carry sufficient supplies for the intended duty, bearing in mind that en-route water replenishment as practised in steam times is no longer available. These are obviously conflicting requirements, hence the need for high thermal efficiency to minimize fuel and water consumptions is important not only to keep supplies costs down but also to allow the smallest possible tender and so maximize the fraction of the cylinder power which is available at the coupling between tender and trailing load.
What form might a locomotive satisfying these criteria take? In 'Whither Steam Now?' I made the case for a 4-6-0 of the size of a BR Class 5 (a Class 5GT) capable of over 2 500 drawbar horsepower at around 80 m.p.h. In an engineering sense small is beautiful, and the improvements in component design which thanks to L. D. Porta are now established technology would enable such high power capacity to be realized In a relatively small, simple, cheap and 'manageable' locomotive ('manageable' because the larger a locomotive is the greater the design and operational problems tend to be). To design such a locomotive one could take the BR Class 5MT drawings as a basis and alter them wherever necessary, for example as follows.
The deep narrow firebox would be retained, as also therefore plate frames (but with very robust horn stays), although the frame might be made into a much stiffer box-type structure ahead of the firebox. The type of fuel, and hence combustion system, would be optional. Technically and operationally oil would be much preferred, but coal would retain that real locomotive smell, and if used could be burnt in the Gas Producer Combustion System (GPCS) or (ideally) as micronised coal, both systems requiring some care in coal selection and preparation and micronised coal firing also requiring some r & d work. A deep narrow firebox is ideal for the GPCS and allows optimum de-ashing arrangements (continuous ash discharge from the fire by means of an automatic but regulatable grate shaking mechanism, and a large self-emptying ashpan).
A highly efficient exhaust (e.g. double Lempor) would create the draught necessary for intense turbulence in the long-arched firebox (the key to good gas phase combustion) and would allow the heat transfer surfaces of the exhaust steam combustion air preheater, boiler tube bundle and superheater to be proportioned for optimum heat transfer. Finned superheater elements would be used to give some 450'C steam temperature at full boiler load, a surface type exhaust steam feedwater heater would be fitted, and careful attention would be given to the boiler insulation.
Spherical roller bearings would be used for the driving and coupled axle and crankpin bearings, and spring-loaded wedges would be fitted, resulting in a complete absence of knocks at all times, even at maximum power after accumulating high mileage. The wheel centres would be of the boxpok type, the coupled wheel springing would be compensated for better riding, and the leading bogie would ideally be of latter-day American pattern, having a cast steel frame, roller centring, and roller bearing axles (spherical rollers if the bearings are inboard or taper roller "package" bearings if outboard).
Lightweight Timken-type split roller bearing crossheads would be fitted working in multiplebearing slidebars, and the ultra long travel Walschaerts valve gear pins may also have sealed roller bearings (Caprotti-driven poppet valves could be also considered, but may be ruled out on both cost and technical grounds). All reciprocating components would be as light as possible, using alloy steels where necessary, to minimize the reciprocating balance (ideally zero). The cylinder component design and materials (pistons, piston valves, rings, liners, packings, etc.) would follow the practice successfully established by Porta, and piston tail rods would be fitted to minimize piston head and cylinder liner wear. Each cylinder assembly would be extremely well insulated (inside 'sealed for life' welded-on clothings wherever possible), and could also incorporate a steam jacket to keep it hot whenever the locomotive is in steam.
Whether the locomotive would be a 2-cylinder simple, 3-cylinder simple or 3-cylinder compound would depend on the thermal performance required, there being a trade-off between successively better performance and greater complexity and capital cost (the improved detail design together with the lower individual piston thrust and easier balancing of the 3-cylinder types would be expected to result in them having similar maintenance cost to a 2-cylinder simple). In all cases the utmost internal streamlining - from the dry pipe entrance all the way through to the blast nozzles - would be absolutely essential. For a compound this is especially important downstream of the high pressure cylinder as receiver steam is at moderate pressure and therefore of large volume, presenting the designer with quite a technical challenge should thermally-desirable resuperheating be attempted. For high speed service limited external streamlining, to reduce frontal drag without impairing appearance, would also be appropriate, something along the lines of Porta's 4-8-0 'La Argentina' without the coupled wheel valances, or the German Class 10 4-6-2's of 1957, and German type exhaust deflectors would also be fitted.
Modern materials which operate 'dry' need to be investigated for rubbing surfaces such as axlebox guides, to reduce the lubrication requirements, but where conventional materials are necessary very extensive mechanical lubrication would be used, fed from a large capacity oil tank, the aim being to entirely eliminate the crews' responsibility for lubrication. Great care would be taken to avoid lubricants contaminating the tyres, and all means to ensure good adhesion would be used, starting with 'state of the art' sanding gear.
In the fully enclosed steam-heated cab attention would be given to obtaining optimum vision ahead for the crew and the most ergonomic layout of the controls. The appearance of the tender would be designed to harmonize with that of the engine, and it would be constructed to have the minimum tare weight and drag coefficient and to give good vision ahead from the cab when running backwards. Whether of bogie or rigid frame type, its axles would be fitted with "package" roller bearings, and the engine - tender drawgear would act to enhance vehicular stability. To be allowed to operate at high speed on densely signalled lines, braking would have to be 'state of the art' (no "grandfather rights" would apply on Railtrack, for example, so any new steam locomotive would almost certainly have to satisfy the same braking requirements as modern traction). All axles would be braked and the tender braking force would have to be automatically adjusted to allow for the diminution in weight as supplies are used up, to make full use of the tender's actual adhesive weight at all times.
These, then, are some of the features proposed for the Class 5GT. They might not seem very revolutionary stuff, for the aim is to keep the essentially correct Stephensonian format and to do the simple things well by means of improved detail design, this being the key to achieving a performance which would be in an altogether higher class than that of yesterday's steam. Such a 4-6-0 would be adequate for all present mainline duties in the UK but if, for example, 15 coach specials were to be worked over the old Highland Railway main line, or if a larger locomotive were required for working overseas, then the design would need enlarging to, say, a 4-8-0. One of the beauties of the concept is that being small and designed for the restricted British moving structure gauge, it could run virtually everywhere else that has standard gauge tracks, and could thus be a "universal" locomotive which, if demand were great enough, could be produced in sufficient numbers to significantly reduce the unit construction cost. It would, of course, be able to run on any standard gauge preserved railway that can take a 20 ton axle load, but would be operated at far below its potential in such service.
The above has outlined one answer to Paul's challenge in Locomotives International No.54. It is, I believe, a technically realistic proposal, for it is based on the very hard-won experience I received working on locomotive development projects in South Africa and China, an experience which imparted a sense of realism both in regard to the possibilities of steam locomotive development and to what can be expected of the environment in which improved locomotives must work. However it is simply an idea, and if the very tepid published response which the deliberately provocative 'Whither Steam Now?' produced is anything to go by, it will remain simply an idea. If the will is there of course something can be done, but behind will lies desire, and the enthusiast community must show that it wants such a locomotive rather than just wanting to recreate the past, for it to stand a chance of materializing.
What is needed is for influential voices in the railway enthusiast community to reach a consensus concerning the desirability of further steam locomotive development and the exactform such development should take. Discussions on these issues are likely to produce as many different ideas as there are participants, but these would have to be merged into a common proposal behind which all could unite and which would then have to be energetically promoted in order to generate the necessary financial backing and hence move forwards. Experience tells that this is most likely to be achieved if the project has a single leader with a clear vision of what has to be done, and who Is able to promote this vision sufficiently to get the wholehearted active support of the necessary team.