New build steam and the fuel problem

HAVING now retired from my employment that included independent assurance of main line steam locomotives, I now feel free to air my opinions on the existing fleet of UK steam locomotives and the prospects for new builds in light of the forthcoming fuel and image crisis. This is not going to go away!

A number of new-build locomotives are currently in construction at various stages, but they are all as close replicas as can practicably be made of the inefficient types that ran on this country’s railways up to 1967, employing technology not advanced since 1950, when 8% thermal efficiency was regarded as outstanding.

It grieves me sorely that virtually no attempt is made to remedy this situation, despite an interval of nearly three-quarters of a century. The 5AT was a bold try, but failed to attract funding, a position which in my view resulted entirely from misplaced attitudes (I was quite looking forward to being involved in the approval of that!).

Improvements

If the reader is old enough, let him or her contemplate the improvements in the internal combustion engine-powered road vehicle over that interval, with efficiency and power a lot more than doubled, servicing intervals and engine lives quadrupled (at least).

Some of the technology already exists, as evidenced by David Wardale’s admirable but frustrated efforts in South Africa by applying the concepts of his predecessor,

L D Porta. Porta’s work did not reach its ultimate potential, as he had a three-fold improvement in efficiency in his sights compared with the then-best current practice. While Porta had made some improvements in reliability and the maintenance bill as well, this does not appear to have been his main focus, so there is plenty of scope left there for further development. Even with modern improved lubricants, it appears there is still the need for major attention such as piston and valve examinations every 30,000 miles, which is little short of laughable.

Efficiency is important, because one of the limiting factors on the output of a steam locomotive is the rate of heat release in the firebox. If you can get double or even triple the amount of work out of each unit of heat, then it becomes possible to burn lower grade fuels or less fuel in the same firebox for a given rate of work output.

Good steam coal is a satisfactory fuel for burning in steam locomotives, having both a heat release rate that is high and matches existing locomotive designs, and a good energy density both in terms of mass and volume.

All other solid fuels of which I am aware are not so good. Indeed, I have personally fired a 2ft gauge locomotive on wood, some of it being old sleepers impregnated with creosote. In volume terms, the specific consumption was something like 10 fold compared with the same locomotive on coal.

This just goes to show that you cannot simply empty the tender or bunker of an existing loco of coal and fill it with wood and expect to get very far or run very well.

Efficiency improvement and a decreased expectation of the work to be achieved are essential, and this includes the range before refuelling is necessary. There is also the issue about just what rate the footplate crew can be expected to ram solid fuel through the firehole.

Let us therefore consider what the world really needs, and that is something to sustain our heritage railways as places the masses can be entertained and educated about our industrial and transport history.

The parameters for a typical standard gauge application could be as follows:

■ No such railway has a speed limit exceeding 25mph for public carrying trains. A maximum speed capability of say 30 mph is enough.

■ To minimise heat exchange losses in the cylinders, piston speed should be as high as possible, and taken together with the speed limit, this suggests a coupled wheel diameter no greater than 30in, which is plainly impractical with a stroke of 24in, so some compromise may be necessary. Whatever is done, the stroke to diameter ratio needs to be maximised.

■ A high axle load is undesirable in the interests of minimum track damage and wide availability.

■ Tractive effort should be enough to start eight coaches up 1-in-40. This suggests a requirement for a loco with an absolute maximum power of about 1500bhp, but this would naturally be away from its optimum efficiency point.

■ To be capable of burning a wide range of low grade fuels.

■ Bi-directional operation.

■ Low rates of wear/fatigue/ corrosion.

■ Efficient auxiliaries as well as main engine. (Majority of vacuum / compressed air to be produced as a result of wheel rotation, with direct steam powered ejector / compressor only to be used when stationary.)

■ Maximum heat recovery from exhaust steam.

■ Large on board volume for solid fuel unless a recovered oil firing system is used.

■ Low standby losses.

■ Finally, it needs to look and sound like a generic traditional steam locomotive. Styling is entirely optional. Two outside cylinders with piston valves driven by Walschaerts valve gear would be satisfactory, as long as they were fully in accordance with Porta’s principles. The smell, however…

To maximise engine efficiency, the following established technologies should be employed:

■ Steam jacketed cylinders, compounding, very high superheat and very high pressure. More on these to follow.

■ Highly efficient steam exhaust arrangements, for which the starting but not necessarily final point is Lempor theory.

■ Rolling element bearings wherever possible, which would also reduce maintenance costs.

New look?

So what would this look like?

The tractive effort, axle load and ultimate speed parameters suggest something like a 0-8-0 chassis. For the speeds in question, unpowered guiding wheels are not necessary, but again, more on this later. Since the wheels are so small, four axles could be fitted in the wheelbase of a typical ‘main line’ 0-6-0, thus enabling the curving performance to be satisfactory.

There is even scope for flexibility by arranging the suspension almost as though it were a 2-6-0, since a large proportion of our standard gauge heritage lines are curvaceous

Market-leading new-build steam makes its debut: On September 21, 2008 A1 Peppercorn Pacific No. 60163 Tornado, still in grey primer, makes its first passenger-carrying trip during running-in trials at the Great Central Railway, from where it was withdrawn in January for a major overhaul. However, will future restrictions on coal-burning locomotives require allnew designs of steam locomotives?

branch lines rather than straightish main lines.

It is unlikely a tank engine could carry enough fuel, unless this was oil. For solid fuels other than coal, a tender is vital for any decent length of run, and it may even be necessary to fill this with fuel and displace the water tanks to the loco chassis. This falls under the heading of detail trimmings to suit individual applications, and merits no significant research and development budget.

I mentioned earlier the need for compounding, plus very high steam pressure and temperature in order to permit thermodynamic efficiency. ‘Too complex’ I hear, but wait. In large marine practice, four stages of expansion was not uncommon. In order to extract the best possible amount of work from the steam, condensing (which I am not advocating for a locomotive (yet)) was employed, and this would have resulted in impractically-large fourth stage cylinders. Turbines were therefore commonly substituted for stage four, as on Titanic.

High pressure

I propose that for a locomotive, this should be turned on its head. Turbines can be built that can happily handle very high pressure and temperature steam, so use one for the first stage and let it exhaust into an upgraded conventional reciprocating engine at realistic established steam conditions.

Now, since this turbine is the high pressure stage, it need only be small. In fact, its reduction and reversing gearbox will probably be larger.

How the power from this turbine reaches the rails is an open issue, but I visualise a right-angle final drive gearbox on an axle, of the type commonly employed on diesel hydraulic multiple units and locomotives. This could be one of the coupled axles, or if you insist on building a 4-6-0 instead, the bogie axles. Or possibly even the tender axles. The turbine would be rated at about one half of the overall maximum power requirement as long as it fed the coupled wheels.

All the above elements sound relatively easy, but what of the steam generator? ‘Tank’ type

(i.e. in the case of locomotives, firetube) boilers have not been tried successfully above 300psi. We need much more. Some work was undertaken with water tube boilers for locomotives, but significant further research is needed. In particular, feed water quality would need to be very good, and a reverse osmosis plant at the source would be virtually mandatory. At least one railway has one already. Remember, however, that we are targeting higher efficiency, so the quantity required ought to be less than half that for a 1950s technology locomotive doing the same work.

Try it

I have not addressed everything in the above. How about chrome plated piston rings like on diesel engines? Would they work?... no idea until someone tries it!

Do we need to reduce reciprocating mass? (Yes). Computer aided engineering would remove surplus metal from crossheads and rods, but why on earth are pistons all flat, instead of conical so they could be made thinner, just like on high speed marine engines?

All the above is just pie in the sky unless funding can be attracted. Who stands to gain? Well, apart from anyone who wants to see a steam engine hauling a passenger train in 20 or 30 years’ time rather than not at all, heritage railways of which there are at least 10 in the biggest league have the most to lose.

Colossal task

I’m not volunteering to lead this. Make no mistake, it is a colossal undertaking, but if the development costs are shared 10 or a dozen ways, and ultimately, each of those takes a couple of production units, then a large part of the development cost could perhaps be recovered by selling further copies.

The secret is to productionise a fleet of common items. No more randomly selected one-offs!

One further possible contributor to steam’s longevity has been aired already by others, and that is to sneak into the train formation one or two battery EMU power cars. These could provide tractive effort when starting and climbing, and regeneration when descending or decelerating, recharging their batteries.

A side benefit would be a reduction in the brake block bill.

The general public need never know... unless that became part of the educational message.

Eddie Draper B Tech. C Eng. M I Mech E (retired), Wingfield Park, Alfreton,

Derbyshire