Loco developement ex Tornado thread

To my knowledge, all of the W&LLR fleet have Lempors and I think some might have GPCS fireboxes too.

 

Except for "Dougal" they do. I think the new boiler for "Joan" has provision to enable GPCS experiments to be carried out in the future. Lempor exhausts were fitted in order to improve steaming, reduce fuel consumption and enable effective spark arresting equipment to be fitted. "Before" and "after" tests were carried out in respect of each installation and some of the results are shown on Martyn Bane's "Steam and Travel pages" website. The statistics make interesting reading

In order to preserve the traditional appearance of the older machinery I understand (anecdotally you will appreciate(!) that some of the installations are less than the absolute theoretical ideal. In the case of the Romanian locomotive the Lempor installation is nearer the ideal and actually improves the appearance of the recipient as a bonus.

The lessons are there but I am not sanguine there is a widespread willingness to learn from them.

P.H.

 

Isn't No. 87 on the Welsh Highland fitted with a Lempor exhaust? Anyone who has worked on it, or travelled behind it can have no complaints about performance, or noise!

 

Surely the fact that there is a number of Lempor fitted locos out there demonstrates that the lessons are being learnt and applied where needs be.

 

Not widespread though, is it?

The arguments on both sides are compelling.

In one corner, you have minimal, if any, visual impairment on the locomotive (as evidenced by Paul H's comments about the designs of the systems on the W&LLR), coupled with provably improved efficiency.

In the other, you have a valid question as to the necessity of such changes - after all, we're in this for heritage not to develop/improve steam, and the provable success of steam locos 'in the raw' without modification, even if they aren't quite as effective as they might potentially be.

My thoughts? It's something for a case by case basis. We mustn't lose sight of our heritage credentials. At the same time, improvements may be made, if not in a majority then in a sizeable minority of cases, that would render smaller locos capable of harder work without undue wear, and unlock potential fuel savings - both potentially valuable tricks up the sleeve in a difficult future.

 

That pretty much sums it up. I would expect to see more Lempor conversions appearing in the future, but as has been stated on here, it can be tricky getting the optimum design without enlarging the existing chimney. A few thousand pounds is maybe not a bad investment if it allows you to add an extra carriage when required, or cure a shy steamer on a normal load.

 

I think compounding is actually much less of an advantage in locomotives than in marine applications. I also wonder if the geography again favoured the application in France over the UK.

Firstly, to get a theoretical advantage from compounding, you need the biggest temperature change between inlet and outlet. Marine installations utilised condensers (which also helped recycle water) and re-heating of the steam between high and low pressure cylinders; however, the plant needed to get it to work well was relatively bulky - not a problem on a ship but problematic on a railway locomotive, even a broad gauge one. Ships also tended to operate for long periods at a more or less constant power output and engine speed, which allowed careful optimisation of the machinery. You can have a compound without all the paraphernalia, but the efficiency gain is not as great as you might expect, particularly when compared with a locomotive with efficient valve gear and a skilled crew. In the late nineteenth / early twentieth century, when there were a fair number of experiments with compounding in the UK, efficiency gains of about 10% were reckoned to be possible, but similar gains could be achieved by superheating, better valve design and streamlined steam passages (which were also being seriously developed at the same time), and those routes gave similar efficiency gains at lower capital cost. Churchward - who certainly couldn't be accused of being blind to technical developments elsewhere in the world - extensively tested a 4 cylinder De Glehn compound against one of his own 4 cylinder simples, and on that basis chose simple expansion as the basis for all future development on the GWR. I suspect he knew what he was doing.

It's the same argument as to why steam turbines were never really successfully applied to steam locomotives.

For compounds on a steam locomotive, typically the low pressure cylinder(s) is fed with "live" steam until speed has built up to 15 or 20mph; thereafter the locomotive is swapped to compound working. This gives the geographical point: compounding will only really give any gains if the loco is working for long periods at high output. In a stop-start environment, with relatively closely spaced stations, you spend a lot of time not actually working in compound mode. So again that favours a country with a relatively low population density, and stations a long way apart, like France - or the US, for that matter, where there were also successful compounds.

I believe in France not only did loco crews get better technical training than in the UK, but there was also widespread payment of coal bonuses. Coupled with technically complex compound locos with independent valve gear where the high pressure and low pressure cylinders could be notched up independently, there was a financial incentive for loco crew to really learn how to drive their locomotives as efficiently as possible and thus win on the coal bonus.

Tom

 

They also got a bonus for recovery of lost time to ensure "coal dodging" was not taken to excess!

It always struck me that Churchward was seeking to prove that "his" locomotives could perform as well as the imports rather than progress the science (or is it the art) of design a step further. He was unfortunate as the empirical increase in the size of steam passages initiated by Du Bousquet of the Nord in his smaller wheeled 4-6-0s came slightly after the three Atlantics arrived on the G.W.R. Twenty years were to elapse before Chapelon established scientifically that these increases were, themselves, not enough.

It took a long time to realise that compounding, superheating, improved valve events, streamlined steam passages and better draughting were not alternative means of attaining the same goals but complementary to one another. This realisation was and, I fear still is, not universal

Simple or compound expansion we can all regret with hindsight how profligately the coal resources of this island were used because they appeared so plentiful as to render concerns about thermal efficiency seemingly pointless.

 

... and perhaps if the optimum dimensions cant be reached your loco will still sound a bit like it used to. The other aspect is that for the new builds (or new reassemblies in the case of GW locos) If you are having to construct your front end from scratch then the cost of building your lemport ype isnt not much different from a 'conventional' exhaust.

 

I suggest that the Turbomotive was a remarkable success for an experimental prototype. Unfortunately, WW2 prevented any development.

 

I think "partial success" is the most you could say about the Turbomotive; certainly not a remarkable success.

Previous steam turbine designs had had condensers (to give better thermal efficiency) and, because there was thereby no exhaust and no conventional blast, they also had fans to maintain a forced draught. These features were causes of much unreliability on earlier steam turbine designs; Stanier removed them and allowed steam to emerge from the turbine straight up a conventional blastpipe, but by doing so, a lot of the theoretical thermal advantages of the turbine were lost. As such, the locomotive had reasonable reliability (at least relative to previous steam turbine designs) but only at the expense of any gains in theoretical efficiency.

The loco also had reduced power in reverse (cause of at lot of operational problems, particularly at stations when backing it's load in / out of the station before / after departure).

Steam turbines, like multiple expansion reciprocating engines, are devices that work well with a lot of ancilliary plant and when they can be operated at near constant power output for long periods of time. As such, they are ideally suited to work on ships (or indeed, power stations) where the design can be optimised to really exploit the theoretical efficiency gains; however, those conditions don't apply on a steam engine that has to do lots of stopping and starting.

So I don't think you can claim that the Turbomotive was in any way a remarkable success; the most you can say is that, unlike other steam turbine locomotives, it didn't disgrace itself in comparison with conventional designs.

Tom

 

My apologies, I meant not to imply that Turbomotive was very successful but that it was worth remarking that it was a success.

 

Ah, that interpretation makes more sense!

I think the Turbomotive was a valiant attempt to break the Stephensonian mould. And unlike several other experimental locos of the same sort of era (the Paget engine; the Fury, the Leader etc), at least it did decent revenue earning service for its owners. The problem, in my view, was that by time various features had been omitted from the design in the interests of reliability (notably the condenser and forced draft), the turbine no longer held much of a thermodynamic advantage over a conventional reciprocating engine! A case of throwing the baby out with the bathwater...

Incidentally, what was the TE like at zero speed? One advantage of a conventional locomotive (and disadvantage of an internal combustion engine) is that you can develop maximum torque at zero rpm, which is obviously essential for stating a train! An internal combustion engine needs some kind of torque converter (which could variously be an electric generator and use the electricity to power a motor; or a fluid coupling; or a clutch which inevitably has to go through a period of slipping between zero speed and the speed where the engine speed is matched). The descriptions of the Turbomotive I have seen say that the connection from turbine to axle was via a dog clutch (which is either engaged or not, i.e. can't slip). That implies that on starting, the turbine must have been at rest, the clutch engaged and then steam admitted. In that scenario, does the turbine generate torque the moment it starts to rotate, just as a reciprocating steam engine does?

Tom

 

As a one-off, Turbomotive was indeed a success. OK, as said, the reverse turbine was found to be 'wanting' once the thing went into service, but that wasn't exactly a major issue, had it been developed further. A slightly larger unit could easily have been fitted. Also, it is quite possible that some sort of condensing arrangement, as per the Swedish locos, would have been considered in the furtherance of the concept. Sadly though, as already mentioned, WW2 put a stop to further development, & after WW2 there wasn't the will to continue with it. A pity, in many ways.

Mark

 

I am not suggesting that preserved locomotives should, en masse, be put through the Porta or indeed the Chapelon mill. Though in some circumstances a select appication would, and has been proved, to be of significant value.

I find it peculiar that so many people still believe that the loudness of a locomotive's exhaust is in some way always related to it's power output and that a locomotive that makes relatively little noise whist working is not producing any significant output.

I suspect that most readers of the forum will have viewed the "Charter Trains Under Threat" posting in the What's Going On section.

From feeling that 75mph is quite fast enough, now folk are thinking that the movement needs higher speeds. That maybe so. I suggest that better acceleration is also required. Welcome to the clock ticking. There is no such thing as standing still. If you do not react to the pace of events around you, you will find yourself in an awkward situation.

If events are bringing about changes that make the future of steam traction as a spectacle on the mainline less likely to continue. What happens next? Are locomotive owners going to be willing to run their engines at 85-90mph? It has been argued on these forums that this would be asking too much of ageing machinery. Operations could contract to just a handful of routes. But for how long would this last?

It has been left too late to present a locomotive with capabilities that are such that would convince authorities that steam is capable of standing on it's own. At least on the main, trunk routes. Best prepare for getting used to a "box" assisting on all occasions.

If only the later generations of locomotive designers in this country had not fundamentally stood still. Brings me back round to Riddles again.

 

In terms of speed I suspect that all the rail authorities will require long term is that steam specials match approximately the speed of regular freight traffic on the strategic routes. That would be the most pragmatic approach.

 

Got to agree with most of where you are coming from here, and it maybe that the last Locomotives standing are the newbuilds, of which in their original design form only Tornado is a potent main line machine...
Still taking exception with the Riddles bashing im afraid - New steam design stopped as far as BR (not Riddles) was concerned in 1953 unless you count rebuilding the Merchant navies as design. Even Duke of Gloucester was an upscaled Brittania, and though there wasnt much radical about it it was dismissed because corners were cut in its construction and a result it didnt work 'straight from the box'. The Guy to all intents was shown the door for persisting with steam -putting forward 'radical' designs would have seen him pushed through the even sooner
Porta was at this time still working out his ideas in Argentina and perhaps wasnt viewed as being Credible
The first opportunity in this country to put his ideas in practice was perhaps the Bulleid rebuilds - no longer under Riddles auspices, followed by development of the industrials still being built... which did actually happen.

 

I believe it was only the reverse turbine which drove though a dog clutch; the forward turbine was permenantly engaged, even when running in reverse. This created a 'windmill' effect, which had to be dealt with. The reverse dog clutch had to be fully engaged before steam could be applied to the reverse turbine itself; there was an interceptor to ensure this.

 

1. Has anyone said this in this discussion? Can't say I recall such remarks.
2. You can add as many Porta and Chapelon tweaks as you like but I doubt you'll get a loco that will accelerate load 12 as fast as a 91 on load 8. In Germany they seem to be able to run shorter trains on many steam special, thus giving a better power to weight ration and better acceleration but until we have a situation where UK operators can make money on such short trains then it's still going to be a matter of pathing heavier trains on an increasingly busy network and there's the real problem.
3. You can bang on about that as much as you like but seems you choose to ignore others who have given adequate explanation as to why things panned out as they did in the UK. I'll also refer you to the fact that relatively simple two cylinder locos of simple expansion have outlasted all the relatively complicated compounds in regular service. The advanced French designs were a French solution to a French problem but they were overtaken by events in the end.

 

IMHO, the recipe for longevity of steam on the main line is reliability and a decent power/load ratio. In any analysis of delay/failure due to steam traction the following would probably feature high up on the list : Shortage of steam (including dirty fires/poor coal), hot bearings, air brake problems and adhesion.

Tornado has been cited by some on here as being one of the more reliable performers, and I suggest that is in part due to several of its original and improved design features:

Steam production - large grate and a decent exhaust system

Hot bearings : Roller bearings all round

Air brake problems : Installed standby air pump

Adhesion - not an awful lot than can be done here, but the A1 Trust have worked to improve the reliability of the sanders, and have switched to a more modern air sanding system.

Now I'm not advocating series production of A1's, but I do worry that other new builds may only perpetuate the design short-comings of the originals, and may find themselves confined to heritage lines in the not too distant future. Clearly you can't just uprate a narrow firebox loco to 51sq ft, but you can look at bearings, draughting, braking and sanding without necessarily affecting the overall look of the machine. Of course some of these measures may add to the initial build cost.

As for power/load ratio, that's a matter of economics, and unless we accept a box on the back, maybe ticket prices are going to go beyond the reach of mere mortals in the long term?