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RLBH

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  1. The only common locomotives between the two studies were the 2-Do-2 and the 1,200hp Bo-Bo - the LMS plan called for just eight of the latter, compared to 91 2,100hp Co-Cos! Oddly enough, the LMS didn't see a need for any shunters either, sticking to purely main line electrification and letting steam handle the yards. The two mixed traffic locomotives, and the two heavy goods locomotives, were mutually exclusive - the LMS study called for the 1,800hp 2-Co-2 and the 2,100hp Co-Co, whilst the LNER reckoned the 2-Do-2 would do all the regular passenger work needed and standardised on the Co-Co for everything else. Even the Bo-Bo was proposed to have high commonality with the 1,800hp Co-Co, although steam thinking does seem to have led them to try to finely matched locomotive power to train size. Speed improvements were expected, but through better acceleration and maintaining speed on gradients rather than higher maximum speeds. The authors of the reports were aware that higher speeds were possible, but considered them inadvisable with unbraked wagons and traditional axleboxes. Their remit was, after all, electrification - not the general improvement of rolling stock and operating practices. For the same reason they recommended electric boilers for train heat. One gets the impression that the LNER had a reasonably good handle on how to electrify and what it was capable of, and wanted to use government money to try and sell it to the board, while the LMS were trying to make the case that it was too expensive to bother with. The LNER proposal to electrify everything on the former Great Northern section, except for the most marginal of branches, showed much better return on investment than the LMS study for heavily trafficked, steep main lines and nothing else.
  2. One of the findings of the studies done for the 1931 Weir Report was that if you totally electrified a railway system, about half of the mileage was in goods yards and sidings. But if you only electrified those parts of the goods yards and sidings where a locomotive might run, you still did virtually all of it. Which points to the importance of diesel shunting locomotives, that way you only need to electrify the exchange sidings. Interestingly enough, both studies (one LMS, one LNER) done for the Weir Report were done by Merz & McLellan, and they found that electrifying the branch lines was a better proposition than doing main lines only, because of inefficiencies brought in by changing engines. The LNER study proposed that a lot of branch line working would be done by three-coach multiple unit trains, which may have been replicated in the GWR study - this would explain a surprisingly small number of locomotives. The 1931 locomotives were: A 2,400hp, 110 ton, 2-Do-2 for heavy express passenger work A 1,800hp 2-Co-2 for light express passenger and fitted freight work A 2,100hp, 108 ton, Co-Co for 40mph goods trains A 1,800hp, 108 ton, Co-Co for 35mph goods trains up to 900 tons A regeared version of this with a train heat boiler was proposed for fitted freight and excursion traffic A 1,200hp, 72 ton, Bo-Bo for 35mph goods trains up to 600 tons, or 1,200 tons working in multiple A 720hp, 60 ton, Bo-Bo shunting locomotive Some of these sound similar to the proposals for the GWR scheme, with some evolution.
  3. An obvious missing route occurred to me recently: seemingly the only valley in the whole of South Wales that doesn't have a railway up it is the Usk Valley above Abergavenny. Such a route might well have been promoted to give the GWR access to Brecon and to the Mid-Wales Railway, competing with the Brecon & Merthyr. It would also serve Crickhowell en route, and no doubt a number of smaller places.
  4. American railroads and the British government take the same capital-limited approach to electrification - while it saves money later, they'd rather not spend the money now to get the benefit. Diesel traction may be more expensive in the long run, but you can buy more or fewer locomotives depending on the budget, rather than having to commit to an expensive programme of electrification up front then stick with it to see the benefits.
  5. I seem to recall that the LMS pair actually did less damage to the track than the later BR 1Co-Co1 arrangement, despite the higher axle load, because the suspension was superior.
  6. I've imagined the hills around Shap being much higher to force the main line to Scotland across Stainmore, so all those extra hills must have come from somewhere!
  7. Which is indeed why my 'Domhnall Beag' scaled-down Big Boy is intended to work 60-wagon trains over a steeply graded route with lengthy sections of single track... unfortunately, I believe there's only one such line in the UK, and it only saw that level of traffic when there was a war on!
  8. It would look decidedly less odd as a Co-Co, I think. Not much use as a way of using spare 91 bits, though.
  9. More Deltics are always welcome, but surely a single 18-cylinder engine would require less maintenance?
  10. A bit more, in fact. As a unique, diesel-hydraulic, equivalent to a Deltic, it would probably have been immensely popular with enthusiasts, regardless of how well it performed!
  11. Unless of course you have eyewatering vertical curvature. But if you're trying to avoid buffer locking in the vertical plane, it's probably a better solution in the long run to find the Civil Engineer and beat them repeatedly with a copy of the design standards until they fix the alignment.
  12. Indeed, and my terminology was deliberately vague because of that. When a horsepower figure is quoted for a steam locomotive, it's usually 'at rail' or drawbar power - which of course aren't quite the same thing. When it's quoted for a diesel locomotive, it's almost invariably the brake power of the prime mover, which is entirely different again and much smaller than either.
  13. It's a bit of a stretch, but you could probably equate the firebox to the diesel engine itself, the boiler to the generator, and the cylinders to the traction motors. Electrical machinery typically has about 90% efficiency, so that transmitting 80% of the engine's output to the wheels is fairly straighforward. Early diesel-electrics achieved a bit less, so the 65 to 70% of a well designed firebox and boiler doesn't look too bad. Inconveniently, the thermodynamic cycle takes place at opposite ends of the system, but it's them that lock in the inefficiency of steam. The best steam locomotives built only used 15% to 18% of the energy in the steam - Porta's ideas about improving thermal efficiency notwithstanding. That limits them to about 12% of the energy in the fuel being turned into power at the rail. By comparison, a realistic diesel engine can turn 40% to 50% of the energy in the fuel into crankshaft motion, which with realistic transmission losses gives them 30% to 35% efficiency overall. On top of which you get the advantages in availability and labour saving. Steam is really a losing proposition unless you have cheap labour and cheap coal. Missing the transmission losses is one of those mistakes that seems obvious in hindsight, but was probably forgivable - those writing the specifications had likely never had to think about it, because transmission losses aren't really a concern for steam or early DC electric locomotives. In the latter case, they do exist, but are palmed off on the electricity generating company and the electrical engineering department, so the locomotive engineers don't really have to deal with them. And it's remarkable how well 'fixing' the transmission efficiency issue solves the issue of diesel Types mapping on to steam Power Classes. Just looking at the Riddles classes for BR and the War Department: Duke of Gloucester is right at the top of the Type 4 band; the other express Pacifics she worked with are firmly into Type 5. The 9F, Britannia and Clan all equate to Type 4s - the first two are pretty close to the Peaks, the Clan is at the bottom end of the range and very comparable to a Class 40. The 5MT and 4MTs all equate to Type 3s, as do the WD 2-8-0 and 2-10-0s. The 3MT, 2MT and Hunslet 0-6-0 are all Type 2s. That all seems broadly correct in terms of work undertaken. Steam was generally limited by tractive effort rather than by power. So it makes sense that in a classification system which is based on power, the smaller steam locomotives will be rated fairly highly. That's why almost any steam loco could put in a decent performance on a branch line freight working, but a Class 08 diesel shunter isn't much use for anything outside a goods yard. The rough rule is, a steam locomotive can pull at speed anything it's capable of starting, whilst a diesel can start anything it's capable of pulling at speed. Even the smallest, least powerful diesel locomotives had tractive efforts comparable to the largest diesel locomotives - the sole exception being the LNER U1, which cheated! I've tried coming back the other way to equate diesel & electric traction to steam locomotive power classes; that's easy for freight (all the main line locos are 9F!) but very difficult for passenger rating. Partly because the BR power factor formula is a bit of a fiddle to make things come out 'right', and partly because diesel locomotives have a serious lack of grate area and boiler tubes.
  14. What I suspect happened was a two-pronged failure. I think they did accurately determine the power that could be sustained by steam locomotives, without fully appreciating the benefits that being able to mortgage the boiler brought in terms of temporarily exceeding what would be called a 'continuous rating' on a diesel locomotive. Perhaps more significantly, I don't think they accounted for drivetrain losses. A steam engine rated at 2,000hp delivers that straight to the wheels. A diesel-electric locomotive loses about one-quarter of its' rated power between the engine and the wheels, and a diesel-hydraulic tends to lose about one-third. So, equalling an 8P rated at 2,000hp needs a 2,650hp diesel-electric, or a 3,000hp diesel-hydraulic.
  15. You'd expect any engine replacement to be with the standard Paxman engine - unless parts for the Rolls Royce engine were readily available at the relevant depots, their improved reliability might well be offset by increased costs resulting from being oddballs.
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