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GWR 94xx Pannier Tanks, ex-Edward Thompson Thread.

Discussion in 'Steam Traction' started by Jimc, Aug 18, 2021.

  1. huochemi

    huochemi Part of the furniture

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    The front and back ports have to take both live and exhaust steam alternately. If we assume a fairly typical port width of 2", then in practice in full forward gear it seems to be usual that the port never fully opens to live steam i.e. it is uncovered by less than 2". On the other hand, when acting as the exhaust port, it is typically more than fully uncovered by the valve head apart from at the very short cut-offs (the lap creates this asymmetry). The difference in volume of live and exhaust steam is roughly accommodated by the period which the port is uncovered in its alternating roles i.e. 180 degrees in the exhaust phase v. something rather less in the admission phase, plus the greater amount the port is uncovered. (cut-off percentage is the proportion of the piston stroke during which the port is open to live steam by any amount, so reducing the cut-off not only reduces the actual maximum port opening but also the time the port is open by any amount).

    The attached abridged valve event table from 44767 (port width 2", lap 1 1/2") gives some idea of the actual valve movements for this loco. There are several interesting points arising. The live steam opening is referred to as "port opening"; "exhaust travel" is the movement of the valve head in relation to the port while it is in the exhaust phase. As the port is only 2" wide it means that in the exhaust phase the relevant head moves nearly 1 1/2" beyond the inner port face in full gear. Another point to note is that although the cut-off is very uniform front and back, the actual port openings are not uniform at the longer cut-offs (which suggests that for 44767 at least the time the port is open to live steam has more effect on balancing the work front and back than the port opening, on the basis that the designers have balanced the cut-off rather than the port opening. This also suggests that setting valves is not all about making the movement of the valve heads relative to the ports the same, at least not at all cut-offs). Another point worth noting is that at very short cut-offs, virtually the entire port opening is due to the lead (being Stephenson's gear, this increases as the cut-off shortens, which may be an advantage of Stephenson's over Walschaerts).

    44767_valve_events.jpg
     
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  2. pete2hogs

    pete2hogs Member

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    Always liked the 15xx. Remember seeing them as station pilots at Paddington ca. 1961. For me a really good looking engine, and should have been an indicator of te way forward had nationalisation not taken place.
     
  3. Jimc

    Jimc Part of the furniture

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    [​IMG]
    Just as a further thought on the genesis of the 94s. This big bruiser is a Rhymney S1 class (photo stolen from 88D models https://88d.uk/Home.asp )
    At 56tons 8cwt it was nearly 25% heavier than a 57xx. The 94s seem to have been ordered to replace big 0-6-0Ts like these as well as the 0-6-2Ts. Their close cousins the S class were rebuilt with Std 10 boilers as used on the 94s, so their was good experience of how useful a heavier 0-6-0T would be.
     
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  4. jma1009

    jma1009 Well-Known Member

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    ... Except that the 94xx class never supplanted the 56xx class in the South Wales Valleys Lines and saw very little use here.

    Have you got a copy of Eric Mountford's book on Caerphilly Works?
     
  5. Jimc

    Jimc Part of the furniture

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    According to RCTS at one stage 94xx allocations were London 32, Bristol 10, Newton 22, Wolverhampton 16, Worcester 19, Newport 26, Neath 37, CV 41. with the others on the Lickey incline. I would expect them to supplant pre group classes, not locomotives with plenty of life left.
     
  6. GWR4707

    GWR4707 Nat Pres stalwart

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    Just a little bounce, 65 years ago yesterday, 31 October 1956 saw the completion of pannier tank No 3409 at the Meadowhall, Sheffield works of the Yorkshire Engine Company. This was the last engine of a pre-nationalisation design to be built. (taken from the GWS Facebook account)
     
  7. WesternRegionHampshireman

    WesternRegionHampshireman Well-Known Member

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    I would tend to agree with other members that they didn't need to rope in other tank engines as they had plenty to go round, in fact, it would be fair to say that during the final years of Western steam, they had a surplus of tank engines.

    While other regions
    (Southern) seem to just steal Ivatts and Fairburns for the LMS and BR Standards.
     
  8. 30854

    30854 Resident of Nat Pres

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    Oy, moosh .... Them's fightin' words ... Brighton built it's share of Fairburns (and Riddles Class 4 2-6-4Ts) and then some ! :Punch:

    It's a shame so much of the 'native' Brighton fleet emerged from WWII completely "kerry packered" - I guess that's what happens when maintenance gets farmed out to 'foreign' works - and many turns which had used 2P or 3P LBSC power needed Fairburn and BR class 4s to replace 'em. :(
     
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  9. WesternRegionHampshireman

    WesternRegionHampshireman Well-Known Member

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    Spoken like a true Southern man! :p
    If your on the subject of outside workshop building outside engines, ALOT of 9400's and 5700's/8750's were built outside of Swindon.

    Few 8F's were built outside of Crewe.
    48624 = Prime example.

    Hell! Ivatt 2-6-0's were built in Swindon.
    46521 = PERFECT example.

    The thing about this topic was saying about how the Western Region had many tank engines to their reserve, while other regions tended to sway towards BR designs.

    The Southern is THEE prime example as, weither built or borrowed, had BR, Ivatt and Fairburn designed tank engines or any BR design for that matter.
     
  10. Jimc

    Jimc Part of the furniture

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    The Southern had a specific problem didn't they. Whereas other lines had been updating their steam engine fleets in the 20s and 30s the Southern had been putting as much of their money as they could into electrification. So come a desperate need for modern steam engines they had nothing on the drawing board except for Bulleid's flight of fancy which didn't really address the need.
     
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  11. WesternRegionHampshireman

    WesternRegionHampshireman Well-Known Member

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    My point exactly!
    Finally somebody gets it! :Woot:
     
  12. Jamessquared

    Jamessquared Nat Pres stalwart

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    But in the long run their strategy was vindicated ;)

    Tom
     
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  13. Jimc

    Jimc Part of the furniture

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    Submit it would be hard to argue against the electrification policy being correct. To me the question mark has to be whether the steam engine budget was spent to best advantage in the Bulleid era. I don't have any kind of handle on SR locomotive stock and what all those light Pacifics were replacing, but I do wonder if some of them should have been something equivalent to the Ivatt 2-6-2Ts.
     
  14. Jamessquared

    Jamessquared Nat Pres stalwart

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    It’s on my to do list (but I keep not doing it) to plot the rise and fall; but I think the light Pacifics were basically replacing antiquated 4-4-0s (Stirling, residual Adams, Drummond etc).

    (Edit: see below)

    From memory (can’t remember where I saw it now) the Bulleid plan for steam was four classes: MN, WC/BB, Q1 and Leader. Shunting engines would presumably have been 350hp diesels. The strategy was probably sound but the execution was, respectively, near miss, near miss, excellent and least said the better. The probably could have done with modern a 2-6-2T, but in place of Leader rather than the light Pacifics, which were there to replace passenger and mixed-traffic 4-4-0s.

    Tom
     
    Last edited: Nov 2, 2021
  15. Monkey Magic

    Monkey Magic Part of the furniture

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    Let's flip it around. Surely the Southern had it right almost all the way through. Given the general direction of travel - ie declining rural traffic, competition from cars, increasing use of dieselisation and electrification - is investing in building lots of tank engines a good use of resources? The 94xx, Ivatts managed under 20 year careers, the BR standards even less (it stands in even starker contrast to previous generations and how they had cascaded down).

    Why would you invest huge sums in declining traffic? Surely better to concentrate your resources on where the money is not where it isn't.

    The Southern went from steam to electric, skipping the whole dieselisation years (with a few exceptions). Whereas, the WCML had to go through loco changes and double headed 50s north of Crewe, the ECML took until the 1990s and the lines out of Paddington have had to wait for the second decade of the 21st century to be electrified and they still require boutique bespoke and more costly rolling stock to run their services.

    The SR was late to the end of steam - but is that necessarily a bad thing considering how poor the return on investment the first generation diesels were ie the hydraulics, etc. Of SR based modernisation designs I think the only locos that can really be said to have been failures are the 71/74s and that was because the boat train traffic vanished.

    When you think about steam hauled express passenger services post 1945 - the SR was building and using a modern design, the LNER had the new almost 80 Thompson and Peppercorn pacifics, the LMS was building an updated 10 year old design, while the GWR was building locos to a 25 year old design and relying on locos that were already over 20 years old. The SR went from steam to electric on its key routes into London and the Bulleid designs were effective in ensuring that steam could be run right until the end.

    The reality is that no amount of 2-6-2s were going to save the Padstow, Sidmouth branches etc. Maybe if Metro-Cammell had produced the 101 5 years earlier... but even then I am doubtful.
     
  16. Jamessquared

    Jamessquared Nat Pres stalwart

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    Further to this, I have got the data in reasonable form.

    Here is what the SR acquired and disposed of in the 1941 - 1947 period, i.e. the years in which Bulleid was building first the MNs and Q1s, then the WC/BBs. (Haven't got the figures for 1948 - 1950 but I think broadly more of the same.


    1941
    Aquired:
    6 * Bulleid MN 4-6-2

    Disposed:
    1 * Stirling R1 0-6-0T

    1942
    Aquired:
    40 * Bulleid Q1 0-6-0
    4 * Bulleid MN 4-6-2

    Disposed:
    1 * Adams X2 4-4-0
    1 * Adams X6 4-4-0
    1 * Stirling R1 0-6-0T

    1943
    Aquired:
    None

    Disposed:
    1 * Adams T1 0-4-4T
    1 * Adams O2 0-4-4T
    1 * Adams T3 4-4-0
    1 * Adams T6 4-4-0
    2 * Adams X6 4-4-0
    1 * Stirling R / R1 0-6-0T
    1 * Stroudley D tank 0-4-2T


    1944
    Aquired:
    1 * Bulleid MN 4-6-2

    Disposed:
    5 * Adams T1 0-4-4T
    1 * Adams A12 0-4-2
    1 * Wainwright D 4-4-0
    2 * Wainwright H 0-4-4T
    1 * Stirling O / O1 0-6-0
    2 * Stirling F / F1 4-4-0
    3 * Stroudley D tank 0-4-2T
    1 * R J Billinton E4 / E4X 0-6-2T
    1 * R J Billinton E5 / E5X 0-6-2T
    1 * D E Marsh I1 / I1X 4-4-2T
    1 * D E Marsh I3 4-4-2T
    2 * D E Marsh H1 4-4-2

    1945
    Aquired:
    9 * Bulleid MN 4-6-2
    20 * Bulleid WC / BB 4-6-2

    Disposed:
    1 * Adams T1 0-4-4T
    1 * Adams O2 0-4-4T
    1 * Adams A12 0-4-2
    1* Adams T3 4-4-0
    1 * (Adams era) Southampton docks shunters 0-6-0T

    1946
    Aquired:
    32 * Bulleid WC / BB 4-6-2
    1 * Bulleid era USA 0-6-0T
    1 * Adams 415 class 4-4-2T (Not built, but acquired to capital stock)

    Disposed:
    2* Adams T1 0-4-4T
    11 * Adams A12 0-4-2
    1 * Adams X6 4-4-0
    1 * Stirling O / O1 0-6-0
    3 * Stirling F / F1 4-4-0
    4 * Stroudley D tank 0-4-2T
    1 * D E Marsh I1 / I1X 4-4-2T

    1947

    Aquired:
    18 * Bulleid WC / BB 4-6-2
    13 * Bulleid era USA 0-6-0

    Disposed:
    1 * Adams T1 0-4-4T
    14 * Adams A12 0-4-2
    9 * Drummond K10 4-4-0
    1 * Wainwright C class 0-6-0
    1 * Wainwright D 4-4-0
    8 * Stirling F / F1 4-4-0
    3 * Stirling B / B1 4-4-0
    3 * Stroudley D tank 0-4-2T

    So in that period, they acquired:
    • 20 large pacifics
    • 70 light pacifics
    • 40 modern 0-6-0 goods engines
    • 14 modern 0-6-0T shunting engines
    • 1 antiquated 4-4-2T passenger loco for very niche duties
    They lost
    • 35 * assorted 4-4-0s (passenger and mixed traffic)
    • 2 * 4-4-2 passenger locos
    • 27 * 0-4-2 mixed traffic locos
    • 3 * assorted 0-6-0 goods locos
    • 14 * assorted 0-4-4T passenger locos
    • 11 * 0-4-2T passenger locos
    • 3 * assorted 4-4-2T passenger locos
    • 2 * assorted 0-6-2T mixed traffic locos
    • 4 * 0-6-0T shunting engines
    That's 145 acquired and 101 disposed - it was the only time in SR history that they built more locos than they scrapped.

    Bear in mind by that time (late 1940s), the Stroudley designs would typically have been about 60 - 70 years old; the Stirling and Adams designs about 50 - 60 years; the Drummond designs about 40 - 50 and the Wainwright / Marsh about 40 years old; all of them with boilers about 30 - 40 years old.

    Tom
     
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  17. Jimc

    Jimc Part of the furniture

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    Don't forget steam was capital cheap and running cost heavy. Its inevitable that if traction type is being changed over some of the old style will have a very short life. The last of the GWR broad gauge had very short lives. The question is whether a its more cost effective to have short lived stock or to keep a collection of old crocks running. Not a question that is easy to answer.
    In the event the SR had a good number of modern 2-6-2 and 2-6-4T - BR standards and cousins. The calculation before the war was that electrification came with enormous savings in running costs, especially staffing, and the reduction in the size of the fleet dealt with the oldest stock. When further electrification stalled that stopped working.

    That's a remarkable set of numbers. Not only is it more locomotives, its much larger ones. If, as a crude estimate to allow for locomotive size, you count wheels, then the replacements (868 driving + 546 carrying) were double the withdrawals (422 driving + 304 carrying). Nothing like that was happening on the GWR, whose fleet was if anything gently contracting, I don't know about other lines. I wonder what on earth was going on with traffic patterns to provide work for all that extra locomotive capacity. To get back on topic the 210 GWR 94s, for instance, were equal in numbers and on average smaller in size than the absorbed 0-6-0T and 0-6-2T they were replacing.
     
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  18. Jamessquared

    Jamessquared Nat Pres stalwart

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    Bear in mind it was the only time the SR built more locos than they lost - you could see it as a reaction to the 1930s when they hardly built any locos, but scrapped plenty.

    Hopefully this chart is self explanatory. Four figures are plotted: the green and blue bars are the number acquired and disposed each year (*); the thin black line is the net change each year; and the thick red line is the total steam loco stock (right axis).

    Picture 1.png

    (*) An anomaly of how I count is that a reboilering (e.g. A1 --> A1x) doesn't show up; but substantial rebuilds such as the K 2-6-4T --> U 2-6-0 rebuilds show as a certain number lost, and the same number built, in 1928; similarly in 1926-7 there is a loss of 10 * Wainwright D, and a gain of 10 * Wainwright / Maunsell D1, net change zero.

    Tom
     
    Last edited: Nov 2, 2021
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  19. bluetrain

    bluetrain Well-Known Member

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    Moving forward to 1948-51, more new WCs/BBs replaced one of your favourite types - the Drummond T14 4-6-0. There was also a clear-out of the remaining Brighton B4s and B4Xs - which generally seemed to have lives a little shorter than the contemporary Wainwright D and Drummond T9 engines.
     
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  20. Jimc

    Jimc Part of the furniture

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    Mmm, but in the 30s the big electrification schemes were kicking in, so the reduction of the steam fleet was balanced by a big increase in the electric fleet. Unless there's evidence that they scrapped far too much in the 30s, which seems unlikely, then what was going on? Especially as the big increase seems 1945/ post war when the GWR was having a big purge of old crocks kept on for the duration.

    I think, though, the GWR built many more locomotives than the SR during the war, and I'm not sure the 1 in 1 out principle was running then. I think there were easily a couple of hundred, mostly Halls, (4-6-0MT) pannier tanks and 2-8-0/2-8-0T.
     
    Last edited: Nov 2, 2021
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