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Tank v Tender Locos

Discussion in 'Steam Traction' started by johnofwessex, May 17, 2017.

  1. LMS2968

    LMS2968 Part of the furniture

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    The classification system started on the Midland, where it was very strictly imposed. It was modified under LMS and BR authority. It was also used practically on the LMS and LMR to assess loading criteria; the Crabs of both types were uprated - on paper - because the work they were doing on weekend excursions was in the 6P category and there weren't enough genuine Class 6 locos otherwise available to cover it. While this was a misuse of the system, it does show that it was in operation.

    While other Regions might or might not have used the ex-LMS system as such, I'd suggest that there was some similar means of classifying locos and loadings in force.
     
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  2. Copper-capped

    Copper-capped Well-Known Member

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    @LMS2968 could you expand a little on what you mean by loading criteria? Thanks :)
     
  3. Jamessquared

    Jamessquared Nat Pres stalwart

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    I suspect such classifications were of most use during mergers, i.e. after the grouping or after nationalisation, when headquarters' staff had to rapidly get to grips with an enlarged stock and form a means of reckoning between similar types from different constituents.

    As an example, when the SR formed, they developed a classification that had four parts - a letter (P / G / M / S) to denote passenger / goods / mixed traffic or shunting locos, followed by three numbers that denoted haulage capacity, range and braking capacity. Apart from in Holcroft, I've never seen it discussed in detail. Certainly I don't think it was of much practical day-to-day use by Shedmasters, but was probably helpful when there was a need to move locomotives to "foreign" parts, such as when ex-LSWR T9s went to the Eastern Section; or large numbers of ex-Ashford N and U class moguls went the other way to the Western Section.

    Tom
     
    Last edited: Jun 3, 2017
  4. Jamessquared

    Jamessquared Nat Pres stalwart

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    Coming right back to the OP's question, and one very practical thing I don't think has been commented on is the limitations imposed by the cab on a tank engine.

    For example, take @johnofwessex's question "why wasn't the SDJR 7F built as a tank rather than a tender loco?" From that ever-reliable source Wikipedia, the grate area is apparently a bit over 28 square feet. For a narrow firebox engine, that means the grate must be something like 8 feet long. That in turn means the fire irons would have to be about 9 feet long. Those are pretty unwieldy even on a tender engine, but on a tank engine you get the additional issue of manoeuvring them within a cab. At the very least, the cab would have to be long enough to withdraw such an iron straight out of the firebox. (Anyone who has ever thrown out the fire on an older tank engine without the benefits of a rocking or drop grate will appreciate the problem). So quite apart from issues already discussed on this thread, I suspect that design considerations mean a loco with a large grate starts to get impractical without having a similarly large cab - which then cuts down on the length available for a bunker, decreasing range ...

    Tom
     
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  5. The Saggin' Dragon

    The Saggin' Dragon Part of the furniture Staff Member Moderator

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    Were not some of the 7fs at one time fitted with tender cabs?
     
  6. Jamessquared

    Jamessquared Nat Pres stalwart

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    Yes ...

    [​IMG]

    But look how huge the combined cab is. Now imagine turning a 2-8-0 into, say, a 2-8-2T with that size cab. The trailing wheels would be about where the cab steps are - where would you put the coal bunker?

    Tom
     
  7. 8126

    8126 Member

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    I know I use these as an example quite often, but... a big boiler 2-8-2T, you say? That's a Lord Nelson-sized grate, so I've no idea how they wielded the fire irons in that relatively small cab, but they must have done somehow. Still, I doubt they had the coal capacity (4 tonnes) that would have been needed for 7F duties (and appetites) - small water capacity is acceptable on something that's going to stop a lot, but insufficient coal capacity to make it back to the depot is much more of a nuisance. I suppose you could make the 7F a 2-8-4T, but then the braking capacity might still have been a bit marginal for the duties in question, even if you gave it bogie brakes.
     
  8. LMS2968

    LMS2968 Part of the furniture

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    Each route, say Euston Carlisle, would be split into sections, say Euston - Tring, Tring - Rugby, etc., in each direction. A series of times over those sections for various classes of train would then be fixed according to the timetable, and the maximum limits in tons (Load Limits) arrived at for each class of loco over that stretch for each specified time. For example, A pacific might be allowed 600 tons on the slower timing, but only 420 on a very fast one. A 5XP would be smaller loads on each of the same time / load sections. A non-stop Euston - Carlisle working would be limited by the section with the lowest load limit.
     
    Last edited: Jun 3, 2017
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  9. peckett

    peckett Member

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    Being a Midland man ,being worked by Black 5 s and 5Xs(Jubilee ) in my time, I could never imagine a Crab (class 5 )being booked to work a express .Several sheds including Leeds ,Nottingham Derby had allocations of all three classes,Nottingham turning out a Crab for the Robin Hood express ,Leeds one for The Thames Clyde .I don't think so. As far as shed Forman were concerned a Black 5 was a Black 5 ,a 5X a 5X a Crab a Crab. I think for one short time Crabs were classified 6P/5F.
     
  10. LMS2968

    LMS2968 Part of the furniture

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    As said in Post 61, it was bureaucratic exercise only; no-one had any idea of using the Crabs on normal Class 6P work. Throughout the week they were on their normal diet of goods, Fast Fitteds, parcels, the odd local passenger, etc. It was only at weekends when their 6P rating came into use on excursions. But they were classed by BR as 6P5F above the Black Fives' 5P5F, probably on account of their higher tractive effort.
     
  11. Eightpot

    Eightpot Well-Known Member Friend

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    I can't understand why this country (as far as tender engines were concerned) never cottoned on to the German system. A large diameter tube was mounted in the tender in line with fire hole door, and the fire irons went into it handle first. All the fireman had to do was to pull out the desired iron, and straight into the firebox with it, then after use simply push it back into the tube. True, firemen were issued with suitable gloves to do this, but no messing about turning and wielding hot fire irons in the cab.
     
  12. LMS2968

    LMS2968 Part of the furniture

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    Edit: These are some for a BlacK Five:
    [​IMG]
     
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  13. Copper-capped

    Copper-capped Well-Known Member

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    Very interesting - a piece of railway working I had never considered. Always learning - thanks for that!
     
  14. John Stewart

    John Stewart Well-Known Member

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    Thanks for this. I could never understand why the Crabs were 6p5F. The other way round, possibly!
     
  15. gkerr9623

    gkerr9623 New Member

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    I'm a bit late to this discussion but I've read through everyone's comments with interest. A couple of points -

    Power classification; BR rated the GNR Ivatt Atlantics as 2P, despite the work which they had been required to carry out in LNER days (deputising for Pacifics etc.) which you might argue was at least in the class 5 range. But they had small cylinders in relation to the boiler size and therefore low tractive effort. Getting one started with a heavy train required enginemanship of the highest order, especially on a wet rail.

    Brake power on tank engines - I get the point about the need to stop unfitted freight trains and a tender brake is a valuable addition. Some tank classes, e.g. GCR Robinson 2-6-4 tanks and the Thompson Q1 rebuilds, were deficient in this respect. Yet the GWR relied entirely on tank engines for its internal coal traffic in South Wales, the coal coming downhill in heavy trains from the valleys to the ports. Did these classes, e.g. 5600 and 4200 classes, have much better brakes than large tanks locos on other railways?
     
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  16. RLinkinS

    RLinkinS Member

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    Peter Smith, in his book about the Somerset and Dorset, wrote that a 5600 was tested on a freight and the brake power was so poor that it shot through Radstock "as though it was on roller skates". So their brake power could not have been very good. Perhaps the wagon brakes were pinned down when descending the valleys

    Sent from my SM-A105FN using Tapatalk
     
  17. johnofwessex

    johnofwessex Part of the furniture

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    There were regular attempts to replace the 7F's which usually ended when the fitted head on the test train had to be calle don to bring it to a stop.
     
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  18. Fred Kerr

    Fred Kerr Part of the furniture

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    That said I can recall in the early 1960s when an Aston Stanier 'Crab' was a regular performer on the Birmingham - Yarmouth (via Rugby, Seaton and Peterborough) dated service and - I presume as noted by you - on seaside excursions during the holiday period when demand meant the use of any available motive power however outrageous.
    A personal experience came in 1962 when an annual trip on the 'Waverley" from Nottingham to Edinburgh had hopes of an A4 forward from Leeds following the trial by Haymarket of using the displaced locomotives on the Waverley from Edinburgh to Leeds hence returning on the northbound service. Much to my chagrin the trial had finished and the best that Leeds could offer was a single Stanier 5 in the shape of 44852; at least it kept reasonable time to Carlisle where the regular Gresley A3 took the train forward.
     
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  19. LMS2968

    LMS2968 Part of the furniture

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    It has to be said that the S&D 7Fs had a superb brake. Even the Stanier 8Fs, which did have a good brake, where not held in the same regard. The 7Fs' only problem was to deposit iron filings all over the slide bars, which led to their getting Ferodo (asbestos) lined blocks on the leading wheelsets, or possibly all engine wheels.
     
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  20. RLinkinS

    RLinkinS Member

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    Were any other steam locks fitted with Ferodo brake blocks?

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