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Edward Thompson: Both sides of the story - lecture Feb 2018

Discussion in 'Steam Traction' started by S.A.C. Martin, May 2, 2012.

  1. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Having spoken at length to a gentleman in charge of belpaire locomotives which also received round topped boilers (the N7s) the costs to build and maintain the former versus the latter were interesting to say the least.

    The Thompson designed boiler was superior in every conceivable way from an economic to build and maintenance point of view on the LNER and that is why many locomotive classes received replacement round topped boilers on the LNER.

    However I happily concede that the belpaire boilers on other railways may have had different cycles of maintenance, given the advantages of the belpaire firebox.

    The big difference gents is that on the one extreme, you have the GWR with a small number of standard belpaire boilers for which the presses and skill set to build them is still available and then at the other extreme you have the LNER with over 160 different types in 1941. Thompson wanted a more GWR style situation on the LNER and wasn’t able to achieve that.

    Re dispelling myths - you’re very kind Pete - but please direct your thanks to the late Peter Grafton and Dick Hardy.
     
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  2. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    I hope nobody thinks I am belittling the excellence of a belpaire boiler - far from it. My view is LNER centric, I do not profess to speak for other railways.

    The layman to the GWR can however clearly see and acknowledge the excellence of their boilers both in steam raising and in their approach to standardisation. Workmanship too.

    As I said previously, different extremes. The LNER found belpaires more costly no doubt because there were a huge variety of types to maintain across dozens of classes.
     
  3. Steve

    Steve Resident of Nat Pres Friend

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    I've covered this before but I can't remember why. in a nutshell, it comes down to the design of the boiler, rather than type. The N.E.R. round topped firebox illustrated had large radius bends in the platework, the firebox top was not flat and the water spaces gradually increased in size once clear of the restricting frames. The greater stay length contributed to flexibility, needed to cope with differential exapnsion. A badly designed Belpaire would have a sharp ogee bend, sharp firebox corners and parallel water space. All the latter would be potential problem areas The Churchward Belpaire boiler did not feature any of those poor design points.
    NER Firebox.jpg
    Comparing boiler repair costs is always going to be difficult. Generally, locos were shopped on a mileage basis and not boiler condition. However, it was common to carry out certain repairs at each overhaul. Cook (Raising Steam on the LMS) states that the LMS G10¼S boilers had their stays replaced at the first general repair, again at the second and a new firebox at the third, regardless of condition. Cook also states that the class 7 (Ivatt) boilers built for the 2-6-2T's at Crewe cost £1888 each and the same boilers but for the 2-6-0's at Swindon cost £2252.
     
  4. 8126

    8126 Member

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    Interesting to note that while nearly all "new" design on the Southern used Belpaire fireboxes, until the Pacifics appeared the mainstay of the heavy fleet was of course the round-top taper boiler of Urie descent on most of the 4-6-0s and with a shortened version on the Schools.
     
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  5. Jamessquared

    Jamessquared Nat Pres stalwart

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    Surely that says more about the constraints Maunsell designed under than the relative merits of the two types of boiler design? The King Arthurs were designed in a hurry to give time for a proper express design to be worked up, so they just did a light touch going over of the Urie N15. The S15 was a similar light touch redesign, and shared a boiler with the King Arthur. The Schools was constrained by the Hastings line tunnels, so had a round top boiler to enable narrower cab to be fitted, and to keep the weight down. Where Maunsell has a relatively clean hand in boiler design, he chose to use Belpaire fireboxes - the various moguls, Lord Nelson etc.

    Tom
     
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  6. pete2hogs

    pete2hogs Member

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    As I said earlier, I doubt there is any difference in steam raising ability and the round top is cheaper to build. The LNER found it cheaper to maintain, but its very difficult to compare as the different methods of cost control used by the grouping companies were never brought totally in to line even after nationalisation. You would have to find some evidence to justify the difference in first cost by boiler performance, and I doubt there is any way of isolating just that without it being influenced by blastpipe design and many other factors.

    No design succeeded or failed due to the shape of the top of the firebox :)
     
    Last edited: Mar 3, 2018
  7. Hermod

    Hermod Member

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    The Germans made about 2000 locomotives with Belpaires between WW1 and ca 1925.
    From that time no new designs had Belpaires and quite some of the 2000 had new round top boilers.
     
  8. 8126

    8126 Member

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    I suppose my point was that on the Southern expedience trumped dogma to a greater degree than on the rest, perhaps.

    Of course, Gresley built a lot of Belpaire-boilered engines of existing classes, some of them given almost as much of warming-over as the King Arthurs received, but I can't really imagine something like the Schools or the Z being done on the GWR or LMS. Maybe I'm wrong, they fitted a very particular need and were no doubt cheaper for using existing tooling, but I can't think of any comparable examples.
     
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  9. Jamessquared

    Jamessquared Nat Pres stalwart

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    I was wondering about ways to try to isolate costs of Belpaire vs round top fireboxes while keeping as much else as constant as possible. An obvious example was to compare the Lord Nelsons against 857, "Lord Howe", which was fitted with a round top boiler, all else remaining unchanged.

    At first sight, the round top boiler was considerably more expensive to construct (£2,790 vs £2,330). However, the round top boiler was made from a high nickel steel with the intention of allowing thinner (and lighter) boiler plate, so I don't think a straight comparison is really valid. Moreover, I cannot find any per-mile boiler repair charges for the two.

    So - case unproved either way. The only other thing to say is that, when the round-top boiler needed a new firebox in 1945, it was lain aside and Lord Howe was returned to service with a standard (Belpaire) boiler, but that would be a logical decision simply in terms of shed standardisation unless the round-topped boiler showed a massively dramatic advantage over the Belpaire, which seemingly it didn't.

    Tom
     
    Last edited: Mar 5, 2018
  10. Copper-capped

    Copper-capped Active Member

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    I'd be surprised if there weren't some studies done by the big four, (well, perhaps only three of them!), along the lines of cost/benefit. It would probably need to be instigated by a CME sitting on the round vs belpaire fence.
     
  11. Fred Kerr

    Fred Kerr Part of the furniture

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    Remembering that the boiler is the container for both steam passages and steam raising I would presume that the firebox studies would be included as part of any investigations. Given that Gresley turned to Chapelon for assistance with steam passages on his Pacific designs - especially the A4s as Super A3s - I therefore presume that the LNER's combination of firebox and boiler was clearly accepted as best option for the passenger work they were undertaking.
     
  12. pete2hogs

    pete2hogs Member

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    My memory may be at fault here (I'm getting old!) but wasn't the LN round-top boiler a larger design intended to try out ideas for a proposed Maunsell pacific?
     
  13. Jamessquared

    Jamessquared Nat Pres stalwart

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    Yes, you're right. The boiler design was very different from, say, a Urie-derived round topped boiler (S15, King Arthur etc). The one fitted to Lord Howe had a large combustion chamber and was made of a high-strength alloy to allow thinner plates and a reduction of weight. All of which makes any attempt to draw more widespread conclusions from a cost comparison between boiler types in otherwise identical locos essentially impossible, sad to say.

    Tom
     
  14. Jimc

    Jimc Part of the furniture

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    The trouble with comparisons is what do you compare... Churchward had a NER style large diameter round top firebox constructed for a Badminton,. The end result was getting on for 3/4 of a ton heavier than the same locomotives with a Std 4 boiler. Should you compare cost of ownership per ton, per unit steamrate or what? We know that around the turn of the century Churchward tried a whole raft of boiler variations on the Badmintons, also including Serve (finned) tubes, two different sizes of taper boiler, parallel belpaire boilers, steel fireboxes... Its fairly obvious what conclusions he came to, but less clear as to exactly why he did so. In his paper "Large Locomotive boilers" he says that "less trouble" is experienced with belpaire fireboxes and foaming is less of an issue, but there's not as much detail as one might like.
     
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  15. pete2hogs

    pete2hogs Member

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    On the other hand the LNER were the only company that never had a boiler failure in one of their locos.

    We can bang our gums on this stuff from here to eternity but we simply don't know which is better Belpaire, Swindon 'improved Belpaire' or round topped, let alone all the variations of firebox staying etc.

    I'm an LNER man, my father worked for them , and I believe they made the right decision regarding fireboxes, but I'm not about to say anyone else was wrong to use an alternate. The only reasonably comprehensive trials that compared locos with round top and improved Belpaire boxes were the 1948 trials which did not take into account maintenance costs, which as already stated we have no basis for comparison. What they did prove was that there was marginal or no difference between round top and improved Belpaire fireboxes as traffic machines.
     
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