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Current and Proposed New-Builds

Discussion in 'Steam Traction' started by aron33, Aug 15, 2017.

  1. MellishR

    MellishR Resident of Nat Pres Friend

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    A firebox is far more complex and expensive to build from scratch than a boiler barrel, so that would have made some sense if they were using all of the 8F firebox, but my understanding is that they have actually thrown much of it away as well as the barrel.
     
  2. Richard Roper

    Richard Roper Well-Known Member

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    Which makes it all the more galling that 48518 was dismembered for this project. It also could be the fate of 7027's boiler if commonsense doesn't prevail, sadly.

    Richard.
     
  3. Hirn

    Hirn Member

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    Yes indeed: the new build 47xx was being redesigned to go mainline with small diameter cylinders and narrower in the width across to get clearances generally over Network Rail. They have been cast and the recycled set originally to be fitted abandoned. The newly cast set will also lower the centreline of the boiler more elegantly to enable the locomotive to go under reductions in the height of the loading gauge since privatisation.

    Obviously, the smaller pistons would mean a smaller tractive effort - ie the ability with the increased adhesion to restart and accelerate a long heavy train - but a new boiler could readily be made for a higher pressure 250 psi (not 225 psi) which would redress the loss of tractive effort. The Kings boiler is an enlargement of the boiler as finalised for the 47xx and always ran with 250 psi and they have always been maintained at that pressure. Making a smaller version of a King boiler for the King pressure should not be a high risk exercise and it would enable much fuller advantage to be taken of what the 47xx could do

    Basically what is proposed for expediency,will blunt the point of creating a 47xx anew and looks to waste the money, goodwill and intellectual effort spent on the new cylinders. The full blown 47xx with all axle loadings under 20 tons could anywhere any pacific could but with more adhesion. It would have a lower maximum speed than a loco with 6 foot driving wheels but with a thorough investigation if Tornado can have been formally allowed a speed increase of 15 mph I would have thought 10 mph more for the Night Owl ought to be possible. But maximum speed is not all what enable you to make a good reliable overall time is not going slow - as demonstrated long term by Train running in France

    PS The original proposal of the Castles was for a 4-6-0 with the 47xx boiler this was too heavy for a 2o ton axle load, as for a long time now major renewals have been done for 25 tons, this might be the time to make two similar new boilers one for the 47xx and one for a Castle as it was first meant to be before got a the present smaller boiler. (Whatever may have happened to the loading gauge clearances in the last 25 years the maximum axle loads have not been reduced but rather
    extended.)
     
    Last edited: Sep 14, 2022
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  4. 242A1

    242A1 Well-Known Member

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    So what you are proposing to build is not a 47xx, it is not even a look alike. You are wanting more of a mixed traffic 2-8-0 which is roughly based on GWR practice. This would not satisfy the desires of the Group engaged in trying to create this machine.

    They could perhaps fund a less expensive design of boiler with the cladding designed to disguise what lay underneath The Diagram 100A has the same 5' 6" diameter at the smokebox tubeplate as the GW number 7 and it is far more highly regarded by some modern boiler designers than anything which came out of Swindon and it has a proven capacity for good evaporation. The engine could be provided with fittings (chimney etc.) which allowed it to run on the mainline and also with a set which would offer an external appearance more faithful to that of the original. This mongrel may not be a cat but there are many ways of skinning it. Is it worth the trouble? Only those engaged in the project can really answer that and I suspect that they are desperate to see it completed in their lifetime. After that it is debatable whether there will be sufficient continued interest.
     
    Last edited: Sep 15, 2022
  5. Hirn

    Hirn Member

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  6. Gav106

    Gav106 Well-Known Member

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    So can we get the 4F boiler from avon valley and turn it into a 2P.......they are doing the fowler tender already......
     
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  7. MellishR

    MellishR Resident of Nat Pres Friend

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    Given the original intention (even if deferred until further notice) of main line operation it certainly made sense for the new 4700 (new, not a replica, just like Tornado and the P2) to have smaller cylinders than the originals. It then would make equally good sense for 4709 to have a 250 psi boiler (just like the P2). If and when main line operation happens it will obviously also need the electronic gubbins, and air braking equipment will be at least highly desirable. All those changes from the originals would be for the same reason, suitability for main line operation, just like the P2's changes. Just like the P2's changes they would have minimal effect on the external appearance (depending where the air pump goes).

    The end result would be a new 4700 looking almost identical to the originals, the only major external difference being reduced height. Why should that not satisfy everyone (especially with the new boiler, identical to the Swindon No.7 apart from the increased pressure, removing the need for the Castle boiler)?
     
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  8. clinker

    clinker Member

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    Can the parts of the 8f boiler being 'used' be clarified please? in the terms that I am used to using (road steam) the 'firebox' is just that, part of the pressure vessel that is 'Simply' a five sided open bottomed 'Box' which contains the fire. If this is then considered in terms of the assembly that it forms a part of there is an 'Outer wrapper' whether belpaire or round topped, which is of appropriate dimensions for the firebox to fit inside, with a surrounding water and steam space, the outer wrapper is then 'closed' front and back by a 'Backhead' a the cab end and a throatplate to which the barrell is fixed and fitted at the front, the bottom of the waterspace being closed by a 'Foundation ring' and the whole lot being stayed together. This assembly would be termed the 'Back end', so can some-one please clarify just how much of the 8f is actually incorporated into this assembled conversion?
     
  9. 242A1

    242A1 Well-Known Member

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    I agree with you in that the best approach would be to go down a similar route to that taken with the P2. A redesigned number 7 boiler would be a costly one off but it could be done given the funding and the necessary time. The A1 Trust made a good choice in that their boiler was a modified version of a boiler which was already built to work at 250 psi and this design was also suitable for more than one locomotive design.

    The No. 7 boiler would be heavier than the originals if it were built in a conventional manner and it would cost more than the boilers currently being completed for Tornado and 2007. Has anyone looked at the original boiler design with respect to increasing the working pressure? Probably not. Have the 4709 group put the building of a replica boiler out to tender?

    They could perhaps save some money by having the boiler constructed using more modern methods but their would be the cost of the revisions to the design to make it suitable for this method to be considered.

    If the decision was taken to proceed along the new boiler route how long would it take for such an item to be funded and delivered? I suspect that the 4709 org would have significantly reduced membership by the time this would come about. Tempus Fugit and all that.
     
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  10. Hirn

    Hirn Member

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    Reply to 242A1 post no.4764 at 7.47 pm 14/9/2022

    The changes proposed would be the minimum needful. I don't think the new build is worth doing to be something looking like and only running to and fro with something like four carriages.

    I think the main thing is what the spirit of this recreation should be - I am much obliged to 30854 for raising the point here - but different people are bound to have different ideas.
    As a boy I had quite a difference with somebody: to me the radiator on a then new Rolls Royce was a fake because it didn't actually contain the coolant - if you drilled a hole in the side nothing would come out. I don't see how making a smaller boiler seem larger than it really is should be a good thing to do

    It seems to have been - plenty of accounts - a most successful locomotive.

    It was Churchward's final locomotive and some have called it his masterpiece.

    They were regularly on an overnight turn Birkenhead to London on through fast freight - they would go the distance.

    In the 1950s they all had new boilers and the the only material difference I know of was to shorten the superheater elements.

    There was a detailed memory of one sweeping into London at a steady 80 mph and riding quite reasonably. A precursor of the 9Fs turning in really fast express passenger speeds?

    Some locomotive designs seem to be remarkable sprinkled with stardust beyond what one can explain: the haulage ability of the Stirling singles about 1900 and the general excellence of the A4s - neither with huge grates. It seems the 47xx was this sort of thing, in the 5os with the huge Summer Saturday passenger traffic they were put on it. Any really successful locomotive is a sophisticated compromise but if one cannot tell quite why one cannot be sure what to safely change for the different without compromising the remarkable.

    Both the LMS and the GWR built limited numbers of Kings and Pacifics to haul a limited number of really heavy trains and on GW main line the 47xxs seem to have been roped in when there were not enough Kings and no trouble arose.

    I say nothing against the 100A boiler but being shorter the No 7 boiler would steam better than the No 12 on the Kings and I'm not sure that was reckoned a poor boiler.
    You would surely not have the same delicate balance between turbulent flow in the tubes - the Reynolds number - the resistance thus caused and the back pressure at the blast pipe necessary to overcome it short of creating the No 7 boiler. A smaller, lighter boiler would compromise the adhesion.

    My strong support for the proper boiler is not to create any hybrid and if it was a mixed traffic locomotive, it was heavy mixed traffic as a passenger locomotive it was heavy passenger, if not absolutely as fleet hardly very much slower than the various 4-6-0s.
     
    Last edited: Sep 15, 2022
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  11. Thompson1706

    Thompson1706 Well-Known Member

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    If it were possible, put on display the new 47xx alongside an original version and ask people which is which. How many would know the answer ?

    Bob.
     
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  12. Hirn

    Hirn Member

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    Reply to Clinker post 4768 on September 15th 2022

    The Wrapper, only the wrapper.

    Bemuseingly I understood the rest of the boiler was all replaced: for the sake of that one plate they forwent the possibility of 250 psi and the simple advantage of having an all new boiler. It also made many people less sympathetic to anything to do with Didcot, speaking for myself I only supported the Night Owl despite it and because at the time 4709 was being made apparently at arms length, away from Didcot.
     
    Last edited: Sep 15, 2022
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  13. Matt37401

    Matt37401 Resident of Nat Pres

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    Your just asking for the ‘All Great Western Engines look the same’ statement to be trotted out again aren’t you? ;)
     
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  14. 30854

    30854 Resident of Nat Pres

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    I can't tell a Fire Fly from 18000 either. Maybe I'm overdue for a visit to the optician.
     
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  15. Matt37401

    Matt37401 Resident of Nat Pres

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    In all seriousness, I’d love you to speak to my mother who’s a volunteer at the SVR, to her 7802/12 and 2857 are all the same engines to her. The only difference to her is 2 out the 3 have nameplates.
    Please bear in mind she’s not completely ‘Normal’ either.
    I dread to think how she’s going to get on with 4930…
     
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  16. 30854

    30854 Resident of Nat Pres

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    Can I take it she works somewhere other than the loco dept or workshop*? Anyhoo .... since when can any aficionado of one particular company's output be considered vaguely "normal" ? And considered normal by who, precisely?


    *if you come back with a photo of your mother welding up a boiler throatplate, I may have to revisit some of my own preconceptions!
     
  17. Thompson1706

    Thompson1706 Well-Known Member

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    No - i'm saying that if you put an original condition loco next to a new build with minor alterations how many people would know which is which.

    Bob.
     
  18. Hirn

    Hirn Member

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    Last edited: Sep 15, 2022
  19. Glenmutchkin

    Glenmutchkin New Member

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    Maybe one could be painted purple to help.
     
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  20. Jamessquared

    Jamessquared Nat Pres stalwart

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    Oh, that’s easy. One is just the lifeless hulk of a locomotive that will seemingly never move under its own power again - and the other is 18000.

    Tom
     

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