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Brighton Atlantic: 32424 Beachy Head

Discussion in 'Steam Traction' started by Maunsell man, Oct 20, 2009.

  1. Eightpot

    Eightpot Well-Known Member Friend

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    Recent communications from the Brighton Atlantic group have suggested one of John Chester Craven's or a K Mogul. Can't see them doing an SE&CR loco. Can it be that the E class actually proposed to be built by the Bluebell Rly itself, or another group within it?
     
  2. Dan Hill

    Dan Hill New Member

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    I think a Craven 'Jenny Lind' was part of the Bluebell's Long Term plan, as well as restoring the line's Craven era carriages as part of a complete traing.

    According to quotes in Steam Railway a Craven loco was ruled out because it wouldn't be much use for pulling trains. It also says a K mogul (which I remember was a few years ago estimated at costing about £3million) was considered as was a Marsh I3.
     
  3. Paul42

    Paul42 Member

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    The same group. The K and I3 have very complex bogies etc so they looked at non Brighton alternatives and came up with the E.
     
  4. fisher

    fisher New Member

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    I am glad this has broken cover at last in today's Steam Railway. Having heard about it a couple of weeks ago I was initially disappointed that it wasn't a Brighton loco, but the proposal has grown on me over as I have got to understand the E class in more detail. To be honest, not a class I had much knowledge of before, perhaps overshadowed by the D class. However, the more I have looked at the features of this loco, particularly with the extended smokebox, the more I think it has that balance between elegance and industrial purpose that not many classes carry off. Great Central atlantics are another, but that is a separate story. I also really like the logic of something which is relatively simple to build. It will therefore be an easy decision for me to carry on Beachy Head standing orders to support this project.

    There is another thing that occurred to me, albeit thinking a bit further into the future. It provides a great opportunity to create the Bluebell's version of pure Edwardian Train. OK, I know you could use some of the existing SECR locos, but maybe there is an opportunity for a parallel programme to complete the birdcage trio set, possibly packaged into some sort of heritage grant application to run in parallel with the E class build towards the latter stages of its construction.
     
  5. Spamcan81

    Spamcan81 Nat Pres stalwart

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    What’s the Middle England Nylon Sock Association got to do with it?
     
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  6. Sheff

    Sheff Well-Known Member

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    [Apologies for the late arrival of this post as I just discovered it sat on my laptop from yesterday!] ........

    Quite simply, if you treat the machine as a 'box' the inputs are cold water, coal and ambient air. The outputs are work, hot gas and exhaust steam.

    So you lose the latent heat of the steam, which as Steve's diagram clearly shows is the majority of the energy going to the cylinders. There is no escaping this, unless you have a heat sink within the box to utilise this low pressure, but high thermal energy stream. The same applies to power stations with steam turbines (typically 35% efficient thanks to vacuum condensers) , unless you have a local heat sink handy such as a chemical plant.

    Several of the factories owned by the company I worked for (and others such as refineries) operated Combined Heat & Power plants (CHP) with overall efficiencies as high as 90+%, as all the exhaust steam was used for process heating and the condensate returned to the boiler house. We used various techniques to wring the last joule out of every kilo of steam, such as mechanical or thermal recompression if we had an excess of low pressure steam and need a supply at higher pressure. Turbines also had steam take-offs at different stages along the turbine. Achieving a perfect steam/power balance was always holy grail. The last resort was to use steam reducing valves to supply low pressure users directly from the HP main as this meant power lost at the turbines.

    It would be difficult if not impossible to apply much of the above to the steam locomotive, other than feed water and combustion pre-heating, though in winter you could employ thermo-recompression of exhaust steam for carriage warming. However, in all cases you would need to take into account the reduction in volume for blast generation.
     
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  7. Cartman

    Cartman Member

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    That E class is a nice machine and a good choice for a next project. Looks like it would be powerful enough to handle a decent load, plus, all important! you can have it in SECR, Southern green or BR black!

    Best wishes and good luck to the group
     
  8. ross

    ross Member

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    I have learned more from this chart and the associated posts and explanations than I ever learned in school. For the benefit of the less educated, could anyone direct me toward a similar illustration of the efficiency, or lack thereof, of internal combustion power. I do understand quite a bit about IC engines, and had some success at making them give more power than manufacturer intended, but I still don't grasp why they are regarded as inefficient
     
  9. John Petley

    John Petley Well-Known Member

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    I must admit, an E Class is surprising choice. I'm disappointed that the K class seems to have been kicked into the long grass, but ultimately, it's only right that the people who are going to build it should have a major say in what they build. It's also a bit surprising that a big-wheeled 4-4-0 was chosen as they are far from the obvious locos that spring to mind for working trains at 25mph on a line which does have some steep gradients. Having said that, 30120 seems to manage five-coach trains on the Swanage Railway with no problems and they are expecting the T3 to be equally happy on such duties. I would have preferred an E1 as we have an example of an original Wainwright 4-4-0 even if its home is a long way from the Bluebell (or SE&CR metals for that matter) and it is highly unlikely ever to steam again - after all, the D1/E1 rebuilds were among the finest pre-grouping 4-4-0s.

    At the end of the day, however, E class locos did work over the line (See page 122 of Klaus Marx' encyclopaedic work on the Lewes & East Grinstead Railway) they are very handsome machines and most important, the group planning to build it reckons it will be as straightforward as a new-build can be, especially given the expertise the loco department has gained when it comes to Wainwright locos, so I offer them my full support (which, I hope over the years will include some cash support). I'd be interested to hear Tom (James Squared)'s thoughts on this announcement as he does seem particularly partial to SE&CR engines.

    Rather than start a livery debate, here's an interesting alternative subject - a number debate. Will the new E be a replica of an earlier machine or will it take a blank number which was never used? The SE&CR's numbering was particularly chaotic so there probably is a number somewhere between 1 and 752 which was never allocated to any loco.
     
    Last edited: Jun 28, 2019
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  10. Jamessquared

    Jamessquared Nat Pres stalwart

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    Exactly so, and that is the root of the inefficiency in steam locos. If you multiply typical cylinder efficiency with Steve's figures of available energy (say 12%, for that combination of working pressure and superheat), you get the typical steam loco overall efficiency that is in the region of 8 or 9%. The vast majority of the wasted heat, i.e. inefficiency, stems from the fact that your input is water but your exhaust is steam, immediately throwing away everything represented by the vertical line in Steve's diagram labelled "Latent Heat (Boiling)".

    Tom
     
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  11. mdewell

    mdewell Member

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    Without wishing to get to far off topic, the following link might be of use https://en.wikipedia.org/wiki/Engine_efficiency
     
  12. Steve

    Steve Part of the furniture Friend

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    You can be dubious if you like but the figures were arrived at by scientists far more clever than me. Let’s try a simple approach in an effort to better explain it. Start with a cold vessel and heat it up. You will go through the process of water heated up to boiling then being turned into steam. When all the water in the vessel is steam it will start to build up pressure as more heat is applied. If you then pass tat steam through a superheater it will increase in temperature but not pressure, exactly as the diagram. The trouble with a steam loco is that you are using steam and adding cold water so it is not a static condition. However the figures apply per pound of steam. It is simple thermodynamics.
     
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  13. JohnElliott

    JohnElliott New Member

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    The proposal on the notice board suggested 516.
     
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  14. ghost

    ghost Well-Known Member

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    Is the spare C class tender of a suitable size/design for use on the E class?

    Keith
     
  15. huochemi

    huochemi Member Friend

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    Simple thermodynamics sounds like an oxymoron.:eek:

    One suspects thermodynamicists tend to talk in temperature and heat rather than pressures (I guess that is why they are called heat engines). Attached is the chart of the steam inlet and exhaust steam temperatures from the BR performance report on 71000. This also shows how the heat converted into work is limited by the temperature drop through the cylinders. It seems to show that without superheat, the heat drop would be very limited, but also that increasing superheat temperature is somewhat offset by increasing exhaust temperature, but this is certainly outside my comfort zone.
     

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  16. Jamessquared

    Jamessquared Nat Pres stalwart

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    Re the Wainwright E: there has been a debate played out in the pages of Atlantic News over the last few years as to a "next project", and the Wainwright E was mentioned in a long list of locos discussing pros and cons of buildability, usefulness and fundability. So it wasn't a total surprise to me when I found out some weeks back, though still not what I had immediately thought might happen. If you look at late Victorian/ Edwardian design, many designers ended up building essentially a large passenger loco (normally a 4-4-0); a goods loco (normally an 0-6-0); a passenger tank loco (often an 0-4-4T or 0-6-2T) and a small tank loco (generally an 0-6-0T); the E class will enable us to have examples of all four types from one designer in service together.

    As has been mentioned by @Paul42, it does I believe still need formal ratification within the railway's governance processes.

    A for the actual decision, and the costs:
    • The railway had a spare tender, which was broken up about 15 years ago on account of twisted frames and a rotten tank. However, the wheel sets, axleboxes, buffers, brake gear and other fittings were retained and can be reused to construct a new tender. That probably saves a six figure sum relative to constructing an entirely new tender.
    • A set of cylinders for the C class was produced from CAD / poly patterns a couple of years ago. They will go in the C class at its next overhaul, but essentially the E class cylinders are very similar - extra wall thickness to account for slightly larger diameter - so the CAD can be largely reused with a small modification.
    • Mechanically, the loco is fairly simple. For example, vac brake only rather than the combined air and vac that would be needed on a Brighton loco. The reverser is a steam reverser for which producing parts helps sustain the other Chatham locos, and is far simpler than the combined air-operated screw reverser of something like the Atlantic. The feed is again from injectors for which we have patterns rather than the K class Weir pump. The frame layout is far simpler than on a Brighton loco and there is more space between the frames than there would be on a K to fit less stuff, making construction easier.
    • The boiler is unsuperheated. Superheating adds another six figure sum to construction (for the header and elements) and adds a maintenance overhead, a figure that in stop-start heritage line conditions can never be recouped in coal saving.
    So as a practical proposition, it works out quicker and cheaper by some considerable margin than say a K class while still delivering an operationally useful loco.

    Tom
     
    Last edited: Jun 28, 2019
  17. 30854

    30854 Part of the furniture

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    Re: E class ..... enquiry ..... how does the Belpaire firebox compare with the round topped variety (as fitted to the D class), regarding cost, difficulty etc.?

    I'm assuming the survival of the D at the NRM weighed in favour of the later E .... though I have to admit to a fondness for the (admittedly more utilitarian looking) Maunsell rebuilds.
     
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  18. MellishR

    MellishR Well-Known Member Friend

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    I confess that thermodynamics was one area of physics that I grasped less than most. However I can't let the bit-in-bold pass. As soon as any of the water boils it generates a much greater volume of steam. In a normal boiler in more-or-less steady-state operation the pressure is high and remains high, most of the heat being used to turn water into steam with a large change of volume but no change of pressure: that is the latent heat that we've been discussing.

    I direct attention to this bit from https://en.wikipedia.org/wiki/Steam_engine#Efficiency "One principal advantage the Rankine cycle holds over others is that during the compression stage relatively little work is required to drive the pump, the working fluid being in its liquid phase at this point. By condensing the fluid, the work required by the pump consumes only 1% to 3% of the turbine (or reciprocating engine) power and contributes to a much higher efficiency for a real cycle." That is the essential feature of steam engines and why they were invented.

    In the absence of a condenser, with exhaust steam being vented to the atmosphere, the remaining energy in that steam is indeed wasted, but even with a condenser a lot is wasted. Ultimate thermodynamic efficiency depends on the temperature at which the remaining heat flows out. In a power station (if not combined heat-and-power) the huge cooling towers are there to get rid of the remaining heat at as low a temperature as possible.

    But we probably should pursue this no further, unless it deserves a new thread of its own.
     
  19. jnc

    jnc Member

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    I'd go for that. Very educational.

    Noel
     
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  20. Steve

    Steve Part of the furniture Friend

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    You are indeed correct in saying that, once steam is generated in a closed vessel, there will be a rise in pressure but, when this occurs, the temperature at which the water boils will increase and more energy is required to increase that temperature and change the remaining water into steam. I should have omitted the word 'all'.

    If the mods want to move the posts into a different area, that's fine with me.
     
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