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Bulleid Pacifics - Past or Present

Discussion in 'Steam Traction' started by 34007, May 13, 2008.

  1. Matt37401

    Matt37401 Part of the furniture

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    Well, there's at least one MN that won't run again... Although it's doing a pretty good job as an educational tool.
     
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  2. aron33

    aron33 Member

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    True, at least 35029 is doing its part in keeping future generations educated on steam.
     
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  3. John Petley

    John Petley Well-Known Member

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    I think you'll find it's 16 light pacifics:- 34007/16/23/27/28/39/46/53/59/67/70/72/81/92/101/105. Next one likely to be 34010.
     
  4. Gladiator 5076

    Gladiator 5076 Member

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    257 Squadron has just past my window on a low loader so it is now out of Herston Works, hopefully in service shortly.
     
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  5. 46118

    46118 Part of the furniture

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    Sir Keith Park is leaving the SVR at the end of the year and will see out the rest of its ticket at Swanage. (From the SVR GM's words it looks like an amicable separation).
     
  6. Bulleid Pacific

    Bulleid Pacific Part of the furniture

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    Indeed. Having read the SLL update, its due to anticipated works capacity (or lack thereof) at Bridgnorth in 2022, at which point, there may be a slot at Herston; a condition of one of the key donors to the locomotive was that it should not languish for too long before overhaul commences.

    The SVR fleet also seems to be better placed to meet timetable requirements over the next few years than when SKP arrived, whilst Swanage probably need something to bolster 34072, hence the move. So I think a pretty sensible development all round.
     
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  7. John Petley

    John Petley Well-Known Member

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    With 34070 out of action earlier than planned, 31874 looking like it won't be ready as soon as hoped and 30053 being withdrawn at the end of October, 34053 will certainly find itself being put to good use in the early part of 2018. However, given Manston is planned to be turned around pretty quickly and Eddystone was originally meant to be back in action at some point next year, it will be interesting to see what transpires. It's hard to imagine that Swanage will want to be running four Bulleid Pacifics. And then there's Sidmouth.......

    On a different note, it was good to see 34053 when it visited for the "Strictly Bulleid" weekend. I enjoyed a run behind it and also got a good photo of it leaving Swanage with the goods train on the Saturday afternoon of the Gala. About half a second after I took the picture, the sun went in! I remember thinking, "I've done pretty well considering this may be a one-off visit by 34053 to its former stamping ground ." When I heard the news that it was coming back on a more long-term basis, I couldn't resist a smile as after being so delighted by my photographic success in April, it may not prove to have much rarity value after all.
     
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  8. Bulleid Pacific

    Bulleid Pacific Part of the furniture

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    Such is the way of things. You can never say never in this game.
     
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  9. Matt37401

    Matt37401 Part of the furniture

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    Absolutely.
     
  10. bonniville

    bonniville New Member

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  11. BrightonBaltic

    BrightonBaltic Member Account Suspended

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    Quick query... just how does the (in)famous Bulleid steam reverser actually work? Firstly in the plainly visible sense, as in, are the fine cutoffs (e.g. blazing around at 15-20% with the regulator in the roof) nearest the central neutral? I remember reading that, improperly adjusted/maintained, they could jump into reverse at speed, with destructive consequences. Secondly, what actually goes on between the lever and the valve gear?
     
  12. Big Al

    Big Al Resident of Nat Pres Staff Member Moderator Friend

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    This is a starting point for you. http://www.bulleidsociety.org/21C123/21C123_Valve_Gear.html

    The problem, apart from choosing arguably the more inferior design in the first place, was the linkage that introduced plenty of play and a certain randomness in the settings. That said, they were not the only problematic locomotives. In his book, Jim Evans comments on the Q Class and the fact that 35% could mean anything between 25% and 45%.
     
  13. BrightonBaltic

    BrightonBaltic Member Account Suspended

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    For the 35011 group and any that follow in their footsteps (or indeed owners of existing flat-tops), is there anything that can be done to improve the rigidity of that linkage?
     
  14. Steve

    Steve Resident of Nat Pres Friend

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    The reversers you are talking about essentially consist of two cylinders, each with a piston and connected by a common piston rod. This piston rod is connected to the valve gear weighshaft, just as the reach rod would be on a conventional reverser. Of the two cylinders, one is the steam cylinder and one is the hydraulic cylinder. The hydraulic cylinder is entirely filled with oil so that there is oil on both sides of the piston. The two ends of the cylinder are connected by a valve, sometimes known as the cataract valve or orifice valve. This valve is normally closed. To move the reverser, a lever in the cab is moved and this admits steam to one side of the steam cylinder, depending on the direction that you want to move the valve gear. However, nothing else happens because the piston rod is effectively prevented from moving because there is a hydraulic lock on the hydraulic cylinder. If the cataract valve is then opened, oil can pass from one side of the hydraulic cylinder to the other and the piston rod can move, so adjusting the valve gear. Shut the cataract valve and that movement stops. On a Bulleid, all this is controlled by one lever. To alter the valve gear you move the lever in the selected direction. This moves the steam valve to open one side to steam and the other to exhaust, just as with a slide valve on a loco cylinder. You then rotate the lever slightly and this both admits steam and opens the cataract valve. How far you move it effectively controls how fast it reacts. When you get to the required position you close the valve and this locks everything in that position. There is an indicator in the cab to show you where the valve gear is set.
    The problems come when the cataract valve starts to leak as the position you have set tends to wander. You get similar if there is any air in the system. The indicator linkage can also become worn and you don't get an accurate indication. Operation of it does require a bit of finesse. If you are ham fisted you can't make minute alterations and it becomes quite easy to go from forward to reverse when you are near mid gear.
     
  15. BrightonBaltic

    BrightonBaltic Member Account Suspended

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    Steve, thanks so much. So what can be done to ensure the cataract valve doesn't leak? Modern PTFE seals? Is there anything fundamentally wrong with it when it's in good shape and properly maintained?
     
  16. Jamessquared

    Jamessquared Resident of Nat Pres

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    I've got more experience of the ones fitted to our Wainwright locos and they are excellent. But they are also highly accessible for servicing. I'm sure that difficulty of servicing was at the root of the issues with the reversers on Bullied Pacifics, rather than anything inherent in the design.

    Tom
     
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  17. Steve

    Steve Resident of Nat Pres Friend

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    The steam reverser on the NER Q6 is very similar and i find that it works very well provided that you fill the oil cylinder during prep. However, there is never any requirement to go near mid gear in use. There are five marks on the scale and I never run nearer to mid gear than the second mark; probably about 30%.
     
  18. Steve1015

    Steve1015 Active Member

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  19. Bulleid Pacific

    Bulleid Pacific Part of the furniture

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    Considering that's better than what they looked like in 1967, and this being the anniversary year, then it makes a bit of a statement that it was not always gleaming paintwork. Suspect it'll go in for overhaul once 34105 is finished, as apart from the cosmetics, it is essentially complete. What'll happen with 34058 is anyone's guess, but I suppose there's always the chance that it will replace 35005.
     
  20. Shaggy

    Shaggy Active Member

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