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What Ifs, and Locos that *rightly* never were.

Discussion in 'Steam Traction' started by Jimc, Feb 27, 2015.

  1. The Saggin' Dragon

    The Saggin' Dragon Nat Pres stalwart Staff Member Moderator

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    Also the Raven NER Pacifics?
     
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  2. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Ha, fair point. Very wrapped up in Gresley at the minute! I will re-word accordingly.
     
  3. 2392

    2392 Active Member

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    Indeed I always took the remarks about Gresley using the Pennsy K4 Pacifics, as the germ of an idea for the design base for his A1s. OK they weren't a direct copy, understandably due to the loading gauge differances. Speak of the loading gauge [i.e. height and width wise] the Yanks are/were quite surprised at how "small" our big mainline express locomotive are compared to their even mixed traffic types.

    Equally the Stephenson were quite the magpie, when it came to adapting and incorporating ideas into their designs. for instance he multi-tubalor boiler on Rocket had been used a few years earlier in France, the blastpipe had been patented by Trevithick to name but two items they brought together in Rocket. They could have avioded paying the patent fee as there design was slightly different to Trevithick, though did as Robert had met Trevithick whilst in Latin American and struck a friendship.
     
    Last edited: Apr 25, 2017
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  4. Jimc

    Jimc Part of the furniture

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    That's one of the tales, yes. There are others, but too OT.
     
  5. MarkinDurham

    MarkinDurham Well-Known Member

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  6. clinker

    clinker New Member

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    Whilst I can't be specific about the examples given, It's worth pointing out that Uniflow cylinders are not necessarily single acting, the term uniflow simply indicates that the steam is admitted at one end of the stroke (nominally TDC) and exhausted at the opposite end (nominally BDC), ie the steam flows in one direction. The Atkinson Uniflow engines were double acting with shuttle exhaust valves in the pistons which were both hollow and ported to prevent compression of residual exhaust steam (at nominally atmospheric pressure) due to being non condensing engines.
     
  7. Eightpot

    Eightpot Part of the furniture

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    Scan 745.jpg
    Drawing of Atkinson steam wagon engine (6-3/4" bore x 10" stroke), ball valves operated by a sliding camshaft for steam inlet, and ports mid-way along the cylinders for exhaust.
     
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  8. clinker

    clinker New Member

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    Also shows shuttle valve in piston, and the inlet porting arrangement is 'interesting' to say the least, the Sentinel engine had the valves (4 on a Sentinel) at the 'top' end of the cylinder, with the 'external' port feeding to the bottom end, and a cam for each valve, thus avoiding porting around the 'valve stem' guide, presumably Atkinsons arrangement avoided paying royalties.
     
  9. Eightpot

    Eightpot Part of the furniture

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    Looking closely at the drawing I can't see any 'shuttle valves'. What I believe to be the case is that the piston is hollow, presumably to cut down reciprocating weight, and with separate ends held in place by what appear to be longitudinal studs.

    The Sentinel engine you refer to would be that of the 1923 'Super-Sentinel' with the valve chests at the front of the engine and external pipe connection to the back of the cylinder. The 1927 different 'DG' engine had staggered poppet valves at each end of the cylinder (eliminating the external pipes which were merely filled with steam only to be exhausted up the funnel. Apart from very early examples, the loco and railcar 2-cylinder engines (based on the waggon 'Super-Sentinel' engine) also had staggered valves. The 1933 'S-type' 4-cylinder single acting engine had the valves in the cylinder head and in I/C terms could be likened to a 'T-head' side-valve 2-stroke engine with the same type piston and connecting rod arrangement. This relied on the piston rings as the seal preventing (not very successfully) steam and cylinder oil getting into the crankcase. This is why they needed a special lubrication oil that would (or should) separate out the oil from water that could be drained off when cold. From what I can make of it cylinder bores on these waggons only lasted about 40,000 miles before sleeving or replacement. The 6-cylinder railcar engines did have orthodox piston rods, glands and cross-heads so wouldn't have had the same problem. The 'S-type' waggon arrangement was essentially a compromise due to the need to cut down the unladen weight of the vehicles by being much more lightly built than the earlier chain-drive waggons.
     
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  10. clinker

    clinker New Member

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    Looking again, I can see the that these are longitudinal studs on this drawing, however I have seen a drawing showing shuttle valves, possibly in M Kelly's undertype waggon book. The engines using the shuttle valves would have had less back pressure than those without, since the shuttles would give much nearer to line for line exhausting, which begs the question of which came first? did the shuttles give insufficient engine braking? without the shuttles residual steam would have had to compress on the exhaust stroke, which may have helped with engine braking and also raised the pressure in the cylinder until the point of admission, which may have allowed less inlet lead and still given a better filling of the cylinder. WRT the inlet porting arrangements, even the early Super Sentinel waggon arrangement must have been superior to that shown here.
     
  11. johnnew

    johnnew Active Member

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    The exchange of ideas with the Stephenson's was also through their James connection.


    Sent from my iPad using Tapatalk
     
  12. Corbs

    Corbs Well-Known Member

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  13. 240P15

    240P15 Active Member

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  14. MellishR

    MellishR Part of the furniture Friend

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  15. D6332found

    D6332found New Member

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    Back to reality, what about the GCR Robinson Pacific? Larger Grate than the 4-6-0, and rebuilt with Caprotti?
     
  16. sir gilbert claughton

    sir gilbert claughton Active Member

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    what if.......

    Stanier had gone to the LMS but didn't have a Royal Scot chassis to play with .

    Would he have built the Compound Castle ?
     
  17. sir gilbert claughton

    sir gilbert claughton Active Member

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    the Wooton firebox does not lend itself to a 4-6-0 . an enlarged H1/2 would likely have been a Pacific .

    rather like the 1922 A1 I suspect
     
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  18. sir gilbert claughton

    sir gilbert claughton Active Member

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    Pearce designed the Scissors gear that was fitted to no/40 . that engine kept the gear until it was rebuilt as a Castle
    Deeley , and the Midland , got a bit upset about that because , as you say Deeley took out a Patent on the design .

    the GWR were able to demonstrate that Pearces work predated the Deeley design , and at the time he had no knowledge of it , so the GWR were entitled to use it .

    Churchward did not use it again , however , because the eccentrics prevented the gear being disconnected ,and the engine moving itself with a disconnected gear in the event of a breakdown
     
  19. ruddingtonrsh56

    ruddingtonrsh56 Member

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    Was Caprotti gear around in the 1920s? The first usage of it in Britain that I'm aware of was that of post-war Black 5s...

    Just googled it and it was invented in 1921. So not until the twilight of Robinson's career. Although had he taken the job of LNER CME offered him, and designed a Pacific of its own, it would have been very interesting to compare 3 different designs of 4-6-2 on the newly formed LNER...
     
  20. 242A1

    242A1 Active Member

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    Have a look at the through cylinder cross section of 242A1. The inside, high pressure cylinder, has the valves underneath it. We are used to valves placed in this position not working at a satisfactory level on engines built in the UK. This was most certainly not the case with the French 4-8-4. This being a compound, built to include the best locomotive knowledge of the day within the limits and constraints of being a rebuild, was built to include high steam chest volume and optimised receiver volume. The 152/2-10-4 was a more advanced design benefiting not only from 242A1 but also from the six cylindered 160A1 and was to be able to maintain 6,000ihp. The design work was completed and construction commenced. The initial locomotive was never completed before the decision to build the type was reversed. Exactly why will never be known. The modern traction afictionados had been humiliated enough by the 4-8-4. Chapelon's engines could always exceed their predicted outputs, you can guess what was coming. The fuel argument was interesting. Chapelon's engines could work on French coal and his were not the only ones. Du Bousquet's mixed traffic 4-6-0s, the preserved example used to be at the Nene Valley, are just one example of a design that could cope quite well with the local product. So which industry could not function without imported fuel? And why was the blame for this need placed at the feet of steam traction?
    So yes, the 152 has valves under the inside cylinders, Chapelon could get them to work very well in that position, it also gave more freedom when it came to the positioning of these cylinders. All in all, the best machine designed in Europe up to that time. We might have had one. But no, and no 240P either. Or 242A1, no 160A1 either. I suppose that we should be thankful for the 231Es that survive.
     

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