If you register, you can do a lot more. And become an active part of our growing community. You'll have access to hidden forums, and enjoy the ability of replying and starting conversations.

Preservation Loco 'Exchange' Comparisons

Discussion in 'Steam Traction' started by ruddingtonrsh56, Feb 1, 2021.

  1. Paulthehitch

    Paulthehitch Well-Known Member

    Joined:
    Feb 13, 2020
    Messages:
    1,090
    Likes Received:
    1,093
    Gender:
    Male
    Location:
    Hayling Island
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    Sounds as if the ''Friends of Dugald Drummond and William Pickersgill'' have had a Chapel meeting :rolleyes:
     
  2. jnc

    jnc Well-Known Member

    Joined:
    Apr 3, 2012
    Messages:
    1,511
    Likes Received:
    2,706
    Gender:
    Male
    Location:
    Western Atlantic
    Heritage Railway Volunteer:
    No I do not currently volunteer
    But the force on the track is from the total weight of the engine, not just the un-sprung weight of the axles; the total weight will not vary that much between the two bearing types (certainly less than between different engine types)?

    Maybe there's some sort of resonance thing going on with the springs (and maybe the track deflection too), in which case the un-sprung weight of the axles could well be a factor in that resonance?

    It would probably take detailed dynamic modelling to say for sure - something not really possible even in the more technically advanced latter operational steam days, that probably takes a computer (much as calculations concerning aerodynamic flutter were one of the first applications for Konrad Zuse's early computers - although his calculations were not detailed finite analysis, which I won't get into here). The re-work for the new P2 involved that sort of work, but I don't know if they looked at the bearing type issue.

    Noel
     
  3. Jamessquared

    Jamessquared Nat Pres stalwart

    Joined:
    Mar 8, 2008
    Messages:
    26,100
    Likes Received:
    57,414
    Location:
    LBSC 215
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    Or possibly that the demands of working an intermittent service on a short heritage line lead to a different idea of optimal than working on a mainline with much longer duty cycles, less stop and start operation and massive workshop capacity in the background?

    Tom
     
  4. Paulthehitch

    Paulthehitch Well-Known Member

    Joined:
    Feb 13, 2020
    Messages:
    1,090
    Likes Received:
    1,093
    Gender:
    Male
    Location:
    Hayling Island
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    Or the ''don't 'old with them improvements tendency'' just as probably.
     
  5. Allegheny

    Allegheny Member

    Joined:
    May 8, 2015
    Messages:
    625
    Likes Received:
    308
    Gender:
    Male
    Heritage Railway Volunteer:
    No I do not currently volunteer
    I would agree with you if we were talking about perfectly smooth track. If there is a bump in the track, or other unevenness, the unsprung weight would have to ride over the bump, with the sprung weight being isolated by the springs. Once it has gone over the bump the resonance between the unsprung weight and the flexibility of the track could continue for a little while.

    If there is any data on the stiffness of the track, as well as typical springs, and the relevant sprung and unsprung weights, it should be possible to do some calculations.
     
    jnc likes this.
  6. Hermod

    Hermod Member

    Joined:
    May 6, 2017
    Messages:
    985
    Likes Received:
    283
    Gender:
    Male
    Location:
    Klitmoeller,Denmark
    Heritage Railway Volunteer:
    No I do not currently volunteer
    The imortal Chapelon is cited somewhere for stating that most of claimed superheat improving cylinder efficiency could be won back by rearrangement of heating surfaces in a saturated boiler and then having longer liner and ring life.
     
    ragl likes this.
  7. 30854

    30854 Resident of Nat Pres

    Joined:
    Mar 8, 2017
    Messages:
    12,172
    Likes Received:
    11,493
    Gender:
    Male
    Occupation:
    Retired
    Location:
    Brighton&Hove
    Heritage Railway Volunteer:
    No I do not currently volunteer
    Was that an idea ever tested in hot metal?
     
    35B and Paulthehitch like this.
  8. Allegheny

    Allegheny Member

    Joined:
    May 8, 2015
    Messages:
    625
    Likes Received:
    308
    Gender:
    Male
    Heritage Railway Volunteer:
    No I do not currently volunteer
    I had been mulling over Chapelon's logic for reheating, but not superheating some of his compounds. For a similar superheat temperature, you would expect the HP cylinder in a compound to be considerably hotter than the cylinder in a simple engine, and this might have lead to difficulties. If you could then also extract some intermediate pressure steam, before it passed through the reheater, and do something useful with it such as using it in an injector, there might be some thermodynamic advantage in the arrangement.
     
  9. Cosmo Bonsor

    Cosmo Bonsor Member

    Joined:
    Dec 10, 2014
    Messages:
    221
    Likes Received:
    500
    Gender:
    Male
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    Steve, yes I think E4s were very good, or more to the point well matched to the work required of them. I spent a lot of time on 473 when we were running it after its last overhaul and it felt quite punchy and smooth running. There may well be an element of NIH which affects all engines which were novel or ‘foreign’ to the crews of the day. Brighton engines with an air brake were liked by crews familiar comfortable with it. A lot of the radials lasted until quite late especially after the cull in the 50’s which got rid of a lot of frankly poor or mediocre Brighton stuff which implies they were useful things. I knew a fitter who rated the E6s highly. The slide valves were below the cylinders and they would run very freely when coasting, but were a pain to work on. I think Tom is right, horses for courses and heritage railway operation has its own set of conditions not necessarily met by ‘yer flashy modern gadgets with all the gizmos on ‘em’. Back in a bit, I’m off to set fire to a wicker man…

    Right that's the incomers, with their fancy London ways dealt with.
    As for ride quality, I’d overlooked the components below the tyres. It is noticeable when you go over some bridges that you feel the ride firm up. I think the answer is a complicated one with many variables. If there are any clever engineers who can do the sums it would be very interesting.
     
  10. johnofwessex

    johnofwessex Resident of Nat Pres

    Joined:
    Apr 6, 2015
    Messages:
    9,185
    Likes Received:
    7,226
    Gender:
    Male
    Occupation:
    Thorn in my managers side
    Location:
    72
    Heritage Railway Volunteer:
    No I do not currently volunteer
    The last CEGB Steam Colliers had triple expansion engines with superheat, the superheated steam then heated the steam going into the LP cylinder cooling it before it went into the engine so it doesn't carbonise the lubricating oil.
     
    ragl likes this.
  11. LMS2968

    LMS2968 Part of the furniture

    Joined:
    Sep 1, 2006
    Messages:
    2,987
    Likes Received:
    5,084
    Gender:
    Male
    Occupation:
    Lecturer retired: Archivist of Stanier Mogul Fund
    Location:
    Wigan
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    That makes my head hurt!
     
    MellishR likes this.
  12. 242A1

    242A1 Well-Known Member

    Joined:
    Dec 3, 2006
    Messages:
    1,558
    Likes Received:
    1,299
    The 6 cylinder 2-12-0 was tested with interstage superheat. The h.p. cylinders worked at a long cut off and so were not particularly prone to losses through condensational artefacts. It was found that the h.p. superheat could be removed with negligible impact on efficiency. So far as Chapelon's engines go the only time they gave trouble due to lubrication issues was on the 4-8-0s when the wrong grade of oil was supplied for the bogie axleboxes. While the use of atomisers continues the quality of lubricants will always be degraded before it reaches its area of application.
     
    ragl likes this.
  13. johnofwessex

    johnofwessex Resident of Nat Pres

    Joined:
    Apr 6, 2015
    Messages:
    9,185
    Likes Received:
    7,226
    Gender:
    Male
    Occupation:
    Thorn in my managers side
    Location:
    72
    Heritage Railway Volunteer:
    No I do not currently volunteer
    OK, my explanation leaves something to be desired, but look at

    https://www.shipsnostalgia.com/threads/triple-expansion-steam-engine.26717/

    Penultimate post

    These reheat engines interest me because the principle is clever and simple. On NEM engine with the full reheat system, the boiler steam going to the HP is used to re-heat steam leaving the HP (via a tubular heater). This means the steam temperature can be higher than would otherwise be possible on a reciprocating engine because the boiler steam is de-superheated by the reheat system, yet at no loss because the heat 'lost' is added to the IP steam. I believe the same principle is applied to the last of the Skinner marine engines, the compound uniflows (one still running commerically I believe).
     
  14. 8126

    8126 Member

    Joined:
    Mar 17, 2014
    Messages:
    823
    Likes Received:
    962
    Gender:
    Male
    A few thoughts on some of the topics of the day...

    Resuperheat without HP superheat in compounds was tried as a variation on 160A1, with I believe acceptable results, and the obvious advantage that where you would otherwise need very high steam temperature for acceptable expansion performance, the peak steam temperature was the highest of either HP saturation or LP resuperheat. 160A1 also had steam jackets on the cylinders, so if you put HP steam through the steam jackets, with a restriction on the exhaust passing to the intermediate receiver, the steam pressure in the jacket can be above the average of the steam in the cylinder, which keeps you out of condensation losses.

    The harsh ride with roller bearing axleboxes is interesting. I believe the extra unsprung weight, particularly of cannon boxes, is probably a strong contributing factor - unsprung weight is bad for ride on any wheeled vehicle. However, one other consideration is that plain bearings, once on the move, ideally support the load on a film of oil with no metal to metal contact at all, whereas rollers are lubricated but not intended to establish a hydrodynamic film. A thin oil film is suprisingly stiff, but also will tend to dampen vibration. Same goes for the white metal layer to an extent; no it shouldn't be deforming, but it won't ring like a piece of hard steel. In practice the operation is more likely to be a mixed regime, some metal-to-metal contact with a partially established oil film, but it's still fundamentally more likely to dampen vibration than rollers, so will feel less harsh.
     
    S.A.C. Martin, jnc and LMS2968 like this.
  15. bristolian

    bristolian Member

    Joined:
    Jul 25, 2005
    Messages:
    399
    Likes Received:
    124
    Gender:
    Male
    Location:
    Huntingdon. Formerly from Bristol.
    Heritage Railway Volunteer:
    No I do not currently volunteer
    34105 had a reputation as being a bit of a poor steamer, according to Peter Smith.
     

Share This Page