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Gradient profiles of Heritage Railways - List in Post 1

Discussion in 'Heritage Railways & Centres in the UK' started by Jamessquared, Jul 24, 2013.

  1. NeilL

    NeilL Member

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    Are you wondering about engine and fire efficiency being affected by reduced oxygen levels?
     
  2. Jamessquared

    Jamessquared Nat Pres stalwart

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    The summit of the Bluebell is marked at the site at 125m, which is 410 feet.

    Tom
     
  3. Ploughman

    Ploughman Well-Known Member

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    An Altitude or other local known height is not needed to work out a gradient.
    All that is needed is to establish a known difference in height between 2 or more points and from that a gradient can be worked out.
    In an NERA publication on Track Gradients in the North East there is a warning given about relying too much on published gradient information or from official gradient plots.
    The editor who has spent a lot of his railway career on railway surveying went over a number of lines and in very few cases could he match the published gradient. In most cases there was a noticeable difference.
    Not easily explained away by track renewals or tamping etc
     
  4. pmh_74

    pmh_74 Member

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    Railways were generally built to a 'ruling gradient' and the signs probably reflect that rather than trying to mark minor variations which really, in the grand scheme of things, have little bearing on anything much. Modern surveying techniques can be too accurate for practical purposes - I recently saw some data from a track recording train which had a repeating 5m/15m cycle of two different gradients quoted over several hundred metres. In reality, I concluded that the track was bumpy - and when you are interested in the gradient acting over a complete train length*, this sort of thing isn't that critical. Neither is a "level" gradient which turns out to be 1 in 2000, or a "1 in 100" which turns out to be 1 in 110, etc. When it does get interesting is if the official gradient says up when you can clearly see that it's down - and I have seen that, although it turned out in that case that the old gradient posts were closer to the truth than the official data from the track engineer...!

    I am not a driver but I have heard steam engine drivers say that you can tell when the gradient changes as the performance of the engine changes subtly. I know that some of our drivers do like to look at the gradient posts as it helps them to understand what their engine is doing.

    Phil

    [*In my day job I am dealing with fixed-formation passenger trains with a weight distribution which can be taken as even. I suppose it all changes for a loco-hauled train, where more of the weight is up front!]
     
  5. NBDR Lock

    NBDR Lock New Member

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    It is notoriously difficult to work out gradients as we all generally expect them to look. They are actually vertical curves and any gradient profile must necessarily be an average over a distance. If the points between which the difference in heights is taken are too far apart there can be significant variations within that distance, even if the vertical radius is constant. I believe many of the profiles produced in BR days were worked out from a survey taken at 2 chain intervals.

    Jeffers
     
  6. Ploughman

    Ploughman Well-Known Member

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    Which would put it in the realm of being take one possibly 2 readings each way and move. 100yds being about the limit for accuracy
     
  7. David Verity

    David Verity New Member

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  8. David Verity

    David Verity New Member

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    Phil - a driver would also tell you that the loco crew need to be aware of the gradient as it affects the level of water in the glasses and can give false impression of too much/too little water in the boiler when the loco is on a slope!

    David
     
  9. pmh_74

    pmh_74 Member

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    A good point! Although probably more of an issue on some steeper lines than ours.
     
  10. MellishR

    MellishR Well-Known Member Friend

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  11. Jamessquared

    Jamessquared Nat Pres stalwart

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    Thanks - I've updated the first page accordingly.

    Mods - just wondered if this thread could be made "sticky" as a resource of general and permanent interest, and in the hope of attracting some more gradient diagrams?

    Tom
     
  12. 5944

    5944 Well-Known Member

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    I've got at least one of those booklets somewhere in the loft. The one that made me chuckle was Bala Lake. Quite why they included a line that runs along the edge of a lake, I don't know. The gradient profile was ___________________________________________________________ !
     
  13. Forestpines

    Forestpines Well-Known Member

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    Readers don't necessarily know it follows the lake shore, though. I can think of at least one heritage railway which is apparently named after a lake but is far from level.
     
  14. The Saggin' Dragon

    The Saggin' Dragon Part of the furniture Staff Member Moderator

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    Done - will see how it goes.
     
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  15. meeee

    meeee Member

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    Did they just ignore the stretch of 1 in70 up to Llanuwchllyn then?
     
  16. John Webb

    John Webb New Member

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    No, they didn't! Only about half the line is level. Besides the 1:70 up to Llanuwchllyn, there are several places where the line is going up and down between the level stretches. Generally these gradients are where there are either small valleys with streams or the ridges between these valleys to be crossed.

    But I agree; an updated version would be most welcome - the original was published in parts from August 1998-June 1999 and my copy is well-thumbed!
     
    Last edited: Aug 11, 2015
  17. 5944

    5944 Well-Known Member

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    It might've been Llanberis Lake then, sorry. Whichever one it was, it was completely flat.
     
  18. John Webb

    John Webb New Member

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    Yes - 2 miles of level track at Llanberis Lake railway.
     
  19. johnofwessex

    johnofwessex Part of the furniture

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    So what's the longest stretch of level track in the world/UK??
     
  20. Robin Moira White

    Robin Moira White Nat Pres stalwart

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    Its funny where these things start. I volunteered on the Bluebell in the 90's during my legal training and when living in Haywards Heath thereafter. I started with the line map as a number of the line side features seemed to have different names depending on who you spoke to. Several bridges had 'official' and 'unofficial' names, for example.

    I produced the first version of the line map for my own benefit as a signalman / duty officer and others found it useful. It was hard to get all the line on one sheet of A4. The only way was to distort the linear scale somewhat. Richard Salmon then ably digitised it and has updated it since, in particular to record the achievement of opening to East Gtinstead. The original included an 'aspirational' dotted line' north of Kingscote!

    After it had been handed around in the Bluebell 'traffic' department for some time, a copy of the line map appeared in 'Bluebell News' and was followed by a request for the gradient chart, which appeared the same way, taken from an original Lewes to East Grinstead chart, updated with the changes that had occurred on relaying to West Hoathly.

    It is lovely to know that something I drew on my digs in London over 20 years ago is still useful. I have a draft of the Horsted Keynes to Haywards Heath line map which I must find time to complete.

    Any other stories of how line maps / gradient charts came to be drawn? It is easy to think that any 'serious' railway would 'obviously' have line maps / gradient charts available, but with all things , they only appear by the sweat of someone's brow / pen/ mouse.

    Kind regards

    Robin White
     
    Last edited: Aug 28, 2015

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