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Cold Fires

Discussion in 'Locomotive M.I.C.' started by Cassanova, Jan 19, 2009.

  1. olly5764

    olly5764 Member

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    You are of course quite correct, although an idea that was offered to me once on West Countries, was rather than a true wedge, put a sort of pyramid shaped back end in so you could just tumble the coal into the back corners. That said, on an easy line like the Severn Valley, on the couple of goes I had on Taw Valley, I just fired it like an over size 57xx, with a thin saucer shaped fire.
     
  2. Edward

    Edward New Member

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    Saucer shaped is exactly the word. Same for any wide box engine.

    Narrow box is a different proposition, esp if it has a flat grate.
     
  3. olly5764

    olly5764 Member

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    Don't forget, that also depends a lot on the loco, and the type of work to be done.
     
  4. Black Jim

    Black Jim New Member

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    Thats how I was taught to fire them by ex SR men.
     
  5. martin butler

    martin butler Member

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    As with any wide box you have to have the back filled and yes ive seen and fired a WC both original and re build with the same ammount of fire for me normal procedure would be fill the back corners just level with the door and under the door, have the sides sloping towards the front and leave the front just covered and fire to the front and sides first as soon as the driver opens the big valve open the damper then fire to the middle and just fire where you need it to, as long as you fill any holes it will steam, the line i fired on was 1 in 60 out of Alton so you needed to keep steam presure up but not so much that you would lift a valve going down the other side but with everything shut down ive known a boiler to sit at 200 with no problem
    getting back to the subject a cold fire is generally when an engine is doing its first run of the day in other words the fire box isnt fully warned through and the engine wont make as much steam because its still warming up
     
  6. Big Dave

    Big Dave New Member

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    I have seen haycock fires on ex GW engines when invited onto the footplate at Leamington General in the 60's and a bit before, the fire seemed to go up from the door and they would push the coal further in with the shovel upside down, god knows how they got more coal on the fire but the engines seemed to like it.
    Another thing I remembered about this was they would never top up the boiler to quieten the engine if the water level was OK. in fact the engines would sometimes be really roaring at right away time. I think it was due to Hatton bank just up the line they would use the downgrade to the Avon bridge and leave the station like a bat out of hell.

    Leamington GW station was known as General in the 60's to avoid being confused with the LM station which was Leamington Spa Avenue.


    Cheers Dave
     
  7. SE&CR_red_snow

    SE&CR_red_snow New Member

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    Why should a thick fire, when first built up, damage a firebox?

    It's LOCALISED VARIATIONS in temperature, normally associated with holes in the firebed, that cause all of the issues.

    Yes, in theory a wedge shaped fire might be hotter at the front end where it's thinner. However to make it wedge-shaped in the first place involves building the fire up gradually at the back end, so the disparity is not as great as might be supposed. Let's say for simplicity's sake you build the fire up by firing (all across the) back - middle - back - middle - back - front - back over a 30 minute period. Although the resulting fire would be wedge shaped it would all be in a relatively similar state of combustion upon departure, with little risk of localised damage.

    However a thin level fire will be in just as good a state. The only difference is the thinner fire will require more attention on the move in order to avoid holes developing, or to put it another way there's a far higher likelyhood of holes developing in the first place.

    While it might sound a bit pathetic, it's not always great firing to the back corners on a Bulleid on the move as the multiple jet exhaust makes the fire very hot indeed. Indeed a common trick is to start by putting 5 or 6 shovelfuls directly under the door in order to temporarily black out that bit to reduce the heat whilst firing to the rest. If the cab's rolling around there's also the risk of burning one's arms whilst going for the back corners, though luckily Bulleid pacifics are normally very smooth riding.

    It's also fair to say that holes in the fire around the edges of the box do more damage than thin patches in the middle. The risk of damage at the front end is exacerbated on Bulleids by the thermic syphons IMHO. They're also VERY free-steaming so it's important not to arrive anywhere for a lengthy dwell / runround with too much fire.

    For these reasons I tend to use a compromise between 'saucer' and 'wedge' when building up the fire. Relatively thin in the middle, thicker all around the edges (including across the front under the syphons), but with the sides sloping upwards towards the back, thick back corners and a heavily rounded back end. Probably not the most economical way of doing things in terms of coal consumption but that needs to be weighed up against the costs of maintaining the boiler. On the move it's then a question of gradually letting this burn down and even itself out. Fire mainly to the front 2/3rds of the box and arrive with the middle thin and more of an even saucer all around the edges. Obviously this is a preserved railway only strategy - continuous running for miles on end is a different kettle of fish.

    It's bl**dy difficult to descibe (I'd need some form of 3D graphics software to portray the shape properly, and about a fortnight to model it) but easy to get your head around in practice. Furthermore it looks really nice, and it works!
     

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