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Spark arrester

Discussion in 'Locomotive Engineering M.I.C' started by Eightpot, May 2, 2012.

  1. Eightpot

    Eightpot Part of the furniture

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    Anyone with any thoughts as to a suitable size and material mesh to fit above the chimney on a steam loco?
     
  2. John Webb

    John Webb Member

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    Were spark arresters fitted above the chimney? I would have thought that would have been too restrictive on the steam and fire gases being exhausted by the blastpipe arrangements. I am aware that they used to have screens in the smokebox to catch ash etc.
     
  3. baldric

    baldric Member

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    Some were fitted, several panniers were fitted like that based at Didcot for working in the ordnance depot, if you see one you will know it!
     
  4. Eightpot

    Eightpot Part of the furniture

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    Perhaps I should have added that it is for a Sentinel Loco, and it doesn't have a smokebox as such.
     
  5. stan the man

    stan the man Member

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    I have taken advice by the fire brigade as to what size embers/sparks would be a problem during dry spells and was told if anything hits the ground bigger than 1.5mm dia in dry weather it would cause a fire. Needless to say my sentinel was fitted was a chimney top fitted spark arrestor of 1.5mm mesh, the secret of not creating draughing problems is to make the spark arrestor much bigger than the chimney top so the exhaust can breathe.

    Stan
     
  6. RalphW

    RalphW Nat Pres stalwart Staff Member Administrator Friend

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  7. Eightpot

    Eightpot Part of the furniture

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    I'm in 'don't know' country at the moment on this subject for our application. How long before a 1.5 mm mesh gets bunged up solid? Or melts, even? On the face of it one might as well weld a piece of steel plate on the funnel top. Got some 3mm mesh to hand so am going to try with that first. The thinking is to make a 3" deep sided upturned box about 10" x 15", to be an inch or so above the top of the funnel and attached on the opposite side of the 'swing round' funnel damper.
     
  8. guard_jamie

    guard_jamie Part of the furniture

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    Would two 3mm mesh's a few inches apart work?

    Just a suggestion, I'm not an engineer or physicist, feel free to shoot me down in flames.
     
  9. RalphW

    RalphW Nat Pres stalwart Staff Member Administrator Friend

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    I was having a chat with my brother last night and as it does, the subject of spark arresters on Sentinel came up. On the waggon he drives there are two baffle plates in the chimney, angled at about 45 deg attached to either side so that the exhaust has to zig zag, where the lower one is welded onto the chimney there is an opening which via a flexible pipe runs down to a box on the chassis. The ash is slowed by hitting the first baffle and then hits the second and falls onto the top of the first where is slides down, into the tube and collection box which is emptied at intervals. The char collected goes right down to 3mm particles so it seems that it is quite effective but has no danger of blocking as a mesh would.
     
  10. Eightpot

    Eightpot Part of the furniture

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    Ralph, this sounds rather like what was known in Sentinel terminology as the "Beehive" type as used on waggons from 1931 onwards on chain drive ones. We have a plain rimmed funnel on the loco, so a separate device is necessary. I've had another look at the mesh and it seems to be more like 2 mm than 3 mm, so we'll try that. Just hope it doesn't melt!

    Nice to see that you have spelt waggon correctly in connection with Sentinel.........apart from my computer automatically deleting the second 'g' which means that I have to go back and re-insert it!
     
  11. Sheff

    Sheff Part of the furniture

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    Bit puzzled there Eightpot.

    Ralph describes a device which sits inside the chimney flue, whereas I'd think the 'beehive' type sounds more like the wire cowl that fits on top of the chimney? So why won't the internal baffle fit you machine? Whether or not it will knock out embers >1.5mm I would be doubtful.
     
  12. RalphW

    RalphW Nat Pres stalwart Staff Member Administrator Friend

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    My spell check has been told to accept both spellings.

    Very quick and crude cross section sketch of the baffle system I meant, not sure of the dimensions but it gives a rough idea. Char collects in the box and has been found very useful being used as the ash pit contents at the sheds on the Preston 0 Gauge Groups layout.



    Baffle sketch_NEW.jpg
     
  13. Eightpot

    Eightpot Part of the furniture

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    Ralph, your sketch looks like the arrangement on the later "S" type shaft-drive waggons, the funnel base of which is different to the earlier chain-drive ones.
     
  14. RalphW

    RalphW Nat Pres stalwart Staff Member Administrator Friend

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    That could be because that's what it's on....I bow to your superior knowledge. :hail:
     
  15. Eightpot

    Eightpot Part of the furniture

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    I'm feeling benevolent today, Ralph, you can stand up now.
     
  16. RalphW

    RalphW Nat Pres stalwart Staff Member Administrator Friend

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    After all that time back has seized up, I think I need the services of a masseuse.
     
  17. Eightpot

    Eightpot Part of the furniture

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    Never imagined that this topic would get back to Bavarian Serving Wenches..............
     
  18. RalphW

    RalphW Nat Pres stalwart Staff Member Administrator Friend

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    You took it there.....
     
  19. jon the trainee

    jon the trainee New Member

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    Have you made a spark arrester for you sentinel yet? Cos I MADE one for William at elsecar heritage railway.
     
  20. Jack Enright

    Jack Enright New Member

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    Why should it melt? If you make an external mesh ball as is fitted on a loco on the Mid-Suffolk, it will be in a constant flow of cold air when the loco is working - and it can't be as hot as the inside of the smokebox, which doesn't get hot enough to melt.
     

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