What are drifting valves

SPsteam Nov 21, 2009

  1. SPsteam

    SPsteam TrainBoard Member

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    What were drifting valves on steam engines? I've heard of them but do not know where they are or what they are employed for. Any help?
     
  2. Chris333

    Chris333 TrainBoard Supporter

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    Found this
     
  3. Hytec

    Hytec TrainBoard Member

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    That raises an interesting question.

    By drawing cold outside air into the valve chambers, thence into the main cylinders, wouldn't that cool the cylinders? Then, when live steam is re-applied to the system, some of the steam initially could condense and create a water-hammer, possibly rupturing the cylinder ends.

    Man, where's Watash when you need an Answer Man.......:tb-wacky:
     
  4. Chaya

    Chaya TrainBoard Supporter

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    I've noticed that by Googling "drifting valve" you can find yourself awash in information about these, but I especially wanted to direct your attention to this link, which is from the Locomotive Fireman's Magazine. I don't think you could do better! History, purpose, diagrams, everything.

    Locomotive firemen's magazine - Google Books
     
  5. chooch.42

    chooch.42 TrainBoard Member

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  6. Tony Burzio

    Tony Burzio TrainBoard Supporter

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    They cool anyway. My cylinders are solid brass, and the atmosphere cools them pretty well. I just push the cylinder cock lever (Hey, I didn't make up the name!) and open the cylinders to the air and allow the water to escape.

    My snifter is mounted on the lower left side of the smokebox. A snifter is a one way valve that is kept closed by the pressure of steam heading from the throttle to the cylinders. When you are drifting, the cylinders can create a suction. The one way valve opens, breaking the suction.

    One time I was drifting downhill and overfilled the boiler. I had a geyser about 3' tall shoot out the stack! Luckily, at my scale the metal is way stronger by ratio than the prototype and can lift the water out the stack. The Santa Fe 3751 did the same thing at the Wye at MiraMar when they were turning the engine.

    The 1:1 SP 10 wheeler at Campo had water hammer and broke the frame. Yep, the frame, not the cylinder heads. It's stuffed and mounted now. Bummer!

    [​IMG]
     
  7. swissboy

    swissboy TrainBoard Member

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    Tony, a technical question of another kind: Why is your post so much larger than the others? I can't read it without having to shift back and forth. And is the top of the picture cut off on purpose?
     
  8. Tony Burzio

    Tony Burzio TrainBoard Supporter

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    You are probably using Internet Explorer, right? Don't do that.

    Yep.
     
  9. swissboy

    swissboy TrainBoard Member

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    Correct, and I use it because I'm one of those guys who just wants to have a convenient way to get to the Internet. I have much easier control over my favorites with IE than with Firefox. Or I'd have to restart from the beginning which is a bother as long as I have a working system. Your post is really one of very few exceptions where things are less convenient then, i.e. if that is the reason.
     
  10. Geared Steam

    Geared Steam Permanently dispatched

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    Your IE is not condensing the image as it should. I'm currently using IE to view this post (work computer) and it is working fine for me. I use Firefox at home and use the "import" feature to import my favorites from IE or a text file.
     
  11. swissboy

    swissboy TrainBoard Member

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    Usually, it does condense the images, but this one it does not. As for the import feature, I just have too many favorites stored, and I grouped them conveniently. I'd have to redo this for no reason other than to use a different system. Just not worth it to me.
     

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