The Impulse Valve (Simpling Valve)

I have puzzled over the drawings of the Impulse Valve for a year or more, and spoken to others who can make no sense of it.

Well finally last week while mulling the design over with a friend, he (I think) correctly fathomed how it is meant to be built and operate…

As drawn there appears to be a plunger in a tube which is operated by a press button. There appears to be no way that this would operate, as it would just admit HP steam to the chamber formed between this plunger and the end of the valve body….

The explanation is that this plunger is in fact a tube! Thus when depressed the steam is admitted to the end of the valve assembly, and then passes down the tube to the valve chest/cylinder. There are hints in the drawing that this is the game, but some of the views are incorrectly drawn which leads to the confusion – and actually I am not even sure it could be reliably constructed as drawn.

I think it would still be hard to make this valve steam tight, but in operation this might not be a practical problem…. Thanks to Neil Davis for figuring this out!

*Simpling or Impulse

In the ME words, Mr. Leak complains that many people incorrectly describe the Impulse Valve as a “Simpling Valve”, and he argues that this is wrong as it does not make the engine run as a simple (which is true) but just introduces a HP steam feed into the LP valve chamber to push the engine off HP TDC if it stops there.

He’s right in the description of what it does, but knowledgeable friends of mine tell me that within the road steam community (Traction Engines) these valves on compounds are always known as “Simpling Valves”… so maybe we can continue to use the term…

3 thoughts on “The Impulse Valve (Simpling Valve)

  1. Pingback: Are we having fun yet? | SY Befur

  2. John

    The drawings in the Model Engineer did not even include the simpling valve so I am even more in the dark than you. I haven’t provided one yet, but will do something when I install the plant, hopefully within the next year or two. The other local has come up with an automatic valve which might be nice, it gives a squirt of steam if needed. My Dad once fired compound locomotives on the railways here, they had a nice de Glehn compound, and they called their one the “God Almighty”. That may have been a true simpling valve, I don’t know. But I gather it gave a terrific boost when needed.
    In practice, the guys with single cylinder engines in boats have no real problems, with an occasional boot on the flywheel being enough when it does decline to start. I know full size marine engines traditionally don’t have flywheels, but they are an asset in these small sizes.

    1. sybefur Post author

      I agree with all you say… The valve as drawn just injects a blast of high pressure steam into the LP valve chest, so it actually renders the HP cylinder useless as its inlet and exhaust would be at the same pressure if you kept the valve open…(so it really does not “simple” the engine, but just applies pressure directly to the LP side if the HP stopped on TDC). But as you say it delivers the steam equivalent of a boot to the flywheel. The deGlehn sounds really exciting!


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