Design to make castings for Soule Speedy Twin Steam Engine

[CI]

I just saw that catalog.
This is a nice print.
I don't think I have ever seen that.
Thanks for the link.

http://vintagemachinery.org/pubs/detail.aspx?id=4445

The trick is that the valve has check valves in it, else the valve would lift off its seat when the steam/exhaust ports are switched.

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[crueby]

Not quite true on the check valves. The flow has to be able to flow both ways depending on the control valve position. The valve does not lift because the surface area on the outside of the valve is so much larger than the surface area inside either cavity, so the net force is always down. The check valve is there to pressurize the chest so that effect works, it does not prevent backflow in the passage. The other manufacturers  got the same result without a check valve by having a direct pipe from the throttle valve chest.

[CI]

I need to set up a 3D simulation of the Speedy Twin with the D-valves and check valves.
I think there are two ball-check valves in each D-valve; I need to look closely at a Speedy Twin D-valve again.

I have heard of the Speedy Twin D-valves described as "semi-balanced" valves.
I know what a balanced valve is, but semi-balanced is a bit of a head scratcher.

"The other manufacturers  got the same result without a check valve by having a direct pipe from the throttle valve chest."
I am not understanding that because there is a direct passage on the Speedy Twin from the reversing valve to each steam chest, and if it were external, there would be no change.

I will have to look at the drawing again, and perhaps mark up some steam flows in red, and exhaust flows in blue for both directions of engine run.
It is rather odd how a Speedy Twin D-valve and ports work.
One way I envisioned it was with just a normal steam chest, and a normal D-valve, and then I envision wrapping the steam chest around either side of the D-valve, and tucking it under two more D-valves, one on each end of the central D-valve.

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[crueby]

Oh. Wait a minute. I misread the diagram in the patent - the single check valve is in the center chamber of the valve only, I was thinking it was in the two outer chambers! My mistake there - they are taking steam as it goes to the cylinder to pressurize the chest through that valve, when the pressure is balanced or higher in the chest, the valve closes. Still, result is that the chest gets pressure. On the other manufacturers engines, they took a line directly from the input steam to the throttle/direction chest to the cylinder chests, so the cylinder chests were always pressurized.

And yes, drawing it up in 3D and coloring the passages helps a lot - I had the same learning curve when I first did Marion's version of it.

[crueby]

CI - just sent you a PM with some diagrams that may help out.

[CI]

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