# Did a Superheated loco SOUND different?



## lownote (Jan 3, 2008)

I imagine the whistles would sound different, maybe.

But did the Chuff sound different on a superheated loco? 

Superheated steam, as aI understand it, would be at higher pressure and would have very little condensate--ti would be "dry" even as it was exhausted. So I suppose an engine designed for superheating would have a different sound?

Also I believe that piston valves typically replaced slide valves in the same period when superheating became common, and that it was typical to add piston valves and superheating at the same time. I may be wrong about that. But the tow things together, you would think, would produce a very different sound.

Does anyone know the answer?


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## Semper Vaporo (Jan 2, 2008)

Whistle and whistle valve design and operator adeptness (known as "fist") had as much effect on the sound of the whistle as pressure and dryness.

A superheated loco would have a "Sharper bark", or a "Crisper chuff". A saturated engine would actually sound "wet"/"slobbery". But both would sound different with different loads and operating style, and a dozen other variables would vary the sound quite a bit.

When superheating came about, it took too much energy to move the valve against the friction caused by the greater pressure of the steam pressing on the back of the valve. The valve gear needed to be "beefed up" to handle the additional stresses. The slide valve also wore much more quickly due to the excess pressure holding the sliding surfaces together. There were dozens of patented designs of "balanced valves" to try to overcome these problems, but the piston valve was the ideal replacement. There were companies that sprang up to create "upgrade mods" to a slide valve/steam chest to convert it to a piston valve, and many engines received this upgrade without getting a superheater installed (less energy used to operate the valve gear meant more energy to tow a load and with less wear on the parts there were lower maintenance costs).


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