[modeleng] Re: Naive question

  • From: John Browning <jgb7573@xxxxxxxxxxx>
  • To: <modeleng@xxxxxxxxxxxxx>
  • Date: Mon, 19 Mar 2012 16:02:36 +0000

Superheated steam implies higher pressure. A Slide valve is relatively large 
especially in full size, so this higher pressure on a larger area implies 
higher friction. Better lubrication is required to deal with this, however, 
superheated steam is hotter and tends to break down lubrication.
 
It's not an absolute. There are plenty of locos running with slide valves and 
superheated steam. But you get much less friction with a piston valve as the 
pressure is even all round, rather than on a relatively large flat surface.
 
Hope that helps.
 
John
 

 

> To: modeleng@xxxxxxxxxxxxx
> Subject: [modeleng] Naive question
> From: peter.chadwick@xxxxxxxxxxx
> Date: Mon, 19 Mar 2012 15:23:20 +0100
> 
> I keep reading in all the books that flat valves and superheated steam 
> don't go too well together. 
> Why? I can't see it being down to port area......
> 
> Peter Chadwick
> Swindon
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