piston rings for steam

[Anatol]

I've read the piton O ring thread here, and also found this article online, about using graphite filled ptfe.
http://modelengineeringwebsite.com/Steam_piston_rings.html
I know cast iron is the traditional material, does anyone have experience with PTFE or other materials: plastics or metals?
thx!

 

[lennardhme]

Hi Anatol,
That's a timely question.
At the meeting of my local ME club [MSMEE] Friday, the keynote guest speaker was a rubber chemist, who gave an excellent talk on rubber & its characteristics,
types, uses, etc. He used the clubs overhead projector to highlight his points.
My lasting memories [the presentation was quite technical, & I would have liked the slides to be left a little longer to help absorb the info] was that synthetic rubbers aren't nearly as good as the real thing, & that viton O rings should not be used on full sized steam engines -a fact that is quite well known as they quickly deteriorate, but the same problem doesn't happen with model sized steam engines. He said that this was an "anomaly" which at the present time could not be explained. So the mystery continues.
Hope this is helpful, although I realise its not a definitive answer.
Lennard.