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Piston Rings etc

5" Gauge Pansy

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Robert Starling08/06/2011 18:56:29
3 forum posts
Currently machining gunmetal cylinder block for 5" gauge Pansy but I am a bit out of touch with what is used for piston ring material these days. Originally LBSC used graphited yarn which is still available but I suspect some use silicone 'O' rings which are available from Chronos or Blackgates. How well do these wear ? ( I have some minor blemishes in one bore which might be the result of slag in the casting and am concerned that the 'O' ring might tear on this). I have also come across an article in which piston rings were made from 35% graphite filled PTFE but have no idea where to obtain this in the small quantity needed. Other modellers experiences and advice welcomed.
nipper09/08/2011 21:00:52
32 forum posts
Hi robert. I have used silicon 'O' rings in my Pansy for many years and they seem to last quite a long time certainly 300 or so miles and then they were changed because the pistons were out. If the bores are rough it may be a problem suggest honing out the bore to see if it cleans up, remember that the bore is not critical with an O ring, within reason, as you make the piston and ring groove to match the ring and the bore. Alternately I have heard of filling the blowholes with araldite and then cleaning up the bore. I know this is probably a bit late but all the best with it .
JasonB09/08/2011 21:07:59
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25215 forum posts
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Not sure of the dia you need but Noggin End do the filled ptfe
 
mick H10/08/2011 07:39:23
795 forum posts
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Robert,
 
I have used silicon "O" rings which ran well for a while but their performance petered off quite quickly. On subsequent examination, they did look sad. I spoke to the supplier, Polly Engineering, and was told that I should have used Viton rings, especially if I was using superheated steam. I took this advice and have had no problems with the Viton. Polly do a good range of Viton rings.

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