[modeleng] Re: Is piston rings : Was Lack of mail - just testing

Tony, you may want to consider sneaking in an Aluminum tube as a cylinder liner 
and then use rings made of square faucet packing packed in grooves in the 
piston.  Just a thought, as "O" rings will do quite well.

Al


--- On Fri, 9/5/08, Tony Wells <oaksfield@xxxxxxxxxxxx> wrote:

> From: Tony Wells <oaksfield@xxxxxxxxxxxx>
> Subject: [modeleng] Is piston rings : Was Lack of mail - just testing
> To: modeleng@xxxxxxxxxxxxx
> Date: Friday, September 5, 2008, 10:49 AM
> Partly so that Mike doesn't feel too lonely ... ;-)
> 
> As I am finally back on line (curtesy of a new modem!) a
> question for all of 
> you steam engine experts ... I have been asked to make a
> model steam engine 
> out of wood, for demonstrating their operation with. Whilst
> there is to be a 
> "boiler", propulsion will be via compressed air,
> most likely an electric car 
> tyre pump, by the way, so there definitely and deliberately
> won't be any 
> temperature problems to burn any fingers, let alone set
> fire to it all!
> 
> As it will be all wooden construction, there will be some
> small movement due 
> to humidit and temperature fluctuations, more than likely,
> and so I am 
> worried about how to ensure a permanent seal between the
> piston and the 
> cylinder walls, as metal piston rings would only move with
> temperature 
> changes, and then not to any noticeable amount. I had
> thought about using 
> neoprene O-rings, tight fitting enough to still form a seal
> if it all 
> slackens up a bit, but can anyone recommend anything better
> please? I had 
> also thought about greased hemp or even string, but would I
> need to knot it, 
> with the knot then causing an obstruction, for instance.
> 
> With thanks in anticpation,
> 
> TonyW.
> 
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