Ok I will come clean, its for a Royal Enfield 250 cc engine. The two crankcase
halves have a 3/16 passage for (I think a low pressure return) are just butted
together with a bit of sealing gunge and no gasget. So what type of material and
what size and depth seating do I need?
David

--- In halfinchlivesteamforum@..., "Simon Wass" <simon.wass@...>
wrote:
>
> Your experience of using o rings is totally opposite to that I experience. I
> only use red or white silicone rings and they have quite a good stretch and
> compression range. If a piston is a bit tight I simply skim the groove
> deeper and lo and behold the fit is freer, its the same for piston rods
> although I measure the od of the ring whilst it is on the rod and bore to
> suit.
> O rings are amazing if used correctly to suit our applications, remember
> they are designed for super high pressures in hydraulics etc and the fits
> need to be tighter, our fits need to be far less so need common sense
> applied, which is where most who fail are failing.
>
> ----- Original Message -----
> From: "John" <catboat15@...>
> To: <halfinchlivesteamforum@...>
> Sent: Wednesday, May 27, 2009 6:12 AM
> Subject: [Half inch live steam forum] Re: O ring query
>
>
> > Also remember the "rubber" or elastic material of an O ring is not
> > compressable like convential packing. So the cut out for the ring must be
> > wide enough to allow the ring to flex and expand out to the side as it is
> > squeesed between piston and cylinder wall or shaft and gland.
> >
> > To me "O" rings were the greatest invention since mixing gin with bitters.
>