Clupet piston rings

Asquith,

Thanks for the link to the Evans saviour/collector. I didn't realise that they were made horizontal and as twins. Also some fairly late dates - and . Also that Evans was taken over by Weir Cathcart, Glasgow (I presume this is Weir of pump fame?), given as builders of the pump.


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The 'Shopswarf' account is interesting - it seems to show an overlap in the "ring gap" area, that looks tricky. I don't quite understand how this was done, despite mention of milling.

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Now I am wondering how rings work in a steam cylinder. In an IC engine, the compression rings work by receiving say 500 psi working on their top and inner faces. This pushes the ring down to seal against the lower ring groove face, and outwards to seal against the cylinder bore. Hence the importance of flat surfaces on the ring grooves and lower ring faces, also why blow by occurs when the ring can no longer follow taper and ovality in the bore. (I used to work with guys who drilled very small gas ports in their piston crowns, porting combustion gases directly to the compression ring, these only remain carbon-free for short term drag racing etc).

Presumably the Clupet, despite having sawn 'inner' faces, still does a similar job? I wonder if the Clupet was also aimed at worn bores, having perhaps greater flexibilty to follow less-than perfect cylinder bores?

I seem to recall (from the 's, was it "Sealed Power"?) that made a multi piece compression ring with overlapping portions to achieve the zero-endcap of the Clupet. Aimed at high performance engines from memory.

I am reminded of the multi piece oil control rings popular for worn engines - two thin chrome plated steel rings, kept apart by a spacer and pushed into contact with oval and tapered bores by a strong expander behind.

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