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Post by ron on Dec 8, 2006 21:41:43 GMT
Being used to automotive practice I thought piston rings should be fitted in their own groove, however the ST No9 I've nearly completed has the 2 rings in a common groove [which I've seen used on compressors] whereas the Simplex I've just started has the rings in their own separate grooves as per automotive practice, anyone any thoughts on the pros and cons of either system? Both engines cylinders have the same bore but the Simplex has almost twice the stroke.
Ron
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JohnP
Hi-poster
Posts: 186
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Post by JohnP on Dec 10, 2006 13:50:07 GMT
Ron,
Well I've no experience of two rings in one groove, but here we go anyway....
A piston ring should seal by being pushed by pressure on to the low pressure face of the groove. A ring that is so tight in the bore as to be dragged along by the piston isn't doing its job properly!
There's a path on the high pressure side for gasses to get "under" the ring and push the ring outwards to aid the seal there. The only advantage I can see to fitting two rings in one groove is that the ends of the rings are unlikely to line up and maybe leakage is reduced through that gap.
I suppose another reason for two rings in one groove may be lack of room for the land between the grooves, but I wouldn't have thought that was likely.
JohnP
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