Semi-trapeze ring

[Seadoopilot]

What is a SEMI-TRAPEZE RING and why would you want them , I found the discription on this sight looking for new rings for my Doo
:stupid:

 

[robin savell lloyd]

That may be a question for rotax as I can only find them on rotax aircraft engines [No other kinds of engines] and did not see their purpose or differance. Good luck :cheers:

 

[Gunsrunner]

From memory the semi trapeze ring is like a oil scraper that reduces the residual oil and fuel mixture left on the walls of the cylinder, then you have the compression ring(square).
NOTE: Ring/piston groove clearance can be correctly
measured only on rectangular ring which is
bottom ring.

 

[Chester]

Sea-Doo uses semi trapezoid rings (also known as dykes rings) as the top compression ring in their 2 stroke engines, except for the DI engine. 2 stroke pistons don't actually have oil scraper rings like 4 stroke pistons do. They only have compression rings. Semi trapezoid rings have an L shaped cross section and combustion pressure helps push the ring against the cylinder wall for a tighter seal.
Some good info here: http://www.800-airwolf.com/pdffiles/ARTICLES/part23.pdf
See figure 1.

Chester

 

[kustomkarl]

Good discription Chester....:agree:

Karl

 

[Gunsrunner]

Thanks Chester, i wasn't sure about my answer.