Piston Ring Rotation
Piston Ring Rotation
(OP)
Hi,
Everyone knows rings rotate, does anyone know what forces cause this? It has been observed in Pyrex cylinders, so that rules out cross hatch as the reason. Thanks.
Everyone knows rings rotate, does anyone know what forces cause this? It has been observed in Pyrex cylinders, so that rules out cross hatch as the reason. Thanks.





RE: Piston Ring Rotation
* asymmetric gas flow thru the end gaps producing thrust
* "lumps" on the bore that allow the ring to find "low energy" positions at various orientations as the piston moves down the bore (bore distortion due to cyl pres and/or thermal effects)
* piston rocking combined with uneven ring-piston contact friction about the circumference of the ring grooves
* coriolis effect (a stretch, I know, but pistons do undergo significant acceleration, and I don't remember my kinematics very well)
RE: Piston Ring Rotation
RE: Piston Ring Rotation
Franz
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RE: Piston Ring Rotation
With so many forces at play on the rings, what are the chances that they (the forces) will be in balance and the rings will not rotate? Put something light on a vibrating surface and it moves.
Franz, I'm having trouble imagining how it would take less energy to rotate a heavy cylinder than that lost by the change in rotation of light rings. If we are talking about the vertical movement I can easily see that: "forces required to start and stop the ring movement at TDC and BDC are considerable." Perhaps they are trying to avoid static friction which is much higher than kinetic friction and hope to maintain the kinetic state through rotating the cylinder? cheers, derek
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RE: Piston Ring Rotation
If the piston is vibrating in this manner it will obviously cause the rings to rotate in their grooves.
RE: Piston Ring Rotation
You are correct about static friction versus kinetic friction. When a piston ring comes to rest at top and bottom, there is considerable force required to "break them free".
Take a look at this, I still have some questions about sealing:
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The student has since obtained his Ph.D, partially based on this hypothesis.
Franz
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Piston Ring Rotation
RE: Piston Ring Rotation
http://www.rotatingliner.com and it looks like the info is from 2002. A google search threw up this report from February:
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