Well guys, I guess I'll have to stand corrected on the rings “spinning”. It seems
like half the answers are yea and the other 50% are neh. Although I’ve
reassembled engines before after the machine work was finished, I do not by any
stretch of the imagination conceder myself an ‘engine builder’. I’m not one who
works with engines every day for a living. Nor have I ever had an engine that I’ve
reassembled run up on a dyno to test my work.
I've heard from Jerry recently, he’s not lost in the woods as we thought, and he
says he's seen them rotate in an engine running at moderate speed on a dyno.
Also read this in the link that Richard posted from the Sacramento Sky Ranch:
"Rate and direction of piston-ring rotation varied with cylinder-head pressure and
engine speed. Rates of rotation as high as 1 rpm at an engine speed of 1000 rpm
were observed."
And from Tiny’s “Opinions”: One poster says they rotate because of the
crosshatching due to honing. Another one takes a more comprehensive view of it
and says, “constant loading and unloading in a cylinder. Plus hone pattern, any
out of round, piston rock, uneven radial pressure, even rod side clearance will
make a ring rotate.”
Not really addressing the subject of ring rotation but adding to the understanding
of ring performance is this interesting article about the ring gap from Total Seal:
http://www.totalseal.com/pdf/ts_rings_article.pdf And this opinion, which is both yeh and neh in the same breath:“It is considered
good practice to build a new engine with the ring gaps staggered around the
circumference of the bore. This means that any escaping gas must negotiate a
labyrinth before escaping past the rings. However, while the engine is running,
the rings will tend to rotate around the piston and not remain in the position as
fitted. Many rings will then stick in one spot at random and remain there for the
life of the engine. For this reason, ring position during build cannot be considered
to be important although most engine builders would feel uncomfortable
assembling an engine with the gaps aligned.”
With a little research, I’ve found that there’s a weeks worth of reading one can do
on this subject. After taking a logical look at it I’m convinced that the rings can
indeed move around on the piston. But I still say they don’t “spin” on the piston.
And Gus, I did buy one of those when they were on sale for about thirty bucks.
Fun to play around with and surprisingly accurate, at least it is when compared to
the oven thermometer.
DG
