Do rings rotate?

[Vicky]

Originally Posted by Bob Bidonde

Please explain where does the force that rotates the rings comes from? Pistons cannot rotate. The cylinder does not rotate. So how is it you say the rings rotate in operation?

Ring rotation is explained in paragraph 1.6. 11., on page 37 in the link referenced above.

Interesting read.

Bob

[tbirdtbird]

No description of the origin of the force is provided.

I have torn down engines that I put together and the rings were always right where I put them.

See also Tom Wesenberg's comment.

Compressive forces are pushing the rings out toward the wall

I for one do not believe everything that I read. If I did then this entire forum would have to be taken as gospel.

The article states that rings are rotating 5-15 times per minute. If this were true then in 10K or less miles your piston ring lands would be all worn out.

The actual gap in a hot engine is negligible because the rings expand with heat and the gap is nearly closed, thus very very little compression is lost. The airplane story is a presumption at best

[George Miller]

Originally Posted by Bob Bidonde

Please explain where does the force that rotates the rings comes from? Pistons cannot rotate. The cylinder does not rotate. So how is it you say the rings rotate in operation?

The piston will rock as it changes direction. Also if there is a slight twist in the rods, the pistons will rotate. No they should not be a twist in the rods, but you see it all the time in model a rods. I ques some one does not know you are suppose to check the rods.

[ursus]

The force causing rings to rotate is the same force that causes pistons to suffer wear in the ring lands. What do you measure on a used piston? The gap in the ring groves. Aside from sealing compression, rings also function like bearings. Since the piston is fixed in position, somethings has to give to distribute the forces and dissipate heat. That would be the rings.

[huddy]

Excuse me, but piston ring rotation in aircraft engines is not presumption. This phenomenon is referenced in maintenance literature published by both Teledyne Continental and Lycoming. The technique of waiting and rechecking is also recommended procedure. Google "aircraft piston ring rotation" and you'll find a lot of references, mostly based on real world experience, and several references from the engine manufacturers.

I don't want to get into a flame war over this - it's not that important to me - so this is my last post on the subject. Agree or disagree at your discretion.

[Art Bjornestad]

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Not only 2 strokes. Early 500cc singles like AJ's had rings pinned.

[harleytoprock]

From what I've been told, it's the cross hatch honing marks that make the rings rotate.

[RockHillWill]

I am certainly NOT speaking about Model A engines, but I can attest to the fact that there is significant turbulence in a 'wedge' motor dependent upon valve placement (intake vs exhaust), valve timing and cam overlap.

I built a car in '74-'75 (?) that sat on the pole for the 500 and the following 400 that had the motor built by Chevy engine guru Bill Jenkins, and he was adamant that the rings not only be pinned, but we also drilled the edge of the pistons outer perimeter to add force to the top ring to keep it sealed. I made a die injector in an attempt to trace the air flow in the top end, but it was touchy shutting off the motor in time to 'read' the die vs letting it run and loose the die 'stains'.

[noboD]

Rockhillwill, I THINK Grumpy's idea with drilling holes around the top of the piston was also to shorten the path for the gases to expand the rings so they seal better. Would be great on a race car that gets rebuilt often, holes would probably carbon shut on a street engine. I had forgotten he did that until you mentioned it.

[tbirdtbird]

while we are at it, let's take advantage of this remarkable product from Kale Co for our cars...
http://kalecoauto.com/index.php?main...u8QOkpPCL8XWo2

[Bruskie]

Originally Posted by Mike V. Florida

http://download.ms-motor-service.com...958-02_web.pdf

Section 1.6.11 covers ring rotation.

don't u believe it

[Patrick L.]

Originally Posted by huddy

Excuse me, but piston ring rotation in aircraft engines is not presumption. This phenomenon is referenced in maintenance literature published by both Teledyne Continental and Lycoming. The technique of waiting and rechecking is also recommended procedure. Google "aircraft piston ring rotation" and you'll find a lot of references, mostly based on real world experience, and several references from the engine manufacturers.

I don't want to get into a flame war over this - it's not that important to me - so this is my last post on the subject. Agree or disagree at your discretion.

Yep, the fella I tore this particular engine down with worked at that mentioned engine shop [ Great world wide reputation also] at the time it was torn down and reassembled there. And, I have read both manufactures manuals. I've seen it on other water and air-cooled stuff but could not say how it could have happened or how the engine was assembled.
Its just one of life's little wonderments. As in many things in this life, there will be doubters, thats fine.

[redmodelt]

I torn down a Model T engine that I had put fresh rings and honed the cylinders. I know when it went together the gaps were staggered. When I pulled the pistons to do some work because of oil pumping (the cylinders had to much piston/wall clearance from the get go) , 2 of the 4 pistons compressing rings had the gaps in a row.

[Jim M]

Thanks Mike for a wonderful article. This is one of the few that don't talk in technical jargon but in laymen's language. Gonna print it out for future reference and rainy day reading. My old memory is not what it used to be (confirmed DAILY by my wife....lol).

[Mike V. Florida]

Originally Posted by Bruskie

don't u believe it

Here is a paper from the SAE on measuring something some of you say does not exist, But what do they know right!

http://papers.sae.org/900224/

[amodel25]

High school automobile mechanics class, 1967. We had a rep from Perfect Circle Piston Ring Company give a Forum on pistons and rings. When he was asked about positioning ring gaps opposite when building and engine....."You can position ring end gaps any way you want, run the engine for 30 minutes and if they are still in the same position, I'll buy everyone in here lunch". FWIW

[AL in NY]

yes!!!!!

[Cool Hand Lurker]

I gave a ring to the first girl I wanted to marry. She gave it back. The second girl wouldn't take it because she wanted a new one. I guess you can't rotate some kinds of rings.....

[Clem Clement]

Bob,
Nice hearing from you. We are getting 1/2' here in VA supposedly. You guys OK?

Rings rotate at the rate of 3.1416 times pie + the humidity divided by the number of red heads in yer Model A. (mine baaaaaarely move...

Stay warm, Clem
Divide by the

[Rich in Tucson]

Coriolis effect? If so, I expect one of our South of the of the Equator friends to pipe in with observations that their rings rotated clockwise but now that they sold their car to some fellow in Fairfax, the rings now rotate counter-clockwise...