Piston rings

Biscuit said:

splatt said:

It wont touch the bore in use because the rails will, if fitted as the manufacture intended
There should be no gap because it is a spring, it requires the two ends to touch in place to hold the whole assembly under tension when assembled it requires no heat expansion gap , the rails do
YES it does hold the rails apart, but what you're preaching is that a WWWWWWWWWWWWWWWWWW shaped spacer between the rails with no extra outwards pressure exerted would do the job, have you ever seen the rails fitted to a modern engine, they have no radial tension
There used to be horrible 4 piece rings that worked closer to your special needs, it had a flat pressed spring in the bottom of the groove, a WWWWWWWW shaped spacer and two rails, the spring would break and the rails would no longer scrape the bores

Click to expand...

I think we have exhausted practically all the ways to explain the way three piece oil control rings work.

Mr Dano will never get it. Leave him in peace to continue to put together his trimmed to suit, fluttery oil ring installations. Besides he's just getting nasty now.

To answer his query though. A degree in automotive engineering.

Click to expand...

Can you not even read or you just a passive-aggressive asshole? Make your little pissy little comments to those who advocate or have successfully trimmed oil ring expanders. There is no outward pressure exerted by the expander. It exists to hold the scraper rings in place and make room for the oil scraped off the cylinder walls. It has little more tension than a chain in the radial axis. And I didn't ask about your qualifications because I don't really care. Again, if you would actually read what was posted, I suggested Baz post his since he trimmed an expander with no problems. He must be a rocket scientist. You're probably the guy who invented hidden windshield wipers and eliminated vent windows.

And diesels are irrelevant. Show me one modern motorcycle engine with one-piece oil control rings. There are none because they are obselete.

Here's an article you can read wrong and misinterpret. Especially ignore the paragraph on oil rings. I'm sure you'll think the statement on the experimental integral oil rings means one-piece oil rings are back in vogue.

http://www.hotrod.com/how-to/engine/hrd ... ring-tech/

for your reading pleasure. I think federal mogul has a much larger knowlage base than most on this list. it also states what i have told you. the expander DOES put raidal pressure on the rails !!!

http://korihandbook.federalmogul.com/en/section_24.htm

Danno said:

There is no outward pressure exerted by the expander. It exists to hold the scraper rings in place and make room for the oil scraped off the cylinder walls. It has little more tension than a chain in the radial axis.

Click to expand...

Danno,

Sorry, thought you were asking me about credentials.

Read the article from Hot Rod you so kindly provided. You do realize it is referring mostly to ring and piston packages designed as a unit and applied to modern and race engines right?. I thought we were discussing what fits our Norton's existing style of piston correctly not re-inventing the whole engine with state of the art bits. Another thing to consider is most modern engines are running 0w20 0w30, 5w30, 0w40, 5w40 motor oil. A whole different oil control situation than with 20w50.

And lastly, I don't know why you are all up in my face about my comment to Monsieur pierodn about his desire to use a one piece oil control ring. All I said was I think it would work fine, but not necessarily my choice.

I apologize for getting "in your face" as it were, but is is hard to have an intelligent discussion with gentlemanly disagreement when someone misquotes, misconstrues and twists someone else's statements for the sake of argument.

Three-piece oil control rings have been standard with Hepolite pistons for British bike engines since before the dawn of superior additive packages enabling us to use 20W-50 oil in our machines rather than the straight 50W formerly specified by the manufacturers. I've rebuilt a few in the last 46 years and the only one-piece cast iron oil control rings I ever saw were in an Atlas motor. The replacement Hepolites came with the now-standard 3-piece items. I'm sure someone still sells the old-style rings, but I have no clue as to who it would be? Do Jim Schmidt's lightweight pistons come with one-piece cast iron oil control rings? There are some one-piece oil rings being experimented with, not cast iron, but similar to the 3-piece in material and design. At this point, they are way out of the average person's budget and to my knowledge, not even offered for old motorcycles. So, again, what you can get away with is not always what you should do.

Danno said:

I apologize for getting "in your face" as it were, but is is hard to have an intelligent discussion with gentlemanly disagreement when someone misquotes, misconstrues and twists someone else's statements for the sake of argument.

Click to expand...

I have never quoted any one and changed their words. When I wish to reference a point in someone else's post, it is always like the example above,
the author's EXACT words.

One last thing before I quit on this whole deal and forget about one piece rings for a bit.

After watching the Hot Rod video and then a very short video from hasting, I've come to my own conclusion that we may well be talking about two completely different types of three piece oil ring systems.

The Norton style, also referred to as "Apex" is the one that uses an EXPANDER whose ends should butt. The rails should seat on a flare that runs around inner circumference of the expander compressing it so that when it is installed on a piston that is installed in a bore, pressure is exerted against the wall. This is the type pictured earlier in this thread.

There is another style. Outwardly it looks identical, especially when assembled to the piston. I'm pretty sure this is the type Danno is alluding too. It actually does use a SPACER that can not be considered an expander and it in fact does NOT contribute to any wall pressure as it's only function is to separate the two scraper rails and of course allow for oil passage through the piston. I actually remember installing this latter type in a 650 Triumph twins and as I recall the rails are noticeably thinner than those of the Norton type. One needs to be very careful when installing the piston to the bore as it is very easy for the thin rails to slip out of their groove and get caught between piston and wall.

NOTE: If any one has a copy of Modern Motorcycle Mechanics by J.B. Nicholson, there is a good picture of a Norton's correct oil ring installation on pp 423. If it can be scanned by someone and posted here it could be helpful. I do not have the ability.

I am not aware of any 3-piece oil ring design in which the expander contributes to outward pressure. The whole idea was to reduce ring friction which is about 40% of the friction generated by ANY engine, according to the hot rod article. The article also states that 90% of oil control is done by the second ring, which contributes little to combustion chamber sealing. The light weight of the 3-piece design also helps alleviate ring flutter which is a product of inertia. Very little cylinder wall pressure is required for the scrapers to do their part of the job.

Maybe misquote was a misnomer but misconstrue was not. Asking for my "credentials" to back up the idea of cutting a too-large expander when I neither recommended it or claimed to have done it is a bit out-of-bounds. AS I stated, I would send the parts back and wait for the proper ones.

OK then,,, I'm done.

Every oil ring in the hot rod article the expander exerts the outward pressure, look at the pictures you can see the step on the expander that pushes on the rail forcing the rail against the bores.

direct from the federal mogul web page . lead you to water but you still refuse to learn

Multi-Piece Oil Control Rings
Three-Piece Oil Control Rings

Three-piece oil control rings consist of two thin steel rings, known as rails (segments), and an expander-spacer which holds the rails at the required relative axial distance while simultaneously pressing them against the cylinder wall. With regard to the expander-spacer design, three fundamental styles have become established on the world market and lend their name to the 3-piece systems described below. If the expander-spacer is made from a nitridable steel, then nitriding can provide effective protection against secondary wear.
Whereas in the past the running faces of steel rails were always chromed, today they are increasingly nitrided all over and used in combination with a nitrided expander-spacer in order to satisfy tougher demands on engine durability and stricter emissions legislation. Such a design offers excellent wear protection of the running face and optimal protection against secondary wear between the expander-spacer and rails.
Conformability of 3-piece rings can be optimized by the use of rails with a smaller radial wall thickness.

VF System::
An expander-spacer made from a slotted steel strip bent into a U-shape, the open side facing towards the inside diameter. The expander-spacer is usually made from simple carbon steel and is therefore not nitrided. A similar type in a nitridable Cr-Ni steel also exists.

MF System::
The expander-spacer consists of a Cr-Ni steel strip in which axial humps are formed. Systems with an untreated expander-spacer and chromed rails as well as all-nitrided systems are in use.

SS50 System::
The SS50 expander-spacer, like the MF type, is made from Cr-Ni steel but by contrast the steel strip is humped in the radial direction. Such systems also are in service with an untreated expander-spacer and chromed rails or in an all-nitrided version for tougher demands.


<< previous page Contents next page >>

Danno said:

I am not aware of any 3-piece oil ring design in which the expander contributes to outward pressure.

Click to expand...

Please,
i have two new GPM without rings.
First, these pistons have the top not flat but a litlle bit domed.
What rings i can use, only the stock for GPM or other brand?
Thank you
Piero

Piero,

The Hepolite rings fit the GPM pistons.

I have domed GPM pistons, but mine are aiso marked 'Dunstall' in the casting so I presume they're higher compression than standard. They also have a taller crown.

Have you compared yours to a standard piston?

bill said:

direct from the federal mogul web page . lead you to water but you still refuse to learn

Multi-Piece Oil Control Rings
Three-Piece Oil Control Rings

Three-piece oil control rings consist of two thin steel rings, known as rails (segments), and an expander-spacer which holds the rails at the required relative axial distance while simultaneously pressing them against the cylinder wall. With regard to the expander-spacer design, three fundamental styles have become established on the world market and lend their name to the 3-piece systems described below. If the expander-spacer is made from a nitridable steel, then nitriding can provide effective protection against secondary wear.
Whereas in the past the running faces of steel rails were always chromed, today they are increasingly nitrided all over and used in combination with a nitrided expander-spacer in order to satisfy tougher demands on engine durability and stricter emissions legislation. Such a design offers excellent wear protection of the running face and optimal protection against secondary wear between the expander-spacer and rails.
Conformability of 3-piece rings can be optimized by the use of rails with a smaller radial wall thickness.

VF System::
An expander-spacer made from a slotted steel strip bent into a U-shape, the open side facing towards the inside diameter. The expander-spacer is usually made from simple carbon steel and is therefore not nitrided. A similar type in a nitridable Cr-Ni steel also exists.

MF System::
The expander-spacer consists of a Cr-Ni steel strip in which axial humps are formed. Systems with an untreated expander-spacer and chromed rails as well as all-nitrided systems are in use.

SS50 System::
The SS50 expander-spacer, like the MF type, is made from Cr-Ni steel but by contrast the steel strip is humped in the radial direction. Such systems also are in service with an untreated expander-spacer and chromed rails or in an all-nitrided version for tougher demands.

Click to expand...

Thanks for that. I would be interested in seeing a pull test of a Norton piston to compare the friction of the oil rings with and without the expander to see how much relative cylinder wall tension is increased by the expander. I'm having trouble visualizing how the expander, which seems to have no outward tension of it's own in a cylinder, can add tension to the scrapers, which have their own. I understand how the flared ends limit how far the scrapers can travel back into the groove, but as they move outward (wear) how does the taper move outward with them?

Danno said:

bill said:

direct from the federal mogul web page . lead you to water but you still refuse to learn

Multi-Piece Oil Control Rings
Three-Piece Oil Control Rings

Three-piece oil control rings consist of two thin steel rings, known as rails (segments), and an expander-spacer which holds the rails at the required relative axial distance while simultaneously pressing them against the cylinder wall.




I understand how the flared ends limit how far the scrapers can travel back into the groove, but as they move outward (wear) how does the taper move outward with them?

Click to expand...

Click to expand...

Because the scrapers are spring loaded by the springy expander thingy. But I'm not sure what "taper" refers to.

Danno said:

I'm having trouble visualizing how the expander, which seems to have no outward tension of it's own in a cylinder, can add tension to the scrapers

Click to expand...

It seems the expander is longer than the circumference of the bore, so is compressed against its spring tension to go into place.

Triton Thrasher said:

Danno said:

I'm having trouble visualizing how the expander, which seems to have no outward tension of it's own in a cylinder, can add tension to the scrapers

Click to expand...

It seems the expander is longer than the circumference of the bore, so is compressed against its spring tension to go into place.

Click to expand...

I think that's the pic posted that kicked off the discussion about cutting them down. I don't believe they cam be compressed radially.

If it's compressed "circumferentially," to fit into the bore, I think it must be pushing out radially once it's in place.

Until someone can explain either, I don't think they are in any way compressed. The oil rings (scrapers), like the upper two rings, must be compressed to fit into the bore and must be able to move about in their grooves. I think the expander/spacer only acts as a bottom land for the top scraper and a top land for the bottom scraper as well as a pathway for the scraped oil.

The one in the photo looks longer than the circumference of the bore.

To fit in, it would have to be compressed, or snipped shorter, I think.

Danno said:

Until someone can explain either, I don't think they are in any way compressed. The oil rings (scrapers), like the upper two rings, must be compressed to fit into the bore and must be able to move about in their grooves. I think the expander/spacer only acts as a bottom land for the top scraper and a top land for the bottom scraper as well as a pathway for the scraped oil.

Click to expand...

Danno, once the top and then the bottom scrapers are installed onto the expander that has already been placed into the piston groove, the whole three piece system is locked together. The scraper rails are not supposed move around independently to each other or the expander. However the whole assembly will be free to move about in the piston groove just like a one piece oil ring would. When installed on the piston correctly, it essentially becomes a one piece assembly and as such gets compressed like a single ring would by your ring compressor (or fingernails).