RE: Piston Ring End Gap
 

There are some full scale motorcycle engine rings made of spring steel like the old Slinky toy and about as thin. The theory being that it reduced ring flutter at 18,000 R.P.M. Most if not all piston rings I have used were cast iron but I have no knowledge of metalurgy. I do know that cast iron is very hard and should exibit good wear characteristics. Hence cast iron pistons in Enya engines. I also think cast iron has a very low expansion rate making it a very stable material.

Bill

RE: Piston Ring End Gap
 

Well stated.

Bill

RE: Piston Ring End Gap
 

It's easy to break a cast iron ring expanding it over the piston crown. I won't tell you how I know.

Bill

RE: Piston Ring End Gap
 

How to make own piston ring and which material are used:

http://modelenginenews.org/techniques/piston_rings.html , http://www.alanstepney.info/page27.html , http://www.homepages.mcb.net/howe/NewsMakingRings.htm , http://www.btinternet.com/~sylvestris/rings/rings.htm . [sm=thumbup.gif]

I used the material from brake disc and camscaft, they are made of cast iron. Works wery well in my model engines.

RE: Piston Ring End Gap
 

I just visited the Grant Piston Ring website. One, and possibly the most commonly used, piston ring compression ring is made of "grey ductile iron castings', some are black phosphate coated. What do I know.

Bill

RE: Piston Ring End Gap
 

Web sites 1 - 3 wouldn't open. #4 did and gave me a headache. I have the I.Q. of a houseplant. Thank God Frank Bowman carrys this weight and it only costs me $10.00. Excuse me, I have to go take two Tylenol.[sm=spinnyeyes.gif]

Bill

RE: Piston Ring End Gap
 

I visited this homepage http://auto.sears.com/GRANT-HI-SPEED...ductId=2015375 , there are wrote: Grant uses the latest materials and coatings available to keep pace with the growing trends in today's engines. Materials used are Cast Iron, Ductile Iron and Steel depending on the engine and its specifications.

Also all three materials are used as piston rings. The last piston ring of steel will be coated with chromium, or nitrided. The steel ring will not break of if bending more than the cast iron and ductile iron will do it..

Ductile iron, also called ductile cast iron, spheroidal graphite iron, or nodular cast iron, is a type of cast iron. While most varieties of cast iron are brittle, ductile iron is much more flexible and elastic, due to its nodular graphite inclusions.

Coated piston ring in model engine are not common..

RE: Piston Ring End Gap
 

I has corrected, you can visit there again. The problem was comma after the web adress..

Hahaha, Prof. Chaddock was very precise to explain how to make the pistonring.

RE: Piston Ring End Gap
 

Thank you motorboy.

Bill

RE: Piston Ring End Gap
 

I was going to post earlier that the Surpass II series have plated rings. I'm not sure about Magnum rings, they have an orange looking coating.

RE: Piston Ring End Gap
 

I hope the plating on the OS 70 & 91 Surpass II rings doesn't peel off like it does on the cams

RE: Piston Ring End Gap
 

Note quotation marks.

"Hello,

I don't mind going into detail about my rings and appreciate the questions and concerns. The .004 per inch of bore is nonsense. Cast iron is one of the least expanding or contracting metal there is. That is why it makes great engine and machinery blocks. So if it doesn't expand as much when heated as other metals, minimal gap is needed. And this info along with clearance info is available in machinist Hand books which will show .001 to .0015 ring end gap per 1" of bore, not .004. Evenwhen I was rebuilding Chevy small block 327 CI engines with 4" bore ring gap was to be .004 to .006 with cast iron rings. All large gaps do is waste much needed power in small engines. My ring OD is to cylinder bore so when you get them ungapped they won't fit. Just use a fine 4" to 6" smooth cut file, old ignition point file, emery paper to gap gently squeezing ring sides pulling paper or pushing file from center of ring out, never going toward inside. I don't get upset when someone wants to set their own gaps, I look at it as you want to get the most out of your engines. One other note about cylinder wear is the bottom & top of liner is usually tighter. So if you have a small brake cylinder hone with smooth or fine stones use it at the bottom of the liner to open bore slightly & a few times through liner to get better ring seat. While you're at it tape down 320 grit emery paper to a counter top, flat surface etc. Invert liner on paper & while holding down with one hand gently pull it across paper. Rotate 90 degrees and repeat until liner top is flat . You would be surprised how many liner tops aren't flat and leak. I don't want leaks to be blamed on my rings not giving good compression."

Bill

RE: Piston Ring End Gap
 

I assume that is from Frank Bowman?

RE: Piston Ring End Gap
 

Yep. His piston ring business is just a hobby. It's straight and informed information in my book. Enyas don't utilize head gaskets, unless you want to reduce compression, his method of cleaning up the mating surface of the sleeve is one I've used many times on other engines.

Bill

RE: Piston Ring End Gap
 

Moly coated rings, however, can be a God send during break-in but I don't think model engine manufacturers have caught up with TRW yet.

Bill

RE: Piston Ring End Gap
 

As I recall molybdnum coated rings have a silver cast to them. Wonderful rings for a quick break-in. I probably would not hone the cylinder if I could get my hands on some.

Bill

RE: Piston Ring End Gap
 

Thanks,

Bill

RE: Piston Ring End Gap
 

Sorry, I must have confused you with another poster that said that cast iron was not used to make piston rings. Yes, steel has been used in very high RPM two cycles with chrome bores but I want nothing to do with either. Uh, chrome bores or steel rings that is.

Bill

RE: Piston Ring End Gap
 

I'm not sure what you have against a chromed bore, George Aldrich thought they were great with ringed engines. Some of the earlier ringed Super Tigres had chrome and Motorboy mentioned his Moki M5 was also chromed with rings. Which means my Moki M5 must be too :). I've even got a diesel (ETA Elite Mk2) with a chromed bore but that uses a cast iron piston.

RE: Piston Ring End Gap
 

Chrome bores are fine if plated properly and the cylinder walls don't peel. It is very unlikely that if the bore is not perfectly concentric and true during manufacture that you can ever break it in properly because the chrome is so hard. I consider it a cheap way to manufacture an engine as you do not have the large expense of making a liner and the corresponding port openings. The same with steel rings, they are hard and difficult to break in. In an ideal world a properly manufactured chrome bore and steel ring would not require any break-in at all. Additionally, should the chrome peel on a chromed bore you have only two choices, replace the entire crankcase and cylinder or dechrome and rechrome the bore.

Bill

RE: Piston Ring End Gap
 

Model engines generally have liners. Only a handful are designed without liners. Chrome plating has been around for a long time and is very reliable. There are other technologies in use today. Modern manufacturing processes provide for round and square bores in liners or crankcases. I have a Magnum .91 fours stroke with a true chrome bore on the bench several hundred hours on it and the bore is almost untouched< it has a ground finish, BTW. OS liners are nickel plated today. I've never heard of a four stroke liner peeling, but the two strokes sometimes do. I laugh at the new Acura commercials talking about Nikasil as if it was new. Model engines are rarely "rebuilt". When the wear out they are either scavenged for good parts, given away, or parts are just replaced. The only time anyone rechromes is when parts just can't be had and they can't part with the engine. The time involved in rebuilding a model engine quickly exceeds it's replacement cost for common engines.

Piston ring gap is dependent on the actual operating temperature of the components. While cast iron has a very low coefficient of expansion, if the ring gets hot enough it will still bind in the cylinder. If .001"/1" bore has proven to work, that's great. Model engines seem to be made to the old .004"/1". I'm sure this gives the manufacturer piece of mind that the ring won't seize during break in.

RE: Piston Ring End Gap
 

Well, I guess I'm more of a tinker and engine freak than a flyer. If my HP All-In-One printer scanner, fax, copier breaks at $100.00 I'll trash it and buy another for $100.00 to $200.00. Repair costs? maybe $100.00. My $400.00 Panasonic 5 year old TV. Repair at $200.00 or buy a new flat scren for an additional $300.00? I'll go $500.00 for a new flat screen. I purchase a brand of engine that is unlikely to require much repair if treated properly. It probably could be passed on to my grandchildren. Chrome bores are fine if done right but no one has convinced me that there is a real need for one. The only advantage is that they can be produced at a lower unit manufscturing cost = disposable. I agree with you. As a supreme tinker I want an engine that I can respect in terms of its quality and design from a manufacturer that take prides in their product and not their bottm line. I do not want to join the ranks of the buy it, fly it, discard it crowd. The impatient generation that will not expend the effort to run two gallons of fuel through a new engine and cycle it through many heating/cooling cycles is not my generation. Not a thing wrong with that philosophy it's just one that I don't care to ascribe to. I just love sound engineering and respect quality. Chevrolet came out with a revolutionary four cylinder engine in their Vega. The block was cast of high silicone content aluminum with the pistons running directly in the same material that the block was cast from. It was a beautiful little engine - until it overheated and the cylinders distorted from round to oval. The engine was extensively "hot rodded" after pressing in steel cylinder liners. Low unit manufacturing costs to be sure - and a diposable engine block. I would rather have a 252c.i. Offenhauser that, naturally asperated, would produce nearly two horsepower per cubic inch at 6,600 R.P.M. - all freakin' day! 1,000 vega engines or one Offy. You know I would take the Offy, build a red oak display stand for it and keep it in my living room.

DO NOT get me going about chrome crankshaft journals.

Regards,

Bill:D

RE: Piston Ring End Gap
 

How is a chrome liner cheap? If you are unfamiliar with model engines, I'm saying that many model engines have chromed steel liners inserted into aluminum crankcases. When you get up to 20+CC gasoline engines you see chromed aluminum cylinders (integral cylinder and liner) as standard practise. Your Enya has a steel sleeve that is not plated. An OS four stroke has a steel sleeve that is nickel plated. A Magnum has a steel sleeve that is chrome plated. The chromed steel sleeve will last the longest. Very few glow engines have chromed aluminum cylinders in modeldom, mainly racing engines, the only exception are Saito four strokes that have for some time now have had chromed aluminum bores like gasoline engines. I've never heard of the chrome failing. Saito engines are light for their size.

RE: Piston Ring End Gap
 

I have never seen problems with chromed cylinder. The best material combination between ring and cylinder are carefully selected from many years of experience through the development of engine construction. Chromium and cast iron goes very well together such as cast iron cylinder with chromed piston rings or chromed cylinder with cast iron rings.

As rule: never run same material togheter except the cast iron can run together as you will find in the older engine from old days.

I has experienced the flassed piston ring in the Peugeot 406 cars with the last engine EW10J4 in a short period due poor piston ring construction, it has nickel layer at outside of the pistonring in in upper compression ring. The piston ring are running in the engine block of cast iron. We replaced the piston rings in a short period cause the customers have complained about engine had high oil consumption. Later EW10J4 are improved, zero problem.

Do not forget the liner are in the picture: The liner will expand where will led the ring gap will increase with increased working temperature. The cromed aluminium liner/cylinder will expand more than steel liner, also a bit more wide ring gap.

Edit: corrected wrong word..

RE: Piston Ring End Gap
 

Yep, another reason why I wouldn't want a chrome on aluminum bore. and the cylinder liners are usually steel and the piston is cast iron. Good rings are cast iron running in a steel bore. Chrome rings? Maybe molybdenum coated. Moly rings break in quickly. Chrome rings do not. If the aluminum cylinder expands at a faster rate than the chromium, where does that leave the chromium?

Another fellow posted that ring gap was of little significance on a small model engine. "All large gaps do is waste much needed power in small engines." My little Enya .46 has a ring end gap of .011". Let's compare my .46 Enya to a 400c.i. Chevy V-8. Assume that both engines have a zero ring end gap amd the Enya has a .011" hole drilled through the piston crown.

* 400 divided by .46 = 870
* 870 x .011 = 9.57"
* 9.57" divided by 8= 1.20"

Could we assume that the Chevy V-8 would have to have a 1.20" hole drilled through each of it's piston crowns equal to the .011" hole in my .46?

I'm lousey in math so check me out here.

Regards,
Bill