The great O ring discussion

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gbritnell

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Gentlemen,
I have been following the O ring discussion in another thread and have read several others in the past. Most of the builders on this forum have been machining and making engines for quite some time. That being said I have trouble understanding why there is such an aversion to making actual piston rings. If one follows the discussions about O ring use there seems to be more negatives than positives in their use. It seems everyone has their own guidelines for using them, type, O ring, X ring, material, Viton, neoprene, piston fit, loose, tight, cylinder wall fit, tight versus loose. When using piston rings there are hard numbers and data for their use. I feel that using O rings is taking the easy way out. Granted for a novice builder who would just like to build his first engine and hear it run I understand their thoughts but for the rest of us that have two or more engines under our belt I don't understand the aversion to making and using piston rings. Having built many engines over the years and following other's builds the biggest challenge in getting an engine running, bar none, is getting the valves to seat and seal properly. Hours can be spent machining the valves, seat cutting, lapping and pressure testing but yet we all accomplish this task one way or another. In building an engine there's so many somewhat complicated parts that need to be made, gears, cams, valves and crankshafts to name but a few and yet here again we are all able to do this but mention the word piston ring and some people get cold chills. To me making rings is one of the easier machining exercises connected with building an engine. You turn a piece of iron (very easy to machine) to a given I.D. and O.D. You then part it off to a given thickness. You break the edges then split the ring. If using the Trimble method a fixture needs to be made for heat treating. This is just another simple machining project. Now the heat treating. I don't have a kiln or heat treating furnace, I just use a standard propane torch. When making my fixture I hollow out the bottom so when heating there's not a lot of mass to heat up. Long ago i purchased a jar of Boron powder from a gun supply shop and after multitudes of piston rings I still have enough to last my engine building career. The rings are mounted on the fixture. The fixture is heated up then coated with the powder. The powder turns to a somewhat liquid coating much like silver solder flux. I then place the flame of the torch into the pocket in the bottom of the fixture so that I'm not applying the heat directly on the rings. I then hold the torch until the whole fixture and rings are brought up to a dull red color and once obtained hold it there for 2-3 minutes. The fixture is then allowed to cool and then the Boron coating is washed of with tap water. The rings are then unmounted, cleaned. fitted to the bore and gapped. Trimbles method and several other can be found on the internet for free and give a more thorough explanation in the making of piston rings.
To sum up my dissertation, why not give piston rings a try. It's really not that hard of a job and then you don't have to worry about all the issues of fitting and using O rings.
gbritnell
 

Vietti

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George,

100% agree with your comments re valves.

0 rings are perhaps the easy way out but may have some advantages beyond ease. In my last two engines I first fitted shop made cast iron rings. They worked, but when I switched to 0 rings I felt the compression was better and there was better oil control. On one engine I had added 4 rings/piston with drain holes around the bottom ring for oil control, the 0 ring still out performed it. I do kind of think running regular rings followed by 0 rings had the benefit of a nicely polished bore.

I think too that in a hit and miss engine, 0 rings may be superior because, if loosely fitted, there is no friction when coasting unlike a regular ring

Cast iron rings are attractive to some extent because they are prototypical. But we all take liberties when it come to originality, take ignition systems as an example. All most all our ignition systems are hardly prototypical using a large battery and coil or CDI. That's why I spend time making magnetos, both high and low tension. I admit to using CDI on smaller engines. We all decide how close we are going to follow original practice in our models. Keeps things interesting plus no one sees the rings!

Enjoying the discussion and not trying to be contrary.

John
 

petertha

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Now the heat treating. I don't have a kiln or heat treating furnace, I just use a standard propane torch. When making my fixture I hollow out the bottom so when heating there's not a lot of mass to heat up. Long ago i purchased a jar of Boron powder from a gun supply shop and after multitudes of piston rings I still have enough to last my engine building career. The rings are mounted on the fixture....gbritnell
Good post, George. I've already committed that the next engine will be self made rings. I'm using OS-56 rings for my radial, but its actually more work to hit 5 bore diameters exactly with right finish vs lapping 5 bore diameters the same (whatever that size may be in the end) & sizing the rings a/p Trimble's method.

I'm reasonably clear on the Trimble method & fixtures, but its the scale issue that I'm still fuzzy on. I think the original article had some sacrificial paper which burned in the enclosed clamping fixture? Anyways, can you show a pic of your fixture? Is the boron more about scale prevention or potential loss of carbon? (or are these kind of inter-related). I've seen pictures of rings being heated bare with propane torch until they fell off the gapping pin, but of course, is that the best way?
 
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lantain1982

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I fully support gbritnell`s comments on fitting CI rings. If you have lived through all the problems of your engine construction why not go the extra mile and tackle a sealing medium which will eliminate the above concerns. CI rings will introduce you to a possible range of unfamiliar processes, but this what we are all about. As an aside, if you are concerned about scaling, there is a ring manufacturing process that, by machining the ring to finished size after the stress relieving process effectively removes the scale.
lantain1982
 

vederstein

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Oh hell, not again. This hobby is dying. Why make the barrier to entry more difficult by criticizing how people make their engines? The whole "you're doing it wrong" does nothing but push people away. So what if someone wants to use sealing method over another? Give it up.
 

gbritnell

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HI Vederstein,
When I wrote this piece i chose my words very carefully. In the text there was mention of newcomers to the hobby and then the rest of us. If making piston rings is going to prevent someone from building an engine then I'm afraid they will never get passed the valve and seat process.
Regards,
gbritnell
 

Charles Lamont

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I really don't think George is trying to put anyone off, and I do think it unfair to accuse him of that. (He just wants to encourage them to try doing it properly. ;))

I also assume he is only talking about IC engines. Model steam locomotives have been running successfully with O-ringed pistons for decades, including club workhorses that in the UK may run several hundred (full size) miles a year.

Personally, if I made a steam engine with gunmetal cylinders I would use them. I have a very back-burner loco with iron cylinders, and for them I would always use iron rings. IC engines: iron.

In the video pointed to by kiwi2, I think his ring splitting tool is brilliant, but those rings are far, far too thick. I am no expert on the Trimble method (I prefer Chaddock) but Mr Crispin's heat treatment jig seems to misunderstand the geometric principles of the method.

By-the-way, but perhaps of interest, I have seen numerous full size steam loco piston rings being made. They are turned to size and expanded (after splitting) by running through a swageing tool that has two rollers. The inside roller has edged teeth which crush a series of indents on the inside surface of the ring, thereby stretching it.
 
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tornitore45

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George where did you get Boron powder? I find sources as dietary supplement witch may not be pure boron but just a biological source of boron like iron pill for example are not iron.
 

IanN

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Hi Group,

So many issues!

Personally, I machine cast iron piston rings (or use graphite yarn for steam) because it gives me pleasure - if others want to use o-rings, that is their choice, there is no right or wrong

Regarding Vederstein’s comments about discouraging people from engineering as a hobby: There are far greater issues than a comment about differing techniques at play....

Finally, sources of knowledge: O-ring manufactures publish extensive data on the use of their products and operate technical advice and support lines. Of course accessing these resources requires spending time reading texts and understanding the engineering principles - unfortunately we live in a world where many people are reluctant to make that investment and would prefer to re-invent the wheel through trial and error

I would suggest that most group members can stop reading this post at this point - the bits that follow are simply my opinions on the encroachment of “alternative technologies” in to established practices and these issues cannot be discussed with out causing offence to someone somewhere. Those of a nervous disposition or delicate nature read no further.


I am dangerously near my allotted three score and ten years on the planet and my initial reaction (a good number of years ago) to the use of synthetic O rings as piston rings was “Oh no! Not another new technology to master!”

It was the same with Loctite. I had been making press-fit interfaces for a couple of decades and then they introduce this idea of gluing stuff in place - what is the world coming to?

There is a thing called “progress” - I didn’t vote for it myself, we are just stuck with it.

I have a day job (retirement is for wimps) teaching engineering apprentices and lecturing in engineering. My last job in industry was as Head of Electronics at the European R and D centre of a global corporation that nobody has ever heard of. I spent my time working on time plans, spreadsheets, budgets, while in the labs just down the corridor talented engineers were doing the job I originally signed up for in my youth - hands on engineering research

I left industry when I accepted that if the brilliant young engineers leaving university and college did NOT have better ideas, better imaginations and better visions of the future than I had, then there is something very, very wrong with our education system.

So I teach my students to embrace the opportunities provided by exciting new technological developments, use CAD/CAM, 3D printing, CNC (or at least DROs) while in my hobby I still machine press-fits, turn by hand, and (to my lasting shame) know that I can file a part flat and true to with in a few thou in less time that it would take me to wrestle with the set-up of the part on my mill and rummage through a jumbled box of cutters in my disorganised home workshop. It is a case of “Do as I say, not as I do”

This means I now fall in to the category of “miserable old git”, I have my own chair in the corner of the pub where I can bang my fist on the table, moan about “young people” and start everything I say with the words “Well back in my day .....” (or at least I could do all of that before this virus thingy took off)

I’ll stop now - I have to “FaceTime” my sons so they can listen to me moan about the Six Nations (England has been at war with France for the last thousand years so it rankles to see them at the top of the table) and then we can get on to discuss the cricket umpiring in India....
 

cds4byu

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George where did you get Boron powder? I find sources as dietary supplement witch may not be pure boron but just a biological source of boron like iron pill for example are not iron.
I believe it is Borax powder, not Boron powder, that is referemoved. Borax powder is a flux. Borax is readily available as a cleaning product, at least in the US.

Carl
 

gbritnell

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Actually the powder I was referring to does contain Boron. I purchased mine from an American gun supplier named Brownells. This particular powder is PBC although they carrry several anti-scaling types.
There are several methods for heat treating piston rings. Probably the simplest, which it tried once or twice, is to make the ring, split it then hang it on a piece of steel that is wide enough to create the expanded shape. This is then held in front of a backstop created by using a couple of fire bricks. Heat is bounced against the fire bricks but not directly on the ring itself. When the ring has absorbed enough heat to become plastic it will drop from the piece of steel. I have to admit it has worked for me but only when making one or two rings at a time. For multiple rings the process I use was described in my original posting. The last method or third method for this discussion is the use of a kiln or heat treat furnace that has a temperature control. The rings are made as described and mounted on the expanding fixture. The whole affair is then wrapped in stainless foil (which is also available from Brownells) Before finally folding the foil shut to create a chamber a piece of heavy paper is inserted along with the fixture. The purpose of the paper is to catch fire when the heat has reached the burning point and therefore burn off the oxygen from the chamber. This method has to be used with a temperature controlled oven because there is no way of ascertaining the internal heat if one was to use an open flame.
The controversy in the second two methods is what amount of heat to apply. Mr. Trimble's method calls for a higher heat than some others have recommended. Having never used the oven method I have only heated my ring fixture to a dull red and held it there for several minutes to ensure a complete heat soak. I have engines with many hours on them with no visible oil smoke so the process I used I would consider successful.
gbritnell
The Boron based powder is very toxic and the safety instructions should be followed to the letter.
 

dnalot

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I recently made rings using the Trimble method. An interesting observation was that where I used celo-tape to hold the several wraps of heavy paper around the rings, the rings had no scale at all. The area that was covered with paper but had no tape the rings had some scale.

Mark T
 

minh-thanh

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I totally agree with gbritnell !
With me, making a piston ring is a lot simpler than make a valve and valve seat are airtight
And with my little experience, for a novice, making a ringless piston is enough, not necessarily using o rings.
 

Cymro77

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Fascinating stuff - obviously there are more ways than one to skin a cat! Keep it cool and enjoy the hobby.
 

Longboy

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the o ring solution does kinda defeat the whole point of model making
Well....no it does not. Simple, effective, durable and available components enhance and grow interest in modeling engines as in many other hobbies. If carburetors, gears, design software, ignitions, casting kits were not available, this hobby would revert back to the exclusivity of retired journeymen tinkering for months/years on outstanding but obscure projects. The easy, a shortcut, a purchased item incorporated in your model is not a disgrace nor considered improper. One can always try traditional methods buying the tooling and materials to make components and evaluate the outcomes. This gives one another notch in skill level.....but not necessary in building a quality item. Not everyone building engines can spend hours a day in the shop and many youngsters with an interest in machining can feel intimidated self engineering some of these finer engine parts and never invest in our corner of making model engines.
 

coulsea

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A very enjoyable thread. I recently had a comment to one of my posts about my way being unnecessary ( no i am not offended) and it made me think about the right and wrong ways of doing things. model building is generally just a way for people to enjoy themselves so if you are having fun you are doing it right. if you are not interested in ignitions buy one, if you don't want to make rings buy them, any kind. I buy all my steel because I don't have an iron ore mine
Please keep sharing the way you do things because I might want to do it that way next.
 

el gringo

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Gentlemen,
I have been following the O ring discussion in another thread and have read several others in the past. Most of the builders on this forum have been machining and making engines for quite some time. That being said I have trouble understanding why there is such an aversion to making actual piston rings. If one follows the discussions about O ring use there seems to be more negatives than positives in their use. It seems everyone has their own guidelines for using them, type, O ring, X ring, material, Viton, neoprene, piston fit, loose, tight, cylinder wall fit, tight versus loose. When using piston rings there are hard numbers and data for their use. I feel that using O rings is taking the easy way out. Granted for a novice builder who would just like to build his first engine and hear it run I understand their thoughts but for the rest of us that have two or more engines under our belt I don't understand the aversion to making and using piston rings. Having built many engines over the years and following other's builds the biggest challenge in getting an engine running, bar none, is getting the valves to seat and seal properly. Hours can be spent machining the valves, seat cutting, lapping and pressure testing but yet we all accomplish this task one way or another. In building an engine there's so many somewhat complicated parts that need to be made, gears, cams, valves and crankshafts to name but a few and yet here again we are all able to do this but mention the word piston ring and some people get cold chills. To me making rings is one of the easier machining exercises connected with building an engine. You turn a piece of iron (very easy to machine) to a given I.D. and O.D. You then part it off to a given thickness. You break the edges then split the ring. If using the Trimble method a fixture needs to be made for heat treating. This is just another simple machining project. Now the heat treating. I don't have a kiln or heat treating furnace, I just use a standard propane torch. When making my fixture I hollow out the bottom so when heating there's not a lot of mass to heat up. Long ago i purchased a jar of Boron powder from a gun supply shop and after multitudes of piston rings I still have enough to last my engine building career. The rings are mounted on the fixture. The fixture is heated up then coated with the powder. The powder turns to a somewhat liquid coating much like silver solder flux. I then place the flame of the torch into the pocket in the bottom of the fixture so that I'm not applying the heat directly on the rings. I then hold the torch until the whole fixture and rings are brought up to a dull red color and once obtained hold it there for 2-3 minutes. The fixture is then allowed to cool and then the Boron coating is washed of with tap water. The rings are then unmounted, cleaned. fitted to the bore and gapped. Trimbles method and several other can be found on the internet for free and give a more thorough explanation in the making of piston rings.
To sum up my dissertation, why not give piston rings a try. It's really not that hard of a job and then you don't have to worry about all the issues of fitting and using O rings.
gbritnell
Gentlemen,
I have been following the O ring discussion in another thread and have read several others in the past. Most of the builders on this forum have been machining and making engines for quite some time. That being said I have trouble understanding why there is such an aversion to making actual piston rings. If one follows the discussions about O ring use there seems to be more negatives than positives in their use. It seems everyone has their own guidelines for using them, type, O ring, X ring, material, Viton, neoprene, piston fit, loose, tight, cylinder wall fit, tight versus loose. When using piston rings there are hard numbers and data for their use. I feel that using O rings is taking the easy way out. Granted for a novice builder who would just like to build his first engine and hear it run I understand their thoughts but for the rest of us that have two or more engines under our belt I don't understand the aversion to making and using piston rings. Having built many engines over the years and following other's builds the biggest challenge in getting an engine running, bar none, is getting the valves to seat and seal properly. Hours can be spent machining the valves, seat cutting, lapping and pressure testing but yet we all accomplish this task one way or another. In building an engine there's so many somewhat complicated parts that need to be made, gears, cams, valves and crankshafts to name but a few and yet here again we are all able to do this but mention the word piston ring and some people get cold chills. To me making rings is one of the easier machining exercises connected with building an engine. You turn a piece of iron (very easy to machine) to a given I.D. and O.D. You then part it off to a given thickness. You break the edges then split the ring. If using the Trimble method a fixture needs to be made for heat treating. This is just another simple machining project. Now the heat treating. I don't have a kiln or heat treating furnace, I just use a standard propane torch. When making my fixture I hollow out the bottom so when heating there's not a lot of mass to heat up. Long ago i purchased a jar of Boron powder from a gun supply shop and after multitudes of piston rings I still have enough to last my engine building career. The rings are mounted on the fixture. The fixture is heated up then coated with the powder. The powder turns to a somewhat liquid coating much like silver solder flux. I then place the flame of the torch into the pocket in the bottom of the fixture so that I'm not applying the heat directly on the rings. I then hold the torch until the whole fixture and rings are brought up to a dull red color and once obtained hold it there for 2-3 minutes. The fixture is then allowed to cool and then the Boron coating is washed of with tap water. The rings are then unmounted, cleaned. fitted to the bore and gapped. Trimbles method and several other can be found on the internet for free and give a more thorough explanation in the making of piston rings.
To sum up my dissertation, why not give piston rings a try. It's really not that hard of a job and then you don't have to worry about all the issues of fitting and using O rings.
gbritnell
Gentlemen,
I have been following the O ring discussion in another thread and have read several others in the past. Most of the builders on this forum have been machining and making engines for quite some time. That being said I have trouble understanding why there is such an aversion to making actual piston rings. If one follows the discussions about O ring use there seems to be more negatives than positives in their use. It seems everyone has their own guidelines for using them, type, O ring, X ring, material, Viton, neoprene, piston fit, loose, tight, cylinder wall fit, tight versus loose. When using piston rings there are hard numbers and data for their use. I feel that using O rings is taking the easy way out. Granted for a novice builder who would just like to build his first engine and hear it run I understand their thoughts but for the rest of us that have two or more engines under our belt I don't understand the aversion to making and using piston rings. Having built many engines over the years and following other's builds the biggest challenge in getting an engine running, bar none, is getting the valves to seat and seal properly. Hours can be spent machining the valves, seat cutting, lapping and pressure testing but yet we all accomplish this task one way or another. In building an engine there's so many somewhat complicated parts that need to be made, gears, cams, valves and crankshafts to name but a few and yet here again we are all able to do this but mention the word piston ring and some people get cold chills. To me making rings is one of the easier machining exercises connected with building an engine. You turn a piece of iron (very easy to machine) to a given I.D. and O.D. You then part it off to a given thickness. You break the edges then split the ring. If using the Trimble method a fixture needs to be made for heat treating. This is just another simple machining project. Now the heat treating. I don't have a kiln or heat treating furnace, I just use a standard propane torch. When making my fixture I hollow out the bottom so when heating there's not a lot of mass to heat up. Long ago i purchased a jar of Boron powder from a gun supply shop and after multitudes of piston rings I still have enough to last my engine building career. The rings are mounted on the fixture. The fixture is heated up then coated with the powder. The powder turns to a somewhat liquid coating much like silver solder flux. I then place the flame of the torch into the pocket in the bottom of the fixture so that I'm not applying the heat directly on the rings. I then hold the torch until the whole fixture and rings are brought up to a dull red color and once obtained hold it there for 2-3 minutes. The fixture is then allowed to cool and then the Boron coating is washed of with tap water. The rings are then unmounted, cleaned. fitted to the bore and gapped. Trimbles method and several other can be found on the internet for free and give a more thorough explanation in the making of piston rings.
To sum up my dissertation, why not give piston rings a try. It's really not that hard of a job and then you don't have to worry about all the issues of fitting and using O rings.
gbritnell
 

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