A new attempt at making piston rings
- Thread starter Brian Rupnow
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Actually, when inserted into the cylinder, the ring will deform at the point of highest stress which will be directly across from the gap and then contact the bore in only two points. This stress point is where, in your video (and I do enjoy watching your videos), your rings broke during installation.
As Dave said, the rings made by the "Duclos" method will never have 360 degrees of contact with the cylinder. Of course, that's not saying that they won't be 'good enough' for some engines to start and run. If the rings are made properly with 360 degrees of contact, the engine won't need to be spun for long periods with an external power source to wear the rings and bore into each other. And, by the way, during that 'run-in' time if the engine is sucking fuel through the carb from a filled tank, the rings will likely be washed with raw fuel and wear quickly away even quicker at those two points of contact. However, after a while, those points on the ring will wear down enough for the bore to begin changing shape. At some point, the clearances between the rings and bore might be reduced enough to get the engine started, but the now non-circular cylinder will be forever mated to those particular rings. None of this is optimal, but serendipity might help the engine eventually start. And that might be OK for an engine that was built for display and just needs to run for a few minutes before being put up on a shelf.
Another concern I would have with the 'Duclos method' is heating the rings without a fixture to keep them flat. I'd be worried about the rings warping during heat treatment especially in a bench top setup where the heating is quick and relatively non-uniform. The rings need to wind up flat because their lower surface is an important sealing surface to the piston during combustion.
A light test is easy to do, but a fixture in conjunction with a bright flashlight in a dark room is needed. Significant diffraction effects limit what can be seen with the naked eye while holding the ring up to a window and such a cursory check can't be relied upon. Also, when heated uncontrollably in open air, there can be a bit of scale build-up on the rings' o.d.'s that needs to be polished away. This scale will also affect the contact area as well as light test results.
There's very little additional work involved with with Trimble's method which is time proven and has science and common sense behind it. As others have said there is a lot of misguided info out there on ring making.
All in all, though, a very entertaining thread. - Terry
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No real progress today. I'm all worked out!!
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Dsage is right, you have to start with the right diameter I.e. fits the cylinder perfectly, before any heat treatment or splitting.
Today, I test with some of my rings
With a slightly small piston, with this piston I'm sure the engine has almost no compression
And with a small part of the ring that is not in complete contact with the cylinder, with a little bit of W40 oil, they have good compression
Edit : The upper ring is similar to the 2nd ring , but less so . I forgot to take picture
With a slightly small piston, with this piston I'm sure the engine has almost no compression
And with a small part of the ring that is not in complete contact with the cylinder, with a little bit of W40 oil, they have good compression
Edit : The upper ring is similar to the 2nd ring , but less so . I forgot to take picture
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Harglo
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Harglo
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Hello Brian
Just watched the struggling to get the top ring on an bingo its become 2 pieces. It some what common practice to take a few thou of the top end of the piston up to the grove. That said should reduce the risk of breaking. I have a star engine with just one ring compression is good.
Harvey
I'm six days in on what was supposed to be a fairly simple project. So far, I have not been successful. I am getting lots of advice from people who have plainly never made piston rings, and though I know they wish to help, it only confuses things. I have tried the Philip Duclos method of ring making, and people have immediately jumped in and told me that is a terrible way to make rings, and they will end up crooked and it's no wonder they don't work. It worked for Philip, and he was sure enough of the method to include it as part of his book. His method for machining the ring outer diameter was #1--Calculate ring o.d. (Same as i.d. of cylinder.) #2 Since he cut the rings with a 0.020" slitting saw he multiplied the diameter x pi to get circumference, then added the slitting saw thickness to the resultant circumference and then divide the answer by Pi to achieve his final ring diameter (which in my case turned out to be 1.006")I don't have a heat treat furnace, and don't plan on buying a heat treat furnace. I did find out that the flame from an oxy acetylene flame was far too hot, so I went and bought a bottle of propane and it worked much better with a cooler flame. I have looked at simple fixtures which the rings are mounted on and then held flat by means of a big flat washer bolted to the fixture to squeeze the rings flat during heat treat. I'm not sure if the fixture should be the same diameter as the i.d of the rings before they are cut, after they are cut, or after they have been stretched over a spigot to spread the gap. Some people advocate turning the o.d. of a stack of rings held in a fixture (after heat treat) to ensure they are perfectly round on the o.d. This sounds like it would be the answer, but the rings are definitely not round on the i.d. at this point after being split and heat treated.
I have not been successful----yet. A fellow from Switzerland has posted his rings and fixtures on another forum, based on the Chadock method and he has had good success. This is the method that makes the rings a couple of thou oversize and then clamps them in a fixture and takes a skim off the outside diameter to ensure that the rings are perfectly round. Since the rings actually "float" a bit on the piston, the o.d. doesn't have to be perfectly concentric with the inside diameter.
Hello!
I thought you said you have a pottery kiln. If so why not build the proper fixture and heat them to 1100 for 3 hours and be done with it. Just wondering.
Just spreading them .150 isn't enough. They need to be in the fixture to hold the ring correctly. If not the stress of being spread is being transferred to the spot directly across from the gap. When heated the ring can deform and create a flat spot across from the gap. The fixture helps to spread the stress evenly around the ring and greatly reduce the chance of distortion.
The heat treat is another thing that needs to be done fully or no point. 1100 for 3 hours. It is done to stress relieve the material. It takes a long time to fully relieve all the stress. If not then the ring will slowly lose wall pressure.
The Trimble method is the most work of all the ring making methods. If all steps are followed without any shortcuts it will yield the best rings of them all.
I thought you said you have a pottery kiln. If so why not build the proper fixture and heat them to 1100 for 3 hours and be done with it. Just wondering.
Just spreading them .150 isn't enough. They need to be in the fixture to hold the ring correctly. If not the stress of being spread is being transferred to the spot directly across from the gap. When heated the ring can deform and create a flat spot across from the gap. The fixture helps to spread the stress evenly around the ring and greatly reduce the chance of distortion.
The heat treat is another thing that needs to be done fully or no point. 1100 for 3 hours. It is done to stress relieve the material. It takes a long time to fully relieve all the stress. If not then the ring will slowly lose wall pressure.
The Trimble method is the most work of all the ring making methods. If all steps are followed without any shortcuts it will yield the best rings of them all.
No pottery kiln here, just oxy acetylene, propane, and wifes kitchen oven which I have been warned to stay away from.
Hi Brian !
That's exactly what I thought and did, but I don't have the furnace. I just heat the rings with a gas torch, heat them very slowly , try to heat the ring in all directionsand try to stay at that hot temperature for at least 5 minutes.
I've tried the ways everyone says it, and I've been successful, In some cases, the rings that look "good" are less (or I made a mistake in those cases).
I've been several times with this way and the rings are always fine with me
That's exactly what I thought and did, but I don't have the furnace. I just heat the rings with a gas torch, heat them very slowly , try to heat the ring in all directionsand try to stay at that hot temperature for at least 5 minutes.
I've tried the ways everyone says it, and I've been successful, In some cases, the rings that look "good" are less (or I made a mistake in those cases).
I've been several times with this way and the rings are always fine with me
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The moral of the story and the reason there is so much debate about this subject is that there is more than one way to skin this cat and as long as proper procedure and attention to detail are observed different methods may produce a running engine.
I love math, but as an engineer practical consideration force me to ***** when accurate is accurate enough.
There is much debate about the shape of the ring once is compressed inside the cylinder.
The Chaddock/Trimble method involve predistortion by forcing the gap open and annealing.
The method approximate the theoretical shape required to a high degree, at least theoretically.
On the typical 1" bore of our engines the circularity error by using the "cold" method may be 0.0001" an then the ring may still conform to the cylinder but with different radial pressure around the circle.
The method I described previously (I did not invent it and have no emotional attachment to it) makes a ring with a longer circumference and then remove the excess leaving a gap. Squeeze the gap close to slide in the cylinder. No annealing required.
Other people have made engines that work. Do they reach the highest theoretical compression exhibiting the least drag? Probably not, but the engines run.
Any engine would have zero compression at 0.01 RPM but when the compression phase happens in 50mS (600RPM) a small arc of daylight between ring and cylinder is not goin to impact compression. Let's not mention the presence of oil and the fact that the pressure of ignition pushes the ring into contact with the cylinder from behind.
Brian since this is your first attempt at making ring you will find out, like all of us do, that after studying the literature you still have to develop your personal mojo. Listen to everyone and then make up the ring with your own method.
When talking about the gap one has to specify whether he refer to the relaxed gap or the compressed gap when inside the cylinder. For all practical consideration the compressed gap is there for expansion regardless of the process used to make the ring it can be accounted in the machining OD or neglected entirely and filed away later either way wont change the result much.
I love math, but as an engineer practical consideration force me to ***** when accurate is accurate enough.
There is much debate about the shape of the ring once is compressed inside the cylinder.
The Chaddock/Trimble method involve predistortion by forcing the gap open and annealing.
The method approximate the theoretical shape required to a high degree, at least theoretically.
On the typical 1" bore of our engines the circularity error by using the "cold" method may be 0.0001" an then the ring may still conform to the cylinder but with different radial pressure around the circle.
The method I described previously (I did not invent it and have no emotional attachment to it) makes a ring with a longer circumference and then remove the excess leaving a gap. Squeeze the gap close to slide in the cylinder. No annealing required.
Other people have made engines that work. Do they reach the highest theoretical compression exhibiting the least drag? Probably not, but the engines run.
Any engine would have zero compression at 0.01 RPM but when the compression phase happens in 50mS (600RPM) a small arc of daylight between ring and cylinder is not goin to impact compression. Let's not mention the presence of oil and the fact that the pressure of ignition pushes the ring into contact with the cylinder from behind.
Brian since this is your first attempt at making ring you will find out, like all of us do, that after studying the literature you still have to develop your personal mojo. Listen to everyone and then make up the ring with your own method.
When talking about the gap one has to specify whether he refer to the relaxed gap or the compressed gap when inside the cylinder. For all practical consideration the compressed gap is there for expansion regardless of the process used to make the ring it can be accounted in the machining OD or neglected entirely and filed away later either way wont change the result much.
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Hi Brian
I hope at the end of your ring saga you will write a preferred method.
I have made several engines and only two have run and they have all finished up for show and not for running, always through lack of compression be it rings or valve
seating.
Graham
I hope at the end of your ring saga you will write a preferred method.
I have made several engines and only two have run and they have all finished up for show and not for running, always through lack of compression be it rings or valve
seating.
Graham
jack620
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I do wonder how much of the loss of compression and leakage comes from the width and the depth of the groove. According to some articles which I have read a part of the seal is caused by the gases getting behind the ring and pushing the ring against the cylinder wall. Obviously you can have a perfect fitting face but if the groove is too wide and/or too deep the gases can leak around the ring. Where is this point? I have had cases where the groove is not deep enough and the piston will not fit in the cylinder. I have also had cases where I have tried to run the engine and when I removed the piston and the ring was stuck in the groove after removing the piston.
Gordon
Gordon
One more thing: there will be 3 cases:
1 / My cylinder is not really round
2 / The ring is not round
3 / (1) + (2)
So check your cylinder is round?
Because if the cylinder is not round you will not know where you are wrong
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Gordon, as long as the ring is free to move without excess freedom the ring would press against the upper surface of the groove when the piston accelerate downward. This seals the top but some gas must escape to create pressure behind the rings. Every engine has some blow-by pressurizing the crankcase but must be minimal.
Damn. You guys just put me down the rabbit hole of Circularity vs. Roundness.
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