Piston rings?

Hi everyone,

I've been planning on building an IC engine for a while now. I've done some pretty extensive research, but I can't seem to find any of the specifics of doing the Trimble method. I know I need to cut them on the lathe, polish, and cut them (I know there was a tool that could be made for better consistency, but I can't find any info on it) and then place them into some sort of fixture to hold them open and not allow oxygen in. I can't find anything about this fixture either. Then, they need to be heated to 1100°F and air cooled.

If I'm missing anything else, please let me know. This is the only step in the build that would hold me up. All info is appreciated.

Thanks!

Jason

I have read a lot of posts here about piston rings, and there are so many different methods that I have begun to forget the in's and out's of all of them.
I got a good article from Model Engine Builder about piston rings, but will have to locate the exact issue in order to point to that.

Here are some piston ring discussions, on this thread:

https://www.homemodelenginemachinis...de-my-piston-rings-no-heat.33973/#post-375443

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Go to Modelengineplans.com. it's the Jerry Howell site. He has a complete explanation on making rings

Maybe this is the link George is referring to:

http://model-engine-plans.com/engineeringtips/pistonrings.htm

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I had an extensive chat with a metalurist. 1100F for 3 hours. He was very adamant about the temperature and time.

The Trimble method can be found in old issues of Stricktly IC magazine.

O rings are another option as is just getting a good fit between piston and cylinder in which case you don't even need rings.

"Model Engine News" How to make piston rings.
Link

Mike1

pyro said:

Hi everyone,

I've been planning on building an IC engine for a while now. I've done some pretty extensive research, but I can't seem to find any of the specifics of doing the Trimble method. I know I need to cut them on the lathe, polish, and cut them (I know there was a tool that could be made for better consistency, but I can't find any info on it) and then place them into some sort of fixture to hold them open and not allow oxygen in. I can't find anything about this fixture either. Then, they need to be heated to 1100°F and air cooled.

If I'm missing anything else, please let me know. This is the only step in the build that would hold me up. All info is appreciated.

Thanks!

Jason

Click to expand...

Hi Jason
I've made several piston rings for my ic engines with great success. Check out one of my YouTube videos...

I hope that helps.
Good luck.
Andrew

I believe that for our model usage, simple is better, and the quality of the cast iron is more important than scientific temperature control. I make my own rings by turning them from the over-length skirt of the piston while still in the lathe (already at the correct diameter to fit the piston/bore), I cut them off with a toolpost mounted die grinder and wheel to provide a nice smooth edge. Afterward, I break them and clean up the broken ends with emery paper. I then determine the desired gap distance (SWAG) and turn a piece of round stock of that diameter as a spreader.

Set up a couple fire bricks to hold the round stock in horizontally, stretch the ring gap over the roundstock, heat with a weed burner propane torch until uniformly cherry red and until it drops off the round stock form, falling into a cup of water.

I usually make at least a couple extras because, I'll admit it, this isn't the most scientific method, and sometimes they're not perfect, but since this is such a quick operation, it doesn't matter. a quick run across fine emery paper on top of a flat surface (I use a sheet of heavy glass) to clean up any scale and finalize the fit in the ring groove, and they're good to go.

I don't use O-rings, and I've made these type of rings for all my engines to-date with excellent sealing and longevity from 3/4" up to 2 1/2". A decent cross-hatch on the cylinder, plenty of oil during a non-running seating period, and all the compression needed.

John W

The Trimble method is the one used by most members of the Bay Area Engine Modelers. The one change from his approach is he calls for a 1200-degree heat which changes the metal. 1100 degrees held for one hour and then allowed to cool naturally while still in an SS wrap works best. Then the rings are cut with a very small saw to keep the edges square and smooth. Almost all of the V-8s and smaller engines have these rings. They usually don't smoke and do last for years.

Thanks for all the replies. I can see the varying techniques just in here

I guess now my questions would be how do you hold a certain temp? Would some firebricks and a MAPP torch suffice? What kind of fixture do I need to make, is it essentially just a rod oversized to hold the rings open?

Jasonb said:

The Trimble method can be found in old issues of Stricktly IC magazine.

O rings are another option as is just getting a good fit between piston and cylinder in which case you don't even need rings.

Click to expand...

Unfortunately, I can't find the Strictly IC magazines anywhere. At least not the ones with the Trimble method.

AndrewW said:

Hi Jason
I've made several piston rings for my ic engines with great success. Check out one of my YouTube videos...

I hope that helps.
Good luck.
Andrew

Click to expand...

I actually stumbled across your video in my research! It seems like it worked well for you. My only concern is the way you heated them, I worry that running a torch back and forth may cause them to slightly warp. I'd need to make quite a few and I'd like them to be as consistent as possible. I'm probably going to go with the fixture that I've seen some others make.

The numerical part of the Trimble article is this
bore 1.000
depth 0.043 (ie radial depth of ring, the piston groove has to be a little deeper)
spread 0.150
these dimensions are scaled up or down linearly with your actual bore. these are the dimensions for a "medium" tension ring, right in the middle of his graph of constraints (not so stiff as to break when installing it, not so weak as to not provide enough wall tension during intake stroke), my engines have been happy with this.

the "depth" is very critical, .045 makes a ring that is near the limit of breaking during installation, .041 is near the limit of not enough wall pressure. The article makes it clear that the "spread" is a dowel that touches the gap at mid-diameter of the ring, IE not contacting at the inside corner as a flat bar would (a picture would be worth a thousand words here, maybe I'll photo the article...),

also if you have already ground the "installed gap" then that gap needs to be added to the spreader dowel diameter (though this dimension is much less sensitive than the ring depth by a factor of 10, IE a dowel that is .020 off is similar to a depth that is .002 off as far as staying within the constraints goes)

the thickness of the ring is up to you, I have a .027" wide grooving tool so I make mine .025" thick, thinner is better for less friction, thicker is better for nothing that I can think of (I made the mistake of thicker rings for my V12, that engine has so much friction it is a beast to turn over).

the rings should be made of G40 gray cast iron, 40 kpsi tensile strength, gray (flake graphite). this stuff is getting hard to find, at least in USA, stock up if you can !


Aside, StrictlyIC ownership has passed to Paul Knapp, who is sitting on them and not making copies available, which makes no sense to me, so I'd have no issue with making a photo copy of mine and posting it here, but its a very long article, and I think I'd prefer to just make a couple drawings from scratch to clarify what dimensions are what, shout-out if you want to see some drawings.

peterl95124 said:

the rings should be made of G40 gray cast iron, 40 kpsi tensile strength, gray (flake graphite). this stuff is getting hard to find, at least in USA, stock up if you can !

Click to expand...

Speedy still appears to carry if this is what you are referring to?
https://www.speedymetals.com/c-8388-round.aspx

This may have discussed before but would Durabar be a bad choice? I was gifted a chunk I was going to use for liners & considered same for rings

peterl95124 said:

Aside, StrictlyIC ownership has passed to Paul Knapp, who is sitting on them and not making copies available, which makes no sense to me, so I'd have no issue with making a photo copy of mine and posting it here, but its a very long article, and I think I'd prefer to just make a couple drawings from scratch to clarify what dimensions are what, shout-out if you want to see some drawings.

Click to expand...

Some drawings would be fantastic, I'll take whatever I can get!

pyro said:

Hi everyone,

I've been planning on building an IC engine for a while now. I've done some pretty extensive research, but I can't seem to find any of the specifics of doing the Trimble method. I know I need to cut them on the lathe, polish, and cut them (I know there was a tool that could be made for better consistency, but I can't find any info on it) and then place them into some sort of fixture to hold them open and not allow oxygen in. I can't find anything about this fixture either. Then, they need to be heated to 1100°F and air cooled.

If I'm missing anything else, please let me know. This is the only step in the build that would hold me up. All info is appreciated.

Thanks!

Jason

Click to expand...

They not hard to make.

I have cast iron , brass and pipe.
Cast iron last longest and pipe is cheapest.

I just ring the cut ring apart on one side.

There should a little calculator or just eye ball.

Dave

petertha said:

Speedy still appears to carry if this is what you are referring to?
https://www.speedymetals.com/c-8388-round.aspx

This may have discussed before but would Durabar be a bad choice? I was gifted a chunk I was going to use for liners & considered same for rings

Click to expand...

problem is "durabar" is more of a company name than an alloy specification, you need to know which of the many alloys they supply that you're considering, they do make a "gray cast iron" but that's not what you typically get on for example eBay.

This is the specification from Speedy metals for their round gray iron rod.
Nice material; I have purchased some of it.

As noted below, gray iron is getting more attention in the casting world, especially ductile iron, which is cheaper to cast than steel, and as strong or stronger than steel.

.

pyro said:

Some drawings would be fantastic, I'll take whatever I can get!

Click to expand...

these are the dimensions for "medium" tension rings, less likely to break during installation, but still sufficient wall pressure for intake stroke (what I've always used)

looks like doing this drawing has been good for me, because in my last set of rings I accidentally did a digit-transposition 0.043 ---> 0.034, and my rings are too thin, will hopefully do better next time !!!

I've left out the drawing and dimensioning for Trimble's "mandrel" because, at least to me, his description is too ambiguous, and requires notching the mandrel in order for the dowel to be correctly located, IMHO this was a poor design choice. But I'll do that in a subsequent post if/when I decide I've sufficiently dis-ambiguated what Trimble wrote.

and as Mike Rehmus has said, the temperature to stress-relieve the rings is only 1100-F, not 1200-F as Trimble states, and if you don't have a digitally controlled furnace, you'll probably end up with annealed rather than stress-relieved rings, and they won't be stiff enough so you won't get the best seal during intake stroke

as a final note, I have still had to lap my Trimble rings to get them to pass the "light test" in a precision ring gage. YMMV...

GreenTwin said:

This is the specification from Speedy metals for their round gray iron rod.
Nice material; I have purchased some of it.

As noted below, gray iron is getting more attention in the casting world, especially ductile iron, which is cheaper to cast than steel, and as strong or stronger than steel.

Click to expand...

Yup, that's the stuff (with "flake" graphite) !!!

(stay away from "ductile iron", that's not the stuff, it has "nodular" graphite which does not have the same self-lubricating / non-galling properties we desire)

peterl95124 said:

these are the dimensions for "medium" tension rings, less likely to break during installation, but still sufficient wall pressure for intake stroke (what I've always used)

looks like doing this drawing has been good for me, because in my last set of rings I accidentally did a digit-transposition 0.043 ---> 0.034, and my rings are too thin, will hopefully do better next time !!!

I've left out the drawing and dimensioning for Trimble's "mandrel" because, at least to me, his description is too ambiguous, and requires notching the mandrel in order for the dowel to be correctly located, IMHO this was a poor design choice. But I'll do that in a subsequent post if/when I decide I've sufficiently dis-ambiguated what Trimble wrote.

and as Mike Rehmus has said, the temperature to stress-relieve the rings is only 1100-F, not 1200-F as Trimble states, and if you don't have a digitally controlled furnace, you'll probably end up with annealed rather than stress-relieved rings, and they won't be stiff enough so you won't get the best seal during intake stroke

as a final note, I have still had to lap my Trimble rings to get them to pass the "light test" in a precision ring gage. YMMV...

Click to expand...

Thanks for the drawing, that makes it very easy to follow. Now I just need to figure out how to heat them up consistently.

While on the topic of material, how's the gray cast iron from McMaster Carr found here?