How I made my piston rings. No heat

[josodl1953]

Hi Paul,
It may be a coincidence but the cold method is also described in the design of the Edwards Radial 5 engine, dating back to the eighties. I used the method and it gave fairly good results although there is no 100% guarantee that all are OK. You have to make a bit more and select
the best ones.

Greetings from Holland,

Jos

 

[paulc]

paulc !
Thanks for sharing another way to make rings !
I have a question :
If use this method, when I perfect the ID and OD of ring , I can just do it one by one, right ?

Yes that's correct the turning mandrel would hold one ring at a time, well mine did. Once the ring is in the turning mandrel you can imagine how quickly it would be to get the OD to finish size.

You could of course have the turning mandrel hold more than one ring at a time just so long as you can get the all the gaps shut and clamps tight before final OD turning. The tapered sleeve I made to do this would obviously only close one ring.

Once you have milled all the ring gaps, the final lathe process is super fast.

 

[paulc]

Hi Paul,
It may be a coincidence but the cold method is also described in the design of the Edwards Radial 5 engine, dating back to the eighties. I used the method and it gave fairly good results although there is no 100% guarantee that all are OK. You have to make a bit more and select
the best ones.


View attachment 134682

Greetings from Holland,

Jos

This method is similar, but rather than making a slotted tube. I just make one ring blank at a time and then mill the gap into each ring blank individually.
Also the tapered sleeve I use for closing the individual ring gap prior to clamping, I feel is going to do a better job of closing the ring evenly rather than using chuck force to squeeze the cantilevered "tubes" gap closed.

My hit rate was 100% well that is as long as I turned the OD to my correct finished size and had the gap clamped fully shut when I did so.

Cheers Paul.

 

[paulc]

I buy rings from Hastings Piston Ring company $1 per set. They have all bore diameters, all thicknesses & all designs. I can't make a set of rings for $1. Rings are sold by, bore diameter, thickness, design, not by engine model number or engine serial number. I bought 8 sets of rings to rebuild an engine for $9 plus $6 postage. At age 72 I don't have time to make my own rings I might be dead tomorrow.

Interestingly watching the Hastings promo video below I can see that the professionals also first machine the gap to width then finish turn / grind the OD, ID and faces. They do not appear to split, spread and heat treat the rings to form the gap.

 

[ozzie46]

I tried to look up 1.000 bore x .030 ring top and second groove and a .050 oil ring and got a no data found alert on Hastings site. Did I do some thing wrong?

Ron

 

[almega]

I checked the Hastings site and they only go down to a minimum of 1.125" so for those of us making engines whose bores are less than 1.125, we will have to make our own. I didn't see any pricing at $1 each so, Rocket Man could you provide a link for where you are buying your rings?

 

[Motorman1946]

Hi Paul, I like your method of making piston rings but have a query which may sound stupid - how do you mill the gap in the rings? I am definitely missing something here.

Where I'm coming from is say the bore is 1 inch dia then the ring gap is going to be in the order of 0.003". I have no way of milling a 0.003" gap in a milling machine, even a hacksaw is going to give a far greater gap than that.

Or do you split the ring, open the gap up and hold it open in the mill and then mill a thou or two off each gap face, but then the faces may not be parallel.

As I said earlier - definitely missing something here!!

Chris

 

[methuselah1]

When I was building Les Chenery's gnome engine, the cylinder bores were 0.745" diameter.

Eventually, I worked out why. He was turning his rings to 3/4", then cutting them through with a 1/64" slitting saw. Instant, automatic gapping. I also wedge and roast my rings, but otherwise, like Les wrote in his construction notes- "I don't know what all the fuss is about".

-Andrew UK

 

[Motorman1946]

Having re-read the thread all through, I see Paul says the gap to machine is the same as for the heat treat Trimble method, which I can understand and helps answer my original query - I was missing something! - but what sort of gap is that/inch of bore, 40-60-80-100 thou?

Andrew's 1/64" for a 3/4" bore would suggest a 40thou/inch gap to machine, is this enough to provide the necessary pressure for a non-heat treat ring, or would a bit more be prudent?

Chris

 

[methuselah1]

Having re-read the thread all through, I see Paul says the gap to machine is the same as for the heat treat Trimble method, which I can understand and helps answer my original query - I was missing something! - but what sort of gap is that/inch of bore, 40-60-80-100 thou?

Andrew's 1/64" for a 3/4" bore would suggest a 40thou/inch gap to machine, is this enough to provide the necessary pressure for a non-heat treat ring, or would a bit more be prudent?

Chris

Chris, I don't know where you got the 40 thou per inch figure!

Here's how Les was working. Remember, we're dealing with circumference here...

0.75" x Pi (rounded up to tenths) = 2.3562"

0.745" x Pi = 2.3405"

The latter subtracted from the former = 0.0157"

1/64" = 0.1562"

So his resulting gap was around the 1 thou mark, agreeing with the "thou per piston inch diameter" rule of thumb. Plus, no double turning required at this size.

-Andrew

 

[internal_fire]

This technique seems to be the same one recommended by William H. Morewood in Building the Raritan, published in 1977. It is probably a lot older than that.

I used this method successfully many years ago when I built my Raritan.

Gene

 

[Motorman1946]

Andrew - it was an approximation from your statement that the gap of a 3/4"ring was cut with a 1/64" slitting saw (before heat treatment); 1/64" is very roughly 30 thou, so 30 thou on 3/4" dia equates roughly to 40 thou/inch dia.

Remember I am looking for what gap to cut the rings before the rings are machined to OD and ID according to Paul's method, to achieve the necessary degree of tension on the ring against the bore on completion, not the final ring gap in the bore when completed.

Perhaps a misunderstanding of statements!!

I agree that a final clearance of 1-2 thou ring gap on a inch dia ring would be about right in the bore. I was trying to put a figure against Paul's "desired size", of what size gap to mill in the construction phase before machining the rings to size.

Anyway, getting closer. Have resolved my lack of understanding of how to machine the desired size of gap in the construction process, I would just like to know what the team think is a good size gap to machine; there is presumably a 'rule of thumb' for this, that's why I was asking the "40-60-80-100 thou/inch for bore" question, see what other folk use.

Chris.

 

[methuselah1]

Chris, 30 thou is close to 1/32", not 1/64"!

-Andrew

 

[Motorman1946]

Ha ha Andrew - you spotted my deliberate mistake, what was I thinking of?

So that would make the gap about 20 thou/inch dia - which doesn't sound enough, do you not think?

Chris

 

[GreenTwin]

I made a set of rings for the green twin engine I made, using the heat expansion method, and I got some distortion.
I was able to straighten out the rings, but I was not really pleased with seeing my rings get warped.

I tried machining oversized rings a few years ago using the cold method, but I could not get accurate ring thicknesses.
Given the information paulc has posted here, I am sure that I will be able to follow and use the cold method.

I think for me it is just a matter of knowing the exact proceedure with the exact tooling/jigs, in oder to successfully make cold rings.

I have heard a lot of positive comments on the simplicity of the hot method, but I really want to master and use the cold method, and so the next break I get, I will try the cold method again, and get it right this time.

Thanks for everyone who shared ring making info.
Much appreciated.

Pat J

 

[paulc]

Hi Paul, I like your method of making piston rings but have a query which may sound stupid - how do you mill the gap in the rings? I am definitely missing something here.

Where I'm coming from is say the bore is 1 inch dia then the ring gap is going to be in the order of 0.003". I have no way of milling a 0.003" gap in a milling machine, even a hacksaw is going to give a far greater gap than that.

Or do you split the ring, open the gap up and hold it open in the mill and then mill a thou or two off each gap face, but then the faces may not be parallel.

As I said earlier - definitely missing something here!!

Chris

Yes you are missing it. The gap I'm referring to is not the closed gap ie not the gap when the ring is compressed and in the cylinder bore, no no but rather the fully sprung open gap ie the gap the ring would have when outside the cylinder. When the ring is in the bore the gap is near zero. In fact mine was zero and I let the immediate wear / bedding of the rings on the early runs set the in cylinder clearance gap.

See its the fully sprung open gap that is machined when the ring is whole. Then the gap is physically forced closed for final turning of the meat you left on the ID and OD when you made the ring blank. When the ring is released from the turning fixture the gap springs back to wide open. When the ring is finally installed into the cylinder proper the gap again becomes closed and you know the ring is round because you turned it that way.

So we are not splitting the ring at all, no need. We are machining the wide open, finished gap in the milling machine. I just clamped the ring blank down flat on the mill table, and then nibbled away the ring gap with a small end mill.
Hope this helps.

 

[GreenTwin]

Paulc

Yes I undestand what you are saying.
I looked at this years ago, and studied it in detail, but never got time to work it all out.
I did a search on my hard drive a minute ago, and found an article by Kozo Hiraoka in Live Steam, "Part 4, The Pennsylvania 0-4-0 Switcher in 1 1/2" Scale", September/October 1998.
I skimmed the article a minute ago, and apparently he is using a non-uniform ring thickness for uniform wall pressure, and a staggered end gap (not sure if that is the correct terminology).
The staggered gaps are machined as you say, with a mill in the milling machine.
He uses a forked clamp to secure the ring while it is being milled.

I will have to stud Kozo's article in more detail when I get time, but it seems like a good method, and it apparently matches the method you are using.

I would probably not take the time to machine the wall an ununiform thickness, since all the rings I have ever seen have a constant section, and seem to work fine.
The staggered gap method seems pretty simple, and I will probably try that.
.

 

[paulc]

Paulc

Yes I undestand what you are saying.
I looked at this years ago, and studied it in detail, but never got time to work it all out.
I did a search on my hard drive a minute ago, and found an article by Kozo Hiraoka in Live Steam, "Part 4, The Pennsylvania 0-4-0 Switcher in 1 1/2" Scale", September/October 1998.
I skimmed the article a minute ago, and apparently he is using a non-uniform ring thickness for uniform wall pressure, and a staggered end gap (not sure if that is the correct terminology).
The staggered gaps are machined as you say, with a mill in the milling machine.
He uses a forked clamp to secure the ring while it is being milled.

I will have to stud Kozo's article in more detail when I get time, but it seems like a good method, and it apparently matches the method you are using.

I would probably not take the time to machine the wall an ununiform thickness, since all the rings I have ever seen have a constant section, and seem to work fine.
The staggered gap method seems pretty simple, and I will probably try that.
.

I personally would not bother with the staggered gap nor the non uniform ring section. Way too complicated for what you need and to be frank I doubt would offer you any noticeable advantage.

I would say that any piston ring of about 1-1.2 mm in width with any sprung gap that closes fully when in the bore and the ring is truly round on the OD when in the cylinder. Will work perfectly on any engine made in this forum!

 

[Motorman1946]

Yes Paul - I had realised what I was missing in understanding what gap you were talking about!

Now my query on your method is reduced to what rational governs the size of the uncompressed ring gap you cut in the mill before the final OD and ID are machined.

Since I first read your first post I have caught up with another article on making piston rings without heat, written by Tom Schwartz, I think for Model Engine Builder, quite a while ago. His article goes into quite some detail on the theory behind his method and gives calculations/formula to calculate what sizes to make rings for different size bores and different ring materials and different fuel. Quite comprehensive. He also gives drawings of the fixtures to enable the rings to be made.

Amongst the formula is one for calculating the size of the initial gap to be milled before the ring is finished, which is the total of the compression gap and the final ring bore gap. The major difference in his method to yours, I think, is that he calculates the size of the ring in its expanded form based on bore diameter plus 10 thou and the compression gap plus final bore gap for the OD, and the ID is expanded OD minus the ring thickness . He then compresses the rings and machines 10 thou to give the OD to size as per your method, but not the ID which has been already set.

I hope I set that out clearly!!

Chris

 

[GreenTwin]

I personally would not bother with the staggered gap nor the non uniform ring section. Way too complicated for what you need and to be frank I doubt would offer you any noticeable advantage.

I would say that any piston ring of about 1-1.2 mm in width with any sprung gap that closes fully when in the bore and the ring is truly round on the OD when in the cylinder. Will work perfectly on any engine made in this forum!

I probably would not bother with the staggered gap, but good to know the method.
Perhaps I will make some staggered gap rings for the bragging rights, but day-in day-out rings with a straight cut work fine in engines all over the world, and are pretty much the standard, although I occasionally see a staggered gap ring out there.
.