A new attempt at making piston rings

[Brian Rupnow]

minh-thanh--- I don't hate anyone. I am not a hater. I envy some people their skill or luck, but hate is a big word to use on people with the same hobby as myself. There are some people on the forums, that I like better than others, but that's more about their attitude than their mechanical abilities.

 

[Badhippie]

http://users.tpg.com.au/agnet/make piston rings.htmlBrain if this has already been posted to you sorry about the repost. If it has not then please take a look it has some of the most defined information about rings, pistons, cylinders, anywhere. Also one of the easiest ways to make rings there is without all the misguided information. If you follow the links inside the page you will find information from some of the words leading experts that back up the findings with 100% pure facts.

Good Luck
Tom

 

[Brian Rupnow]

Badhippie--Thank you. I have seen this before, but I will read it thru again. There is a lot of information there.---Brian

 

[Charles Lamont]

General Question--When you make rings, do you machine the outside diameter of the rings after they have been heat treated? I'm trying to get a handle on this. The Trimble method does have a final "Skimming" step where the o.d. of the rings is turned after the ring is heat treated. I believe that many people make rings quite successfully without this final machining operation.---Brian

In Prof. Chaddock's method, there is a final skim.

 

[Brian Rupnow]

After finally getting the complete Trimble method of ring making, I see that I have been misinformed. Trimble does not call for a final "cut" on the outer diameter of the rings. In fact, he strongly recommends against it. He strongly suggests that the o.d. of the rings be brought to a very high degree of finish in the initial sizing before being parted off. He suggests that the rings be machined to about 0.0015" to 0.002" oversize, then using a "fine India stone" to remove all tooling marks, then brought to final size with 400 grit paper on a flat strip of metal. He recommends a "mirror finish" on the o.d. of the rings, and that the o.d. of the rings is the same as the bore of the cylinder.. He also disagrees with breaking the ring manually in a vice, and provides design for a "cleaver" which cuts the ring much more cleanly than breaking them.
Revised 07-june---I misread the tolerance.

 

[Badhippie]

Brian
Your welcome yes there is a lot of information there. I hope some of it will help you in your quest.
Thanks
Tom

 

[Jasonb]

He suggests that the rings be machined to about 0.010" oversize, then brought down to within 0.0015" to 0.002" over using a "fine India stone" to remove all tooling marks, then brought to final size with 400 grit paper on a flat strip of metal

Read it again or you will be there all day with that India stone.

To save others getting confused this is what he says

He roughs the OD to +0.010" then bores.

He then turns with his finest feed and best finish possible the OD to + 0.0015 to 0.002"

Then get out the stone and take it down to +0002 to 0.0005"

Then polishes it down to finished size with abrasive paper.

To be able to do this you really need to know the exact size of your bore, don't just assume all yours are 1" as your reamer may be cutting oversize and any honing or lapping will increase the bore and an old digi calliper is not the most accurate tool to measure it with.

 

[Steamchick]

If I remember correctly, not a given, only one of the three rings was a compression ring. One was to lubricate the cylinder wall, one was to seal the oil in the crankcase from getting into the combustion chamber and one was for compression. The only justification for more compression rings is the chance that one of them would work properly.

Hi Gordon, I guess we come from different parts of the industry, and possibly at different times.
I started in the mid-1960s and I think the oldest engines I re-bored and honed came from the 1930s. At least a few Austin 7 side vale engines, some old diesels (with cast-iron pisotns, rings etc.)...
I have only ever come across a single oil control ring used. But if this is a proprietary oil ring design it may be a pair of steel rings with a spring steel carrier. No use for models anyway.
But I do remember 3 compression ring pistons, and (memory may be wrong...) I think these were old diesels with cast iron pistons, but there may have been some Ali pistons for diesels with 3 comp rings.
The principle of multiple rings is simply to replicate the multi-staging of pressure drop, as with labyrinth seals, Tesla's non-return valve, turbines, etc... to reduce the volume of blow-by gases that pressurise the crankcases. But the principle of mimic is in the number of rings is to reduce friction, accepting the increased blow-by.
If you have a 2-stroke engine using the crankcase as the charging pump, then increased blow-by can be tolerated, as on the next stroke this just means a tad more gas in the cylinder.
I'll reiterate what I remember of the Hepworth and Grandage ring manufacture (as they made millions of rings every year that went into engines in a pre-run-in condition):
1. Machine the ring blank to correct diameter for being "sprung open".
2. Slit, with a gap equal to final gap plus amount of sprung-open gap that will dissappear when compressed.
3. Install in a cylinder of size plus finish grinding diameter, and clamp a pack of rings onto the mandrel.
4. Install mandrel with rings in grinder and finish grinding to size.
5. Install rings on a loose mandrel in a slave bore of size, and "Barrel" finish with finest lapping compound oscillating axially in the bore and rotating 10 to 30 degrees between each oscilation. This is to maintain the perfect circle from grinding, not make an out-of-round into a circle. This simply finishes the surface, so from first start in the factory, the engine has the planned compression and blow-by, and surface finish to avoid the need for running-in. (Modern customers don't know what "Running-in" is all about!).
If good enough for the car industry, it should work for the model... I think?
Perhaps the issue is the sizing of bores as setting gauges, lapping bores, etc...or the amount of spring in small rings? (Is that the reason for annealing?). Maybe the fitting process is distorting the rings from their perfectly made circular shape? Perhaps the annealing is changing the shape of the cast iron (it does!)...?
Try making steel rings from rolling flat wire instead?
Perhaps it is the bore, not the rings?
What does marking blue show the contact points to be?
Maybe I should try making some myself so I can learn to eat humble pie when I am wrong?
Enjoy,
K2

 

[DKGrimm]

OK, Brian. I've followed this thread for four weeks, now. I've read and re-read every thread. I've downloaded and read and studied all the references. It's crunch time. I've got a 4-cylinder scratch-designed engine that needs only the rings to put it together, so it's time to choose a method and bite the bullet. I'm going to go with the Tom Walshaw / Prof Chaddock method. I've used these methods before, once with very good luck, and two or three times not so much. I've developed some rationale for doing it this way, and have some opinions about why this is the best way to try to proceed, but I don't think I'll add those to the pool here until after I see how it works out.

Wish me luck.

Don

 

[Steamchick]

Good luck Don!
To boldy go.....
K2

 

[Gordon]

I seem to be missing something using the Trimble method. I have an engine I have been working on and have used the Trimble dimensions and methods but I apparently have missed something. I can put the piston with rings in the cylinder and I have good compression. I try starting the engine and it starts and runs for a short time but before I can get the adjustments made I am loosing compression. When I remove the piston the rings are stuck in the bottom of the groove. I can clean things up with carb cleaner and the rings again are free again in the groove. Reinstall and repeat above. I have checked the depth of the groove and if anything I am just a little too deep. I can insert a .002 feeler gauge in next to the installed ring. I have checked the bore and it is right on with a dial bore gage. No taper or out of round. Piston is 1.25 dia aluminum. Cylinder is cast iron.

Trimble shows an expanding mandrel to bring the ring to the proper width where he talks about taking off a few thousands but earlier he talks about starting with the ring only about .001 over width and then getting to final size with wet/dry sandpaper on a flat surface.

The only thing I can think of is that I am using the wrong aluminum but it is the same aluminum I have used before. Any idea what I am missing?

Gordon

 

[Brian Rupnow]

Please note that I have changed the tolerance on the Trimble note on post #325. I had it wrong.---Brian

 

[DKGrimm]

I seem to be missing something using the Trimble method. I have an engine I have been working on and have used the Trimble dimensions and methods but I apparently have missed something. I can put the piston with rings in the cylinder and I have good compression. I try starting the engine and it starts and runs for a short time but before I can get the adjustments made I am loosing compression. When I remove the piston the rings are stuck in the bottom of the groove. I can clean things up with carb cleaner and the rings again are free again in the groove. Reinstall and repeat above. I have checked the depth of the groove and if anything I am just a little too deep. I can insert a .002 feeler gauge in next to the installed ring. I have checked the bore and it is right on with a dial bore gage. No taper or out of round. Piston is 1.25 dia aluminum. Cylinder is cast iron.

Trimble shows an expanding mandrel to bring the ring to the proper width where he talks about taking off a few thousands but earlier he talks about starting with the ring only about .001 over width and then getting to final size with wet/dry sandpaper on a flat surface.

The only thing I can think of is that I am using the wrong aluminum but it is the same aluminum I have used before. Any idea what I am missing?

Gordon

Weird! Almost seems as if some foreign agent hacked your break-in lube.

Don

 

[mayhugh1]

I seem to be missing something using the Trimble method. I have an engine I have been working on and have used the Trimble dimensions and methods but I apparently have missed something. I can put the piston with rings in the cylinder and I have good compression. I try starting the engine and it starts and runs for a short time but before I can get the adjustments made I am loosing compression. When I remove the piston the rings are stuck in the bottom of the groove. I can clean things up with carb cleaner and the rings again are free again in the groove. Reinstall and repeat above. I have checked the depth of the groove and if anything I am just a little too deep. I can insert a .002 feeler gauge in next to the installed ring. I have checked the bore and it is right on with a dial bore gage. No taper or out of round. Piston is 1.25 dia aluminum. Cylinder is cast iron.

Trimble shows an expanding mandrel to bring the ring to the proper width where he talks about taking off a few thousands but earlier he talks about starting with the ring only about .001 over width and then getting to final size with wet/dry sandpaper on a flat surface.

The only thing I can think of is that I am using the wrong aluminum but it is the same aluminum I have used before. Any idea what I am missing?

Gordon

You may have debris circulating in your oil, and it may be getting trapped in between your valves and their seats and causing the loss in compression. Everything must be really clean before being final assembly. What you're discovering trapped in your ring groove may be a symptom and not the root cause of your problem.

By the way, that ring groove is a sealing surface for the ring needs to be machined using good practice for a smooth surface finish. Also, heat treatment may leave crud on the rings, and that on the ring exteriors is most easily polished off while the rings are still stacked in the Trimble heat treat fixture. I polish the individual sides of my rings after heat treatment on a glass plate using 600g grease with the ring a simple hand-held fixture. This is when I remove the final thousandth for their fit in the piston groove. I doubt that the piston alloy you used is the source of your problem unless it was so soft that you got a lousy surface finish on the grooves.

To me, it sounds more like a cleanliness problem. To be honest, I see lots of posted photos of model engine interiors that appear (admittedly they could be photo illusions) to be so full of crud on their surfaces that I wonder how the engine ever runs at all.

As careful as I try to be with my ring making and final assembly cleanliness, always including the use of magnetic drain plugs, I still see a very fine metal accumulation on the drain plug over time. Since most of the metal in my engines is aluminum, I can only assume this crud is coming from the rings as they polish themselves to the cylinders. I'm pretty sure that after all my efforts on the valve seats, I don't want that stuff ending up in them or in the engine's bearings - especially if they're open ball bearings. - Terry

 

[Brian Rupnow]

Today I had one of those wonderful, drop in, 8 hour jobs from an old customer. Design fixtures in the morning, send off to customer for approval, get immediate approval, make detail drawings, then machine like a fiend until suppertime. I don't want any "big" jobs, but I love those one day deals. I'm having a grooving tool ground for me at a local shop to make piston grooves, and todays work will pay for that with money left over.

 

[dsage]

Terry:
Could you post the annealing temperature you use for rings. As I mentioned above I believe it is the one mistake in the Trimble article and it should be avoided.

 

[Brian Rupnow]

My current understanding is 3 hours at 1100 degrees.----Brian

 

[dsage]

1100 what? C or F.
Where did you get that?
Trimble says 1475 F which has been disputed by some as damaging to the cast iron.
I'm not saying your wrong I'm just pointing out that some believe a mistake was made in the article.
Don't start until this has been confirmed.

I usually heat to a dull red in a dark room. Which would be a litle lower than the 1100 if you meant F.
Although these types of things are usually stated in C.
I'm not saying I'm right either.
That's why I had hoped Terry would chime in. He has done a lot of research (as usual).

Here is a chart. Down the page a bit. There's a big difference between 1100 F and 1475 F in color.


https://www.hearth.com/talk/wiki/know-temperature-when-metal-glows-red/
I'm sure others will chime in on how they just "Blast them with a torch". But I think it behooves you to get it right.

BTW if you read it Trimble does not state a time. Only that the rings themselves must truly reach the correct temperature being that they are inside a fairly heavy fixture. I guess there's no "too long" so.....

 

[Brian Rupnow]

That would be 1100 degrees F with a 3 hour soak time. I have tons of input on this one, and everybody is recommending something different. This is why I bought a heat treat oven. I am hoping that I can make working rings, and that I can set up a standard and repeatable process for doing so.

 

[werowance]

Brian, remind me, did you use store bought rings in the Webster engine? or which engine was it you used store bought ones? the first engine you used store bought ones (incase you did multiple ones)
reason I ask is thought maybe that engine would be best to "test" with since you know that engine already works on store bought ones