Author Topic: A new attempt at making piston rings  (Read 10433 times)

Offline Brian Rupnow

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A new attempt at making piston rings
« on: April 21, 2021, 03:18:57 PM »
Let me start out by saying that I have made my own piston rings in the past---and failed dismally. I was so disheartened by my failed attempt that I went to Viton o-rings and never looked back. Now I have ten or twelve years engine building experience, and I am going to try again. I have a 1" bore side shaft engine which I built a few years ago with a Viton ring, and it runs very good, and has incredible compression. I have chosen this engine because I can undo the con-rod bolts and remove the piston without disturbing any of the other engine settings. This will require that I machine a new piston and two rings.

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #1 on: April 21, 2021, 03:34:26 PM »
After considerable reading of books by Malcolm Stride, Philip Duclos, L.C. Mason and various posts by George Britnell, I have  compiled this list of things related to ring making. This information is not "absolute", as some of the information given by one author tends to disagree with information given by a different author.
« Last Edit: April 21, 2021, 04:30:53 PM by Brian Rupnow »

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #2 on: April 21, 2021, 04:13:06 PM »
The drawings below show the piston "as built" for one 1/16" cross section Viton o-ring, and the same piston redrawn for a piston that accepts two cast iron o-rings to match the rings supplied by Debolt. (I will be making these rings to the same dimensions as two rings purchased from Debolt for my Vertical i.c. engine-2021). Note that nothing on the piston changes except the information relating to ring width, depth, and location.


Offline fumopuc

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Re: A new attempt at making piston rings
« Reply #3 on: April 21, 2021, 04:35:03 PM »
Hi Brian, may be it is worth to watch this video.
https://youtu.be/DsW2IxQfshA
In my understanding very usefull.
Kind Regards
Achim

Online mikehinz

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Re: A new attempt at making piston rings
« Reply #4 on: April 21, 2021, 04:36:08 PM »
Brian, I'm following this with interest as I'm building my first I/C engine, a Webster, and am using a Viton o-ring, but in the future, I definitely want to attempt making cast iron rings and comparing them to an o-ring in the same engine, just as you are doing on this project.

I always enjoy reading your posts and watching your work progress!!

Mike
MIke
Wichita, KS, USA

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #5 on: April 21, 2021, 06:35:11 PM »
The first thing I wanted to check was---Does my .062 wide cutting tool cut an .062" groove in cast iron on a straight in plunge cut. Apparently not. The cutting tool does actually mike at .062 wide", but the slot it cuts in cast iron on a straight in plunge measures 0.057" wide. The top of my cutting tool has a strange shape to it (as bought) so next thing I'll try is grinding it flat and then do this test again.

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #6 on: April 21, 2021, 06:52:59 PM »
Okay--After a regrind of the top surface of my parting off tool so that it is absolutely flat and a second groove cut in cast iron, the groove is still measuring .057" wide. That's okay. As long as I know, then I can live with that. I could regrind an hss toolbit to give me an exact .062" groove, but I don't really want to have to do that.

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #7 on: April 21, 2021, 07:48:55 PM »
This is an "end" of cast iron that I have had for years. It has been turned down to 1.000" outside diameter and bored to 0.898" inside diameter. Now comes the parting off and deburring. I will get as many .063"-.064" wide rings out of this as I can.

Offline crueby

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Re: A new attempt at making piston rings
« Reply #8 on: April 21, 2021, 08:12:00 PM »
Following along with great interest here - have never attempted piston rings. If I read the plans right, the bore of the ring material is made to match the OD of the bottom of the groove they will go in?

 :popcorn: :popcorn: :popcorn:

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #9 on: April 21, 2021, 08:50:28 PM »
Crueby--the radial distance between the inside of the ring and the bottom of the piston groove is supposed to end up at 0.003".
I was able to part off 6 rings with no problem.  The math is a little weird, and I don't really know why. The ring closest to the right side of the page is 0.070" wide, but was supposed to be .062" wide. I set my parting tool against the end of the piece in the lathe, then using my DRO I moved it 0.125" towards the headstock. In theory that should have taken a cut .0625" wide and left a ring .0625" wide. After cutting and measuring the first ring, I moved the cutting tool 0.005" towards the headstock and took another cut to clean up the end of the stock. All subsequent moves were limited to 0.115" and that yielded rings approx. 0.065" wide. That should be about right because the rings still have to be cleaned up on both sides with some fine emery paper.

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #10 on: April 21, 2021, 09:53:34 PM »
Here we have the six rings, polished on both sides with 150 grit, then 600 grit emery paper on a flat cast iron surface with some wd40. The thickness of each ring is printed inside the ring. I will lap that 0.064" ring a bit more and bring it down to 0.061" thickness.
I don't know if I can bring the 0.070" ring down in thickness by lapping, but I will find out. The recessed fixture that I held the rings with while lapping them is in the picture, with an 0.040" recess in the face, but it doesn't show up very well. One of the websites I looked at before undertaking the making of these rings suggested deburring the inside corners/edges with a circular porcelain stone. I don't have such a thing, but will call around to my tooling suppliers in Barrie and see if I can buy one.

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #11 on: April 21, 2021, 11:18:41 PM »
The two rings that were "overthick" both came down to 0.061" with a bit more lapping. I've read so much about making rings in so many different places, I can't remember where I read about the porcelain sharpening stone that was used to deburr the inside edges of the rings. Maybe I had it wrong. Maybe it was "ceramic" sharpening stone. It looked to be about 3/8" diameter x 4" or 6" long, and would have to be a reasonably fine grit. If anybody knows where I can buy such a thing in Ontario, Canada, please let me know.---Brian

Offline crueby

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Re: A new attempt at making piston rings
« Reply #12 on: April 21, 2021, 11:33:03 PM »
Lee Valley tools carries them, they are based in Canada, lots of sharpening supplies. I just got some diamond plates from them.

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #13 on: April 22, 2021, 12:10:23 AM »
Thanks Chris--I was just checking them out. They have a store in Vaughn, about 30 miles from Barrie.---Brian

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #14 on: April 22, 2021, 01:11:20 AM »
Due to Covid shutdowns and my own impatience, I will wrap a piece of 220 grit emery cloth around a wooden dowel and use that to deburr the inside/edges of my rings. Someday, when this damned plague is over, my wife and I will drive down to Vaughn and pick up one of these tools from Lee Valley Tools.