Author Topic: A new attempt at making piston rings  (Read 20063 times)

Offline crueby

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Re: A new attempt at making piston rings
« Reply #45 on: April 25, 2021, 03:06:36 AM »
We're rooting for you!
 :popcorn: :popcorn: :popcorn:

Offline Art K

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Re: A new attempt at making piston rings
« Reply #46 on: April 25, 2021, 03:35:59 AM »
Brian,
Here's hoping everything goes well this time around. I haven't tried making my own ring cause I have no way to properly heat treat them. I don't trust my ability with a torch.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Laurentic

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Re: A new attempt at making piston rings
« Reply #47 on: April 25, 2021, 10:59:46 AM »
Regarding machining rings round, splitting them and then expanding them to fit on a mandrel to heat treat them, I am with Roger on this, I think they will end up being slightly out of round by virtue of expanding them to make it fit over the mandrel and then being set at that out of round by the heat treat. 

I think as Roger says they need clamping back to fit snug with the correct, or previous, ring gap on a finishing mandrel and skimmed round again.

Maybe they need the OD to be made slightly oversize so then they can be skimmed back to bore ID after heat treat?

I can understand it will be more stiff to push the piston with two CI rings down the cylinder than a piston with a vitron ring, would expect that as the CI rings will be pushing hard on the bore walls, but as Roger says, they need to fit tight all the way round not just in odd spots!

Just my two pennys worth!

Chris
« Last Edit: April 25, 2021, 11:11:32 AM by Laurentic »

Offline Doc

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Re: A new attempt at making piston rings
« Reply #48 on: April 25, 2021, 02:31:00 PM »
Brian,
Here's hoping everything goes well this time around. I haven't tried making my own ring cause I have no way to properly heat treat them. I don't trust my ability with a torch.
Art

Propane torch works very well just put your ring with it spread about an 1/8 inch from a backing plate and aim for the middle at a distance with the torch and slowly move torch closer until ring just starts to glow red then leave it cool slowly.

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #49 on: April 25, 2021, 04:31:58 PM »
Piston and newest set of cast iron rings has been installed on my old Rupnow Vertical Engine. I am getting firing and smoke from exhaust but it's not a self runner yet. This is promising though. I never even got firing on the sideshaft hit and miss engine when I had the piston and rings on it. I have it set up with the electric motor right now, and I'll give it an hour and a half to help bed the rings in. If that doesn't work, I will pull the cylinder off and hone it to give a cross-hatch pattern on the inside of the cylinder.

Offline Hugh Currin

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Re: A new attempt at making piston rings
« Reply #50 on: April 25, 2021, 06:33:10 PM »
Brian:

If I remember, the Trimble method requires the spreading of the rings for heat treatment to be at the center of the ring width. He gives the design for a fixture in his Stricctly IC series on rings. Mr. Trimble, in the same series, presents an analysis of the difference in using a fixture and spreading the rings by pushing the inner points of the ring.

I think your fixture holds the gap apart pushing on the inside of the ring. This could be part of the problem. Also, you mention they fell off the fixture without much heat. Were you able to heat the whole ring up evenly? You may need even heat to hold the required form.

Hope this is of some help in this most excellent adventure.

Thanks.

This is a picture of my heat treat fixture and the new rings--the rings were individually spread over the vertical pieces of 1/8" plate and the torch was applied more or less on the center of the rings.
Hugh

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #51 on: April 25, 2021, 07:09:31 PM »
After being ran by the electric motor for 1 1/2 hours, the compression has improved, and when I try to start the motor with my electric drill it fires right along as the drill turns it under power, but when I remove the drill the motor just runs down and quits. The inside of the cylinder was a mirror finish from running it so many times with a Viton o-ring on it.--So---I pulled the cylinder off and set it up on my mill with a 3 stone brake-cylinder hone, and gave it 20 linear strokes with lots of wd40 at about 100 rpm. This has removed the mirror finish and left a herringbone hone pattern on the inside of the cylinder. Now the engine is out in the garage being "run in" with an electric motor for another hour to see if the compression will come up after an hours running.

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #52 on: April 25, 2021, 08:35:48 PM »
The cross hatching didn't really help at all. At this point in the game I've tried everything I can think of, and had no real success.---Ah Poop!!!    So----What did I learn today? Well, for one thing, the heat from an oxy-acetylene torch is way too hot. I barely touched the rings with the flame and they immediately turned bright yellow and fell off the 1/8" steel spreaders they were hanging from. That can't be right. Tomorrow I will buy a refill for my propane cylinder, and hopefully use a cooler flame to heat treat any future rings.  What else--Well, although the rings I am waiting on from Debolt are 1/16" thick, the actual rule of thumb for home made rings is that they should be from 1/25 to 1/30 of the bore diameter. I have a 1" bore, so the rings should be from 0.040" thick to 0.033" thick. That is one heck of a big difference from 1/16".  In his book "The Shop wisdom of Philip Duclos", he gives a tutorial on making piston rings, and he arbitrarily chose a radial ring thickness of 0.050" and it worked well for him. If it worked for him, then it should work for me. I think I have one stub of fine grained cast iron left, so maybe tomorrow I'll make some rings using Philip Duclos' measurements.
« Last Edit: April 25, 2021, 09:26:26 PM by Brian Rupnow »

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #53 on: April 25, 2021, 09:42:38 PM »
I just found an article which says that the width of the spreader used in the heat treat fixture should be 15% of the bore diameter. In my case that would be 0.150" (For a 1" bore). That is slightly less than the 3/16" used in the Duclos' book and slightly more than the 1/8" which I used today.

Offline crueby

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Re: A new attempt at making piston rings
« Reply #54 on: April 25, 2021, 09:45:30 PM »
So rules of thumb only work if you have a standard size thumb?   :shrug:

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #55 on: April 25, 2021, 11:06:25 PM »
Chris---So far this has been a fruitless enterprise. Not sure if I will eventually do this successfully, but I'm learning things.---Brian

Offline john mills

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Re: A new attempt at making piston rings
« Reply #56 on: April 25, 2021, 11:42:35 PM »
what do the rings that have been run in the engine look like have they look like they are rubbing evenly are the wear marks even .i would like the rung in to be with combustion pressure  running with a motor would tend to glaze up the surface so no further bedding in can take place .i have not made rings using heat treatment .i have always made them by rough turning then cutting the gap calming with the gap closed and then finally turning to finish size.i have made lots of full size rings from different materials small dia  to larger rings 1meter dia done with out heat treating after.  i know some rings for models have been done by setting to shape by heat treating heating needs to be done evenly
John

Offline Doc

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Re: A new attempt at making piston rings
« Reply #57 on: April 26, 2021, 02:07:14 AM »
I know my longer videos don't seem to be liked but here is a video anyway on heat treat and how not to put a ring on lol now this it for a .750 bore. When I finished the engines it took a little bit to get them running but ran just fine with them after I gt the timing and fuel mixer sorted out.


<a href="https://www.youtube.com/watch?v=JWzBmkCDU3c" target="_blank">http://www.youtube.com/watch?v=JWzBmkCDU3c</a>

Offline Brian Rupnow

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Re: A new attempt at making piston rings
« Reply #58 on: April 26, 2021, 02:07:15 PM »
This morning I got up and machined 5 new rings from a piece of grey cast iron to 1.006" o.d. x 0.906" i.d. x 0.055" thick. I'm going up to the local hardware and buy a tank of propane. When cut with a 0.020" slitting saw heat treated and and taken down to 0.050" thick on some emery paper on a flat surface they will be exactly as built in the Philip Duclos book. I will recut new ring grooves on my test piston and then see what happens.

Offline gbritnell

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Re: A new attempt at making piston rings
« Reply #59 on: April 26, 2021, 03:25:34 PM »
Hi Brian,
I have been following your thread and I don't understand where the .006 larger diameter comes from. I have always turned my rings to whatever my bore is. After heat treating I always do a light test in the bore and generally have very few rejects. As for the ring end gap I usually go .002 per inch of bore. Here again I have never had rings bind up in the bore. I break my rings with a cleaving tool and then adjust the gap after heat treating
« Last Edit: April 26, 2021, 03:30:32 PM by gbritnell »
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