Model Engine Maker
Engines => Your Own Design => Topic started by: Brian Rupnow 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.
(https://imagizer.imageshack.com/img923/8524/SY2gPr.jpg)
-
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.
(https://imagizer.imageshack.com/img923/6541/vdjzBR.jpg)
-
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.
(https://imagizer.imageshack.com/img924/1060/0GDWMc.jpg)
(https://imagizer.imageshack.com/img922/6996/1o5kQA.jpg)
-
Hi Brian, may be it is worth to watch this video.
https://youtu.be/DsW2IxQfshA (https://youtu.be/DsW2IxQfshA)
In my understanding very usefull.
-
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
-
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.
(https://imagizer.imageshack.com/img924/4795/XzocbJ.jpg)
-
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.
-
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.
(https://imagizer.imageshack.com/img924/9021/h6mODb.jpg)
-
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:
-
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.
(https://imagizer.imageshack.com/img923/6937/pxRFJz.jpg)
-
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.
(https://imagizer.imageshack.com/img922/3678/kmveQS.jpg)
-
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
-
Lee Valley tools carries them, they are based in Canada, lots of sharpening supplies. I just got some diamond plates from them.
-
Thanks Chris--I was just checking them out. They have a store in Vaughn, about 30 miles from Barrie.---Brian
-
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.
-
And here we have a quick and nasty round ceramic file (220 grit emery paper glued around a turned broom handle), and my rings are all deburred on the inside/edges. Tomorrow I will break them in a vice, file the ends, try them for size in a cylinder, and then heat treat them.
(https://imagizer.imageshack.com/img922/5323/0VjSZz.jpg)
-
Looking good so far :ThumbsUp:
How were you measuring the 0.62" ring groove? If the grooving tool measures 0.62" and enters the groove it must be at least 0.62". Feeler gauges might give a better answer.
I have found that the better the finish inside the ring the less likely they are to break when fitting.
-
The rings have all been split. This is a very simple procedure where part of the ring is clamped in the vice and one half sticks out the end of the vice where it can be grabbed by my finger and them and gently pushed back and forth until it cracks. You have to be careful with your pushing and pulling, as you don't want to snap the ring in two pieces. At this point in the game, the rings are still the same i.d. and o.d. as they were when machined.
(https://imagizer.imageshack.com/img922/7135/dwdHtB.jpg)
(https://imagizer.imageshack.com/img922/8591/Yu8ZKA.jpg)
-
Hi Brian. The military taught me how to make (and break) piston rings. Take a crosscut chisel, place the ring on a round bar firmly held in the vice, place the chisel at 45 degrees on the ring and whack it! Never broke one ever... :LittleAngel:
John
-
I now split mine with piano (music) wire side cutters.
-
I have made a heat treat fixture on which to mount the rings. Trial and error showed me that making the inside diameter of the fixture 0.942" diameter and forcing the rings over it resulted in a 1/8" gap between the ends of the ring. I truly felt that if I spread the rings any wider they were going to break. The rings are tightly compressed between the two discs to keep the broken ends of the rings perfectly in line. The back-side of the fixture has been hollowed out so it will have less mass to heat up. I will heat fixture and rings to a cherry red with my oxy acetylene torch, being sure not to let the torch flame play directly on the rings. The ring ends will be filed after the heat treat is finished and the rings demounted.
(https://imagizer.imageshack.com/img924/1070/iARJ6K.jpg)
-
What is the purpose of spreading the rings on the fixture? I know very little about how IC rings work.
-
The idea is to open up the gap and then use the heat treatment to 'lock' this in so that when the rings are compressed back to their nominal size there is a pressure against the cylinder wall to start the sealing process. The gas pressure behind the rings then increases the sealing force.
-
Brian,
I'm not sure about your method of expanding the rings! It seems like you'll be changing the whole diameter. The Trimble fixture is calculated to expand the ring to maintain the proper diameter.
-
The idea is to open up the gap and then use the heat treatment to 'lock' this in so that when the rings are compressed back to their nominal size there is a pressure against the cylinder wall to start the sealing process. The gas pressure behind the rings then increases the sealing force.
Ah - gotcha - thanks!
-
After being heated cherry red, and left to air cool, then a little bit of clean-up, the rings have all taken a new "set" and the gaps remain open about 1/8" after they are removed from the fixture. I have seen on Youtube where some people heat the rings to cherry red, then drop them into a bucket of oil or water while they are still cherry red. I have no idea why they do that, and I've never read anything saying that this is a part of the process. My next step will be to square up the broken ends and test fit them into a cylinder to check that I have about 0.004" gap between the ring ends.
(https://imagizer.imageshack.com/img922/9757/ZspxFc.jpg)
-
You may find this useful.... http://www.jerry-howell.com/PistonRings.html
Don
-
The six rings are finished and properly gapped to 0.004" when installed squarely into the cylinder. As far as I can tell, I've made six good rings.---A funny thing about cast iron---it grows when it's heated, and when it cools off, it doesn't return to the dimension it was before. It is always a bit larger, even after it cools down. I knew about this from a previous experiment and I know that the two stroke airplane engine crowd will sometimes heat up a piston to "grow it a little" if they aren't running tight enough to get good compression. It shows up here because after these rings were split they would still fit down into the 1" cylinder bore perfectly. After being heat treated, before having the ring gap filed, they would no longer fit into the cylinder. I expected that, but it's still kind of surprising.
(https://imagizer.imageshack.com/img922/525/UZf2wj.jpg)
-
Brian,
I'm not sure about your method of expanding the rings! It seems like you'll be changing the whole diameter. The Trimble fixture is calculated to expand the ring to maintain the proper diameter.
George--I'm not 100% sure of it either, but it seems to have worked very well. I'll know for sure after I get a piston made and try them out. When I done this kind of thing ten years ago and wedged the gap open with a piece of plate and then heated the rings one at a time until they dropped off the plate it didn't work. the rings I made were definitely not round after that process.
-
This is the side shaft hit and miss engine that I will be trying these rings on. It runs like a charm with the single Viton ring on the piston. I'll know after I make a new piston and put a couple of these new rings on it how successful I was at ring making.
https://www.youtube.com/watch?v=13Bb69SoVzk
-
This is the new cast iron rings mounted on the new cast iron piston. The old piston with Viton ring is setting beside it. No real drama. Lots of lubricating oil and a bit of breath holding, and the new rings went into place without threatening to break as they were being installed. Next test will be to see if new piston with rings will fit into a 1" reamed cylinder.
(https://imagizer.imageshack.com/img924/4823/ADAUa4.jpg)
-
This was the last test prior to putting the piston back into the engine. I had to absolutely convince myself that the new piston and rings would indeed pass thru a 1.000" diameter hole. If not, that's a good way to break rings or bugger up the end of the cylinder. It did show that the cylinder needs about a 20 degree overall tapered lead-in to compress the rings as the piston enters, but once in there it slides along nicely without any scraping or gouging. The hit and miss engine this is going back into doesn't have a lead machined into the cylinder, so it might get interesting. I am not going to disassemble the engine to machine a tapered lead into the cylinder, so I will have to create some kind of ring compressor to get the piston back into the engine.--Maybe a hose clamp?
(https://imagizer.imageshack.com/img922/2286/iAsWaT.jpg)
-
I have used a zip/cable tie in the past: used pliers to wind up the tension.
-
The piston and rings went back into place with flat screwdrivers, fingernails, and prayer. Everything is back together and hooked up. I'm getting pops and farts but no continued action. Considering that the new rings do have to "wear in" a bit for a really good seal, I may move my operations out to the main garage and hook it up belt driven by my electric motor.---I'll leave the sparkplug electrics turned on, and if I've lived right it should begin to fire after its ran in for a while.
-
No Joy. Everything is hooked up and is currently being driven from a a 1/4 hp electric motor out in my main garage. Ignition is on and there is fuel in the tank. No puffs of smoke, no backfires--nothing. I pulled the sparkplug out and had a look at it, and it fires when laying out on the block at the correct time in the cycle. I even tried a squirt of "quick start" ether, but nothing happened. I'm going to let it run out there for an hour, and if it doesn't do something interesting I will put the old piston with the viton ring back in it to make sure it runs. That video link I posted is from about three years ago, the last time I had it running. I have discovered one thing related to cutting ring grooves and parting off rings. That little (1/16") wide parting off tool that I have isn't stable. It flexes when in the cut, so you can't trust what it is doing. Before I go any farther down this road, I will grind a 3/8" HSS tool to give me an exact .062" width. It makes me crazy when you know that a tool of a given width is cutting a different width than the width of the tool itself, on a plunge cut.
-
The key thing I found was the next stage when you clamp them again and skim the outside diameter otherwise they are not actually round. If you remove the piston I expect you will find the ring has limited contact with the cylinder (polished segments and dull segments).
-
Two pictures here----One shows the set-up in my garage trying to get the motor to fire with it's new piston and rings---didn't work!!---Don't know why yet. Second picture shows a tool ground by Philip Duclos to part rings off with or to cut ring grooves in a piston. Damn----that's a lot harder to do than it looks. I tried to more or less "free hand" such a tool, but it didn't come out nearly as nice as the Duclos tool. Tomorrow I will dummy up some guides on my grinder and try again to grind this tool from HSS.
(https://imagizer.imageshack.com/img922/456/e2rL6M.jpg)
(https://imagizer.imageshack.com/img923/457/58t5Au.jpg)
-
The key thing I found was the next stage when you clamp them again and skim the outside diameter otherwise they are not actually round. If you remove the piston I expect you will find the ring has limited contact with the cylinder (polished segments and dull segments).
I have never had to re cut OD after heat treat. I have had a few rings that failed due to my failing the heat treat operation but if done right they should be round and fit correctly.
-
All of the rings have been individually placed into the cylinder and the end gap set to 0.004". Is it too stiff?--Well, it feels a lot stiffer to turn the engine than it did with one viton o-ring. Is it sealing? It is very hard to tell, but I don't think it is. My next move here is to put the old piston and viton o-ring back in and make damned sure the engine will run that way. As I said in an earlier post, the last time that engine ran was about three years ago when I made the video. Is it firing?--yes, but very intermittently.
-
That was settled quickly. New piston and rings out, old piston with Viton ring in---and engine runs lovely. Engine is MUCH easier to turn over by hand with old piston and o-ring. The rings aren't round. They have shiny wear spots in some areas and seemingly "untouched spots" in other areas. George Britnell questioned the fixture I made to expand these rings when heat treating them, and it appears he was right. The new piston I made seems fine. Onward and upward---try a different way of making some new rings.
-
I am going to try my next ring and piston combination on this engine, just because the piston is easier to get at and the cylinder is easy to remove. Also, this engine runs a bit faster and I don't have any hit and miss mechanism to think about.
https://www.youtube.com/watch?v=EGYhhk8S54A
-
Time for Ringmaking-Take2. I am now going to make 4 more rings using the Trimble? method. I do have a 0.020" slitting saw. So---the rings will be turned to (3.142+.020)-3.142=1.006" o.d. and 0.898" inner diameter. This will give an inner diameter the same as rings I have purchased form Debolt. They will be cut to 0.063" thick. Instead of being broken, these rings will be cut using my 0.020" slitting saw. No farther work on cleaning up the i.d. nor the o.d. nor the thickness, until I have spread them individually over a 3/16" piece of steel inserted into the sawn gap and heat treated them to cherry red and then allowed them to air cool. Then they will be polished to 0.062" wide and cleaned on a sheet of emery paper on a flat surface, then positioned in the cylinder bore and if needed the gap will be filed to give a 0.004" wide gap.
-
So here we are---Just like Deja-vu all over again. These rings are identical to the first rings I made, except the o.d. is 1.006" and they are saw cut with a 0.020" slitting saw instead of being broken by hand. Heat treat comes next.
(https://imagizer.imageshack.com/img922/7714/vWQcP5.jpg)
-
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. The rings heated up very quickly and dropped off the fixtures, and have taken on that 0.125" distance between the ring ends. I have cleaned up the i.d. and the o.d. and dressed the sides with emery paper laid on a flat surface. The only observation I made is that it certainly didn't take much heat to get that sawn 0.020" gap to open up to 0.125". Tomorrow I will pick the best two rings and put them on the new piston and try this experiment again.
(https://imagizer.imageshack.com/img923/8500/PQN0GQ.jpg)
(https://imagizer.imageshack.com/img923/8985/HnPKFk.jpg)
-
And to close out the day---When these rings were pushed squarely into the cylinder, they had a 0.004" gap, without me having to do any filing on them.---Amazing!!! Then with much breath holding, butt clenching, and #30 lubricating oil, the rings were installed on the piston. They were much harder to get on the piston than the previous set I had made. I was sure I was going to break them, but they did slide on, very reluctantly, and snuggled down into the ring grooves on the piston. The next question was "Will the piston fit into a 1" bore with these new rings on it?" I have a round piece of cast iron with a 1" reamed hole through it, and a 20 degree tapered lead to help compress the rings while the piston is persuaded to fit into it. It did fit. Not easily, but it did. Tomorrow I am going to put this new piston and rings into my Rupnow Vertical Engine and hope it will run. I did start it today, as can be seen in the video, so with nothing changed except the piston and rings I am off to bed. Wish me luck for tomorrow!!!---Brian
-
We're rooting for you!
:popcorn: :popcorn: :popcorn:
-
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
-
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
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
So rules of thumb only work if you have a standard size thumb? :shrug:
-
Chris---So far this has been a fruitless enterprise. Not sure if I will eventually do this successfully, but I'm learning things.---Brian
-
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
-
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.
https://www.youtube.com/watch?v=JWzBmkCDU3c
-
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.
(https://imagizer.imageshack.com/img924/9625/NhhfAL.jpg)
-
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
-
Hi George---I'm making this set exactly to Philip Duclos's book, "The shop Wisdom of Philip Duclos". The only real difference between this set of rings and the last set is that these rings are only 0.050" thick and are spread on 0.150" pins, ready for heat treat.
(https://imagizer.imageshack.com/img922/5357/xf6bH4.jpg)
-
This is the third batch of rings immediately after heat treat. I bought a new cylinder of propane, and there is a huge difference in the heat from a propane torch and that of an oxy acetylene rig. It took longer to heat each ring to a cherry red and it gave me a chance to heat the rings more uniformly before they dropped off the 0.150" diameter spreaders they were mounted to. Next step will be to deburr the inside and outside and bring the sides down to a uniform 0.050" thick.
(https://imagizer.imageshack.com/img924/226/4evedJ.jpg)
-
No real progress today. I'm all worked out!!
-
I'm six days in on what was supposed to be a fairly simple project. So far, I have not been successful. I am getting lots of advice from people who have plainly never made piston rings, and though I know they wish to help, it only confuses things. I have tried the Philip Duclos method of ring making, and people have immediately jumped in and told me that is a terrible way to make rings, and they will end up crooked and it's no wonder they don't work. It worked for Philip, and he was sure enough of the method to include it as part of his book. His method for machining the ring outer diameter was #1--Calculate ring o.d. (Same as i.d. of cylinder.) #2 Since he cut the rings with a 0.020" slitting saw he multiplied the diameter x pi to get circumference, then added the slitting saw thickness to the resultant circumference and then divide the answer by Pi to achieve his final ring diameter (which in my case turned out to be 1.006")I don't have a heat treat furnace, and don't plan on buying a heat treat furnace. I did find out that the flame from an oxy acetylene flame was far too hot, so I went and bought a bottle of propane and it worked much better with a cooler flame. I have looked at simple fixtures which the rings are mounted on and then held flat by means of a big flat washer bolted to the fixture to squeeze the rings flat during heat treat. I'm not sure if the fixture should be the same diameter as the i.d of the rings before they are cut, after they are cut, or after they have been stretched over a spigot to spread the gap. Some people advocate turning the o.d. of a stack of rings held in a fixture (after heat treat) to ensure they are perfectly round on the o.d. This sounds like it would be the answer, but the rings are definitely not round on the i.d. at this point after being split and heat treated.
-
I for one applaud your approach of researching what can be found in the "prior art", applying your own logic and experience to devise a method within the constraints of available tools and materials, and documenting the results, good or bad. In the end I think you will be successful, and we all stand to benefit from your work.
-
The key to the Prof Chaddock skimming fixture is a setting ring ~2 thou oversize. The clamping fixture has a guide section that it a good fit in this and then the clamping section is 2 thou under size. This ensures that the rings are aligned on their OD, not a possibly distorted ID.
As ever I never have exactly the pictures I want, but this is making the rings for my horizontal engine after heat treating the same way that you did.
-
And this is making the rings for the diesel which has a compression pressure of around 400psi. Both have nominal 1"/25mm bore.
-
RogerB---I may have to resort to that method where the outer diameter of the ring is skimmed to make it perfectly round. I am not having any success here, and I've basically tried everything I have read about and still can't get any compression. Did you do that skimming of the o.d. with a cutting tool or with a surface grinder?---Brian
-
The surface was skimmed with a turning tool. Unfortunately I can't say exactly what but probably a DCMT070204 insert. As I don't have any means of accurately measuring bores I make a plug gauge for the cylinder and then use it with a micrometre to set the sizing fixture diameters. The sizing ring is checked with the plug gauge and a feeler gauge.
-
Roger--Can you walk me thru this? My cylinder has a bore of 1"---25.4mm. My piston has an o.d. of 0.998"---25.35 mm. What outside diameter and inside diameter should my ring blanks be turned to? Did you break your rings in a vice by hand, or did you use a slitting saw? Did you gang a number of rings onto a fixture with a wedge holding them open and then clamp them to heat treat and set the ring gap?---or---did you set the rings up individually on spreader pins and then heat them until they fell off, like I did? I have so much conflicting information right now that I am rather lost.----Brian
-
Brian, I have a file folder with I believe, seven articles, covering the making of piston rings that I would be happy to share with you if you are interested. Some of the articles have been written by many of the fellows that we all know, and many of them have been published in magazine articles so I am not comfortable in posting them up here but would email them to you if you like. They are all pretty good articles I believe, lest I would not have archived them.
BC1
Jim
-
Jim - is one of the articles on model ring making by Tom Schwartz by any chance? He describes a method of ring making that does not use heat treatment, which is different. I have heard good reports of this method but apparently it is a bit laborious as it requires making various mandrels and fixtures first. This did feature in a magazine at one time.
Chris
-
Bearcar1--If you could scan and email that info to me I would forever be in your debt. Ring making is the only thing that I haven't mastered in the twelve years I have been building model engines, and I really want to learn how.---Brian brupnow@rogers.com
-
Brian, I will put together the way I produce liners, pistons and rings and post it on here.
-
Say Chris, one of these articles does employ a no-heat process but I am not certain as to who the original article author was. :shrug: I just hope that Brian will be able to distill enough information from these articles so he can complete his quest successfully. :DrinkPint:
BC1
Jim
-
Following this thread with interest. Somewhat related question (not to making them though) - are cast iron piston rings appropriate for use on steam engine models too? Low pressures/speeeds, would they still seal well on steam vs the higher impulse pressures on IC engines?
ChrisR
-
Yes, they would seal on steam engines as well. I think that bronze would be used on steam engines because of the rust issues with cast iron rings.
-
Following this thread with interest. Somewhat related question (not to making them though) - are cast iron piston rings appropriate for use on steam engine models too?
Yes, you probably know that John Ramsbottom developed the split piston ring back in the late 1800s for steam engines and they immediately replaced hemp packing that was used to seal the pistons in existing engines (where possible) because of the improvement in power, efficiency and maintenance they provided. However in smaller sized models they can be a bit easy to break :facepalm2:
Anything over about 19mm diameter is ever so easy to make but for the smaller sizes its best to make some spares as they tend to break going over the piston ::) And it was standard to fit two rings in the same piston groove with their gaps on opposite sides of the piston in steam engines.
Jo
-
Thanks Jo/Brian!
-
I suggest the following method, without heat treatment, which I use regularly for cast iron piston rings.
First, you have to find the right cast iron, centrifugaly cast iron, without the crust.
1) Cut rings in a tube of iron with for external dia the dia of the bore plus the elasticity gap on the circumference and a small margin for turning.
I take 3.5 mm for this gap for a 25 mm dia and 2.5 mm for a 20 mm dia. piston.
This makes the outside diameter of the iron tube for a 20mm ring ((20 x 3.14)+2.5)/3.14 = 20.8 mm; or 21.3 with the margin for final turning.
The thickness of the ring is 1 mm in these diameters, with a clearance of 0.2 mm at the bottom of the groove; the inside dia of the tube for a 20mm piston ring is therefore ((17.6 x 3.14)+2.5)/3.14 = 18.4
Rings of the height of the piston groove (1 to 1.25 mm) are carefully cut with a thin, sharp tool, carefully deburring the exposed faces, so that only the side of the cut is left to be cleaned on a fine abrasive paper.
2) The 3.5 mm (or 2.5 mm) cut is removed from the circumference with a jeweller saw; this cut can be angled, if you wish; this is a delicate job to do as it will give the final inner dia.
By closing the ring completely with a thin brass wire around the ring and twisted, (a more convenient set-up to close the ring could be made !), the inside dia should then be the final internal dia of the ring, and this closed ring should fit on a mandrel turned at this diameter.
(The ring groove on the piston of course is at this diameter, minus a 0.2 mm clearance.)
3) This mandrel has a screwed washer in front of it to clamp one or a few rings and keep them closed on removing the brass wire; the exact external dia of the ring required is then finished and polished on the lathe.
On dismantling the ring from the mandrel, the ring is ready to fit the piston after removing sharp edges with a Norton stone, which is sufficient to give a final gap on the closed ring.
and it's over.
The elasticity of the rings obtained in this way is good; the compression after running in is top notch.
-
Thank you Zephyrin.---Time for an update on what is happening with this. I don't have any problem with machining the rings to size on o.d., i.d. nor width. The width is easier than you would think, because cast iron machines very easy and is very easy to cut down in width on a piece of emery paper on a cast iron surface plate. Solution there is to make sure and cut the rings a few thou "over-width". Cutting the ring grooves in the cast iron piston is easy, but you have to really pay attention to the width of the groove you cut. This is one of those weird times when "what you see" isn't necessarily "What you get". I don't know why, but a 0.062" parting off tool gives me a 0.055" wide slot on a straight in plunge cut. You need to have the ring in your hand and keep trying it for fit in the groove you are cutting. Recommended groove width is 0.001" wider than the ring, with square sides, no taper. The groove should be .003" to 0.004" deeper than the radial width of the ring. When pushed down into place in the groove, the groove has to be deep enough for the ring to set below the outer surface of the piston groove.------------I don't have any problem breaking the ring on one side by putting the ring partially into the vice and pressing sideways on the ring with my fingers.------I don't have any problem cutting the ring with an 0.020" slitting saw like Philip Duclos recommends. Heat treating the ring and doing the same heat treat to all of the rings with a "gag" piece holding the ring open doesn't seem to be a problem, except that you can't really use an oxy aceytlene torch.--Too hot. Too fast!!!! Flame from a propane torch seems to do a much better job.----I don't have a problem setting the heat treated ring into the cylinder squarely and checking the gap, and no problem filing the gap with an ignition points file until it reaches 0.004" wide.-------------Fitting the ring over the piston and down into the groove isn't as much of a problem as you would think---just use lots of #30 lubricating oil and a bit of thumb pressure and patience.--------It's not a problem to hold the cylinder up to a bright light and check that no light is coming past the sides of the ring (Which means that that ring is bad and won't seal.)-----The problem comes when after all of these things are looked after properly, the rings are not sealing in compression. My belief, and that of many people reading this post, is that the outer diameter of the ring is not perfectly circular, and as a consequence is not tightly contacting the wall of the cylinder. Chadock (A ring guru) agrees with me/us. So---What to do? The only thing left to do is to assemble all of the rings on a fixture, align all of the rings with a slide on fixture that aligns the outside diameter, and then clamp them, remove the slide on alignment tool, and then take a cutting pass on the outside diameter of the rings to ensure that they are perfectly round. The outer diameter of the ring does not have to be completely concentric with the inner diameter. This cutting pass can be made by either a very sharp tool or by a toolpost grinder, or by lapping.----and should be less than 0.001" deep.
-----The problem after doing all of this is that the rings aren't se
-
Ok here’s how I make my liners, pistons and rings. This description is for a nominal 25mm bore and the pictures are from two different builds.
The liner is bored to around 0.1mm under nominal size. I only have a dial calliper to measure with so I can’t be more precise. Take care at this point that the clamping pressure from a chuck etc. doesn’t force the bore out of round :( Next the bore is lapped using an Acro barrel lap and 40 micron diamond paste at 250 rpm. When I feel even contact all along the bore and the machining marks have gone it is cleaned in the ultrasonic bath with an industrial detergent.
I then make a close fitting plug gauge to fit the bore. (You can do this the other way round, make the plug gauge first and lap the bore until the plug gauge fits which is probably better for a multi cylinder engine).
The piston can then be finished to size, what size? For a cast iron piston in a cast iron liner probably 0.05mm (2 thou) under the size of the plug gauge, for an aluminium piston 0.1mm (4 thou) undersize but this can be alloy dependant. It is better to have too little clearance as if the piston starts to pick up when running you can always polish a little off the diameter. The ring grooves are then cut with a 1.5mm blade type parting tool (because that’s what I have) The depth is not critical so long as it is more than the thickness of the ring but not so deep as to part the top off the piston (done that :toilet_claw: ). The surface finish on the lower face where the ring seals against the piston is important.
On to the rings. These are bored to give a thickness of around 1.5mm, I don’t think that it is that critical, and the inside of the bore is polished to reduce the chance of breaking when fitting (either abrasive paper wrapped round a wooden dowel or a round abrasive stone (never a finger!!!! :o )). The outside is then finished to the size of the plug gauge as the rings will grow when heat treated. The rings are then parted off to a nominal 1.5mm with the same parting tool as before, deburring as much as possible on the way. I split the rings with a pair of piano (music) wire rated side cutters.
The mandrel of the heat treatment fixture is turned half a ring shorter than the number of rings I want to treat. I could do some clever sums to determine the diameter of the mandrel but I just turn it down until the ring blank fits with a gap of around 3mm (1/8”). The fixture is then clamped up and heated to a moderate red heat with a Camping Gaz plumbers type blow lamp and then allowed to cool.
Next up I make the sizing ring for the skimming fixture. This is bored so that the plug gauge and a 2 thou feeler gauge are a close fit. It needs to be wide enough to cover the planned number of rings and the land on the fixture. The skimming fixture is an offcut of mild steel bar bigger than the finished size of the rings and long enough for the planned amount of rings. I wouldn’t recommend trying more than four at once. It is first turned down to a close fit in the sizing ring and then the front part is turned approx. 0.1 mm (4 thou) smaller. This is checked with the sizing ring and a 4 thou feeler gauge. It is then drilled and tapped for the clamping screw ( 6mm or ¼” is what I have used). The first 6mm or ¼” is then parted off and drilled clearance for the clamping screw.
-
Part 2
The rings are then carefully deburred and the gap is set to 6 thou in the sizing ring. The required number of rings are loaded into the sizing ring and the ring is slid onto the fixture. The clamping plate is then screwed in place and the sizing ring is slid off. If you have a DRO you can probably set the cut directly but I tend to touch the tool on the sizing land and then go in 0.2mm and skim the rings. I then polish the rings with abrasive cloth and check that they fit in the liner. Finally I polish the faces of the rings, checking that they fit in the grooves with some clearance, what is some? At this size I have around 0.1mm (4 thou) clearance. Again I don’t think it is that critical. The important point is the finish of the sealing surface between the ring and the piston.
The final step is to put it all together and start the engine. I spent months trying to get my 3cc vertical engine running, it did run with an O ring but it wasn’t until I developed the procedure above it would run with a cast iron ring. The subsequent engines have all started first time, set the timing 10-20° BTDC, crank it with a drill and open the needle valve until it starts. Running will probably be poor until the carb and timing are fine-tuned but it runs.
I hope this helps but as ever please ask for clarification. The piston ring is not stand alone it is part of a system.
-
Hi Brian,
on the setup described on my previous post, the rings are held fully closed on a mandrel for the final turning, which obviously is truly circular, the crucial point for rings as you mention it.
And if the ring is too large you have the possibility to remount it on the mandrel to remove a fraction of an hair, if the mandrel is still in the lathe chuck !
nb : the mandrel I describe is a crude version of the turning setup shown on the Roger's tutorial...
you may notice on the rings on the picture I show that inner and outer dia are not concentric : a very slight eccentricity of the mandrel (+0.1 mm under the cut), allows to reduce the thickness at this place and to distribute the compression of the ring on the cylinder wall more evenly on the whole perimeter, I m not sure of the effectiveness of this refinement, but I simply saw that the rings of the old Micron 10cm3 engines were like that !
-
Thank you, Roger and Zephyrin.----Brian
-
My no heat method of making piston rings has been covered in my numerous past projects. My first rings were made for my live steam locomotive. Cast iron rings in a cast iron cylinder. The engine has been running for over 20 years without problems. I used my method on my current Otto Langen project, and as you can see in the video I just posted in that project thread, they seal quite well.
-
There is no joy in Mudville today. I put a new piston and two rings I had purchased from Debolt in the newest vertical i.c. engine-2021 and had no compression. I squirted some oil down the sparkplug hole and had lots of compression. The new rings are not sealing. I drove the engine for 2 hours with an electric motor, hoping that the rings would "bed in" and seal, but it's not happening.----So---I have one trick left. That is to build a fixture as per Mr. Chaddock, and turn the o.d. of the rings to be perfectly cylindrical. That is exactly why I bought the toolpost grinder. I doubt my ability to take a 0.0005" depth of cut with a lathe tool, but with the grinder it may be possible.
-
Here we have Mr. Chaddocks fixture for turning the outer diameter of piston rings to make them truly round. The sleeve in my hand has an internal bore of 1.00". The rings are sprung into the sleeve, the sleeve with rings in it slides over the part held in the chuck, then the washer on the very end is tightened down with the bolt, which squeezes all of the rings together. The o.d. of the 1/4" thick washer is slightly smaller than 1", so after the bolt is snugged up tight, the sleeve is slid off over the washer, leaving the rings ready to be turned or ground to a perfect diameter. I am going to use my toolpost grinder to do that.
(https://imagizer.imageshack.com/img924/9332/FOb6Rv.jpg)
(https://imagizer.imageshack.com/img924/7931/NsxxQs.jpg)
(https://imagizer.imageshack.com/img924/5914/rn7bxU.jpg)
-
I'm not absolutely sure of what I'm doing here, but that has never stopped me before. I wanted to have a good "visual" on the rings to know when I had reached a point of perfect roundness, so I coated everything with blue layout dye before I went to bed last night. This morning I mounted my toolpost grinder and taking .002" depth of cut, I made repeated passes over the rings until all the blue was gone. At this point, knowing my rings are perfectly round, I will dismount them from the grinding jig and try them into a cylinder.
(https://imagizer.imageshack.com/img923/3889/7g8yhd.jpg)
(https://imagizer.imageshack.com/img923/8664/kVbYN7.jpg)
-
Brian - may I respectfully suggest covering the lathe bed before using your grinder, all that grit that will come out the grinding process will not be good for it!!
Chris
-
I didn't "true the wheel" with a diamond dresser. I did buy a diamond dresser to true the wheel, but didn't use it this time. (I still have to cobble something up to hold the diamond dresser while I do that, just haven't got that far yet.) Keep in mind, I haven't done this before, and mostly I wanted to try it out for "process". The rings were extra rings that I had made, but they weren't that great. I don't expect to actually use these rings, but I had to try the new fixture and grinder out for "process". There are a couple of things I will change, but they mostly relate to the tooling. I find that when using my 3 jaw lathe chuck that if I take anything out of the chuck, it is almost impossible to put it back in the chuck and not have the outboard end wobbling. I am going to investigate using a tailstock support for the free end to make it run true, but I have to investigate and see if I have room to do that.
-
I have never been able to reuse a truing fixture in the 3 jaw chuck even by marking where the jaws were. Using the 4 jaw independent is better but for the price of a dog end of steel I just make a new mandrel each time. The sizing ring is always ok (unless you change the bore size :facepalm: )
-
A part of this goose-chase is going to be building an independent support for the diamond wheel dresser. I will have to build this as an independent stand alone item, because I have nothin else that will work to hold it.
(https://imagizer.imageshack.com/img922/7079/utRLsv.jpg)
-
Couldn't you make a clamp that attaches to the tailstock barrel ?
-
Brian, you seem to be going way beyond what anyone else has done :headscratch: If your rings don't seal I can only think that as I have said your bore isn't round or that the size isn't what you think it is. I don't have any internal measuring instruments other than a dial calliper (which is worst on internal dimensions ::) ) so I always make plug gauges.
-
Roger---I've been thinking about the reusability of a truing fixture. I just measured my lathe, and it's about 18" from the end of the chuck jaws back to the far end of the spindle tube. My spindle tube is 1.5" inside diameter. The truing fixture is only 1.125" at it's largest diameter. I think that if I made a bushing to keep the truing fixture centered at the back end of the spindle tube, and match marked it to one of the three chuck jaws, that it should be very repeatable every time I use it. I am trying to come up with a procedure and tooling that is reusable and will give me the same results every time I use it.
-
And there it is---My version of "Diamonds are forever". This stand holds the diamond for truing the grinders abrasive wheel. it doesn't look like much, but there's a days work in that thing. My bandsaw really, really doesn't like cutting 1 1/2" thick plate. It's so slow that I feel like I'm going to start growing moss while I wait for it to finish a cut. I still have to make the plate that goes across under the lathe ways and the piece of 1/2" all thread rod that comes up thru the vertical plate and gets a nut on it to hold everything stable. Those of you who are sharp of eye will see that the design changed a little bit from the model I posted yesterday.--Two 1/2" threaded rods are overkill.
(https://imagizer.imageshack.com/img924/3152/mbjH79.jpg)
-
Brian, I'm one of the many quiet ones on this forum following this and other build threads with lots of interest. I purchased your plans for this engine and have the crankcase and cylinder partially done at this time and looking forward to the day I fire it up.
Having a few years experience operating a cylindrical grinder in the past I would like to make a suggestion on the positioning of your diamond dresser. It's recommended that the dresser be tilted down (in the direction of wheel rotation) 10 to 15 degrees and periodically rotated 1/8 turn to maintain a sharp point. This practice creates facets so to speak. Positioning the dresser horizontally eventually dulls the diamond by creating a flat spot on the face of the diamond. For best results it is also important that the dresser contact the wheel at the point where the circumference of the work touches the circumference of the wheel, referred to as the work/wheel contact. Hope this information is useful to you.
Am looking forward to your success in this ring making process.
Rog
-
The diamond support tower is finished. It all goes together nicely and locks securely in place. Now I am getting posts that say the diamond support shaft should be tilted down 15 degrees. That is not a major problem, just a bit more work. Are we agreed that the diamond itself should still be on the same centerline as the grinder shaft?
(https://imagizer.imageshack.com/img922/8641/JyqSVH.jpg)
-
Are we agreed that the diamond itself should still be on the same centerline as the grinder shaft?
Yes, the optimum set-up would be the grinder shaft centerline, lathe spindle centerline and diamond should all be on the same plane.
Rog
-
One more time with feeling---This time the diamond support is set at an angle of 15 degrees with the center of the diamond on centerline of grinder spindle and chuck all in the horizontal plane. It isn't quite as pretty as the first time around, but form follows function.
(https://imagizer.imageshack.com/img922/7836/WRQv6d.jpg)
(https://imagizer.imageshack.com/img922/2782/0Z3noz.jpg)
-
I thought it was suposed to be tilted down 15 degrees - Brian yours look like it is tilted up 15 degrees!
-
It is tilted up 15 degrees. If it was tilted down, the wheel would pull the diamond out of it's holder. Ahhhh Jeez---Now I'm being told that the diamond tool should be 15 degrees opposite to what I made it.---that it should be angled down at the front where it contacts the wheel.
-
referring to my grinding book mc phersons they where an austrailan manufactor and agent of machine tools
years ago when things wear made hear it says it is good practice set the diamond at or just below centre at an angle of about 15 degrees the drawing shows it angled downwards at 10 to 15 degrees. the diamond should be rotated after every few dressings which has the effect of keeping the diamond sharp. the company has long gone
but i have had the book from when i was an apprentice .i know that work after mar than 50 years in machine shops . John
-
Third times a charm!!!--We're setting at 10 degrees angle and diamond is at or just below spindle centerline. And the moral to this story is Research-Research-Research. I spent two minutes on Google and found all kinds of information about what I am doing here, even drawings. Luckily, I didn't have to make any new fixtures---Just relocated the hole for the shaft which holds the diamond. Anything from 5 degrees to 15 degrees is suitable, so I'm good with this. Arrrrggghhh!!--Let that be a lesson to me.
(https://imagizer.imageshack.com/img924/3818/UiT7fo.jpg)
(https://imagizer.imageshack.com/img922/5865/2TuthP.jpg)
-
There seems to be some confusion on whether the diamond dresser should be angled up or down. That is dependent on the rotating direction of the grinding wheel. The work and grinding wheel need to counterrotate at their point of contact. If the wheel is rotating downward at that point then the diamond needs to angle down. If the wheel is rotating upward then the diamond is angled up. Hope this explains things more clearly.
Rog
-
I have purchased two sets of rings in the past. One set was for a 1" bore engine, and one set was for a 1.25" bore engine. They both worked "right out of the box" with good compression and both engines ran fine. The third set of rings I purchased for my current vertical i.c.-2021 engine didn't work---. Absolutely no compression in an engine that ran just fine with a Viton elastomeric ring. I don't do compression tests other than "can I feel it when turning the engine by hand". I don't do leak down tests. The only other tool I have at my disposal is a fitting that screws into the sparkplug hole and lets me put air pressure into the cylinder with the piston at top dead center on the power stroke. That lets me diagnose the intake valve, the exhaust valve, and the rings. In all of the forty engines I have built, the rings are the only thing that I have not mastered. I've spent about a thousand dollars in the last three weeks, buying equipment to let me know that my "process" in ring making doesn't have some flaw. I keep hearing from others who make rings and have no trouble with them, and I certainly hope that I will come up with a repeatable process for making 1" diameter rings that hold compression.---Brian
-
It's time to pursue cast iron rings that seal properly again. I've just dropped about $1100 on a toolpost grinder and a heat treat oven and controller, and have them set up to work the way they are supposed to. They were bought solely for the consistency they would give to my ring making process. People on all three forums on which I post have suggested that my cylinders might not be perfectly round.--this would be one good reason that a flexible Viton o-ring will seal perfectly but cast iron rings will not.---I don't really believe that, but there is always a chance that I am wrong. All of my cylinders are made by drilling, then reaming, then honing to remove machining marks. Sometimes I lap them with brass laps, sometimes I don't. Since I still have the two rings I bought from Debolt, (Which I assume to be correct) mounted on a piston especially made for them, I guess my next trick will be to make a new cylinder and bore it to 0.005" undersize (not ream) and then lap it with one of my Acrolaps to a perfect 1" diameter, and see if the Debolt rings and dedicated piston will give a good seal in it.
-
Being one of the ones who is concerned that your bores may not be round I question how your cylinders are held when finishing. Hand held and using an Acrolap will ensure round. Held in a 3 jaw chuck and reamed then honed = not round.
-
Brian
Just because you purchased the rings doesn't automatically make them good. Nothing against Debolt they are great folks and have nice products; I hope that you find their rings ok, but I have seen store bought model engine rings that were completely unusable do to being out of round. These were purchased by a friend, and I don't recall where he purchased them. I discovered this when helping him get his engine running, I made him a new pair using the Trimble method.
Dave
-
Tomorrow I get to play detective.---if I do any work. The weather here today was just magnificent, 84 F and sunny. I spent the day mowing lawns, trimming lawns, and helping good wife put bands of adhesive around all of our deciduous trees. We are infested by Gypsy Moth caterpillars this spring, and if they can climb the trees they eat off all the leaves and can kill them. The caterpillars are very small, about 1/16" long and they spin webs. Nasty!!! I will pull the cylinder off the Vertical 2021 engine and check the cylinder bore for roundness using "snap" gauges that are spring loaded---they expand inside the bore, get locked in place, and then are taken out and measured with a micrometer. This will tell me if there is any "out of round" condition in the cylinder. I will visually check the cylinder bore to see if anything weird is going on inside the bore. Then I will visually inspect the rings to see if there are any noticeable difference in "wear patterns" on the surface of the rings. I know that the ring grooves in my piston are cut deep enough---if they weren't the piston with rings on it wouldn't fit into the cylinder. I know that the rings aren't sealing because with a couple of squirts of oil down the sparkplug hole there is lots of compression---without the oil, there is none. If I don't see anything wrong, I will make a second cylinder and see how the piston seals in it.
-
Brian,
Roger's suggestion of an Acro lap is a good one. When I built the Val I made an aluminum part with the fins and pressed in the cast iron liner. If I recall it was left .002 under. I used an Acro lap https://www.travers.com/barrel-lap/p/53-063-038/ (https://www.travers.com/barrel-lap/p/53-063-038/) this one matter of fact. It probably was smooth enough for an O ring but I used a difficult process of milling the rings to the desired height. Then polished them on 600 grit wet dry sandpaper. Ran well as you saw.
Art
-
Art---For the record---I have a complete set of Acrolaps. I use them on pistons which have no rings, where the piston itself must be air-tight in the cylinder.
-
Well Sir, Well Sir--I just got a surprise----It might even be a good surprise. I have the two rings I purchased from Debolt installed on a new piston made especially to suit these rings in my Vertical 2021 engine. I couldn't get it to fire. I drove it with an electric motor for 1 1/2 hours hoping to seat the rings. Nothing worked. It had absolutely no compression. I've been busy buying and setting up a heat treat oven and a toolpost grinder, and just today got back to this compressionless engine. I unbolted it from the test bench in my garage, brought it into my office to do some detective work, and as soon as I removed the cylinder head it became apparent that the head gasket was broken and a piece of it was missing. HUH!!! I put my big fat thumb over the top of the cylinder and turned the engine over by hand, and their is lots of compression and suction. so---First order of things is to make a new head gasket, reassemble the engine, and try to start it again.
-
Nothing is as simple as it seems. The only reason the piston was pushing or sucking on my thumb was because of the oil I had squirted down the sparkplug hole on an earlier test. So, the rings aren't sealing after all. I made a new head gasket, but that's not really where the problem lies. I have pulled the cylinder off and measured it with telescoping gauges and a micrometer, and the top bore taken two places at 90 degrees measures 1.003" and one at 1.004". The bottom measurement taken at two places at 90 degrees apart is the same. I am going to stick my neck out and say that a difference of 0.001" means that the cylinder has not "worn oval shaped". the inside of the cylinder looks fine when held up to a light. After I eat some lunch, I will pull the piston off the con rod and see what wear patterns are on the rings.
-
I'm not sure that it shows up in this picture or not, but there is a very uneven wear pattern on the Debolt piston rings. Some areas are shiny and you can tell they have been in contact with the cylinder wall. Other parts of the ring are still grey/black and you can tell they have not been making contact with the cylinder at all. Now I have to use my secret weapon. None of you have seen this at all, but this piece of tooling was first brought up by Ted Hansen in a 2018 copy of the home Shop Machinist. Its use is to bring the outer diameter of a ring into perfect roundness.
(https://imagizer.imageshack.com/img924/6566/yngYY8.jpg)
(https://imagizer.imageshack.com/img924/7143/BCEkHn.jpg)
(https://imagizer.imageshack.com/img922/4995/SZQXKP.jpg)
-
This is the fun of a Trilobal bore. The diameter is always the same but you can't fit a plug gauge of the same size. Turn a simple plug gauge that will just fit the bore and then compare the measurements to your telescoping gauge.
-
This is the first ring after 20 full "strokes" of the fixture using 400 grit compound with the lathe turning at 60 rpm and 20 full strokes with the lathe running a 60 rpm with 600 grit paste. All of the wear surfaces on the o.d. of the ring have taken on a uniform color and wear appearance.
(https://imagizer.imageshack.com/img924/3774/mzj7Dc.jpg)
-
I must admit to being totally flummoxed. Lapping the o.d. of the rings with my newly made tool has given a beautiful finish to the outside diameter of the rings. They STILL don't seal in the cylinder. The i.d. of the cylinder looks perfect. The rings look perfect. The piston was made deliberately 0.002" smaller in diameter than the nominal 1.000" cylinder bore. The cylinder actually mikes at 1.003" to 1.004" inside diameter. In a worst case scenario, the piston may be 0.005" smaller than the cylinder bore. I could deliberately make a new piston that was lapped into the bore and needed no rings at all, but this entire exercise is about successfully making rings. I truly am at the point where I don't know what to do next.----Brian
-
This UK 20p coin has a constant diameter if you measure with a micrometre, but if your bore was like this there is no chance of a seal. It's an extreme example but hopefully illustrates the point.
-
Hello Brian,
There has been much discussion on this subject for decades and some years ago I found myself researching the subject in some depth. Here a few things I feel are important in making good rings.
The thickness (height) of those rings you have there looks quite large. Various builders experimented here and found better results in reducing this.
Myself , I had excellent sealing right away for 1" bore Westbury Kiwi with 0.022" ring thickness, as opposed to the 0.040" specified in E.T.Westbury's drawings. I made these using Trimble's method in SIC 7/8/9 (except for heat treat temperature).
Bruce Satra (SIC No25) writes that he experimented with rings down to 0.015" thickness with much, much better compression.
With regard to heat treatment, Trimble stated an incorrect temperature (above the critical 720'C). In his publication "An Essay on Piston Rings" (free online) T.D.Walshaw suggested 590'C is the maximum as otherwise "undesirable changes in the material will take place" (Young's modulus reduced). In the same document Walshaw stated that Trimble's heat treatment fixture "does not and cannot create exactly the right shape" and therefore post heat treat trueing of just 0.001" was essential. - I see you already have a solution for this above.
Assume you have been able to source good quality, close grained, centrifugally spun Grey Iron and not S.G. Iron?
With the cylinder bore, I found it impossible to see what was going on here using a bore gauge with the standard 0.001" dial indicator. With this swapped out for an indicator reading in 0.0001" the difference is staggering and you can see exactly what your hone / lap is doing in terms of removing ovality and taper. It amazed me that even a toolroom lathe was not producing a truly circular bore. Until I switched indicators I had assumed all was spot on!
I'm certain if you persevere you'll find the solution to making excellent rings and I look forward to your updates here!
-
nj111--I thought that a ring .062" wide as purchased was too wide. Everything I have read about it (And I have read a lot) suggests making the ring 1/30 to 1/25 of the bore size. With a 1" diameter bore, that comes out to a ring 0.033" wide to 0.040" wide. My reading material also suggests that a ring which is square in cross-section is proportionally correct. I purchased these rings from Debolt and then machined a piston to match the rings, with a ring gap 0.063" wide x 0.055" deep. (The rings are 0.051" thick). I paid $50 for two rings, so I haven't been rushing to throw them away, but I think I've just about ran out of things to do to make them work. I'm more or less "lost in space" now. I could make another cylinder with an exact 1.000" bore and see if that worked with the existing piston and rings. I could make new rings and a new piston to suit my cylinder "as is". I know I could make a new oversize piston and lap it into the existing cylinder and not use any rings, but the whole point of this exercise is to make my own cast iron rings with my own equipment.---Brian
-
As a comparison I'm just looking at a set of new Honda 50 rings, (39mm bore). The height of these is 62% of the radial thickness. (41 thou in height and 62 thou radially) - A similar ratio to what I have made with good success.
-
How does the gap at the ends of each ring work into it? What keeps the pressure from just flowing through there? I've seen some rings made with a tapered overlap, some just square ends. I know next to nothing of metal piston rings, just asking so I can understand better.
-
Rings with plain ends should have a gap of 0.004" between the ends on a 1" bore. As the ring heats up from running the engine, it will get longer. If the ends don't have that gap to expand into, they butt heads with each other and then bulge out and score the cylinder wall.---Brian
-
Thanks Brian!
-
Crueby---As to compression flowing thru the gap in the ring---that 0.004" gap is there only when the engine is cold. As the engine heats up to operating temperature that gap will close to about 0.0015" to 0.002". Events in a four cycle i.c. engine happen very quickly. An i.c. engine idles at about 1000 rpm. That works out to roughly 17 rotations per second. The engine only comes up on compression stroke every other rotation, so it "fires" 8 1/2 times per second at idle. The compression simply doesn't have enough time to leak thru the gap in the rings (at least not enough to affect the running of the engine). That is one of the reasons that a cold engine is harder to start than a warmed up engine.
-
Today I will try a new trick. Conventional wisdom says that a cast iron piston should be 0.002" less than the cylinder bore. Conventional wisdom also says that the piston rings will take care of sealing that .002" diameter difference between the piston and cylinder. I am going to work from the assumption that my new piston, grooved for my purchased rings is perfect. I am going to assume that my purchased rings are perfect. I will make a new cast iron cylinder with a bored hole of 0.996" then use the new 0.998" diameter piston (with the rings removed) to lap the hole in the cylinder to as perfect an air-tight fit as I can get. Then I will put the rings back on the cylinder and fly with that. That is what I did on my vertical hit and miss engine, and it has wicked compression.
-
On two previous engines I have used purchased cast iron rings. They both performed very well. I am at a loss why this engine has no compression when dry, and by dry I mean no pool of oil setting on top of the piston. I have just looked in detail at both previous engines where the purchased rings worked fine, and in both cases I see that I lapped the cylinder with the piston which was to be used in the engine, then added the rings to the piston afterwards. On this current engine where I am having so much difficulty, the piston was deliberately machined to 0.002" less than the cylinder bore. On my engine "Thumper" I made a note to myself saying that even though I had used the piston to lap the final cylinder bore, it wasn't a tight enough fit to run without the rings. There is a lesson for me there. Even though I have read in numerous places that the piston should be 0.002" smaller than the cylinder bore, that doesn't work for me. I just paid $32 for another piece of cast iron 2 1/2" diameter x 4" long to make a new cylinder. I will bore it to almost final size, then use my new piston to lap the bore to final size.
-
Why not lap it with an Acrolap?
-
I could lap it with an Acrolap--I'm just not sure of an acrolap giving me the exact match for the piston diameter. I am a master of machining a little bit , and then a little bit, and then "Oh $hit--I machined too much off"
-
Brian,
The beauty of the lap is that you can bore it a couple .001 under hone it to size then turn the piston to fit.
Art
-
Brian,
Make sure the chuck is NOT squeezing the new cylinder out of round while you hone or lap it to the finished size. The finished cylinder must be perfectly round with no taper, otherwise the iron rings will never seal.
Good luck
Mike
-
So here we have it---Old cylinder in background, new cylinder, and piston acting as a final lap. Bore was brought to "almost" with Acrolap and 600 grit paste, then final bit was done with 600 grit paste and using the piston as a lap. For first stage of lapping, acrolap was held in lathe chuck and cylinder was held in my hand. For second stage of lapping cylinder was held in lathe chuck, and T handle of piston was held in my hand. This can be very, very "grabby"--You have to know when to let go of the handle. Twice it grabbed so bad that I had to let go and shut the lathe off and take piston and cylinder out to my arbor press and use a short length of wooden dowel to press the stuck piston out of the cylinder. Definitely not for the faint of heart!!!
(https://imagizer.imageshack.com/img923/8063/iMdb4W.jpg)
-
Hi Brian, if the piston is lapped to such a close fit, is the ring still needed? Will the piston be a good enough seal as is?
-
Good question!!
-
Chris---Best answer---I don't know. I am still dabbling in something that I don't fully understand. This ring making business is one of those things where I know all (or most of) the theory, but am failing badly with the practical application of it. People with less technical background and less practical experience than me are making rings successfully, but somehow it eludes me. I'm sure that there are all kinds of model engine builders who are making their pistons .002" smaller than their cylinder bore and making perfectly acceptable rings to hold compression, but I'm not there yet. I don't want to start any more engine builds until the fall, and I had hoped that if I spent a bit of time on ring making this summer I would have it mastered by fall. Right at the moment, I'm not nearly so sure of that. I know that an aluminum piston must be .002" smaller than the cylinder bore, because aluminum has a higher expansion factor when heated than iron has, and will "seize" in the bore when the engine heats up if it doesn't have that clearance. I think that the people who have had success with ring making do leave .002" clearance on their cast iron pistons as well, but I'm not 100% sure of that.
-
The news is positive. With new cast iron cylinder, piston, and rings, the engine has high (to coin a new word) Suckability!!! It fired, it ran for three short blasts, but I'm having head gasket issues. The aluminum head has a ring of material that fits down into the top of the cylinder about 0.060". Or, let me rephrase that--It is supposed to extend down into the cylinder about 0.060" minus the 0.030" thickness of the head gasket. A close examination of the cylinder head shows that that ring of material is "hanging up" on the inside of the bore and not letting the head bolts tighten the cylinder down evenly all the way around. I'm going to set the cylinder head up on the lathe and trim a tiny bit off that diameter that is giving me problems.
-
I'm having a no work Sunday---I need it. But the old brain cells keep clicking away. Every thing I read about rings recommends that the ring thickness should be 1/30 to 1/25 of the cylinder bore (and the depth of the ring can match the width so your ring actually has a square cross section). On a 1" bore, that gives a ring width of 0.033" to 0.040". The width of the groove in the piston should be 0.001" greater than the width of the ring itself. So---If I made my rings 0.038" wide, then the groove in the piston should be 0.039"---And 1 millimeter is .0394". Okay, cool!!! Now, where do I buy a 1 mm wide grooving tool? I have googled this and still have no clear answer. I can turn a lathe tool for general purpose turning from HSS, but I don't trust myself to be able to make a 1 mm wide grooving tool. I don't want to spend a zillion bucks on this either. My lathe has a 12" swing, and it has a quick change toolpost on it. I prefer 3/8" square tooling, but in a pinch I can mount 1/2" square tooling. I'm not averse to using inserted carbide if the price for the carbide and the appropriate holder don't break the bank. Since the piston groove will be in cast iron or aluminum, I could even work with 1mm wide HSS and a 3/8" square shank.---Thanks.---Brian
-
I'm having a no work Sunday---I need it.
SNIP
Since the piston groove will be in cast iron or aluminum, I could even work with 1mm wide HSS and a 3/8" square shank.---Thanks.---Brian
Hi Brian. Carbide grooving tools get expensive in small sizes. I have found that a Dremel rotary tool fitted with resin discs cuts HSS relatively easily, removing much of the drudgery associated with grinding fine tooling. You need just a small stub tool, and rake and clearance angles aren't that critical for this job so it wouldn't take much effort to get a result. Have a go!
John
-
why not use a 1/32 parting tool and just step over to get the right width,or just grind down a 1/16 one undersize and do in 2 cuts ??
-
Time has come to cry FAIL!!!! I can not get the engine to fire, even with new piston, purchased new cast iron rings and new cast iron cylinder. Valve timing has been reset, ignition timing has been reset, carburetor has been adjusted to every possible configuration, and the engine doesn't fire. Compression feels cheesy when flywheel is turned by hand. If I squirt a bit of oil down the sparkplug hole, the engine has great compression and starts right up and runs like a trooper until the oil on top of the cylinder has burned away. Then it quits. This is purely the result of too low or no compression due to leaky piston rings and "fit" of piston in cylinder. I have monkeyed with this engine (which ran just great with a Viton o-ring) until I am sick of it. I have received a lot of interesting opinions on ring making, piston making, and state of the world in general from forum members and yes, I do read and pay heed to all of it, thank you. Later in the summer, when I have had time to digest all the new information and I'm not so burned out, I will use my new heat treat oven and toolpost grinder and make a new set of rings 0.038" wide and possibly another new piston with grooves to accept the new rings, I may try again. For now though, I'm whipped. Thank you to all of you who have followed this thread, and for the information given.----Brian
-
I hope you will come back to it in a few months, because I think you will get it. Good idea to take a break for a bit though.
-
Brian
You have spent a considerable amount of time working on the rings and cylinder bore, but have you taken a critical look at the condition of your ring grooves?
I have been thinking about this, and have not see anyone else mention it. The grooves of coarse need to be of proper size but the grooves also need to have a good finish, and the walls perpendicular to the axis of the piston. The bottom surface of the groove is as much of a seal as the interface between the ring and cylinder wall.
Have a look at the attached drawing and you can see what I'm talking about.
If your grooving tool is not dead sharp and square to the world your ring lands may be tapered and not sealing properly. This is a common problem in the old one lung antique engines where they have worn this way over the years. Guys will hone the cylinder and put new rings in the old grooves and then still have low compression. The common procedure to repair this is to re-cut the grooves to square them up and and add a ring spacer above the ring. Or to cut it large enough to stack two thinner rings in one grove.
Hope that maybe this helps.
Dave
-
Dave--the ring grooves were new, on a new piston, and they were as square and true as I could make them. There may have been a bit of chatter in the bottom of the groove, but the sides were both very clean and well machined.----Brian
-
Ok sounds like you have it dialed in.
-
This is a good time to ask a theoretical question. If I had a Viton ring on a piston, and shoved the piston half was down a length of cylinder, there would be no leakage at all past the Viton ring. A Viton ring seals perfectly around it's full circumference. If I stood the cylinder on end and filled the top half with Varsol or any other fluid, none of it would leak past the Viton ring---ever. That is a given. I have done that.---Now, if I take a piston with two cast iron rings on it, each ring having a 0.004" gap between the ends, and the gaps set at 180 degrees to each other, it will leak. If placed half way down a cylinder and stood on end, and if I fill the top half of the cylinder up with Varsol or some similar fluid and left overnight, some of the Varsol would leak past the rings and be puddled in the bottom half of the cylinder. Iron rings are not a perfect seal. The only reason that they work in an engine is that during a typical engine cycle, there isn't enough time for the compression to leak down past the rings. Some does--but there isn't enough time for the compression to degrade below a point where ignition is no longer possible. I ask this, because I would like to make a testing rig which would let me know if a piston and rings were "good enough" to make an engine run.-----------Why would I do that? ---Because on a real engine there is always a lot more involved in changing the rings and piston than just the cylinder bolts. All I can think of is a leak-down pressure test. Problem is, the volume of a 1" bore x 1" stroke engine is so small, it would require far better and more sensitive equipment to do a leak down pressure test than anything I currently have.---And even a leak down pressure test is only comparative. I would have to perform the test on a "good" piston and ring set to form a baseline from which I could measure the effectiveness of my own piston and rings. The ONLY way I know how to test the effectiveness of a ring and piston set, it to put it in an engine and see if the engine runs.---Any comments???
-
Brian Et Al,
I am trying to remember something I saw about piston rings. I can't find a reference but. The gist of it goes like this, If you look at Dave's diagram the force of compression as the piston moves up towards TDC would be sort of like the arrows on top and behind the compression ring helping to force the rings out. It also seems that the ring is also tilted out at the top, also so due to compression forces. This force pushing out the ring is higher as the compression ratio goes up. Don't know that this is helpful but I thought I'd throw it out there.
Art
-
I still think the problem is the cylinder bore. If I look at what you do compared to what I do that is the key difference:
Piston rings: made with far less care and attention than you give.
Ring groves: cut with a cheap 1.5mm parting tool.
Bores: Lapped with an Acrolap and 40 micron diamond paste. Piston and rings made to fit using a plug gauge.
This has always given me good compression and instant starts (not instant good running, that takes more effort).
This engine is nominal 1" bore 2" stroke. All I did to prepare for this video was to remove the generator drive belt.
https://www.youtube.com/watch?v=1Z3wXPAkC2U
-
I kind of had to cringe when Brian described the lapping process of his latest cylinder, it all sounded pretty brutal to me. :shrug:
I agree Roger there still is no guarantee that his bore is truly round, and most of us do understand that roundness can't be measured with a two point contact measuring tool.
Dave
-
This may sound like a stupid question, but if you have compression and you did a leak test and the timing is right, all cab adjustments tried . What about the ignition plug, plug wire and coil. I have seen engines run with poor rings and bad cylinders. Just my two cents….
:cheers
Don
-
This is a good time to ask a theoretical question. If I had a Viton ring on a piston, and shoved the piston half was down a length of cylinder, there would be no leakage at all past the Viton ring. A Viton ring seals perfectly around it's full circumference. If I stood the cylinder on end and filled the top half with Varsol or any other fluid, none of it would leak past the Viton ring---ever. That is a given.
I have done that.---Now, if I take a piston with two cast iron rings on it, each ring having a 0.004" gap between the ends, and the gaps set at 180 degrees to each other, it will leak. If placed half way down a cylinder and stood on end, and if I fill the top half of the cylinder up with Varsol or some similar fluid and left overnight, some of the Varsol would leak past the rings and be puddled in the bottom half of the cylinder. Iron rings are not a perfect seal.
---Any comments???
An observation on using oil to do a sealing test: Piston rings are designed to provide a seal when running in a hot engine, when hot the rings will expand which is why we leave the gap in the rings. While cold there is a gap in the rings so yes the oil will leak through. With an O ring there is no gap so you will get a good hydraulic seal
I have not been following along on this thread so far but looking on the first page there is a single figure for ring gaps :headscratch: Hepolite recommend different values based on bore diameter and application:
Air Cooled Engines: Not less than 0.005" per inch of bore (0.127mm per 25mm of bore)
All other engines: Not Less than 0.003" per inch of bore (0.7mm per 25mm of bore)
Air compressors and refrigerators: not less than 0.001 per inch of bore. (0.025mm per 25mm of bore)
As you can see applications with different working temperatures require different gaps and that gap is adjusted for the diameter of the cylinder bore - all this is to do with thermal expansion of the cast iron.
If your gap is a bit big your model engine will still run but be a bit Smokey and you may get blow through the crankcase. ::). If the gap is too small then when the rings expand the rings have no where to go but into the wall of the cylinder and engine will make a horrible noise as it seizes :toilet_claw:
Jo
-
Question Jo--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
-
If memory serves the Trimble method does not require that the rings be skimmed after heat treat. Have you read the entire article?
If not maybe you should obtain a copy, lots of good information contained within.
Dave
-
As Dave says Trimble goes to great lengths to get a good finish on the OD of the "tube" before parting off the rings so no further work is needed on the OD. I don't skim them either.
I think you are getting muddled up with rings that are sawn, where some methods close these up after sawing on a mandrel and turn the ring to the correct OD
-
Question Jo--When you make rings, do you machine the outside diameter of the rings after they have been heat treated?
No. I turn the rings the same diameter as the bore.
My heating technique is to spread them round a piece of scrap sheet or bar steel of an appropriate thickness. They hang from this while being heated and they will hold on until they take the set when they just fall off. Then just leave them to fully cool naturally. I don't clean up the outside not even to remove the scale which comes off quickly first time they rub up and down the bore.
I "crack" my rings by scoring the inside surface with the boring tool and then holding the ring in side of the vice on the line and just gently twisting the ring with pliers. You get a lovely straight edge which can then be gaped by hand with a needle file.
Jo
-
Thanks Jo!!
-
I've just sent off for the three magazine articles that cover Trimble's method of making rings in strictly I. C. Magazine in the USA.
-
I have just received and read thru the Trimble method of making piston rings. It is very well done, and a bit "long haired" so it will require a bit of concentration to re-read and fully understand exactly what Trimble is saying. He treats the subject "in depth" and does provide very good guidelines for making compression and oil rings for small engines. I would recommend it to anyone who has had trouble making their own rings.---Brian
-
WOO-HOOOO---I just got my second covid shot this morning. Wife and I drove to a nearby town and after they confirmed that we had our first shot in early march and that we were "essential caregivers" to my 100 year old mother they went ahead and injected both of us. Arm is not sore, no hives, no sick feeling (at least so far).
-
I have read thru the Trimble method about three times now, and I probably can get my head around about 80% of it. Only four things really jump out at me. #1---He uses a calculated diameter of round pin on the neutral axis of the ring as his "gag" when spreading the rings for heat treat. #2--He clamps the rings flat in a fixture for heat treating, which makes sense, because that keeps the two ends of the ring in perfect alignment whereas spreading the rings on a "gag" but not clamped flat does allow the rings to "squirm" a little bit and become misaligned. #3--He uses an expanding collet style fixture to mount the rings on one at a time to deburr the inner and outer diameter of the rings on the "blind side" which couldn't be deburred when parting off from the original parent stock. and #4--He is quite adamant about not trying to do any further work on the o.d nor on the i.d. of the ring before mounting it on the piston. To me, his rings look awful damned thin at 0.022" on a 1" piston. I could not make the 1/16" wide rings as purchased from Debolt work for me. That is probably my fault, not Debolt's. I am buying a 1 mm (0.039") wide grooving tool to put the ring grooves into my piston, I'm going to make my new piston from aluminum, not cast iron, and my compression rings will be made 0.038" wide x 0.038" radial thickness.----Brian
-
WOO-HOOOO---I just got my second covid shot this morning. Wife and I drove to a nearby town and after they confirmed that we had our first shot in early march and that we were "essential caregivers" to my 100 year old mother they went ahead and injected both of us. Arm is not sore, no hives, no sick feeling (at least so far).
Terrific, glad you were able to get it!
-
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.
-
Good luck taking 0.010" off with an india stone :'(
Try reading it again, he roughs the OD to +0.010" then bores.
He then turns with his finest feed 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.
-
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.
-
Brian,
That sounds like a good deal!
Art
-
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.
-
A local milling machine cutter sharpening service is currently making this tool for me to groove aluminum pistons for 0.038" wide rings. Actually, his price for a tool as shown here was $60, but a lot of that must have been set-up, because he also quoted me on a double ended tool for 75$. I ordered the double ended tool and will have it sometime this week.
(https://imagizer.imageshack.com/img924/7792/0QrTMA.jpg)
-
I called the toolmaker this afternoon about the cutting tool he is making me and asked about side clearance. He was out, but I left a message. He emailed me back and this is what he had to say.
"Hi Brian
Sorry I missed your call. I was driving.
I intend to put side clearance on the tool. Probably only 2-3 degrees per side. I would put more because it’s aluminum but it’s pretty small. I will also make the tool narrower at the base. Only by .001/.002 but it will give you a cleaner cut. Both clearances will stop the aluminum from smearing and give you a better cutting action. I should have them ready tomorrow and I’ll let you know. Thanks"
Okay--I never claimed to be a tool designer. This guy is good. He has sharpened cutters for me before, and I was impressed by his background and knowledge.
-
Brian, I hate to say this because of all the contributions you have made and the unique engines you have built but sharpening a high speed lathe tool is kind of like machining 101. I use HS lathe tools almost exclusively on both my 6 and 11 inch lathes and must have at least 40 styles in both 1/4 and 3/8 . Making a necking tool like you show is about a 10 minute job. Just saying!
gbritnell
-
George---I have no problem grinding an HSS cutting tool. I do however, have great problems with grinding an HSS tool with any kind of dimensional accuracy. I don't have a Quorn, nor anything like it to let me control depth of cut or angle of cut. If I thought I could grind this tool myself, I certainly would have, and saved $75.00.----Brian
-
Yesterday I ordered a "fine India stone" from Norton. They don't cost much, and I don't have a lot in the way of sharpening stones. I bought a 1" x 4" stone. I have one big double sided stone that I inherited from my dad, and it works fine for sharpening jackknives and kitchen cutlery but isn't something you would use on material chucked in a lathe. Trimble recommends a "Fine India stone" as part of his write up on ring making.
-
Today I picked up my 1 mm (0.039"0 lathe tool from Can-cut, a local sharpening service. Yes, it does have a bit of side relief on it. He made it using a surface grinder. ---Yes, I paid $75 for it, but this is still only about 1/2 of what I would pay for a carbide and toolholder out of USA. Next step will be to machine a holder for this tool and see exactly what width of cut it actually makes in a 1" diameter piece of aluminum round stock.----And yes, I agree with the sentiment "More money than brains".
(https://imagizer.imageshack.com/img924/1412/efm0SQ.jpg)
-
Something very fishy is going on, and I don't know what. My new tool is setting at exactly the correct height (centerline of spindle), perfectly square to the long axis of the lathe, and the tool is ground perfectly square across the end. I made three plunge cuts, using the cross slide to advance the tool into the cut, with lots of wd40 as lubricant. My new tool is set up with very little unsupported "stick out". Then I cut the aluminum round blank on my bandsaw to expose a cross-section of the cut. All of these cuts look crooked to me. I don't think there is any way that a ring can seal against either side of the plunge cut. My cross slide is set at 90 degrees to the long axis of the lathe. Does anyone have an explanation of what may be going on here?
(https://imagizer.imageshack.com/img923/1156/zXNF93.jpg)
-
Cancel that last question.--Investigation shows that tool was setting crooked in holder. I will make a better tool holder and try this again.
(https://imagizer.imageshack.com/img923/4403/9uEXTE.jpg)
-
Okay---Proper tool holder gives perfect grooves. The grooves measure 0.040" wide with my Vernier caliper, so I'd say it's good. The grooves appear at a proper 90 degrees to long axis of part. I'm happy with the new tool.
(https://imagizer.imageshack.com/img922/5355/SbmQIK.jpg)
(https://imagizer.imageshack.com/img923/7554/J3xA9U.jpg)
-
Brian,
That's a good catch on that crooked cutter, glad that you tried a sample cut before ruining a piston.
Art
-
I just got a quote from Caliber Industrial Supply in Ontario for one Thin-bit holder and two very narrow carbide tips (which they sell in minimum quantities of 10) for a grand total of $429.00 Canadian funds. This makes the $75 I just paid for a double ended HSS tool look pretty darned cheap by comparison.---Brian
-
You can definitely get a holder and carbide inserts for less than that $429 - BUT certainly not for $75 without going to questionable import quality, and you can easily keep honing that HSS tool for a long while. Should last plenty long.
-
This is a video I made today, 11-june-2021 of my vertical i.c. engine 2021. I have been trying to make a set of cast iron rings for the piston, and as part of that I built a new cylinder and new piston to accept cast iron rings, but ultimately I was not successful. Finally I decided that I should put this engine back together, so I enlarged the top ring groove to .093" wide x 0.058" deep and put a Viton ring on it. This engine can now go up on the shelf with all of my other engines. I am still after cast iron rings that actually work, but will be trying them out on a different engine that is a lot simpler to take apart and access the piston.----Brian
https://www.youtube.com/watch?v=05WlBP_TUFw
-
And this is one of my other engines which I tried to run cast iron rings on and failed miserably. I have restored the original piston with a Viton ring on it, and of course it runs like a trooper. I wanted to make sure that both engines ran well before putting them back up "on the shelf". This engine is a noisy devil, because the spur gears are not enclosed in a metal housing. I am still pursuing the cast iron ring magic, but I'm not there yet. I have another engine to try cast iron rings on, but it is a much simpler engine to change pistons on.----Brian
https://www.youtube.com/watch?v=LTsawOLaNGU
-
I am going to try this one more time, but there is a possibility that the cast iron I purchased may not be right for the job. Does anyone know if there is a place in Ontario that sells "Meehanite"? I'm having a problem finding it.---Brian
-
There is nothing better than using the right material followed by the right techniques.
Good luck with your search for Meehanite in Ontario, I am sure it will be available. Just a question of finding the right supplier. :ThumbsUp: :ThumbsUp:
Mike
-
Brian - If you don't find cast iron specifically labeled "Meehanite" (a registered trademark) you may have luck finding a piece of Dura-Bar (another brand) from Terra Nova Steel & Iron Inc. in Mississauga. Dura-Bar is another label for continuous cast iron and has been used successfully by myself and others to make rings from.
I've no affiliation with Terra Nova, just had good service when purchasing cast iron from their Edmonton office in small quantity a while back.
Good luck
Charlie
-
Use ductile or nodular iron. Gray the molecular structure is withe graphite flakes where ductile or nodular has spherical structure making the yield strength much stronger thus will have spring without breaking so easy.
-
It's summer time and the livings easy--Kinda sounds like a song, doesn't it. Wife and I have both had our second shots, and we are enjoying summer. My desire to work in my shop is at a very low ebb, but that's okay. We have a visiting grandson this morning who is doing his schoolwork on my wife's computer, so I have found a bit of time to sneak down to my shop. First order of the day was to design something, so I started with Trimble's ring splitter. I am still waiting for my "fine india stone" to arrive, but decided to design the ring splitter in 3D cad. The two square red sections are made from 01 steel, hardened. The rectangular body is aluminum, and the #6 set screws are 3/4" long. The ring shown is 1" o.d. x 0.038" x 0.038".
(https://imagizer.imageshack.com/img922/7380/4EiBCM.jpg)
-
That 3D mode I showed is made exactly to Trimble's drawing. It seems like a case of overkill to me, but since none of my attempts at ring making have yielded good results I am going to follow Trimble's method as closely as I can.
-
So, here we have Mr. Trimble's ring cleaver.---does it work? Well yes, I "cleaved" one ring and I already see room for improvement. When you tighten the screws to push the hardened 01 "cleavers" into contact with the ring, they pop up out of the slots, just as I kind of figured they would. I will add my version of a "hold down" and then we will try this again.
(https://imagizer.imageshack.com/img923/4053/bDCXsI.jpg)
-
Okay, next step is to add the "Rupnow hold down" to the "Trimble cleaver".
(https://imagizer.imageshack.com/img923/7816/67drwp.jpg)
-
So, here we have a Trimble ring cleaver, with a Rupnow add-on. The "add on" keeps the cleaver knives from trying to kick upward out of the guide slots when the screws are tightened. In a perfect world, I would have had a ring to "pose" in the picture, but I'm out of rings now until I make some more. I did "cleave" one piece of a ring, just to assure myself that this thing works, and it does (I don't see any difference from the rings that I broke in the vice with my fingers).
(https://imagizer.imageshack.com/img924/1382/iLa4VD.jpg)
-
Found something out today. Two weeks ago I ordered a "Fine India Stone" from Sharpening Supplies .com on the internet. Today I went searching for it because two weeks should get it from anywhere in the USA. I phoned Canada Post with the tracking number supplied by Sharpening Supplies. Canada Post informs me that the stone shipped out of Sweden a week ago. What???---Sweden?? Okay, maybe I've been had. Of course, Sharpening Supplies never indicated that the stone was coming from Sweden. It doesn't really matter, I don't have any urge to do much machining right now, but still----
-
It's raining here today. I am fully vaccinated and bored, so I went out this morning and made a tour thru my tool shops. Came home and had a sleep.--And now it's time to move a little farther along with my pursuit of making cast iron rings. This time I wanted to modify the piston on an engine which needs no (or very little) disassembly to access the piston. I've decided that my air cooled side-shaft engine is a prime candidate. It runs very well, and by simply removing the two con rod bolts I can pull the con rod and piston out of the engine without doing anything else. The new piston will be aluminum instead of cast iron (mainly because aluminum is cheaper and I have some here). The new piston will be nominally 0.002" less in diameter than the bore of the cylinder. The rings will be 1 mm (0.039") x 1 mm (0.039") in cross section. The rings will be made following the Trimble method as much as I am able to.
(https://imagizer.imageshack.com/img923/441/CmWNGm.jpg)
(https://imagizer.imageshack.com/img924/6852/NIZx3X.jpg)
-
This is a video made today showing the side-valve engine running. I had to mess around with fuel tanks, but other than that the engine runs very well. Next step will be to make the new piston and rings and install them on the engine without changing any of the engine settings.
https://www.youtube.com/watch?v=Qztvrsjyytk
-
This mornings work was to machine a new piston with grooves for cast iron rings, setting alongside the old cast iron piston with a Viton ring. The old piston was 1.006" diameter and was almost an air-tight fit in the cylinder. The new piston is 1.005" diameter. Now I wait until my "fine India stone" arrives from Sweden so I can make the rings.
(https://imagizer.imageshack.com/img923/5097/3FKage.jpg)
-
Tomorrow, if it's still raining I will make the Trimble heat treat fixture. It will be made of the same material as the ring itself, so I don't get into problems with differential expansion factors during heat treat. I only show one ring on there, however it will accept up to six rings at once. The round red rod is the "spreader", and if the heat treat is done correctly the red rod should pull out of the fixture very easily. If the rings are still "gripping" the red rod, then the heat treat hasn't done it's job.
(https://imagizer.imageshack.com/img922/1041/95w9d3.jpg)
-
Hopefully you will see this before cutting metal
That does not look right to me Brian, the spacer rod usually ends up needing to be partly cut into the side of the spigot that the rings fir round. Also the rings are a closer fit on the spigot. If you look closely at Trimble's article you will see that at 0.497 from the ctr his 0.150" dia pin hole will need clearance on the 0.941" spigot. As you have it the rings can move about while tightening the top cap which will affect the gap.
What were the figures you used to arrive at those sizes in your drawing?
-
Today I made the Trimble heat treat fixtures. I managed to hit the numbers "right on", so if my cleaved rings fit, the fixture and the rings go into my new heat treat oven for 3 hours at 1100 degrees F.
I decided at the last minute to make the fixtures from mild steel instead of cast iron, but I don't think it will make any difference. Why is the head turned on that 5/16" cap screw?---I really don't know, but that is the only 5/16" cap screw that I could find around here.
(https://imagizer.imageshack.com/img923/2276/KLOII0.jpg)
-
This is my interpretation of the Trimble deburring station. One side of the ring is chamfered and deburred before the ring is parted from the parent stock. The other side of the ring, after parting off will need deburring and chamfering. This is the station that allows you to do that. The good side of the ring is butted up tight to the shoulder on the blue piece, the the bolt is tightened to pull the yellow piece into the blue, causing it to expand and grip the ring, leaving the second side of the ring exposed so it can be deburred and chamfered.
(https://imagizer.imageshack.com/img924/3892/IxfEvf.jpg)
-
Here we have the internal expanding mandrel, which holds the ring while the "bad" side of the ring is deburred and chamfered. (The other side of the ring was chamfered and deburred before it was parted off from the parent stock). I even have a ring shown on the end of it, although that ring isn't the right ring, it's just one of the old rings I had around. You will notice that the main body of this tool is much, much longer than the solid model.---This is why---My 3 jaw chuck never can grip something twice in a row, without grabbing it a little differently. This shows up with a dial indicator, even if it's hard to see with the naked eye. So, my thoughts were, if I want to use this tool more than once, I should do something to guarantee that I always grip it the same way, in the same place. My lathe spindle is 1 1/2" thru the bore, so on the far end of this 1 1/4" diameter main body I have a ring of material 1.499" in diameter, and have the other end stamped 1, 2, and 3 to correspond with the chuck jaws. When installed, the ring of material is flush with the far end of the spindle. This brings me to a point where there are no more fixtures to build. All I need now is that damned fine India stone which is somewhere between Sweden and here. I am going to call "Terra Nova Steel and Iron inc. in Mississauga this afternoon and see if they will sell me a 12" length of Durabar to make rings from. I doubt very much that I need to do that, but I am not leaving any stone unturned in my quest to make working cast iron rings.
(https://imagizer.imageshack.com/img922/6708/IiZvgi.jpg)
(https://imagizer.imageshack.com/img924/8869/Up4Pyx.jpg)
-
Today my "fine India stone" arrived in the mail. If it had been holding me up on a project I could get really ugly about how long it took to get here. However, it hasn't held me up, as I had three fixtures and a new piston to make before it would be needed anyways, and I just finished the third fixture yesterday. Now all that is left is to make the rings. Wish me luck!!!---Brian
(https://imagizer.imageshack.com/img924/7181/vW8D2x.jpg)
-
Luck!
-
Second oldest grandkid just graduated from public school. She's a pretty girl.
(https://imagizer.imageshack.com/img923/4927/koC5sy.jpg)
-
So-----------Here we are again. A new batch of rings, made from fine grain grey cast iron. I used my "special grind" HSS grooving tool to part these rings off. Each ring is 0.044" wide, which leaves a small bit on each side for "clean up" on a sheet of 600 grit paper. I hit the numbers perfectly on the o.d. and the i.d. and made 8 rings, of which I only need two. My opinion on the "Fine India Stone" that I bought---It doesn't do anything that a piece of 220 grit paper held against a flat file won't do. I may have wasted my money buying it
but I'm trying to follow everything that Trimble suggests. Next step will be to mount each ring on the Trimble fixture and deburr/chamfer the side which was not deburred/chamfered before it was cut off from the parent stock. If these rings don't work, there is enough turned material on the "parent stock" to make new rings 0.045" thick, same as Trimble did.
(https://imagizer.imageshack.com/img924/5480/bDPClu.jpg)
-
The rings have been sanded on both sides with 600 grit paper on a flat cast iron surface plate to 0.038" thick, and tried for fit into the grooves on the piston. This picture is the Trimble deburring fixture that "sorta kinda" works. Ring is placed on end of fixture in a "step" machined in the end of the fixture and then the cone is pulled in by the bolt to expand the fixture and hold the ring for deburring. I don't think I would dare to use a cutting tool on the ring because I'm sure it would fly off. However, it does seem to hold the ring secure enough that I can get in there with a piece of 240 grit emery paper and knock off any burrs, both on the o.d. and the i.d. of the exposed side of the ring.
(https://imagizer.imageshack.com/img924/2933/pdMWfq.jpg)
-
Out of 8 rings, 4 survived the polishing, deburring, and gapping. The four that didn't was because of a mistake on my part. I have a 1.006" hole thru that round piece of cast iron (same as the cylinder bore) and I used it as a guide for gapping the rings to a 0.004" end gap when squarely inserted into the hole. Surprisingly, Trimble doesn't cover this gapping procedure at all. He just says to run a piece of fine emery paper between the cleaved ends of the ring. The surviving four which are on the heat treat fixture will now go into my heat treat oven at 1100 degrees F for three hours.
(https://imagizer.imageshack.com/img922/4615/l7Q2ki.jpg)
-
I would not gap them until after they are heat treated.
Dave
-
Conventional wisdom says that you gap the rings, use a filler piece to open the gap, then heat treat them so the rings "take a set" at the gapped position. These are the rings about two hours after heat treat. Lots of black crud on both rings and fixture, but it seems to brush off very easily. Tomorrow I will take the heat treat fixture apart to free up the rings and clean them individually.
(https://imagizer.imageshack.com/img922/2773/Honx6m.jpg)
-
Conventional wisdom?
I guess that I don't have any of that. :lolb: Good luck with your rings. :ThumbsUp:
Dave
-
All of the black crud came off very easily with a brass bristled brush. The rings have "taken a set" at the required gap (0.150").
(https://imagizer.imageshack.com/img923/4605/IrHfv1.jpg)
-
Rings are installed on piston (lots of 30 weight oil and very deft fingers). Piston is installed in cylinder, rod cap bolts are back on, and engine has excellent compression. I'm not going to try and start the engine tonight. I have trouble sleeping as it is, and if I start this engine tonight I will be too revved up to sleep. This is all looking very positive, and tomorrow morning we will see if the engine runs.---Brian
-
Conventional wisdom?
I guess that I don't have any of that. :lolb: Good luck with your rings. :ThumbsUp:
Dave
Don't worry Dave, as I posted on HMEM Trimble obviously did not either when he described how to gap the rings AFTER heat treat which Brian seems to have totally missed as well as finish turning to width
-
Brian,
What is your final gap be after the ring has been fitted in the bore. Are you working to the typical 4 thou per inch of bore diameter?
Colin
-
The 0.004" gap is put in the ring before it is heat treated. The larger "operating gap" of 0.150 is put in during the heat treating stage.
Ladies and Gentlemen--I have a thrilling announcement to make. My engine runs with my own home brewed cast iron rings. This is the first time ever for me to successfully make my own cast iron rings to run in one of my engines. I followed about 80% of the Trimble method of making rings. This makes me feel very good.---Happy Dance-Happy Dance!!!!----Brian
https://www.youtube.com/watch?v=cupLhD2bC3I
-
Well done Brian,
I am pleased you got the result you wanted, despite all the rude and offensive comments from one person on both this and the HMEM forum.
Mike
-
So, what are my opinions of the Trimble method of making rings? I made the fixture Trimble used for "cleaving" the rings. It works fine, and I will use it because I now have it---But really, I don't think it does a better job of breaking the rings than just pinching the rings in a vice and breaking them with your fingers.
-----The expanding mandrel that Trimble mounts his rings on to machine the side of the ring which wasn't deburred and chamfered before it was parted off from the parent stock.--I didn't feel that it held the ring securely enough to machine the face of the ring, but it did hold the ring securely enough to get in there with a piece of emery paper and do a good polish and chamfer the exposed side of the ring.
-----The heat treat fixture worked really well, because it kept the rings clamped together during the heat treat cycle so they wouldn't twist and deform like they often do when hanging them from a spreader pin or plate and then heating them until they drop off.
----There has been a lot of discussion about how much heat to use on the rings to get them thoroughly heat treated. I bought a small heat treat oven to do this, so I could come up with a repeatable process. I heated the fixture and rings for 3 hours at 1100F and that seems to have done the job very well.
-----When I make rings in the future, I will use this method for making the rings. Also, in future, I will make the rings 0.045" wide, same as Trimble did. (for a 1" diameter piston). I made the rings .038" wide x 0.038" deep because that is a millimeter, which is a standard unit here in Canada. On my next set of 1" dia. rings, my rings will be 0.045" wide x 0.038" radial thickness.
----Thank you all for following my posts, and thanks to those who provided some guidance to me.-------------Brian
-
Congratulations Brian!
Glad to see you got it to work! You showed a lot of persistence in this effort. :ThumbsUp: :popcorn:
Now that you've proven you can do it, are you going to go back and look at some of your earlier attempts to see what the differences are? Do a little post-analysis? Or just go fward and be happy! :)
Great work, Brian,
Kim
-
Good to see they worked out for you in the end Brian
Whether they would have done without me and a few others correcting your wrong interpretations of the Trimble method who knows but I feel its better to offer a point in the right direction that just sit quietly by and just comment at the end.
-
Great to get it figured out, and to well document the Trimble-Rupnow process! :ThumbsUp: :ThumbsUp:
-
Well done Brian, bit of a struggle but you got there in the end and had the result you wanted, a working engine. :cartwheel: :cartwheel: :cartwheel:
Regards,
Colin
-
Also, in future, I will make the rings 0.045" wide, same as Trimble did. (for a 1" diameter piston). I made the rings .038" wide x 0.038" deep because that is a millimeter, which is a standard unit here in Canada. On my next set of 1" dia. rings, my rings will be 0.045" wide x 0.038" radial thickness.
I guess I don't really understand this reasoning, but as I mentioned on HMEM, I'm very glad you have a firing engine, so big congratulations.
1mm = 0.0394" so if you mean a 1mm tool just so happens to result in a ~0.001" clearance to a 0.038" wide ring you chose, I suppose that is a convenience consideration. But what does a so called standard unit in Canada have to do with anything? If its an insert tool, its very likely of offshore origin and nominal thickness. Parting tool inserts come in many width flavors. Grooving tools come in other flavors (often designed around metric circlips or O-rings or whatever). Also just because a tool has a catalog defined width doesn't mean they obey the (tight) tolerance that piston ring fitting requires. Some inserts state a tolerance & others you can measure +/- 0.001 variation across a batch of inserts from the same box. For example a nominal 1mm wide tool that happens to be 0.001" undersize = 0.0384" = 0.0004" clearance on 0.0380" ring (not enough).
There is nothing dictating you have to achieve the finished groove width by a single cutter plunge, that was your preference. Alternatively you can cut on either side of the ring groove face with a thinner tool & completely remove the issue of matching a tool width to a ring width or visa-versa. If you are grinding a HSS to to match you have full control, but again the tool width & ring width is a chicken & egg thing and mm doesn't really factor.
Then regarding the groove depth issue, this is of course 100% controlled by your lathe in-feed & measurement, so nominal/standard mm is a non-issue. You mentioned you would make the rings wider next time, more aligned to the Trimble sizing and that is all I'm trying to clarify. His procedure is: Step-1 determine the appropriate ring width for the constraint reasons he outlined & shown on his graph. Step-2 is factor the desired clearance behind the ring. That yields the target diameter of the piston groove, by whatever choice of tools works to achieve that dimension.
-
This post is not so much about rings, but it does show something very important. I am always amazed at how much a difference in gas tank height affects an engine. When I built this engine a few years ago, I had made a gas tank to fit underneath the cylinder, with a 3/32" diameter check valve in the discharge. This year when I went to start it, I couldn't get it to draw fuel up from the tank. Okay, when these engines set around on the shelf for years, check valves have a tendency to freeze up. That wasn't a big deal, I just grabbed a spare gas tank I had and mounted it on a block of wood. This allowed me to start the engine and see that it actually did run. After putting the cast iron rings in, the engine would run good for four or five minutes and then die, as if it were running out of fuel. When everything else is set at "optimum" and the engine dies for no good reason, I always suspect the gas tank height. In this picture you see a 1.6" tall aluminum spacer under the tank. That fixed it!! Now the engine will run until I turn it off with the switch in the electrical system.
(https://imagizer.imageshack.com/img924/9155/z73lZf.jpg)
-
Well done Brian, your persistence has paid off. And I am sure it will serve you well for future builds.
Regarding the fuel tank height, I guess the carburettor throat only produces so much suction. Of the tank level is low, there will be less fuel flow until eventually insufficient to run the engine.
But of course, with a high level, there is a danger of the fuel continuing to flow when the engine stops, hence the float valve in the traditional automotive carburettor. Perhaps a chicken feeder style, with the level just below the carburettor is called for.
I have followed your journey on the rings and endured the pain with you as each step forward seemed to be accompanied by a step back.
MJM460
-
Brian,
Happy dance is right, who hooo....great to hear it running.
Art
-
The power of persistance :) :) :)
Do you have any thoughts on which steps in the new ring making process made the improvement over your previous attempts?
-
I think that having the correct heat treat fixture and the oven were the two biggest factors. I don't really think that the fancy "cleaving fixture" did a better job than clamping the ring in a vice and snapping it with your fingers. I think some credit has to be given to the expanding mandrel fixture, which lets you mount the ring and really clean up and chamfer the sides of the ring.---Brian
-
Brian, congratulations on getting a very satisfactory result at the end of a difficult process! Your attention to detail and documentation of what you're doing is certainly appreciated!
Again, great job!
Mike
-
Mike---Every once in a while, I run into something that I don't think I'm going to be able to do.---and that worries the Hell out of me. I've always been the man who can do anything, and I hate to think that there is something that has defeated me. I'm happy that I was able to finally get some workable rings and a "process". Not bad for a "geezer". I'll be 75 this Wednesday.
-
Congratulations Brian - both with the piston rings and your birthday - almost like you gave yourself the best present :cheers:
Per
-
Congratulations on your 75th Birthday :ThumbsUp: :wine1: :old:
I offer you fuel injection as your next impossible task ::) :stickpoke: :toilet_claw:
-
I offer you fuel injection as your next impossible task ::) :stickpoke: :toilet_claw:
:lolb: :ROFL: :Jester: >:D
-
And today we get to see how slow the engine will run. I've got about an hours continuous run time on it now, and as those cast iron rings "bed in" the compression gets higher and higher, and consequently the idle speed can become less and less. I'm pretty impressed with this.
https://www.youtube.com/watch?v=4Q1RYoAJbFo
-
Sweet!
-
Very nice, Brian!
I'm glad you told us you had your garage door up! I was starting to worry for you - sitting by the running engine for an hour! :o
Kim
-
When Roger says you are persistent, he know of what he speaks. Good job and thanks for the build record, Brian.