Small Flash Single

[crueby]

Great results from your EasyCast system! Well done!

[vtsteam]

Thank you Ron, and Chris! 

[Kim]

Those look like great castings, Steve!
And excellent use of the E-Z-Bake printer 
Kim

[vtsteam]

Thanks Kim! I think the name E-ZBake is going to stick for this 3d printer. I like it! 

[vtsteam]

Well after a month and a half break from this engine, I'd like to get back moving on it. I've read a few more thi ngs about making rings, and now have less confidence than I did! But I'll try cutting some experimental rings this afternoon, to see how it goes. 

[RReid]

Glad you're able to get back to this project, Steve. Looking forward to the continued progress. Best of luck on the rings!

[vtsteam]

Thanks Ron. I have some concern that I made the ring groove too deep (.052"). I assumed a ring of .050" thickness, but I now think I should have made the groove 0.42"deep  and the rings should be .040" thick. This is for a ~1" d. piston. The problem was, I was looking too closely at the Pisces engine ring specs, forgetting it was a 1.1875" bore, not 1" like mine.

The main problem with what I've done will probably show up as an inability to get the rings on without breaking them.

I was originally going to bore the piston for the wrist pin, then remove from its chucking piece and then bore out the inner waste before making rings. But with present doubts, I'm going to try rings first in case I have to make another piston.

[vtsteam]

I spent a fair amount of time on tooling this afternoon, finished off a roughed out QCT holder I'd had lying around, and ground an HSS lathe tool to mount in it ....this one meant for trepanning a Dyke's ring's inner face. It was getting late but I wanted to try it out so I just chucked a rod of cast iron scrap, a little larger than my piston to try out the tool and holder, and just cut one by eye. I did manage to cut a ring shaped piece of metal, but that's about it! I wouldn't call it a piston ring. 



There was a fair amount of chatter, whose source I'll have to locate. I was able to turn the piece as slow as 30 rpm with the DC treadmill motor setup, and that helped. Most of the chatter was confined to the inner face of the Dykes ring. The outer edge, bore and parted edge looked better.

Because it wasn't cut to any measurements, the ring itself is much wider and thicker than what will be needed. I think making a ring actual size tomorrow will reduce the chatter problem. On this first experiment the land was wider than actually needed. If I bore my stock first, the width of cutting face will be about half of what it was today, which in itself might eliminate the chatter.

There was also quite a large rough burr on the ID from parting off. I can probably get rid of that by boring to ID first and grinding and angling the face of my parting tool so it cuts off a ring on an acute corner edge, rather than parting square across, as it does now.

So, even though my "ring" today was nothing to write home about, it did provide some good direction for tool grinding and process change for a better attempt tomorrow.

[vtsteam]

Here is what the finished ring should dimension out to. The cylinder bore is presently honed to .999" so the ring shown is also .999"




My question now is what dimensions should I make the ring before splitting and heat treatment?  I imagine heat treatment will create some scale and will require some cleanup.  I haven't seen any clear recommendations, other than one mention by Chaddock of a 1 to 2 thou cleanup.

I will be using Chaddock's method of heat treating after splitting the ring by snapping it. Chaddock inserts a gag piece in the gap, sized to 4 times the ring thickness, in this case thickness is .050", so gag piece would be .200". Then heat treatment to cherry red. No mention of cooling rate, No mention of whether we're shooting for an annealed condition either. Or whether post annealing is an advantage.

As mentioned earlier, I probably should have gone with a ring .040" instead of .050" so we'll see how difficult it is to get onto the piston.

I don't know if it would be acceptable to make a ring .040" for this piston since the ring groove was turned for a .050" ring. A .040 thick ring on this piston would result in 12 thou of radial clearance vs the intended 2 thou. ( .024" diametral clearance vs . .004"). My guess is it would require a new piston to be made, but I don't know how important inner diameter clearance is.

As far as overall ring dimensions go, I think I'm going to first try cutting a ring OD of .101" giving 2 thou oversize for the bore, and hope that's the enough for clean up after heat treatment, but not too much. I think I will leave the inner diameters as drawn and see what happens. Fairly likely the first attempt will show the need for some adjustment.

[John Roberts]

I would prefer to force the snapped rings onto a mandrel which gives the same gap. Clamp them together with washers, nut and bolt.
 The rings to my way of thinking will stay rounder after the heat process than wedging then open.
 2 thou clean up is about right.

[vtsteam]

Thanks John! 

I actually made the rings before I saw your suggestion.

First try: I cut the ring blank 2 thou oversize in diameter and bored it to finish ID. I did increase depths by 2 thou. Here I'm parting the first one off:

[vtsteam]

To split the ring, I decided to try notching the inner lip with a needle file. I thought it might break more cleanly that way, since its cross section was "L" shaped. Since this will be a pinned ring, there will need to be a notch there, anyway:

[vtsteam]

To wedge the split open, I needed a tapered mandrel. I was going to make one, but then spied a #2 Morse taper dead center for my lathe. It was a perfect fit.

[vtsteam]

I set the mandrel in my partially opened vise, nose up, with the ring resting on the jaws, and gently tapped the top with a soft hammer. There was a soft "pop" but the ring split not where I'd filed the notch, but diametrically opposite it!   

Best laid plans....... well I decided to keep going with this ring, just to see if there were any other problems down the road, before scrapping it. The first one came fairly quickly as I tried to wedge a flat nut in the gap as a gag piece before heat treating. The ring broke, this time where it should have, at the notch. That was predictable because it was also the the location of highest stress since the gap was opposite.

No problem, I'd turned plenty of stock....on to Ring #2:

II turned and parted off a new ring, and this time decided not to notch it before splitting. I'd just let the ring decide where to do that. Splitting went easily, and I noticed the split was more even and square this time. Looked good. And instead of trying to pry the edges apart to insert a gag piece, I slid an old flat screwdriver into the gap, slowly, like a wedge until I had the correct gap.

This turned out to be a handy holder I could clamp in the vise, for heating the ring. I arranged a firebrick behind the ring to reflect the heat of the torch for a more even treatment. I turned down the lights and rapidly played a mapp torch around the ring from about 8 inches away, making sure to heat evenly. Gradually the color came up and when it reached an even cherry red all around, I gave it about  30 seconds at that temperature before turning off the torch.

Letting the ring cool didn't take long, and this is what it looked like after the heat treatment:

[vtsteam]

Ring #2 really looked the part, except for some small chatter marks on the flat face of the inner lip. But would it fit over the piston without breaking? As mentioned before, this part according to Chaddock's formula should probably have been .040" thick, but I'd made it .050".

I tried stretching it over the piston, and lo and behold, no problem, I was able to slide it down to the ring groove, and back off. I then checked to see if I could fit it in the bore, but nope, and of course it was 2 thou to large when cut. No surprise there. It was also 2 thou thicker than design.

So I spent a fair amount of time lapping the thickness down, cleaning up the outside and inside burrs, and I filed the gap a bit. Eventually I was able to just fit it in the bore. I was gratified to see no light around the ring when I sighted down the bore. It was a really close fit. Also the gap was closed tight.

I worked on this ring a while more and then tried it again on the piston. While the ring needed to be tightly closed to fit the bore, I couldn't bring the ends together when located in the groove. This turned out to be a result of over sizing things  thinking that there needed to be an clean-up allowance after heat treating.

In fact, it seemed that these rings did not need an allowance at all. Oxidation scale was merely a discoloration, with no discernible thickness or diametral loss. With the second ring, it would have been very difficult to rduce inside dimensions now, though it was probably doable with patience.

Instead I decided to turn down the rest of my blank OD to the actual cylinder bore size, and make a third ring. I also altered the edge of the HSS trepanning tool I'd ground earlier for making these rings. I flattened the front rake since it seemed too much for cast iron, and I very slightly angled the outside corner. This change, in combination with a faster feed rate at 60 rpm eliminated the chatter I'd had before.

The third ring fit the bore right after heat treatment, and also fit into the piston groove. It needs a little cleanup of burrs, and a little more gap, since I don't think a tight gap is a good idea. But this one looks like a keeper. There is no daylight in its fit to the cylinder.

Third ring unfinished and uncompressed, but it fits the piston's groove. Piston is upside down in this photo, and will be parted off after the wrist pin bore is finished. The piston crown will be flush with the ring, and is relieved above the groove to suit the upper leg of the ring's "L" shape:



Third ring compressed in the cylinder. Perfect fit all around. The gap is closed here, and needs some relief. The top of the Dyke ring is only .025" thick. The base is .050"





All in all I'm very pleased wth the outcome, and rings have turned out to be much less intimidating to make than I thought. Dyke rings seemed even more daunting, but turned out to be relatively straightforward to make, once I had the procedure down.