A new attempt at making piston rings

[Brian Rupnow]

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.

[Brian Rupnow]

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?

[simplyloco]

I have used a zip/cable tie in the past: used pliers to wind up the tension.

[Brian Rupnow]

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.

[Brian Rupnow]

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.

[Roger B]

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).

[Brian Rupnow]

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.

[Doc]

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.

[Brian Rupnow]

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.

[Brian Rupnow]

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.

[Brian Rupnow]

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.
<a href="https://www.youtube.com/watch?v=EGYhhk8S54A" target="_blank">http://www.youtube.com/watch?v=EGYhhk8S54A</a>

[Brian Rupnow]

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.

[Brian Rupnow]

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.

[Brian Rupnow]

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.

[Brian Rupnow]

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