Flathead V-8

[Dave Otto]

George, do you have George Trimble's article form Strictly IC Magazine? it has been a number of years since I read it; but seem to remember the he went through much of the same issues when he designed and built oil control rings for his test bed engine. I also seem to remember that he had methods to keep from breaking them. I need to dig it out have read it again.

Sounds like you are getting close though.

Dave

[Art K]

George,
I have the opposite problem with my Val engine. The piston cleared on both ends. I did some calculations with some software Steve Huck provided. With a .032 gasket between the cylinder & head & .01 head gasket I was calculating something like 12.7:1. I need to add about .1 or more to the top of the cylinder to get it down to 7:1. A new cylinder is in the works. I really like this engine George, this thing is amazing. On top of that the hose clamps are a stroke of genius. I am looking forward to hearing it purr...
Art

[Mayhugh1]

George,
Thanks for the informative update. I would have thought that the second compression ring would have controlled the oil much better than what you're experiencing. I've always wondered how important special oil rings really are in a model engine, but it seems you'll end up answering that. I guess you're getting about the same result on all the cylinders? I'm sure you already know this, but it's probably best to leave out the oil return hole in an oil ring directly across from the gap.
Hope to see you at Cabin Fever. - Terry

[gbritnell]

Hi everyone,
Thanks for the comments and suggestions. Dave, I have a reprint of Trimbles article from SIC. I printed it out when I sold all my issues of SIC a number of years back.
My compression rings are .033 wide and .045 thick (OD to ID). The oil ring groove is .065 wide by .045 deep. Here's what I'm planning for my first experiment. I'm going to make a ring that's .030 thick. This will leave a .015 gap behind the ring. I'm going to turn the ring then cut a .01 deep (.020 on dia.) x .034 wide slot in the middle which will leave a ring on both ends .015 wide. I'm then going to drill six .034 dia. holes in the ring. These will be spaced on opposite sides of the ring leaving an undrilled area where the ring is cleaved and opposite the break. My hope is that when I open the ring to put it on the piston it won't be stressing the ring at a drilled hole. This is the problem I had with the first design. When I would open them up just enough to go on the piston they would break at one of the drilled holes.
My plan is the oil will collect and be controlled within the upper and lower rings and flow through the 6 holes to the space behind the ring and then into the 10 holes drilled in the piston.
Terry, I think part of the problem is the amount of oil that's being thrown about inside the crankcase. It has a full pressure pump (15 lbs when being turned over in the lathe with the oil cold. It feeds the cam journals first. The cam tunnel is open to the crankcase so the oil squirting out of the sides of the cam journals drips down on the rods and crank. From the cam journals the oil goes to the crank mains and then out to the rods.
On my small OHV inline 4 cylinder engine the compression is great and the engine starts and runs great but it has only 2 compression rings (.75 bore) and it smokes a little. I'm thinking that compression rings won't completely control the oil on the walls. My 302 (1.00 bore) has oil rings and it has never puffed any oil smoke since day one.
Ah the joys of home engineering!
gbritnell

[fumopuc]

Hi George, thank you very much for reporting so in details about your development work. In my oppinion it is very helpfull for every IC engine builder. Thanks again for sharing it with us and as Don mentioned already, no doubts, finaly you will get it running.

[gbritnell]

I have a new batch of oil rings made. I made them as I had described in an earlier post. I'm attaching a few pictures of the new rings.
The were turned from Schedule 40 cast iron. I stacked 2 of them on the drilling mandrel mounted in my dividing head and drilled 8 holes starting at 30 degrees on either side of center. This left a 60 degree space to cleave the rings and a space of 120 degrees opposite the break for support.
I have included a picture of the cleaving fixture which was taken from the Timble article in SIC many years ago. The slot for the 2 pieces of .250 high speed lathe bits is cut deeper than the slot cut at 90 degrees where the ring is inserted. This lets the ring sit squarely to the cutting edges of the bits.
The rings were then mounted back on the tempering fixture for heat treating.

 As a side note I made a practice ring just to check and see  how it would flex after heat treating but rather than mount it on the fixture, which would have necessitated making a spacer bushing, I used a method that some builder have used. This method is to machine the ring, cleave it open and then mount it on a piece of steel to hold the gap open. The ring is then held in front of a piece of refractory material like a fire brick or soldering pad and then heated until it drops from the steel spacer bar. I have to say that I have used this method a couple of times when making odd sized rings for hit an miss engines. The reason I used this method was to eliminate having to made a heat treating fixture for just a couple of rings. Anyway I discovered something that might be helpful should anyone think of trying this method. It works on plain rings but not on a ring with holes drilled in it, like and oil ring. What happens is the stress on the ring while mounted on the steel spacer bar and then heated distorts the ring at the drilled holes so you end up with a ring that won't fit the bore properly.

 After heat treating the rings I filed the ends to the proper gap spacing in the bores and then fitted them to the pistons. I can report that they flexed very well and went on the pistons with no trouble.
How they work once in the bores I can't say yet but dimensionally they seem to work fine.
gbritnell

[Doc]

 Nice looking rings and nice set up for breaking. I need to make me up that unit. I've been calculating the circumference of ring needed then adding in the width of a slitting saw then convert back to dia turn up and the cutting with saw. I like the way you are doing much better my next rings I will give it a spin. Thanks for the pics and nice work you amaze me with it!

[10KPete]

This build has taught me sooo much about the details of IC engines!!

 

Thank you for the excellent words and music.

Pete

[Don1966]

Good to see you have overcome the hurdle George. Looks like you got some good results.

Don

[Hugh Currin]

As a side note I made a practice ring just to check and see  how it would flex after heat treating but rather than mount it on the fixture, which would have necessitated making a spacer bushing, I used a method that some builder have used. This method is to machine the ring, cleave it open and then mount it on a piece of steel to hold the gap open. The ring is then held in front of a piece of refractory material like a fire brick or soldering pad and then heated until it drops from the steel spacer bar..... It works on plain rings but not on a ring with holes drilled in it, like and oil ring. What happens is the stress on the ring while mounted on the steel spacer bar and then heated distorts the ring at the drilled holes so you end up with a ring that won't fit the bore properly.

George: That is an interesting observation. Did the rings spread with the "Timble" fixture come out "round"? I believe his fixture still spreads the rings using only three points. This should create a bending force in the ring and, due to the holes, force them out of "round".  The same as a spacer, though not as bad since Trimble's fixture presses at the center of the ring cross section. I looked back at Mr. Trimble's original articles and he suggests making oil rings just as you have. The "relaxation" of the rings is an annealing so the rings are soft after heating. It may be possible to drill the holes after spreading the rings?

I'll be interested in hearing how well they work. Might be hard to quantify though, maybe compare oil burned initially and after run in. That still won't compare rings drilled before and after spreading.

Anyway, you've created another wonderful engine. Thank you for sharing.

Hugh

[Hugh Currin]

I believe his fixture still spreads the rings using only three points. This should create a bending force in the ring and, due to the holes, force them out of "round".  The same as a spacer, though not as bad since Trimble's fixture presses at the center of the ring cross section.

Hugh

I've changed my thinking. The ring loading when placed in Trimble's fixture is the reverse of the loading when inside the cylinder. That's the basis for Trimble's fixture. The rings will go "out of round" when heat treated, but then flex back to a "perfect" circle when compressed into the cylinder. His method should work just as well for oil rings.

At least that's what I think this morning, it could change by noon though.

Again a great model, thanks again for posting the build.

Hugh

[Stuart]

Why not make them over size on th OD then split them and heat treat.

Then make up a jig in the lathe to clamp them with a washer but fully compressed , turn down to the required dia , then they will be round in the compressed state


Stuart

[Roger B]

Stuart, there is a version of this in Tubal Cain's Model Engineer's Handbook which I have used successfully.

The ring is turned to size, then spilt and expanded. The rings are then compressed in a sleeve 0.05mm (2 thou) oversize  and clamped. The sleeve is then removed and the rings are turned/polished to size.

[Stuart]

That's it Roger

I could not remember the source were I read about it, I have used it and it worked ok for CI rings in a couple of my loco's

Stuart

[Mayhugh1]

[... I tried to start my flathead engine several weeks ago and got a lot of oil into the combustion chambers. If you have read my thread I had made provisions for oil rings but my original design didn't work so I tried to run the engine with just compression rings. I went back and came up with a different style of oil ring and was able to mount them on the pistons fairly easily. When I ran the engine over in the lathe to check things out (without the heads on) I was still getting a little oil past the rings. Not as bad as before but enough to make the engine smoke if I tried to run it. I have made a third rework of the oil rings so I'll have to see how they do.
My 302 V-8 has 2 compression and 1 oil ring and it has never smoked from day one so I'm perplexed as to to what's going on....]

George,
I don't think it's at all unusual for an engine to pump oil up past the rings and into the combustion chamber while it is being 'motored-in' even if all the rings are nearly perfect. You need the pressure of combustion to force the compression rings against the cylinder walls in order to limit the amount of oil being pumped up into the combustion chamber by crankcase pressure pulses created while externally spinning the motor or even the best oil rings can become overwhelmed. It may be time to fire it up and see what you have. - Terry