Oil Rings

This Forum is dedicated to the Hobbyist I.C. (Internal Combustion) Engine Community.

Moderators: JackF, Harold_V

Post Reply
solek
Posts: 58
Joined: Wed Apr 16, 2003 6:19 pm

Oil Rings

Post by solek »

I built two engines with a closed crankcase, Silver Bullet and Little Angle. Both engines run, but the problem is they burn oil, smoke badly. Several plans for other engines show a third oil ring, used on the piston, with the specs for the oil ring.
Now the problem. Cutting a .012" wide X .010" deep in a grove in a .036" wide X .025" thick piston ring. (3/4" bore) Made a mandrel to hold the ring, which is mounted in 3-jaw lathe chuck, and have a motor with a .008" X 1" saw mounted on cross feed. Cut the grove and then cut four .008" slots, in the grove, through the ring. The rings break when I try to put them on the piston.
Does anyone have a suggestion on how to make oil rings, or know someone that sells them?
User avatar
Harold_V
Posts: 20231
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Oil Rings

Post by Harold_V »

Does anyone have a suggestion on how to make oil rings, or know someone that sells them?

I've not been involved in gas engine models, so my idea may be all wet.

If you've worked on auto engines, you know that oil rings are not generally made from cast iron. In order to wipe the cylinders and drain the oil back to the crank case, they use a hardened steel ring, rather narrow, one on top, one on the bottom of a spacer, which permits the oil to run to the bottom of the groove and out the piston through holes drilled in the piston wall for the purpose.

Have you entertained the idea of using a thin heat treated material for the ring, perhaps attempting to duplicate one in an auto? The advantage would be the ability to install it without breaking. Flat heat treated stock is available, which is used for such things as large flat springs similar to those found in mechanical clocks. It wouldn't take much to create a set of rings from a piece.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
solek
Posts: 58
Joined: Wed Apr 16, 2003 6:19 pm

Re: Oil Rings

Post by solek »

Harold thanks for your help.
Went to the small engine shop, and looked at the types of oil rings used on small motors. There were three different types, but the one you write about looks good.
They gave me a piston, which was about 11/4" diameter. The compression rings were .037" thick , close to what I am using, but the oil ring is .075"thick. Noted as we looked a ring sets that the oil ring was about twice the width as the compression ring.
The oil ring had two .013 thick rings with a web to fill the rest of the space. As the web has "teeth" to keep the thin ring out, I will buy the web for my pistons. Can any one help on what .013" metal to use for the thin rings.
Also noted the free oil rings diameter was only about .006" larger then the piston. Must not need much pressure to wipe the oil.
User avatar
Harold_V
Posts: 20231
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Oil Rings

Post by Harold_V »

Harold thanks for your help.
Went to the small engine shop, and looked at the types of oil rings used on small motors. There were three different types, but the one you write about looks good.
They gave me a piston, which was about 11/4" diameter. The compression rings were .037" thick , close to what I am using, but the oil ring is .075"thick. Noted as we looked a ring sets that the oil ring was about twice the width as the compression ring.
The oil ring had two .013 thick rings with a web to fill the rest of the space. As the web has "teeth" to keep the thin ring out, I will buy the web for my pistons. Can any one help on what .013" metal to use for the thin rings.
Also noted the free oil rings diameter was only about .006" larger then the piston. Must not need much pressure to wipe the oil.

The narrow width of the wiping rings is no accident. In order to not float on the oil, they are deliberately narrow.

When you make yours be certain that they aren't very sharp on the corners so they behave as scrapers, shaving the cylinder walls. I would suggest a carefully formed minor radius, perhaps two thou or so, done with a stone, not a file. Between minimum wall pressure and the minor radius, they should wipe well without doing damage. Keep in mind that when you over heat carbon steel it loses its hardness, so a break-in period might be advisable. I'd also suggest breaking the glaze on the walls when you re-assemble the engine. I'm not up to speed on models, but that would certainly be a serious consideration on large engines.

I'm sure I speak for others when I say I'd enjoy a report on how this whole thing goes for you.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
Doug_C
Posts: 1254
Joined: Sat Jan 04, 2003 6:48 pm

Re: Oil Rings

Post by Doug_C »

You could look into spiral retaining rings?

Smalley Steel Rings

This company also makes wave springs to act as your spacer. All this is depends on the available sizes to match your ID,OD requirements.

You would not really need to go with such thin material. Might I suggest a pair of rings setting in the same groove?

If you can image a solid ring with a groove around its outer surface and holes through the cross section around it circumference evenly spaced. Now think of them as actually 2 separate rings set face to face with their ledges pointing inward. This acts as the filler, gives 2 thin rings at the edges, and will ride the cylinder wall independently. The half holes are still there to collect excess oil and direct it back to the crankcase. Some oil is still needed for lubricating the cylinder wall.

If you check out some of the articles in Strictly IC on Piston Rings, you will find that getting a good seat is not as easy as it looks. Creating a ring with constant outward spring and to match a bore is quite the challenge. The problems are where you can scale dimensions, but properties of physics remain the same in the materials.

I have used the George Trimble method on a couple of my projects. It is a lot of work, but one of the only proven methods I have seen, in achieving the goal consistently for small bores.

Can you tell us more about the engine?

DC
solek
Posts: 58
Joined: Wed Apr 16, 2003 6:19 pm

Re: Oil Rings

Post by solek »

The ring write ups by George Trimble goes back a few years, the "Striclty I.C." article I am using is from 1989. Have be using it to make compression rings, but the need for oil rings just started with the last two engines. One key area I miss when reading the article about the oil rings, he made were twice as thick as the compression rings. The person I talked to at PRIME about oil rings said the saw slots were less likely to break, then the drilled holes. Thats why I went with the slots.
Both of closed crankcase engines are Bob Shore designs.
yeriaf

Re: Oil Rings

Post by yeriaf »

I would make the ring twice as wide but in a inverted L section and drill holes thru into the piston.
Brian.
Post Reply