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Tight rings?


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  #1  
Old 02-02-2019, 04:19:47 PM
Pete LaBelle Pete LaBelle is offline
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Default Tight rings?

Hey all -

Working on an old steam engine that came my way. Some time in the past, someone had done some frugal restoration/rebuilding of it, and although it does run, there is a LOT of drag by the rings.

The engine is a 2-1/2" bore by 3" stroke horizontal engine of unknown manufacture (photo attached). The piston looks like it may have one fat ring at one time, but now has 3 compression rings in the same groove.

Rings have a 0.125" x 0.125" cross section, and when pressed into the cylinder, exhibit 0.020-0.030" ring gap.

When the engine is assembled and run, there is considerable drag on the piston that makes the engine labor hard just to run. Turn off the air, and you get an instant stop.

There is plenty of oil (30wt) in the cylinder, and there is no drag by the packing, piston, or the rod. Cylinder is very smooth.

Can I heat up the rings to reduce some of their tension?

Does the engine need to be run in longer to seat the rings? (have over 3 hours so far running at about 200 rpm).

Any other thoughts to consider?

Thanx !

Pete
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Old 02-02-2019, 06:37:57 PM
Lester Bowman Lester Bowman is offline
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Default Re: Tight rings ???

Hi Pete
Nice little engine you have there. Does the piston have a removable " Junk Ring" ( removable plate on piston ) to allow installation of the rings without springing them? If so you might try to replace one or two of the rings with a spacer just to reduce drag.

If the piston is solid with just a groove for the rings I would remove the rings entirely and pack the piston with Graphited Yarn. This will be fine on air pressure and low pressure steam. We don't work our little engines hard anyway.

Why the abundance of DRAG is the question. A 3/8" wide ring is a bit overkill on an engine this size in MODERN thinking. Back in the day they thought the more rings you had the better the compression. Saying that I have found most early steam engines this size use one WIDE ring. On a little 3" bore engine I have with a 1/2" wide ring they had even fitted an inner " spring" ring to provide even more tension. I removed it for low pressure running and the little engine is much happier.

The easiest fix would be the changeover to Graphited Yard Steam Packing. Roll it in with a scarf joint and it will be fine. This is what I would do if my engine had no junk ring leaving ring spacers out of the question. Nice engine!
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Old 02-02-2019, 09:25:27 PM
J.B. Castagnos J.B. Castagnos is offline
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Default Re: Tight rings ???

I've found that the replacement rings we buy for our 2 cycle marine engines have too much wall pressure, making the engines hard to start and reverse. I usually cut .030" from the inside of the ring bore, makes a world of difference. Bore a piece of pipe to cylinder size, leaving a step for the ring to ride against. Drill a small hole and loop a piece of wire through it, insert the ring with the wire in the gap, this will keep it from spinning while boring. Cut going in and the ring will stay in the jig. Face the ring lightly on wet or dry sandpaper on glass to remove any burrs. Try two rings first.
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Old 02-02-2019, 11:46:28 PM
Gary Reif Gary Reif is offline
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Default Re: Tight rings?

Is it possible that the ring groove in the piston is not deep enough to let the rings compress freely without bottoming in the groove. Just a thought.
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Old 02-04-2019, 01:42:47 AM
Pete LaBelle Pete LaBelle is offline
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Default Re: Tight rings?

Hi guys -

Thanx for the ideas.

The piston is one piece, and the rings need to be spread to be put into the groove.

The groove IS adequately deep enough so the rig doesn't bottom out in the groove.

Think I might try going to one ring, and turning a plastic spacer that I can slit like a ring, and take up the piston ring groove width. Not sure that re-boring the ID is withing my capabilties or not.

Keep ya posted.
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Old 02-04-2019, 07:57:22 AM
John C. Neagley John C. Neagley is offline
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Default Re: Tight rings?

I have a friend who has encountered tight rings in the past. He simply lays them on top of the grate/flame of his wife's gas kitchen range and heats them up for awhile. This removes some of the temper and always solves his problem. Some of his engines have ran successfully for many years with good compression and without any further problems. Just thought I'd pass this along without any warrenty.
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Old 02-04-2019, 11:25:14 AM
J.B. Castagnos J.B. Castagnos is offline
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Default Re: Tight rings?

Scribe a line on two of them and grind out with a Dremel, they're only going to be spacers.
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