Another piston ring question

Hi,

As everyone was so helpful with my last question about piston rings, I'd like to ask another. I unwrapped the new rings for my Wolseley engine this afternoon ready for fitting. Surprisingly there were four rings in the pack, whereas there are three on the piston. The first two rings on the piston are identical plain cast iron rings a little over 1/8" thick. The third ring is a slotted cast iron oil control ring about 1/4" thick (the bore is 3"). In the packet I have two identical rings which fit the first two grooves fine. Then I have a slotted oil control ring which is narrower that the original (perhaps by 1/16"), and a very thin ring which is about 1/16" thick. When placed together these two rings are the same thickness as the original oil control ring, and fit neatly into the groove.

So it would appear that I am intended to replace the original oil control ring with two rings. Is this common practice when the correct ring is unavailable? I bought the rings a few years back and now I have a vague recollection of some discussion about this, but I can't remember the details. I just need to decide whether it's okay to fit these rings. I should point out that this is a big, chugging engine which isn't highly stressed (1.5 hp at 700 rpm with a 3" bore) so it's probably going to be more forgiving than modern engines. What do people think?

Any suggestions would be much appreciated.

Many thanks,

Chris

If memory serves, the thin ring is a support for the oil control ring and is fitted below the oill control ring. Remember to stagger the gaps!

All the best,

Charles

Christopher Tidy wrote in news: snipped-for-privacy@cantabgold.net:

It will be perfectly fine to use the new set-up. This is actually an improvement over the original. The thin ring is a 'wiper' and in combination, will do a better job than the original.

On Thu, 19 May 2005 16:35:58 +0000 (UTC), the inscrutable Christopher Tidy spake:

The overlapped pair, with their openings more often offset than aligned, probably keeps more oil from escaping into the combustion chamber.

Engineers probably found that the pair worked better (or broke less frequently) than the original single piece.

Dredging up memories from 33 years ago (auto tech school theory), I believe it provides just slightly better oil control. I remember having installed 4-pc oil rings. Thin upper and lower chromed rings and a narrow center ring with www expanded spring below it.

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Yep!

Harold

The thin ring is only a spacing ring to convert the wider original ring to the more modern width. The thin ring is fitted above the oil control ring in the groove.

Tom

That could be true in this instance. It all depends on how it fits the bore. If it's the largest in diameter, it very well could be a wiper. With the typical 4 piece sets, the thin rings are the wipers, and are made of heat treated steel, not cast iron. You've likely seen them.

Harold

Steel ring inserts for either adapting narrow rings to wider grooves and enabling worn grooves to be turned out to fit standard width rings are commonplace. Using a steel wiper in conjunction with a cast iron oil control ring, well, that is singular indeed. Spacing rings seat on the bottom of the groove and do not protrude past the ring land.

Harold, what's this I hear you're reluctant to put Colchester bearings in your Graziano? :-) Graziano thought they were good enough..

Tom

Chuckle! Not really reluctant. Just too poor. Mind you, I have no quarrel with Gamet bearings (which is what Colchester used). This old retired dude is looking for something more affordable, but I wouldn't hesitate to buy the Gamet variety if all else fails. The original bearings served me well----and owe me nothing. They're still very serviceable, but I'd like to eliminate the .0002" runout that I didn't used to have. Many think it's no big deal, and I can't argue with them, but when you know it can be better, it's hard to ignore.

The number of jobs I ran with only a couple tenths tolerance are hard to forget. I've always considered myself a good lathe hand, but not good enough to work without a tolerance! :-)

Larry Jaques suggested I'd have a hard time putting anything on Mars with that much runout. If I can't trust Larry, who can I trust?

Harold

It's like owning a Ferrari, generic parts don't exist, so one has to suck up the damage to one's wallet. :-( BTW, Colchester use Gamet bearings because they own them. They don't come cheap for Colchesters either.

Tom

Yeah, I was surprised to find they weren't French owned. The name is a real sleeper. I learned it's a good idea to shop----the latest contact was considerably lower in price than I had been quoted before. Gunner really came through.

The supplier is checking to see if there are any substitutes, but I'm not holding my breath. The thought was to get away from the high speed bearings. My machine runs at only 29% of the speed ratings of the Gamet bearings. Could be I could use an angular contact bearing in place of the originals. Could be I'd be asking for trouble, too. Any thoughts on that idea?

Harold

I'd be very surprised if you'd get angular contact bearings that would fit the Gamet bearing dimensions and still compare load rating wise. How are yours preloaded?

Tom

considerably

I've never had the headstock apart, but from indications, there's a threaded collar that establishes preload. Problem is, the manual doesn't address assembly, just shows the exploded view, and so far I've found nothing that indicates preload values of any kind. The main bearing is a double row opposed roller type, with split inner races. I can't help but think that going to a ball type would sacrifice load capacity. One of the things I've given some thought to is adjusting the bearing ever so slightly, with the idea that it might have worn enough to be slack. Question is, how much? If that worked, I'd have no need to change out the bearings. I'd like that!

Maybe I should touch base with someone that has been there, done that. I hate to run blind on something of this nature. Ignorance can get real expensive.

Harold

Thanks for all the helpful responses. It seems like these rings are fine. But I'm not sure whether to fit the thin ring above or below the oil control ring; there seems to be some disagreement here. If it helps the thin ring is approximately 1/16" thick and rectangular in cross-section, with a very small rectangle removed from one of the outside corners.

Chris

That would indicate a scraper ring which should be placed above the slotted oil ring with the rectangular groove next to the slotted ring, ie facing down. You should also check to see if the slotted ring is symmetrical or has a reduced diameter on one side. If so, this side should face upwards to the scraper ring. Most rings in non-symmetrical ring sets have the upper face marked in some way.

Thanks very much for the clarification.

Chris

You can adjust preload? Then by all means do so. Put a dial indicator on the side of the spindle and with a 2' bar in the spindle bore, apply a bit of side to side pressure and tighten up the preload collor a tinsey bit until the indicator shows minimal movement In BOTH directions. And I mean tiny wheenit itsybitsy tightening each time.

Run the spindle at 2000 rpm for 30 minutes and see if there is any unusual heating of the headstock over the bearing location (check temps now before doing this as a reference.

But personally..I think you are guilding the lilly at .0002 backlash. Btw..is that TIR? .0001 each way, or .0002 each way?

Also..did you measure the backlash cold, or warm? Makes a huge difference.

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the s*it out of you for torturing the cat." Gunner

On Thu, 19 May 2005 19:54:27 -0700, the inscrutable "Harold and Susan Vordos" spake:

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