I replaced the bearings with plastic cage ones which may eventually reduce fatigue. Or so I figure. Front one is NSK and the rear one is NTN, I got these from a local bearings store (Bogota, Colombia) and I sure hope they come from a different batch which is likely because they have different cages.

At least I'll be using the culprit or it's victim, the piston, as a brand new keychain.

PropTop,


I also believe the relationship is true in some cases... The causal affect is one-way, i.e. bearing damage shrapnel will score the sleeve/piston, but the thin flakes of nickel are unlikely to make the rear bearing 'go south'...

...But I have seen enough junked bearings in OS engines, in which the P+S were immaculate.


Bearing replacement was the only repair necessary.


I wish you luck, Plugin... NSK should good.

It says Japan on the front shield. but I mistyped the name on my previous post, they are NSK.

I donno, but nickel is very hard.

Quote:

ORIGINAL: Sport_Pilot

I donno, but nickel is very hard.

Is it, Hugh?


Please see the Rockwell C column [link=http://www.metal-mart.com/Guides/Hardness_Nickel.htm]here[/link], for nickel alloys.
Also the bottom table [link=http://www.steelmedia.com/chrome-steel-balls.htm]here[/link], for AISI 52100 and EN 31 bearing steels.

The flaked nickel particles would be pulverized...


For that matter, chromium (true ABC) has a Rockwell C hardness rating of 68-74...

But that doesn't flake. Though nickle is softer, I think it may be hard enough to do some damage, maybe not right away. All it really has to do is jam up the balls so that they slide instead of roll. After a time this will ruin a bearing.

Quote:

ORIGINAL: Sport_Pilot

Quote:

For that matter, chromium (true ABC) has a Rockwell C hardness rating of 68-74...

But that doesn't flake. Though nickel is softer, I think it may be hard enough to do some damage, maybe not right away. All it really has to do is jam up the balls so that they slide instead of roll. After a time this will ruin a bearing.

True, Hugh.

Chromium is much less prone to flaking off, because its bond to the brass/aluminium sleeve is very strong...
Each of its 'islets' is sitting very firmly on the surface.

The damage you describe with nickel is possible in theory, but usually, flaked nickel is not carried back into the crankcase, but rather spewed out the exhaust, or lodged between the piston and the sleeve...

And yes, sliding balls in bearings will noticeably shorten their term...

Now that you're on the subject, what about aluminum shards that get torn of the crankcase, are those prone to cause a lot of damage or are they considerably less harmful than pieces of the bearings?

Plugin,


Since in most engines aluminium parts do not participate in direct mechanical work, against other parts (except the very hard high-silicon piston), it is quite unlikely for aluminium parts to start floating around in the engine.

The back-plate may come into occasional contact with the crank-pin, but this will at most cause a swirl-pattern on it - not major shard separation...

I see, I'm just wondering because from the pictures I've seen, when a little piece of bearing floats around the engine it dents and scratches everything like in Bad Tooth's engine. I was just wondering in the hypothetical case in which shards of aluminum where to go around the engine, what sort of damage could one expect? Could they contribute to damage the bearings even more?

If an aluminium shard is caught in the bearing, it will prevent a ball from rolling, causing it to skid instead...

This can be damaging to the bearing.

Actually, the nickel deposited by the electroless process *is* a lot harder than regular nickel, that's because it contains relatively high levels of phosphorus it's not just pure nickel (which is much softer).

Plugin, do you have some pictures to share? Now you have a fun engine rebuild project

Keeping this in context, remember that the engine will be turning 11-15,000 rpm and is also very hot.....one little thing goes wrong and mayhem happens. Actually I marvel how strong most of our engines are.
Many are operated by guys who don't know or care much about the engine until it fails and then find fault. Some engines are more prone to fail than others and their faults will surface in short order. A little knowledge and care go a long way.

Quote:

ORIGINAL: XJet

Actually, the nickel deposited by the electroless process *is* a lot harder than regular nickel, that's because it contains relatively high levels of phosphorus it's not just pure nickel (which is much softer).

Actually, Bruce, it is actually medium phosphorus electroless nickel that can be heat-treated up to 68 Rockwell C... High phosphorus nickel offers superior corrosion resistance, when applied to steel.

I do not know what after-treatment OS ABN/ABL sleeves undergo, after they are nickel-coated... Do you?

I don't know what OS are doing, but the ENP I'm using here is very hard and used as a bearing-surface in a couple of the assemblies I make. Even a very thin layer provides excellent wear properties is "harder" than austenitic stainless steel.