Quote:

ORIGINAL: gkamysz

If you were an engineer that would be a guess, not even a good one.

OUCH!!! That hurt, Greg....

I am not an engineer by academic degree, but an economist and a software testing engineer by trade.


However, I believe my lingual skills are pretty good...

I am a little more than an acknowledged amateur; as far as bearing engineering is concerned. But I do understand the lingual term 'seal'...


A non-contact bearing seal, isn't... It is just a soft shield, designed to prevent most FOD, but not designed to actually seal the bearing...

So, why the heck does NSK call it a seal?
Is it because shields are normally made of steel; and since a synthetic rubber/plastic material (which cam seal) is used for it, it is called a seal, even though it doesn't???


As to service life and running conditions; The service life of a contact seal in a bearing depends, among other things, on the RPM it is spun.

But it could easily be said that the service life of these contact seals, is much longer than the average life expectancy of a glow engine...


If you can show me the rating in any on-line catalog that says the service life is shorter, please do...

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I am not an engineer by academic degree, but an economist and a software testing engineer by trade.

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And we thought that you were a model airplane engine distributor...

That's the thing Dar, you have a big following here. You can say something and others will take it as absolute knowledge. Some one reading the same might assume a seal is a seal and end up with poor results. If in your experience sealed engine bearing don't leak, say so. I said, in my experience, they do leak and the life doesn't exceed the life of the engine, and you and Paul said I'm wrong even though my first hand experience says otherwise, and even the spec for the type of bearing used in the OS engines I mentioned says otherwise. That's my only point. If you want to learn about bearings look up the information. Every manufacturer is different. Obviously, you didn't take the time to look up what I was talking about and continued to interpret sealed as some impervious barrier. I know you have much technical knowledge, but this was something that I had to point out. Dar, I didn't bring up degrees, nor try to belittle you. I just asked you to prove your position with some backup information. If I employed you as an engineer and that was your answer to the question, you can imagine my response.

Gosh Dar, I wasn't aware that an Engineering Degree was required to post here. The next thing you know they will require a Masters. Slippery sloap here. Doctorate next? I guess I'll have to move to "My Space.com"

Bill

There are some posters here that truly stand apart from the rest due to thier experience and sound advice offered. But, I don't care if Kelly Johnson posts here I'm going to weigh their advice against my personal experience and knowledge gained elsewhere. I hope that no one blindly accepts what any poster suggets without questioning the validity of their staements.

Bill

[sm=thumbup.gif]...

I'll sum up everything Greg said in one word.

YES!.

To continue. Every "sealed" bearing I have seen in a model airplane engine (and that is a fairly large number) will leak fuel through it. Just as an experiment I replaced a shielded front bearing in a 4 cycle engine with a sealed bearing and then squirted WD40 into the breather. Came right out the front end. Then with a pump oiler I squirted Marvel Mystery Oil into the breather and it came out the front end. Left the engine sitting nose down. With no pressure at all it did keep the oil from leaking out but most engines have a pressure in the crankcase while running which will cause oil to flow through the bearing. It did in this engine. I plugged the breather just to see if it would.

Are shielded bearings less expensive than sealed? If so we could save some money.

Bill

Why would you bother?

Seals don't seem to seal against low-viscosity fluids such as fuel but neither do shields.

Whichever way you look at it, leaving the seals on a front-bearing is a good idea and at worst, can't hurt at all.

If the seals *do* seal then the grease will provide life-long lubrication. If the seals don't seal then the engine will provide lubrication by way of the oil that slips past the seals.

Wasn't that what we were trying to figure out in the first place whether to pull the seals or not?

The answer is obviously no.

Agreed.

Bill

Greg, Bill, BW, Ace,


Writing in this forum does not require a degree in engineering...

I became a dealer for several model product manufacturers, after I began writing in this forum.
Most of them approached me; apparently after seeing that I do have some following...

I learn new things every day and have learned from everything I ever did in the hobby.
I also fully comprehend what I read and can easily sort out important facts, from incorrect assumptions (or utter lies...).


Although I am not a mechanical engineer, I have been deep into R/C and engines since 1980; and began building F/F and C/L planes in 1977.

I also have a profound understanding of anything mechanical and of dynamic systems that involve fluid flow...
...And I have the ability to explain intuitively, in relatively simple sentences and in layman terms; what an engineer will have resort to calculus and complicated formulæ to explain.

Furthermore, my explanations can be understood by anyone who puts his/her mind to them, which is the reason I seem to have some following here.


However, there are also some rather challenging individuals here, who insist on 'ruffling my feathers' (Hey, a monkey has no feathers!...), or just like to argue and to bring out the best in me... I have proven some of them wrong and eradicated some 'myths'; previously believed by hobbyists to be words of G-d...


Regarding the matter in hand, Greg; a seal is something that provides an effective seal...

If it does not provides an effective seal; then it is not a seal; and it must be given another name that would not be synonymous with 'seal'.


I challenge any large bearing manufacturer to explain why his company uses the term 'seal', to describe something that essentially doesn't.

There`s alot of different opinions regarding the matter of shield, seal or open bearings.

This is a related/similar thread I just started in the gas engine forums: http://www.rcuniverse.com/forum/m_8430944/tm.htm

Which ones....?

BW,


I sent you a PM.

Dar,

Nobody needs an engineering degree to post here. Just like any other forum, you have to accept that you might be challenged if you post something. I'm sorry that I put you up to the test. I still don't have any convincing answers to support your view. Not even your own experience saying that you have thousands of hours on an engine into which you put a particular sealed bearing. Others have posted their experience. Seals "seal" to varying degrees. You don't seem to accept the fact that bearings seals are made for various applications and the model engine might be more demanding than it looks to the eye.

Unfortunately, we don't have any bearing manufacturers present here, so I think your demand for answers for the use of the term "seal" will go unanswered.

If you still haven't bothered to verify the fact that NSK offers three different types seals, have a look. Their language is quite clear, that they offer the seals for various applications.

http://www.us.nsk.com/library/catalo...20BEARINGS.PDF

http://www.skf.com/portal/skf/home/p...&newlink=1_1_3

Here's one more. Table one is what you are after.

I am often repairing the gearbox in Peugeot car shop, there are rubber sealed bearings in gearbox in gear box house (not in clutch side gearbox house, in other house where the rubber sealed bearings are in between 4. and 5. gear). There are never found grease in rubber sealed bearings, also the grease are replaced with gearoil. So clear the rubber sealed bearing are not 100% sealed. The reason the sealed bearing are used in gear box are to protect the steel particles are entered into the bearing.

Since Greg (gkamysz) showed differnce grade of rubber sealing are made by NSK ball bearing manufacture, the problem with the SKF bearings when i am buying the sealed , there are often marked RS and nothing other grade of rubber sealing in SKF bearings since the seller do not knew all about the bearings..
Do not rely the rubber sealed bearing are complete tight against leakage, they are made to protect the dust are entered into the bearings. The metal sealed bearings are not protected against dust such as saw dust from table saw..
At school we maked own table saw, there are rubber sealed bearings mounted against saw dust from wood and our teacher told to us the former pupil in school had jammed bearings in his table saw due saw dust from wood, it had metal sealed bearings and soon replaced with rubber sealed bearings.

Greg,


After viewing the NSK material, I conclude 2RS bearings have contact seals, which obviously seal much better that non-contact seals do.

The RPM (in grease) these bearings are exposed to in model engines, is well within their ability.

For example, the R6-2RS (grease-packed contact-sealed) bearing, is limited to 20,000 RPM, a level most .40-.56 engines that employ this bearing will never reach in practice.
Q-500 and pylon racing variety engines should use the shielded type bearing R6-Z (36,000 RPM limit)...


The fact that even contact sealed bearings will leak a part of the grease, following long durations of high RPM/high temperature running, is something I do know...

But even the worst running conditions, a model engine can confront bearings with, are not extreme in bearing terms.
...And the duration of these extremes is always relatively short.
The crankcase rarely exceeds 60ºC (140ºF).


Even when a sealed bearing does leak some grease, it will still retain a sufficient amount of it inside, to continue running without risk of failure.
And it is very unlikely to ever happen in a model engine.

As long as a contact-sealed bearing seals, it is unlikely to leak any significant amount of either air, or raw fuel.

RSH seals = high pressure water exclusion. Kind of sound like it might also be an effective crankcase seal. Cool.

Bill

I thought a seal was an animal that balanced a ball on its nose in a circus. Or was killer whale food.

No, your thinking of Seale, Bobby Seale the civil rights activist.

Bill

Why the secrecy or furtiveness?

BW,


I generally deal in Israel.

I would not want people from all over to ask me for quotes, to get better deals elsewhere.


According to RCU rules, the fora and the PM system are not to be used for brokering sales deals...

How about having someone with access to military specs look up what is or is not considered a sealed bearing? Any military will do, just to serve as an example.


Ed Cregger