Lubricating the backs of bearings

[Kevin Johnson]

Sounds like you are tapping out. I can accept that.

Honestly, I have the sense that you need to brush up a little on the physics.

Honestly,I feel you are an experienced builder that cannot prove your case with anything other than "that's the way it's always been done". If you have the physics evidence show it.

The physics has already been presented, hence my comment.

I do not build engines for a living.

[fabr]

So when cleanliness is the key, what advantage is lubing the backs? I have done lots of things “wrong” and had engines live. Does that make it right? Am I then wrong for later doing it the right way? Do I start using trans fluid on my flat tappet cams just because it does not say not use it? I spend tons of time making sure my cylinder bores are clean, why not spend just a bit of time to make sure the bearings are just as clean? I still can’t understand why this thread is so long.

For me it is simple, it is easier to keep my bearings clean when they are dry.

Paul

Bingo! I believe that is the only reason it has become the universally accepted practice. It does not mean an oil film will create or prevent anything.

My old friend used bacon rind and sometimes oil soaked leather belts in place of babbitt before he migrated from the Indian Nation to Cali in the 1930s. Worked too!

A lot of pre-war parts were shipped smothered in cosmoline that would need to be stripped. Seems like someone in AZ did brake testing and those rotors need to be cleaned in order to have reliable and reproducible friction coefficients.

All VW beetles and type 4 vw's were shipped to the Us with every exterior inch of it covered with cosmoline. I steam cleaned a lot of them when first employed at a dealership. We all know about brakes. A rotating disc/drum will develop a hydrodynamic oil/liquid of any kind wedge just like a crankshaft. Not the same thing as a locked in place shell bearing.No rotation to create the wedge especially since there is no oil reservoir to create the wedge in the first place.

[fabr]

Honestly, I have the sense that you need to brush up a little on the physics.

Honestly,I feel you are an experienced builder that cannot prove your case with anything other than "that's the way it's always been done". If you have the physics evidence show it.

The physics has already been presented, hence my comment.

I do not build engines for a living.

There has been zero physics presented here. I didn't say you did it for a living.

[fabr]

On the flip side, there very well may be data showing dry is better but I don’t have the time to find it. I know what does work, so why question it. There are plenty of other things in the engine to question in the quest for performance or longevity. I could imagine heat transfer could make a difference, but like I said I don’t have time to find that data.

Now for the sake of our sanity, I am tapping out.

Paul

So am I .It's been an interesting debate. For the record ,one last time,I do install dry but see zero issue with a slight oil film. Not a single mind will be changed but maybe gave some food for thought. That's how we advance.

[Kevin Johnson]

...
There has been zero physics presented here. ...

Way back on the first page I included a link to a paper on friction -- so from the very start. That was when I proposed getting a graduate student to model a case including a lubricant as a thesis project.

Read the handbooks.

[In-Tech]

On the flip side, there very well may be data showing dry is better but I don’t have the time to find it. I know what does work, so why question it. There are plenty of other things in the engine to question in the quest for performance or longevity. I could imagine heat transfer could make a difference, but like I said I don’t have time to find that data.

Now for the sake of our sanity, I am tapping out.

Paul

So am I .It's been an interesting debate. For the record ,one last time,I do install dry but see zero issue with a slight oil film. Not a single mind will be changed but maybe gave some food for thought. That's how we advance.

You can do whatever you want fabr, and so will I. It's not an intersting debate, you are an idiot and so am I . When you have an environment and are striving for .0008"-0010" and you put some 70 wt engine oil(not gear oil) behind the shell, let us know how that turns out for you

And seriously, if you are really needing to worry about pulling heat from the shell, you have other problems you obviously don't know about. cheers

[Momus]

The point is I have looked and looked for any actual literature that says a film of oil or even a drenching of oil will cause a spun bearing. This IS what you guys are inferring. I have not even found any literature confirming that dry is better. If you guys have it I will stand corrected.

I'm not inferring that at all.

I'm simply stating that it is superfluous and could possibly be detrimental.


Anyone, perhaps apart from yourself, with basic logic skill will realise that no
PHD paper, or other research is going to refute a negative and so will not exist.

Some things are so obviously without benefit that they are not worth countenancing let alone researching.

[treyrags]

I hate to add to a discussion that is 5 pages longer than it should be. Of course the surfaces need to be clean and dry when assembled. But every engine I have disassembled oil has found its way behind the bearing shells. So why is it ok to be there later?

[fabr]

On the flip side, there very well may be data showing dry is better but I don’t have the time to find it. I know what does work, so why question it. There are plenty of other things in the engine to question in the quest for performance or longevity. I could imagine heat transfer could make a difference, but like I said I don’t have time to find that data.

Now for the sake of our sanity, I am tapping out.

Paul

So am I .It's been an interesting debate. For the record ,one last time,I do install dry but see zero issue with a slight oil film. Not a single mind will be changed but maybe gave some food for thought. That's how we advance.

You can do whatever you want fabr, and so will I. It's not an intersting debate, you are an idiot and so am I . When you have an environment and are striving for .0008"-0010" and you put some 70 wt engine oil(not gear oil) behind the shell, let us know how that turns out for you

And seriously, if you are really needing to worry about pulling heat from the shell, you have other problems you obviously don't know about. cheers

Yes ,you are an idiot and so am I if using 70wt oil with .001 or less clearance. I think we can all agree to that?

[fabr]

I'm not inferring that at all.

I'm simply stating that it is superfluous and could possibly be detrimental.


Anyone, perhaps apart from yourself, with basic logic skill will realise that no
PHD paper, or other research is going to refute a negative and so will not exist.

Some things are so obviously without benefit that they are not worth countenancing let alone researching.
[/quote]So,since YOU are simply stating something it is fact? At one time lots of people simply stated the world was flat . Did that make it so?

[fabr]

I hate to add to a discussion that is 5 pages longer than it should be. Of course the surfaces need to be clean and dry when assembled. But every engine I have disassembled oil has found its way behind the bearing shells. So why is it ok to be there later?

FWIW,I have disassembled engines that were still dry between shell and caps/saddles after many tens of thousands of miles. Many were wet and were that way for a very long time as evidenced by the discoloration/staining on the bearing back . None of them had spun bearings though. Every single spun bearing I ever saw was due to lack of oil or lack of clearance or an out of spec bore.

[Kevin Johnson]

I hate to add to a discussion that is 5 pages longer than it should be. Of course the surfaces need to be clean and dry when assembled. But every engine I have disassembled oil has found its way behind the bearing shells. So why is it ok to be there later?

Other people have mentioned capillary action. The backing under compression from "crush" is a type of spring.

It is actually something worth discussing if (say) when an 'in situ' bearing inspection is done, will the release of the bearing crush allow immediately adjacent residual oil to be drawn in? I think this type of inspection is fairly common with race engines. It would be worth knowing that/if there is a potential unanticipated risk involved.

OEM engineers that inspect engines after certification dyno runs (hundreds or even thousands of hours of continuous operation) might be able to offer insights.

[fabr]

Consider this,if the bearing crush is approaching 8MPa which is 1160psi and a 3" main bearing has approx7 sq.in. area there is approx. 9280 pounds of force crushing the bearing into place. How much torque is required to spin the bearing in its bore? I will venture to say there is no way for enough torque to be imparted into the bearing to spin it short of seizure on the shaft . Dry bearing back or "wet".

[Criterion]

I guess it's a bit too agricultural of an example, but has nobody here ever done an in-frame bearing replacement? It's pretty much a guarantee that oil makes it onto the backs of the shells that way.

[Momus]

I hate to add to a discussion that is 5 pages longer than it should be. Of course the surfaces need to be clean and dry when assembled. But every engine I have disassembled oil has found its way behind the bearing shells. So why is it ok to be there later?

Did you hear that loud whooshing sound?

That was the point going over your head.

The discussion is about whether to assemble and engine and deliberately lubricate the bearings and bore.

Engines I dismantle usually have no oil behind the bearings and often the bearings etched ID is printed on the block or rod.