OIL "Cushion" for bearings..

[BuickGN]

Originally Posted By: Bob The Builder
Originally Posted By: Bryanccfshr
The only place it can be "squeezed out" is in locations that are not pressurized. Such as Cam lobes and in modern engines these are relatively low pressure , low friction interfaces. And to tell the truth I see little reason why a more viscous oil is more protective in this situation other than it takes more energy to move it out of the way.

In crank bearings what seems to matter is having adequate volume to maintain a film.
You also reach a point of equilibrium where although a more viscous fluid may escape the bearing more slowly it is also replaces more slowly. As the fluid is thinned it escapes more quickly but is also replaced equally as quickly.



Frankly and without offending anyone named Frank, I have to politely disagree that oil can only be queezed out where the area being lubricated is not pressurized.

I saw a video, and dangummit if I can't find it right now, where an engine had a clear plastic oil pan. There was a camera set up under this engine. I remember specifically that the oil lubricating the crankshaft journals...which, and correct me if I am wrong, is under constant and high pressure oil, was spitting out along the journals. The oil has to go somewhere. It isn't only going to stay in the immediate area of the bearing. It was literally flying off of this crankshaft at a trmendous rate of speed.

I hope I haven't made an idiot of myself and either misunderstood the question or quoted the wrong post. Have a good weekend.


This is how the cylinders are lubricated, the oil slung off the crank from the rod journals. Oil most definately gets pushed out the sides of the bearings.

 

[demarpaint]

So since oil can't be compressed wouldn't a thinner, faster flowing oil lubricate, clean, and cool better?

Frank D

 

[Bob The Builder]

Originally Posted By: demarpaint
So since oil can't be compressed wouldn't a thinner, faster flowing oil lubricate, clean, and cool better?

Frank D


Frankly, it would depend upon the bearing clearances as I believe Steve mentioned. The tighter tolerances and bearing clearances of newer vehicles call for lighter oils. A huge race engine will be built somewhat "looser" than a regular car engine. In this example, we see the race team using maybe a straight 50 or 60 weight oil.

At the expense of gettin shot...this would...ahem...provide a thicker cushion of oil between said and aforementioned "looser" tolerances and clearances....ahem...

An example of the problem we face upon using a thicker oil in a newer vehicle would be not unlike the one I experienced several years back when I tried running 20w50 Valvoline oil in my Toyota Tacoma.

When I fired it up...you could very clearly hear and feel the oil pump going gluppp..glup..woop..woop...glub as it tried in vain to suck this massivley thick oil through the pickup tube and force it through all of the lubrication passages....So, I immediately went back to my usual Castrol Syntec 10w30 I was using at the time, like a good little chap. I'm getting carried away here.

Good night...errr morning.

 

[Gary Allan]

In any of my readings on the topic (and admittedly - as soon as the author starts attempting to illustrate using equations - I grind to a halt. We don't use math in the slums of K-PAX) I integrate that volume and viscosity should be able to be freely exchanged.

I tend to view (in Gary's adaptive view® via proprietary watershed osmotic absorption®) a journal bearing as a turbo charged crescent pump that has no suction head (although, at a certain point - I think the view may be slightly altered).

 

[6point5psi]

We run the lube oil system as if the turbine and generator were in operation even when we're only on the turning gear (8 rpm).
This is at a 50Mw power plant.

 

[6point5psi]

Originally Posted By: Gary Allan
In any of my readings on the topic (and admittedly - as soon as the author starts attempting to illustrate using equations - I grind to a halt. We don't use math in the slums of K-PAX) I integrate that volume and viscosity should be able to be freely exchanged.

I tend to view (in Gary's adaptive view® via proprietary watershed osmotic absorption®) a journal bearing as a turbo charged crescent pump that has no suction head (although, at a certain point - I think the view may be slightly altered).



I look forward to the day I actually know what the He** you said.

 

[demarpaint]

Originally Posted By: Bob The Builder
Originally Posted By: demarpaint
So since oil can't be compressed wouldn't a thinner, faster flowing oil lubricate, clean, and cool better?

Frank D


Frankly, it would depend upon the bearing clearances as I believe Steve mentioned. The tighter tolerances and bearing clearances of newer vehicles call for lighter oils. A huge race engine will be built somewhat "looser" than a regular car engine. In this example, we see the race team using maybe a straight 50 or 60 weight oil.

At the expense of gettin shot...this would...ahem...provide a thicker cushion of oil between said and aforementioned "looser" tolerances and clearances....ahem...

An example of the problem we face upon using a thicker oil in a newer vehicle would be not unlike the one I experienced several years back when I tried running 20w50 Valvoline oil in my Toyota Tacoma.

When I fired it up...you could very clearly hear and feel the oil pump going gluppp..glup..woop..woop...glub as it tried in vain to suck this massivley thick oil through the pickup tube and force it through all of the lubrication passages....So, I immediately went back to my usual Castrol Syntec 10w30 I was using at the time, like a good little chap. I'm getting carried away here.

Good night...errr morning.


I see your point, thanks.........What still confuses me is once that space is filled with a fluid that can't be compressed, and has lubrication properties then all should be good, and the faster it flows in and out, the cooler and cleaner the part should be. I am talking about todays tighter engines, and not racing applications which in your example the thicker oil is the ticket. So someone using a 10W-30 oil in an engine calling for 0W-20 might be shooting himself in the foot if he plans on keeping the car for a very long time.

Frank D

 

[Gary Allan]

Originally Posted By: 6point5psi
Originally Posted By: Gary Allan
In any of my readings on the topic (and admittedly - as soon as the author starts attempting to illustrate using equations - I grind to a halt. We don't use math in the slums of K-PAX) I integrate that volume and viscosity should be able to be freely exchanged.

I tend to view (in Gary's adaptive view® via proprietary watershed osmotic absorption®) a journal bearing as a turbo charged crescent pump that has no suction head (although, at a certain point - I think the view may be slightly altered).



I look forward to the day I actually know what the He** you said.


a journal bearing as a turbo charged crescent pump

Quote:
Pressures on the loaded side run a few hundred psi and oil is squeezed out the side. Oil pump pressure it just to get oil to the low pressure side of the bearing.


Does not a crescent pump do exactly the same thing ..except with suction head instead of being "force fed" (aka 'charged)? That is, the action is very similar ..whether or not the designated functions are different.

Sand the teeth off of this pump and allow the two components to "float".

Quote:
I integrate that volume and viscosity should be able to be freely exchanged.


There is typically no "viscosity" component to the physics involved. Merely a given volume to produce the given pressure required to keep the two surfaces apart.

Hence, volume and viscosity should be able to be freely exchange. Only a given pressure is required. It shouldn't matter whether it's half the volume at twice the visc or twice the volume at half the visc. There would be some limits, I imagine, I don't think a grease gun with a couple of pumps every half hour would work ...but then again, Shannow's report of STP lasting 4 days or so .....

 

[Lazy JW]

It's my understanding that oil actually IS compressible albeit a very tiny amount and not really enough to change the practical dynamics in an automobile engine. But if we are going to pick nits lets get really picky.
Joe

 

[Steve S]

[/quote]So someone using a 10W-30 oil in an engine calling for 0W-20 might be shooting himself in the foot if he plans on keeping the car for a very long time.

Frank D [/quote] Not really there is not a whole lot of difference in the oil viscosity. for example themy 2006 Toyota p/w says 5w-30 in the manual yet a TSB says 5w-20 is the new recommended visc . The Ford OHC engines also did that.

 

[JAG]

Originally Posted By: Gary Allan
In any of my readings on the topic (and admittedly - as soon as the author starts attempting to illustrate using equations - I grind to a halt. We don't use math in the slums of K-PAX) I integrate that volume and viscosity should be able to be freely exchanged.
If this means that for any decrease in viscosity, equal journal bearing protection can be obtained by increasing oil flow rate through it, this is one of the things that is not true. The eccentricity ratio increases (off-centeredness) due to the less viscous oil and what increasing flow rate would do is mostly: increase flow rate. Check out the online Google book in the link I posted. If you see equations, just move on. LOL

 

[Gary Allan]

After thought ....

Quote:
I look forward to the day I actually know what the He** you said.


Remember the first time you saw one of those word problems that looked like? It happened to you somewhere in junior high:

Sally left Chicago at 9a.m. on a train going to Frostbite Falls, ND carrying 2.5 oz of Chanel No.5. At the same time, her cousin Frank was running around a flagpole in Boston. How much does her daughter, laying on the beach in Miami Beach weigh?

Same thing. Just filter out the bee-ess.

 

[Steve S]

Originally Posted By: Lazy JW
It's my understanding that oil actually IS compressible albeit a very tiny amount and not really enough to change the practical dynamics in an automobile engine. But if we are going to pick nits lets get really picky.
Joe
Getting too complicated here the "cushion" is just the time it takes for the oil to get pushed aside or out . Like water skiing. When you let go of the rope you start to sink ,the water is displaced ."some what of a poor analogy". Or maybe better is like in a shock absorber "dampner" the resistance of the oil being forced through the orifaces. Or put a glop of grease on a hard thick metal surface then hit the grease with a hammer the grease cushions the hammer blow as the grease is pushed aside untill there is no grease then it is metal to metal.

 

[demarpaint]

Originally Posted By: Steve S
So someone using a 10W-30 oil in an engine calling for 0W-20 might be shooting himself in the foot if he plans on keeping the car for a very long time.

Frank D [/quote] Not really there is not a whole lot of difference in the oil viscosity. for example themy 2006 Toyota p/w says 5w-30 in the manual yet a TSB says 5w-20 is the new recommended visc . The Ford OHC engines also did that. [/quote]


It could also mean that after testing, and the 5W-20 and 0W-20 have been in use for a while now that maybe it was better for the application. I now see that older cars that once called for 10W-30 and/or 10W-40 have been back spec'd to now use 5W-30. I guess the bottom line is experiment get some UOA's and go from there.

Frank D

 

[Steve S]

Originally Posted By: Gary Allan
After thought ....

Quote:
I look forward to the day I actually know what the He** you said.


Remember the first time you saw one of those word problems that looked like? It happened to you somewhere in junior high:

Sally left Chicago at 9a.m. on a train going to Frostbite Falls, ND carrying 2.5 oz of Chanel No.5. At the same time, her cousin Frank was running around a flagpole in Boston. How much does her daughter, laying on the beach in Miami Beach weigh?

Same thing. Just filter out the bee-ess.

They weigh about the same . No wait,Sally is the mom so the daughter who is laying on the beach in Maimi is a babe so Sally must weigh about 30 lbs more . But as I am old enough to enjoy and appreciate the extra cushion I am not shure about anything.

 

[Steve S]

Changing to 20 wt oils is a way to increase the mpgs "epa cafe" And the 20 wts seem to work.

 

[Bryanccfshr]

Thanks for the explanation Shannow.

 

[Bryanccfshr]

Originally Posted By: Gary Allan
[There is typically no "viscosity" component to the physics involved. Merely a given volume to produce the given pressure required to keep the two surfaces apart.

Hence, volume and viscosity should be able to be freely exchange. Only a given pressure is required. It shouldn't matter whether it's half the volume at twice the visc or twice the volume at half the visc. There would be some limits, I imagine, I don't think a grease gun with a couple of pumps every half hour would work ...but then again, Shannow's report of STP lasting 4 days or so .....

I agree with this within limitations of the physical lmits of the fluid. Another issue is that grease or STP may be great for low RPM high load but it would not perform the cooling function well at higher speed.

 

[Bryanccfshr]

Jag,
Your link is shaping uo to be a very interesting read.

 

[buster]

Great thread. I'm still learning/reading.