what determines film strength?
film strength...
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Correct me if I'm wrong, but isn't it the Basestocks (ie. Group II, III, PAO, Ester)?
Regards,
Oz
Regards,
Oz
Base oil type and viscosity.
Here I go again, gonna stir it up.
Viscosity = film strength.
Film strength is = to hydrodynamic film
Shear the hydrodynamic film, you sheared the film strength. Now you rely on barrier lube properties for wear protection.
Viscosity = film strength.
Film strength is = to hydrodynamic film
Shear the hydrodynamic film, you sheared the film strength. Now you rely on barrier lube properties for wear protection.
Patman
Staff member
But doesn't a 10w30 with a PAO/ester base have a higher film strength than a 10w30 with
a conventional base? I thought that one of synthetics claims to fame was the higher film
strength?
a conventional base? I thought that one of synthetics claims to fame was the higher film
strength?
Exactly how long would the barrier lube last if that is all that you relied on? Just wondering.
For instance if you had a weak base stock with a low film strenght but a lot of barrier lube additives?
Of course PAO based oils have a higher shear strength, but I think what Bob's trying to say is that bottom line....shear strength is determined by film thickness...ie. thicker oils have a higher shear strength. Problem is, they also have higher resistance and are power-robbing. Hence, one needs a balance between thickness and an excellent barrier lube (for just those times).
Dr T., Of course PAO based oils have a higher shear strength
That is one I'd argue about.. better noack,yes, better resistance to oxidation, yes, better cold weather flow, yes, better VI, sure, possibly better ability to extend due to those capablities? maybe, but better film strength? NO.
I have heard arguments that synth's have higher film strength.. I HAVE NOT SEEN THIS TO BE THE CASE. Ok, I'm only one guy with no pieces of paper that establishes that on the bench there's no difference between a mineral 10w30 film strength and a synth 10w30 film strength.
Film strength is relational to viscosity or flow. When an oil is put under a shock load or heavy load of any sort, the science says both at set temps are rated to flow the same. This is given as fresh new oils. Now, if both oils have the same basic flow rate, at 210 deg C, and the oil is at operating temps, then under pressure, the hydrodyamic film will push or squeeze out at the same basic rate.(opps!, forgot, something) Some actually claim a synth has better flow, wow, which is it? better flow? so then it doesn't stay in the compressed area as long thus film strength is compromised or does it flow the same as reported by the labs when being assigned a wt like 10w30? I go with the latter, If synth's flow faster than the mineral counter part then the viscosity would not be the same, it would be different. Anyway, so when pressure is applied when a load is exerted, this will cause the film of any oil to be squeezed, and if the oil system has an open lube system like in an engine, the oil like electricity, will take the least path of resistance. Obviously this is only a momentary thing as new oil will pump right back in place once the load levels out.
So, film strength that is touted by any oil is a film of oil that covers or coats a surface which devides or seperates the two surfaces, is termed as hydrodynamic lubrication as shown in this picture..
When under pressure, any oil will flow out thus leaving a momentary lapse in film the you rely on a barrier lube as shown here...
So, anyway, to tell me one oil rated the same basic viscosity over another has better film strenth has some proven to do as I see film is relational to viscosity and the thicker the viscosity the better the film stregth and as Dr T pointed out, there must be a balance between the two.
Anyway, guess that 's enough ramblin tonite.
That is one I'd argue about.. better noack,yes, better resistance to oxidation, yes, better cold weather flow, yes, better VI, sure, possibly better ability to extend due to those capablities? maybe, but better film strength? NO.
I have heard arguments that synth's have higher film strength.. I HAVE NOT SEEN THIS TO BE THE CASE. Ok, I'm only one guy with no pieces of paper that establishes that on the bench there's no difference between a mineral 10w30 film strength and a synth 10w30 film strength.
Film strength is relational to viscosity or flow. When an oil is put under a shock load or heavy load of any sort, the science says both at set temps are rated to flow the same. This is given as fresh new oils. Now, if both oils have the same basic flow rate, at 210 deg C, and the oil is at operating temps, then under pressure, the hydrodyamic film will push or squeeze out at the same basic rate.(opps!, forgot, something) Some actually claim a synth has better flow, wow, which is it? better flow? so then it doesn't stay in the compressed area as long thus film strength is compromised or does it flow the same as reported by the labs when being assigned a wt like 10w30? I go with the latter, If synth's flow faster than the mineral counter part then the viscosity would not be the same, it would be different. Anyway, so when pressure is applied when a load is exerted, this will cause the film of any oil to be squeezed, and if the oil system has an open lube system like in an engine, the oil like electricity, will take the least path of resistance. Obviously this is only a momentary thing as new oil will pump right back in place once the load levels out.
So, film strength that is touted by any oil is a film of oil that covers or coats a surface which devides or seperates the two surfaces, is termed as hydrodynamic lubrication as shown in this picture..
When under pressure, any oil will flow out thus leaving a momentary lapse in film the you rely on a barrier lube as shown here...
So, anyway, to tell me one oil rated the same basic viscosity over another has better film strenth has some proven to do as I see film is relational to viscosity and the thicker the viscosity the better the film stregth and as Dr T pointed out, there must be a balance between the two.
Anyway, guess that 's enough ramblin tonite.
Film strength is related not to viscosity or flow rate but molecular structure. The molecular structure affects VI,vis,etc.
"Synthetic" molecules can be engineered to have a more appropriate molecular structure to resist breaking from hydrodynamic to barrier lubrication.
Syns can also flow in a turbulent fashion dissipating more heat while maintaining their desired film strength. NON syns flow in a laminar fashion holding heat. A Dyson Theory. You heard it here.
POE type base oils, like in Redline have a stronger film strength than other molecular structures. Thats why esters are being used as EP additives to take the place of metallic plating or coating ads.Non metals that can coat up.
Didn't we discuss this 2 years ago on Noria Bob ?
If the Redline corporate office is reading this please send me a leather jacket,before I post our recent test results of your 10w-30 ! Just in case.
"Synthetic" molecules can be engineered to have a more appropriate molecular structure to resist breaking from hydrodynamic to barrier lubrication.
Syns can also flow in a turbulent fashion dissipating more heat while maintaining their desired film strength. NON syns flow in a laminar fashion holding heat. A Dyson Theory. You heard it here.
POE type base oils, like in Redline have a stronger film strength than other molecular structures. Thats why esters are being used as EP additives to take the place of metallic plating or coating ads.Non metals that can coat up.
Didn't we discuss this 2 years ago on Noria Bob ?
If the Redline corporate office is reading this please send me a leather jacket,before I post our recent test results of your 10w-30 ! Just in case.
BOBISTHEOILGUY said, "Film strength is relational to viscosity or flow"
Terry said, "Film strength is related not to viscosity or flow rate but molecular structure"
----
Bob,
Is Terry one of those know-it-all, "cubical engineers" (as you once said)?
Before pushing your beliefs, you should consult an engineer.
Educate yourself on the purpose and interpretation of oil analysis, and on the importance of high shear/film strength base oils vs last-line barrier additives.
You know, there may be a good reason why some European OEMs favor higher quality base oils with high shear strength. Maybe staying in hydrodynamic lubrication longer reduces real-world engine wear. Not everyone promotes cheaper base oils with loads of barrier additives (that may hurt catalytic converters).
[ August 08, 2002, 03:44 AM: Message edited by: geo ]
Terry said, "Film strength is related not to viscosity or flow rate but molecular structure"
----
Bob,
Is Terry one of those know-it-all, "cubical engineers" (as you once said)?
Educate yourself on the purpose and interpretation of oil analysis, and on the importance of high shear/film strength base oils vs last-line barrier additives.
You know, there may be a good reason why some European OEMs favor higher quality base oils with high shear strength. Maybe staying in hydrodynamic lubrication longer reduces real-world engine wear. Not everyone promotes cheaper base oils with loads of barrier additives (that may hurt catalytic converters).
[ August 08, 2002, 03:44 AM: Message edited by: geo ]
Hey Geo,
It's quite apparent that you are new to these boards. I would hardly call Terry Dyson a Cubical Engineer . He's one of the most (if not THE MOST ) knowledgable lubricant analysts around.
It's quite apparent that you are new to these boards. I would hardly call Terry Dyson a Cubical Engineer . He's one of the most (if not THE MOST ) knowledgable lubricant analysts around.
I think Geo was referring to Bob labelling Terry as a Cubical Engineer...
...just clearing things up.
Oz
I'm really sorry this has stuck in your craw geo.quote:
Originally posted by geo:
Bob labels scientists and engineers with professional experience as "cubical engineers", his pejorative. He fails to understand and appreciate the scientific method, analytical/comparative analysis, etc. Watch out for his opinions.
First, lets get it straight. I never actually call some one a cubical engineer,(at least don't remember doing that) I may refer to their point of view as one. My interpretation of a cubical engineer is someone that is just that, a thinker, with lots of analysis and bench tests but with very little real application real world experience in the trenches. There are many who have and are, but also many that are not more than book smart with some excellent ideas.
Second, I have never considered nor classified Terry as one as he and I know the definition. Now I might say he's thinking like one at one point or another. THIS IS'NT BAD! But he and I both know that our backgrounds would not permit us to be that way, or at least not for long.
What is ment by all of this is, YOU CAN'T THINK OUT OF THE BOX. You're stuck on scientific papers and data that FAILS miserably at really SEEING the WHOLE picture when APPLIED to TRUE REAL WORLD APPLICATIONS. This is thinking like a cubical engineer. Someone that hasn't ever gotten down and dirty up close with engines, designs, repairs, experimenting(not on a bench) and checking out the end results. Was on a shrimp boat yesterday, looking at the rear seal on a detroit two stroke, also, at toyota being showed how some head gaskets actually have rubber gastet rings around the oil drainback ports in the head gasket and how the neutra had made a difference in slowing up a head leak on a seina, As well as discussing with a truck lube center how the grease applications to the drive lines compared to others and how someone came in and did one of those scientific tests with a dab of grease and a hammer.
No, I have not got all the answers but I pride myself in the ability that god gave me and that is I can think out of the box and I sometimes feel it just P O's some people especially when I ask how can that be because this.... I like to think it is more like challenging people to get out and really explain just how it does apply, make them think, come up with more than just a piece of paper that was passed around.
Many and I mean MANY drug companies, do all this experimenting, testing, proving to the fda and other things, then go to market as the best there ever was, then all of a sudden, BINGO THEY FOUND IN REAL WORLD APPLICATIONS THERE IS SERIOUS AFTER EFFECTS. WOW, can't imagine that happening in lubrication theory you think?
Thats what this is all about. So just maybe, people need to watch what you are saying as well especially about others?
Back to the subject, I do have a whole lot more on the subject of flim strength but not the time at this point to put it down on the board but will later as I can see you have been really hammering me because of my out of the box thinking I just needed to jump in and ask you take it easy on me just because I question / or comment differently than what you may think or have learned doesn't make this a bad thing. So please try not to get so defensive.
[ August 08, 2002, 02:39 PM: Message edited by: BOBISTHEOILGUY ]
MolaKule
Staff member
Geo,
"You know, there may be a good reason why some European OEMs favor higher quality base oils with high shear strength. Maybe staying in hydrodynamic lubrication longer reduces real-world engine wear. Not everyone promotes cheaper base oils with loads of barrier additives (that may hurt catalytic converters)."
As I have posted elsewhere, the 5W40 grades are being specified as a compromise between the hotter running Euro engines and economy; a median viscosity with favorable film strength.
For journal bearings, they most likely stay in hydrodynamic regimes for 95% of the time, but valve assemblies and piston ring packs have a lot of boundary friction going on under high load situations.
Since about 1959, just about every automotive engine lube has had some type of barrier additive; with some barrier additives being better than others. I happen to think Schaeffer's and Redline have some good barrier additives for AF/FM applications, while I also believe that Amsoil and Mobil have some good ester AF/FM additives.
If you will look at the profiles and the Off Topic threads, many of us have posted what we do and our interests. I happen to be a working scientist/engineer who also works in the shop with the propulsion guys on a daily basis and often get blasted with fuels, lubes, and such. So call me a "pencilhead" or whatever. I think most of us on this board are "greasers" at heart whether we work in our cubicles or work on our cars.
"You know, there may be a good reason why some European OEMs favor higher quality base oils with high shear strength. Maybe staying in hydrodynamic lubrication longer reduces real-world engine wear. Not everyone promotes cheaper base oils with loads of barrier additives (that may hurt catalytic converters)."
As I have posted elsewhere, the 5W40 grades are being specified as a compromise between the hotter running Euro engines and economy; a median viscosity with favorable film strength.
For journal bearings, they most likely stay in hydrodynamic regimes for 95% of the time, but valve assemblies and piston ring packs have a lot of boundary friction going on under high load situations.
Since about 1959, just about every automotive engine lube has had some type of barrier additive; with some barrier additives being better than others. I happen to think Schaeffer's and Redline have some good barrier additives for AF/FM applications, while I also believe that Amsoil and Mobil have some good ester AF/FM additives.
If you will look at the profiles and the Off Topic threads, many of us have posted what we do and our interests. I happen to be a working scientist/engineer who also works in the shop with the propulsion guys on a daily basis and often get blasted with fuels, lubes, and such. So call me a "pencilhead" or whatever. I think most of us on this board are "greasers" at heart whether we work in our cubicles or work on our cars.
No ones hurting my feelings here
.
Stick with the discussion at hand and lets not end up like the less technical discussions on other boards. Everyone here has something to offer and I learn alot from all that participate.
Hey, there are even cubical engineers here that have translated their brain wave activity into turning wrenches and even driving race cars or flying airplanes and helicopters. The ability to think and execute is a Godly gift in my opinion.
We need everbody contributing so we all can have the satisfaction of SPENDING LESS and GETTING MORE !
Stick with the discussion at hand and lets not end up like the less technical discussions on other boards. Everyone here has something to offer and I learn alot from all that participate.
Hey, there are even cubical engineers here that have translated their brain wave activity into turning wrenches and even driving race cars or flying airplanes and helicopters. The ability to think and execute is a Godly gift in my opinion.
We need everbody contributing so we all can have the satisfaction of SPENDING LESS and GETTING MORE !
Thanks Oz. There is some history here that many may have not picked up from other threads.quote:
Originally posted by The_Oz:
I think Geo was referring to Bob labelling Terry as a Cubical Engineer...
...just clearing things up.
Oz
Bob labels scientists and engineers with professional experience as "cubical engineers", his pejorative. He fails to understand and appreciate the scientific method, analytical/comparative analysis, etc. Watch out for his opinions.
Now, as Terry suggested, let's get back to the discussion.
[ August 08, 2002, 12:18 PM: Message edited by: geo ]
I stated that
Lets take a technical Publication Published by Texaco Inc volume 78.
Definition of Viscosity...
Viscosity, as a general concept, can be defined as the resistance of a liquid to flow or deformation. In common terms, the slower a material flows, the higher is its viscosity.
Now here's where it gets interesting...
IT IS THE VISCOSITY THAT DETERMINES THE ABILITY OF THE LUBRICANT TO MAINTAIN AN OIL FILM BETWEEN THE WORKING PARTS OF MACHINES, THE FILM THAT REDUCES FRICTION AND WEAR. Another term used is FILM STRENGTH
How am I doing so far? Lets include a picture that might help demonstrate this even farther...
This shows two parallel plates separated by a film of oil. The top plate is moving; the bottom is stationary. A force, indicated by the heavy arrow, must be applied to the top plate to keep it moving at a steady speed. Notice that the force is directed along the plane of the plate, not into the plate, so it is a shearing force.. Hmmmm, what bearing or cam in an engine might see this?
There are four simple measuable parameters which describe this physical situation.
Now the shear basic mechanical theory here presents itself as a very common sense approach and all through out this and many other books, film strength of an oil relates back to oil thickness or viscosity which is due to flow rate, even in bearings and gear boxes. To thin of a viscosity oil and the wear climbs, to thick performance suffers, may even retain heat more, but wear will be reduced. Don't believe it still, like Molakule mentioned earlier, why do they run a 5w40 over there? higher viscosity = higher film strength.
So, again, we are back to the basic states of lubrication where hydrodynamic properties of an oil = film strength and hydrodynamic is the film between two surfaces which will squeeze out due to flow rate which is viscosity.
One more point, What equation is used by engineers to determine what viscosity oil to put in their equipment? Viscosity measurements or film strength measurement? Here's another one, If film strength isn't viscosity, where's the film strength measurement so you can compare between different oils????
YEP, THINKING OUT OF THE BOX, THAT IS WHAT I DO.
TERRY
Yes, it has been several years since the last time we discussed this so I have had more time to bone up on your laminar flow concept.
lets approach each one of your comments singularly...
"Synthetic" molecules can be engineered to have a more appropriate molecular structure to resist breaking from hydrodynamic to barrier lubrication"
If I recall correctly as my chemistry really stinks, the molecular structure of motor oils can come in a couple(maybe even more) ways depending on the type of oil we are discussing. somewhere between c15-20.
Hydrocarbon molecules are made of hydrogen and carbon atoms that form the basis of all petroleum, they differ in their configurations. The carbon atoms may be linked in a ring or a chain, each with a full or partial complement of hydrogen atoms. Some hydrocarbons combine easily with other materials.
Conventional motor oil is made up of an inconsistent mixture of long and short chains of carbon and hydrogen atoms. In the extreme heat of an engine, short-chain molecules can evaporate, and unstable molecules can oxidize and break down. Conventional oils used to contain much greater amounts of impurities, such as sulfur, reactive and unstable hydrocarbons, and other undesirable contaminants that were not able to be completely removed by conventional refining of crude oil but now have improved on the newer gf-3's.
Now, let's look at this, I believe you are right about one thing here, the straight chain might be more resistant to oxidation(oxygen atoms) than the hexane as this would not destroy the straight chain if an oxygen atom was to break the chain where as the hexane would be an open chain if the loop was broken. Now how would this help film stength? Guess what, I agree.. It does help the molecular film strength not the hydrodynamic film strength.
I believe I just figured out the BIG SECRET to these big boys advertising....
Lets think about this a minute.. They are not lying about better film strength, If you consider breaking down the molecular level of atoms from oxidations, the film is much higher resistant to oxygen atoms attacking the bond where as the older conventional structure would be more likely to submit to the oxygen faster therefore the film strength on the molecular level would be compromised faster.
I think many have used the defintion of film strength and assume it to mean the base oils ability to resist hydrodyamic shear when in fact it appears they are saying that it resists breakdown at the molecular level instead. I may be wrong, but this would be the only thing that makes sense to me.
In my definition of film strength, and the book I use here, This would not constitute film strength. The atomic/molecular level would not pertain to the defintion of film strength in hydrodynamic property levels.
Syns can also flow in a turbulent fashion dissipating more heat while maintaining their desired film strength. NON syns flow in a laminar fashion holding heat
Definition of lam·i·na (lm-n)
n. pl. lam·i·nae (-n) or lam·i·nas
A thin plate, sheet, or layer.
The only thing I could find on the laminar theory was where it would apply through pipes. Viscosity is very important in flud flow throught pipes. At relatively low flow rates, the flow of fluids through pipes and sucts is a smooth, orderly process, referred to as laminar flow. Under this flow condition, the pressure loss is proportional to the fluids viscosity if the other parameters are hel constant. The flow rate is inversely proportional to the viscosity.
At reativly high flow rates, the smooth, orderly flow process is disrupted and flow becomes turbulent.
Now no where is there anything that relates the molecular structure of the oil as being a part of the equation for laminar flow. The factors used in laminar flow is pipe diameter,D, the average flow velocity, V, and the kinematic viscosity, Vk,is:
Nre=Dxv/Vk. This is for newtonian fluids.
I'm not sure but from what I see, laminar effect on a fluid is measured for pipes, and has no effect according to this. Now, yeah, it might have an effect on oil in an engine but given that this is only when it is in a slow moving lubricant and the most engines are going to produce a reletively higher oil pressure than what laminar could work at there fore, again, this is not taken into effect in a engine application.
boy, I'm beat, 4am here, will look at it again later when I can see straight.
[ August 13, 2002, 07:33 PM: Message edited by: BOBISTHEOILGUY ]
Ok, Now I have time to go a little bit further on this subject,OK, lets follow this through.
Lets take a technical Publication Published by Texaco Inc volume 78.
Definition of Viscosity...
Viscosity, as a general concept, can be defined as the resistance of a liquid to flow or deformation. In common terms, the slower a material flows, the higher is its viscosity.
Now here's where it gets interesting...
IT IS THE VISCOSITY THAT DETERMINES THE ABILITY OF THE LUBRICANT TO MAINTAIN AN OIL FILM BETWEEN THE WORKING PARTS OF MACHINES, THE FILM THAT REDUCES FRICTION AND WEAR. Another term used is FILM STRENGTH
How am I doing so far? Lets include a picture that might help demonstrate this even farther...
This shows two parallel plates separated by a film of oil. The top plate is moving; the bottom is stationary. A force, indicated by the heavy arrow, must be applied to the top plate to keep it moving at a steady speed. Notice that the force is directed along the plane of the plate, not into the plate, so it is a shearing force.. Hmmmm, what bearing or cam in an engine might see this?
There are four simple measuable parameters which describe this physical situation.
- 2. The SPEED of the moving plate, S
- 3. The THICKNESS of the OIL FILM, that is, the separation between the plates, X
- 4. The FORCE required to move the plate, F
Now the shear basic mechanical theory here presents itself as a very common sense approach and all through out this and many other books, film strength of an oil relates back to oil thickness or viscosity which is due to flow rate, even in bearings and gear boxes. To thin of a viscosity oil and the wear climbs, to thick performance suffers, may even retain heat more, but wear will be reduced. Don't believe it still, like Molakule mentioned earlier, why do they run a 5w40 over there? higher viscosity = higher film strength.
So, again, we are back to the basic states of lubrication where hydrodynamic properties of an oil = film strength and hydrodynamic is the film between two surfaces which will squeeze out due to flow rate which is viscosity.
One more point, What equation is used by engineers to determine what viscosity oil to put in their equipment? Viscosity measurements or film strength measurement? Here's another one, If film strength isn't viscosity, where's the film strength measurement so you can compare between different oils????
YEP, THINKING OUT OF THE BOX, THAT IS WHAT I DO.
TERRY
Yes, it has been several years since the last time we discussed this so I have had more time to bone up on your laminar flow concept.
lets approach each one of your comments singularly...
"Synthetic" molecules can be engineered to have a more appropriate molecular structure to resist breaking from hydrodynamic to barrier lubrication"
If I recall correctly as my chemistry really stinks, the molecular structure of motor oils can come in a couple(maybe even more) ways depending on the type of oil we are discussing. somewhere between c15-20.
Hydrocarbon molecules are made of hydrogen and carbon atoms that form the basis of all petroleum, they differ in their configurations. The carbon atoms may be linked in a ring or a chain, each with a full or partial complement of hydrogen atoms. Some hydrocarbons combine easily with other materials.
Conventional motor oil is made up of an inconsistent mixture of long and short chains of carbon and hydrogen atoms. In the extreme heat of an engine, short-chain molecules can evaporate, and unstable molecules can oxidize and break down. Conventional oils used to contain much greater amounts of impurities, such as sulfur, reactive and unstable hydrocarbons, and other undesirable contaminants that were not able to be completely removed by conventional refining of crude oil but now have improved on the newer gf-3's.
Now, let's look at this, I believe you are right about one thing here, the straight chain might be more resistant to oxidation(oxygen atoms) than the hexane as this would not destroy the straight chain if an oxygen atom was to break the chain where as the hexane would be an open chain if the loop was broken. Now how would this help film stength? Guess what, I agree.. It does help the molecular film strength not the hydrodynamic film strength.
I believe I just figured out the BIG SECRET to these big boys advertising....
Lets think about this a minute.. They are not lying about better film strength, If you consider breaking down the molecular level of atoms from oxidations, the film is much higher resistant to oxygen atoms attacking the bond where as the older conventional structure would be more likely to submit to the oxygen faster therefore the film strength on the molecular level would be compromised faster.
I think many have used the defintion of film strength and assume it to mean the base oils ability to resist hydrodyamic shear when in fact it appears they are saying that it resists breakdown at the molecular level instead. I may be wrong, but this would be the only thing that makes sense to me.
In my definition of film strength, and the book I use here, This would not constitute film strength. The atomic/molecular level would not pertain to the defintion of film strength in hydrodynamic property levels.
Syns can also flow in a turbulent fashion dissipating more heat while maintaining their desired film strength. NON syns flow in a laminar fashion holding heat
Definition of lam·i·na (lm-n)
n. pl. lam·i·nae (-n) or lam·i·nas
A thin plate, sheet, or layer.
The only thing I could find on the laminar theory was where it would apply through pipes. Viscosity is very important in flud flow throught pipes. At relatively low flow rates, the flow of fluids through pipes and sucts is a smooth, orderly process, referred to as laminar flow. Under this flow condition, the pressure loss is proportional to the fluids viscosity if the other parameters are hel constant. The flow rate is inversely proportional to the viscosity.
At reativly high flow rates, the smooth, orderly flow process is disrupted and flow becomes turbulent.
Now no where is there anything that relates the molecular structure of the oil as being a part of the equation for laminar flow. The factors used in laminar flow is pipe diameter,D, the average flow velocity, V, and the kinematic viscosity, Vk,is:
Nre=Dxv/Vk. This is for newtonian fluids.
I'm not sure but from what I see, laminar effect on a fluid is measured for pipes, and has no effect according to this. Now, yeah, it might have an effect on oil in an engine but given that this is only when it is in a slow moving lubricant and the most engines are going to produce a reletively higher oil pressure than what laminar could work at there fore, again, this is not taken into effect in a engine application.
boy, I'm beat, 4am here, will look at it again later when I can see straight.
[ August 13, 2002, 07:33 PM: Message edited by: BOBISTHEOILGUY ]
This differs from what I was taught about hydrodynamic lubrication.
In a rotating bearing, i. e., a journal inside a sleeve bearing, the rotation of the journal causes a pumping action that creates a wedge of oil which lifts the journal off the bearing and prevents further contact. The speed and load of the journal will cause the location of this oil wedge to vary slightly inside the bearing, but it'll be at something like the 5 o'clock or 7 o'clock position. This is hydrodynamic lubrication.
In a sliding bearing with a tilting surface, e. g., a Kingsbury thrust bearing, the tilt allows the hydrodynamic pumping action which forms the wedge of oil that prevents the surfaces from contacting.
In an oscillating bearing or sliding surfaces without tilting plates, you have the boundary lubrication situation, or you rely on the oil circulating system's oil pressure to provide the oil film that keeps the surfaces apart.
I don't agree about the slower moving piece showing more wear. I've seen 90 rpm journal bearings and kingsbury bearings with 30 or more years of continued service and never had a bearing changed. The lube? ISO 100, about SAE 30. I've worked on (and inside) diesels that have a speed range from 35 rpm to 95 rpm. Although the bearings are inspected regularly and spares are stocked, it would be unusual to renew a bearing. We're talking about 20 year or more life and lifetime oil in the crankcase--only makeup for leakage, never a change, and standard Texaco, or Exxon, or Chevron, etc. petroleum lubes, with centrifuging and lab tests. Here, though, the crankcase is sealed from the combustion spaces.
Ken
[ August 10, 2002, 09:37 AM: Message edited by: Ken ]
In a rotating bearing, i. e., a journal inside a sleeve bearing, the rotation of the journal causes a pumping action that creates a wedge of oil which lifts the journal off the bearing and prevents further contact. The speed and load of the journal will cause the location of this oil wedge to vary slightly inside the bearing, but it'll be at something like the 5 o'clock or 7 o'clock position. This is hydrodynamic lubrication.
In a sliding bearing with a tilting surface, e. g., a Kingsbury thrust bearing, the tilt allows the hydrodynamic pumping action which forms the wedge of oil that prevents the surfaces from contacting.
In an oscillating bearing or sliding surfaces without tilting plates, you have the boundary lubrication situation, or you rely on the oil circulating system's oil pressure to provide the oil film that keeps the surfaces apart.
I don't agree about the slower moving piece showing more wear. I've seen 90 rpm journal bearings and kingsbury bearings with 30 or more years of continued service and never had a bearing changed. The lube? ISO 100, about SAE 30. I've worked on (and inside) diesels that have a speed range from 35 rpm to 95 rpm. Although the bearings are inspected regularly and spares are stocked, it would be unusual to renew a bearing. We're talking about 20 year or more life and lifetime oil in the crankcase--only makeup for leakage, never a change, and standard Texaco, or Exxon, or Chevron, etc. petroleum lubes, with centrifuging and lab tests. Here, though, the crankcase is sealed from the combustion spaces.
Ken
[ August 10, 2002, 09:37 AM: Message edited by: Ken ]
Bob,
Laminar flow is also important in aerospace. How does that apply to fluids?
Supersonic flow, over a wing, is very fluid like.
If you want more info on laminar flow look at aeronautics. My education on those was just a couple of college classes and basic pilot training. I suspect that may help. Is the inside of an engine close enough to a pipe for valid comparison? I don't know
JJ Bula
Bob - like any other topic on this earth, it can always be taken to a deeper layer and because it cannot be found in Texaco's Publication #78, does not mean that Terry's theory is flawed.
I personally am not qualified to comment on the theories that were put forward here, but it would seem to me (my opinion) that you are just plainly anti-synthetic.
I will keep it simple as you did.......why is it for example that synthetic-based gear lubes have taken over (OEM recommended) in all of the most demanding applications - might it have something to do with film strength? Why incur the extra expense of a synthetic if all of the needs could be met with a conventional?
Why does Schaeffer use such a healthy dose of PAO in some of their engine oils? Could there be more benefit to having this PAO than just oxidative stability? It would seem a waste here as well given that there is already a very good base-stock on the petroleum side not to mention the moly as a barrier additive.
[ August 10, 2002, 11:24 AM: Message edited by: con carne ]
I personally am not qualified to comment on the theories that were put forward here, but it would seem to me (my opinion) that you are just plainly anti-synthetic.
I will keep it simple as you did.......why is it for example that synthetic-based gear lubes have taken over (OEM recommended) in all of the most demanding applications - might it have something to do with film strength? Why incur the extra expense of a synthetic if all of the needs could be met with a conventional?
Why does Schaeffer use such a healthy dose of PAO in some of their engine oils? Could there be more benefit to having this PAO than just oxidative stability? It would seem a waste here as well given that there is already a very good base-stock on the petroleum side not to mention the moly as a barrier additive.
[ August 10, 2002, 11:24 AM: Message edited by: con carne ]
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