Quote:
Originally Posted by aerohead
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* 'The presence of a 'lubricant' between the sliding surfaces drastically reduces 'friction', it's function is to 'separate' the two surfaces and reduce both mechanical and molecular attractions, by filling the depressions in the metal, and by 'plating' all the ridges with a 'monolayer' of oil molecules, often provided by additives. This is the true 'boundary lubrication region' Professor Obert ( Howard Hughes' emergency landing of his H-1 race plane onto a beet field ).
* 'Roughened or porous surfaces can support heavier loads than geometrically perfect surfaces since the minute cavities serve as pockets for oil storage.' Professor Obert.
* 'Porosity or dimpling also provides better cooling of the oil.' Professor Obert.
* ' In engineering practice, boundary lubrication may be obtained :
- at the instant of cold-start
- as a hot machine comes to rest
- in reciprocating motions
- in rocking motions
- reciprocating motions
- with rapid fluctuation in speed
- with rapid fluctuation in load
- when viscosity is too low
- when viscosity is reduced to low value by overheating
- when the oil supply is inadequate Obert
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So... the highlighted conditions above don't occur in engines..?
That would explain why engines NEVER wear out... Or do they..?
How does that happen!?
How does oil pressure decrease with engine age if the rotating bearings never have high points that touch through the oil layer, like a water ski hitting a stone that protrudes from the water.
Quote:
Originally Posted by aerohead
* 'Boundary lubrication can occur in the combustion engine when the pistons and piston rings are at the beginning and end of the stroke.' Professor Obert.
* Reynolds Number effects moves the 'boundary region into the 'mixed-film region, and ultimately into the ' full hydrodynamic region.' It's all a matter of 'relative velocity' between the adjoining surfaces.
* The oil 'monolayer' is always present, there is no 'metal-to-metal' contact as long as the 'surface finish' and oil 'viscosity' remain unmolested, and the engine isn't 'abused.'
* The 'region' of lubrication is dependent upon Reynolds number.
* Oil is perfectly capable of handling tangential mechanical friction associated with:
- Adhesion
- Interlocking asperities
- Chemical and surface reactions
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Same goes for cam lobes and valve lifters. There is always a monolayer of oil present between the two surfaces.
At low ( Reynolds number ) RPM, you'll have 'laminar' flow.
As 'transition' surface velocity is reached, viscous shearing and churning move the boundary flow into ' transitional ' mixed laminar - eddy / turbulent flow.
At greater surface velocity ( high Reynolds number ), full turbulent hydrodynamic viscous friction dominates ( viscosity-dependent ).
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As to an engine having 'hyrodynamic lubrication' or not:
If you're MotorSilk, and hire Southwest Research Institute to dyno test your 'Engine Treatment' as to the ASTM D8114 Sequence VIE test protocol, never running the engine beyond 2,000 RPM ( in a 6500-RPM engine ), never exceed a load factor of 18% (instead of 100% ), never exceeding surface velocities of 5.13 meters/second ( in an engine of 18.4 m/s ), at a maximum power setting of 21.99-kW ( in an engine of 326-kW ), etc., then 'YES', you might talk in terms of ' boundary & mixed film ' region lubrication.
Personally, I'm not prepared to spend the rest of my driving career held to a maximum speed of 33-mph, waiting 2,000-miles for the boron to take affect, required to change the oil every 4,971-miles, all a requirement for experiencing the benefits of boric oxide.
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Ferrous metal debris in the engine can be simply an artifact of the original manufacturing process and break-in according to some reporters.
If it's below 1-micron in size, and if it hasn't settled into a oil-flow 'dead-zone' where it can precipitate out, it may circulate indefinitely, without causing any ill-effects.
My most 'recent' engine is from 1994. It did not come with a drain plug magnet.
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1st;
Lets pretend we are back in the early 19 hundreds before the various additives ubiquitous in the oils of today.
ie: Back when all additives were considered "Mouse Milk".
How did these additives end up in engine oil???
Everyone:
I expect this question to be ignored as usual.
The reason it is ignored is because it is obvious that these additives were tested in labs and then in field tests before being included in the oils we all use.
Avoiding the 'trap' of having to admit that such testing has to have happened for the additives found in today's oils, does not change the fact that they did.
Therefore: Any new additive would have to undergo the the same tests in labs and in field tests. (= real working engines overseen by said labs...)
So far there have been both for oils containing Boric Acid, both in internationally recognized labs and in the engines of early adopters.
It would seem that the
anecdotal evidence linked here by me is being... 'mistaken' for posts by me. i would say that that points to my posts not being read properly, but it may also be a purposeful misdirection..?
One of the 1st lab tests that is done for a new additive is a pin on disk test.
One of the ASTM certifications being insisted upon (with 'no testing allowed') is in fact this 'useless' pin on disk test.
https://www.sciencedirect.com/topics...disk-wear-test
Boundary, mixed and hydrodynamic lubrication:
Everybody knows engines wear out.
Cylinders become oval .
There's a step in the cylinder where the top ring stops.
etc.
When a cylinder is examined for wear, the step in the cylinder at the point where the top piston ring changes direction is the 1st place any and every mechanic looks.
So
physical evidence of increased wear due to mixed and boundary lubrication is self evident, well known and obvious.
Yet an insistence that all bearing surfaces experience only hydrodynamic wear.
However; here is some peer reviewed published research to ignore:
Automobile engine tribology — approaching the surface
School of Mechanical Engineering, The University of Leeds
...The piston ring is perhaps the most complicated tribological component in the internal combustion engine.
It is subjected to large, rapid variations of load, speed, temperature and lubricant availability.
In one single stroke of the piston, the piston ring may experience boundary, mixed
and full fluid film lubrication 9 as illustrated in Fig. 1.
Elastohydrodynamic lubrication of piston rings is also possible in both gasoline and diesel engines on the highly loaded expansion stroke after firing 10 .
The historical development of piston ring analysis emphasises the theme of this paper most succinctly.
...In 1959, Furuhama 11 developed a dynamic hydrodynamic analysis of piston ring lubrication for a piston ring profile consisting of a flat central land bounded by two half parabolas, which incorporated the effect of the cyclic variation of both load and sliding speed.
This pioneering effort correctly identified the importance of squeeze film
action in maintaining hydrodynamic load capacity but the likelihood of surface contact was not considered...
A key research effort in the experimental field was that of Hamilton and Moore 12 in the 1970s who developed miniature capacitance film thickness transducers mounted flush in the cylinder wall to measure piston ring film thickness.
They complemented their experiments on a motored engine with a theoretical analysis 13 , which yielded predicted film thickness values up to eight times greater than those measured.
Brown and Hamilton 14 later accounted for this discrepancy by considering the effect of lubricant starvation on predicted film thickness.
Further theoretical analyses subsequently emerged with increasing degrees of sophistication and fewer limiting assumptions e.g. Refs. 15,16 .
One major criticism of these analyses is that they assume the rings operate in either a full fluid film lubrication regime or in an extremely simplified boundary lubrication regime.
No consideration is given to the transitional mixed lubrication regime, where surface roughness can influence hydrodynamic performance or to the nature of the contact occurring between the surfaces in the mixed and boundary regimes...
The wear factor in the boundary lubrication regimn... is determined from bench test rig experiments using actual components and lubricant at operating conditions of load, speed and temperature indicative of boundary lubrication.
This empirical input to the model clearly exposes our lack of fundamental understanding of the wear processes taking place in such tribological interfaces...
...it has been convincingly demonstrated that lubrication of a ‘hydrodynamic’ nature does have a role to play, the modern cam and follower has traditionally been associated with the
boundary lubrication regime where the role of chemical
actions in thin surface films is vital.
This is linked to the additive package of the lubricant and in particular to
extreme pressure additives, of which forms of zinc dialkyldithophosphate ZDDP are the most common.
This serves to emphasise that, at least for parts of the cam and follower cycle, surface interaction takes place.
Note that data for the mid-stroke region has been presented where least wear of
the liner is encountered and where many traditional analyses of piston ring lubrication predict full fluid films and thus no wear.
https://sci-hub.ru/https://www.scien...43164800003756
NB that the
touching of solid lubricants as used in extreme pressure additives can NOT be considered Hydrodynamic.
Hydrodynamic lift, like aerodynamic lift, is all about a solid object 'floating' in a liquid due to speed differences between them.
Think of a water skier in shallow water:
If the boat stops he will sink down until the ski touches the bottom...
NB
That the replacement of said solid lubricants with a superior solid lubricant film is what BA is all about.
You might also ask yourself:
Why is it that all additives were 'banned' and the companies sued by the FTC,
yet Boric Acid metal surface treatments that are applied via the lubrication system got 'the nod'.
Why the DOE who holds patents on them and why the only additive still being sold as advertised are ones based on BA like MotorSilk CLS bond, etc.. ???
After reading some old threads I have come to realize that all this nonsense is actually about keeping me chasing my own tail rather than doing anything constructive with the knowledge that BA works better than anything else so far added to oils that work in moist, water containing, environments like ambient air.
I now understand the lack of comments. and why.
Silly me!
My apologies.