Redline's Response to my question (two posts up):
So it dosen't matter?
HTHS
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MolaKule
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If you can wait a couple of days I'll have a definitve answer (I will be going to the University Libray tomorrow) as I don't recall the axact wording of each document.
The University has all the ASTM volumes.
The University has all the ASTM volumes.
I can wait. Thanks for checking up on it Molakule.
MolaKule
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Just back from the University Library.
A. I examined the following ASTM specifications from the 2003 ASTM Vol. 05.01 Manual for HT/HS testing (all three tests are still active and none have been superceeded by any others as far as I can tell):
D4741 -00 (Year 2000)
D4683 - 96 (Year 1996)
D4624 - 93 (1993, reapproved 1998)
B. Commonalities
All three Standards use a set of reference oils for calibration of the equipment that range from 1.9 cP to 7.0 cP.
All three measure HT/HS viscosity at rates of 10^-6 seconds@150 C.
All three tests claim "Viscosity under the conditions of this test method is considered to be representive of that at the temperatures and shear rates but not the pressures in the journal bearings of internal combustion engines under operating conditions."
C. Differences of the three tests.
The Tapered-Plug shear rate viscosimeter test (D4741-00) and the Tapered Bearing Simulator (D4683 - 96) requires the use of Regression Analysis or Intercept (mathematical) techniques from a reading of the viscosimeter Torque.
The D4624 Capillary viscosimeter requires the observed dependent variable to be read on a curve.
The D4624 suffers from errors for non-Newtonian fluids.
D4741 and D4683 do not suffer errors from non-Newtonian oil's because they use a set of extra non-Newtonian reference oils.
Bottom Line IMHO: The industry is using both D4741-00 (Year 2000) and D4683 - 96 (Year 1996) test methods, but D4741-00 is the latest HT/HS testing methodology as per the 2003 series of ASTM volumes.
A. I examined the following ASTM specifications from the 2003 ASTM Vol. 05.01 Manual for HT/HS testing (all three tests are still active and none have been superceeded by any others as far as I can tell):
D4741 -00 (Year 2000)
D4683 - 96 (Year 1996)
D4624 - 93 (1993, reapproved 1998)
B. Commonalities
All three Standards use a set of reference oils for calibration of the equipment that range from 1.9 cP to 7.0 cP.
All three measure HT/HS viscosity at rates of 10^-6 seconds@150 C.
All three tests claim "Viscosity under the conditions of this test method is considered to be representive of that at the temperatures and shear rates but not the pressures in the journal bearings of internal combustion engines under operating conditions."
C. Differences of the three tests.
The Tapered-Plug shear rate viscosimeter test (D4741-00) and the Tapered Bearing Simulator (D4683 - 96) requires the use of Regression Analysis or Intercept (mathematical) techniques from a reading of the viscosimeter Torque.
The D4624 Capillary viscosimeter requires the observed dependent variable to be read on a curve.
The D4624 suffers from errors for non-Newtonian fluids.
D4741 and D4683 do not suffer errors from non-Newtonian oil's because they use a set of extra non-Newtonian reference oils.
Bottom Line IMHO: The industry is using both D4741-00 (Year 2000) and D4683 - 96 (Year 1996) test methods, but D4741-00 is the latest HT/HS testing methodology as per the 2003 series of ASTM volumes.
Hi,
this may be so for the API and in NA
The ACEA in use the CEC-L-36-A-90 (2nd Edition) method which if I recall correctly is a Bosch developed test protocol
Some engine Manufacturer's use a variance of this test - usually an extended period - as one element for attaining their "Approval" and listing as such
Many of the oils sold here have the Bosch and/or other test data listed
Regards
Doug
this may be so for the API and in NA
The ACEA in use the CEC-L-36-A-90 (2nd Edition) method which if I recall correctly is a Bosch developed test protocol
Some engine Manufacturer's use a variance of this test - usually an extended period - as one element for attaining their "Approval" and listing as such
Many of the oils sold here have the Bosch and/or other test data listed
Regards
Doug
MolaKule
Staff member
D4741 does reference CEC L36-A90 and the IPS IP 370 test methods.
None of the other two mentioned test methods reference anything but the other ASTM methods.
None of the other two mentioned test methods reference anything but the other ASTM methods.
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How close are the measured values when using D4741 versus D4683?
MolaKule
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Good Question:
Here is the actual wording from paragraph 14.6 "Relative Bias" of D4741-00:
No deltas were given for D4683 verses D4741 or D5481.
Here is the actual wording from paragraph 14.6 "Relative Bias" of D4741-00:
D4683 says the same thing in paragraph 14.3 but adds another that correlation is the same with test method D5481 as well.
No deltas were given for D4683 verses D4741 or D5481.
Hi,
it appears that the updating to D4741 (2000)may have been "motivated" by the regularised ACEA (Bosch) protocol
Regards
Doug
it appears that the updating to D4741 (2000)may have been "motivated" by the regularised ACEA (Bosch) protocol
Regards
Doug
FYI,
If you ever want to get a document summary of an ASTM test method just go to the ASTM website and do a document search:
http://www.astm.org
Some examples:
D4683-04
D4741-00
D5481-04
D4624-93 (1998) Standard has been withdrawn.
[ February 04, 2005, 05:57 AM: Message edited by: 427Z06 ]
If you ever want to get a document summary of an ASTM test method just go to the ASTM website and do a document search:
http://www.astm.org
Some examples:
D4683-04
D4741-00
D5481-04
D4624-93 (1998) Standard has been withdrawn.
[ February 04, 2005, 05:57 AM: Message edited by: 427Z06 ]
MolaKule
Staff member
I looked briefly at D5481 today. It appears to be an updated D4624 with a new math algorithm to better correlate with the other specs. Apparently, the Capillary viscosimeter was off at times by 50% for certain oils.
MolaKule
Staff member
Here is another source:
http://www.techstreet.com/cgi-bin/browsePublisher?publisher_id=39&subgroup_id=9962
http://www.techstreet.com/cgi-bin/browsePublisher?publisher_id=39&subgroup_id=9962
Thanks MolaKule. I'm going to bookmark this thread since this issue comes up periodically in discussion of Redline oil.
Well said Moribund but your answer to III is very very wrong. If you replace high pressures with high shear rates, you'd be correct. If you want to look at viscosity versus pressure, you need to consider the pressure viscosity coefficient or so called alpha coefficient. High pressure actually makes the lubricant more viscous not less. The existance of Non-Newtonian behaviour is the raison d'etre for the HTHS test. By Non-Newtonian behaviour, we simply refer to a shear rate dependant apparent viscosity.
See the following quote from a recent post by Brianccfshr "Q: The fluids I design are subjected to various shear and temperature conditions. "Can PAOs help me balance the protection and energy conservation requirements in my equipment?
A: You bet! PAOs are Newtonian fluids, in other words their viscosities are fairly independent of shear rate. As fluids flow throughout the equipment, they travel through various lubrication regimes and shear environments resulting in viscosity changes for non-Newtonian fluids. "
Most of the applications for these test results are for low to moderately loaded bearings with high fluid intet temperatures and high shear rates. The pressures in these application (high speed gas turbines, high speed automotive bearings) are very low compared to those within antifriction bearings where the load is concentrated on the very small contact points of some balls or rollers. The pressures are so high that the material deforms and thus the term elasto-htydrodynamic lubrication. The HTHS test has nothing to do with high pressures, just high shear rates. If you have high pressure and high temperature but low shear rate, the concept of HTHS is not at all applicable to those conditions. Such conditions exist in many applications and you would not care a ****ed bit about HTHS for them.
1911
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Thanks for clarifying that, 1911, but I already got that from what Molakule quoted earlier:
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Can someone hear please explain what exactly causes high shear rates, as that knowledge would be practically relevant.
Hey Moribundman.......good question,
The brief answer to your query is "a high speed differential between the two friction surfaces you are lubricating. (often it is just the speed of the moving element since in most situations, the other surface is stationary but there are cases where both surfaces can move, like in antifriction bearings where the rolling elements and races can move)
All this goes back to Isaac Newton and his definition of viscosity and the definition of the shear rate. The fluid near each friction surface is thought of as being just about stuck to that surface such that a velocity gradient is developed in the fluid between the friction surfaces.
Since the shear rate is by definition the magnitude of this velocity gradient within the liquid between these two surfaces, higher velocities equal higher shear rates.
In reality, all this is more complicated because higher speeds make higher film thicknesses as do using higher viscosity fluids. In fact, I'd like to see real expert discuss this (I am not a lube engineer/expert even though I invented engineering). One thing for sure is that the work required or energy expended in shearing the lubricant in the load zone is dependent on the viscosity.
Brother Molakule may have given a historical answer to his question #3 but he did not give a technical one. The technical answer is that the apparent or effective viscosity can be shear rate dependent. Thus, the effective viscosity for high shear rate applications should perhaps best be distinguished from the low shear rate kinematic viscosity via another test.
1911
I hope this helps.
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Hope is all we got left at this point.
Are you asking why there is a temporary drop in viscosity in a high shear zone? If that's what you are after, I may be able to answer.
A Newtonian fluid does not change viscosity with a change in velocity. A non-Newtonian fluid's viscosity drops with an increase in velocity.
Dino oil has viscosity index improvers that are long polymer chains which straighten out as the temperature increases. When parts slide past each other at high speed, the polymer chains align making the chains easier to slide past one another, being less tangled. This causes the apparent viscosity to be lower, making it non-Newtonian in nature.
A PAO with little or no viscosity improvers to align at high sliding speeds does not change as much in viscosity, making it more Newtonian in nature.
I hope this is what you were trying to ask. If not, then "Never mind" (like Rosanna Rosanna Danna).
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What I want to know is why some engines can seemingly get away with lower HTHS oils, while others can't. For example, my Audi engine isn't exactly a high-revving screamer motor, and yet it requires a normal HTHS oil, while some other, more powerful, higher revving engines can get away with lower HTHS oil. Where exactly in an engine will that critical shear occur? At the cam lobes, cam bearings, rod bearing, rings, etc? Where?
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