Hi MGM
One of these days we need to have lunch. I'll buy.
I thought I would respond to the letter you posted about the SRV test and the oils that LE has tested in the past. First of all it has never been the policy of LE to do laboratory tests and use them to sell against other companies. However if a customer has a concern and wants to use another companies oil and asks us to do comparative testing, then we will do that for that LE customer. The letter that we are talking about is one of those letters, and was only written for the customer that requested the testing be done.
In the letter that Amsoil wrote in their FAQ's, it said that the main focus of their findings is irrelevant. The main focus was the SRV test and this is what I must address in my response.
In your copy of the Amsoil corporate response you posted that the SRV ASTM D-5707 is a test used for evaluating extreme pressure (EP) properties of greases and that it is used for grease used in front wheel drive automobiles. This test can and is used for many more types of applications other than just grease. Examples;
1. In Castrol's general reference guide, page 3---9 They say "The SRV tester was developed to determine the coefficient of friction, antiwear and EP properties of lubricants under boundary and mixed film condition. Oils that they test on the SRV are;
2 Gear oils
2 Greases (not for CV joints or front wheel drive cars)
2. Plint Tribology testing equipment manual for tribologists page 13 says;
Typical applications for the TE 77 high frequency Friction Machine (SRV) are;
1. Screening Tests for Crankcase and Gearbox Lubricants.
2. Fundamental Lubricant Chemistry Studies
3. Lubricant Formulation Studies
4. Lubricity Testing for Fuels and Lubricants
5. Wear and Liquid Corrosion Studies.
6. Stick-Slip Testing of Industrial Lubricants
7. Boundary Friction Evaluation
8. Grease Evaluation for EP, Anti-Wear and Scuffing properties.
9. Friction, Wear and Failure Testing of Soft and Hard Coatings and Films.
10. Dry and Lubricated Friction and Wear Testing
11. Wear Testing of Engine components;
Cam/Follower, Ring/Liner, Piston Skirt, Valve Train, Fuel Pump.
12. |Fretting Wear Testing.
These are just a few types of tests that are done on the SRV type test machine in addition to the Grease for EP testing that was posted above.
In an article called "Machines and Methodologies for Testing Extreme Pressure and Anti-Wear Properties of Lubricants" Test machines are evaluated to find the best type of tester.
Group 1 Stationary Point of Contact
These are rigs in which the point of contact is stationary on one of the surfaces. They all have simple specimen geometries. Examples include;
Falex
4-Ball
Timken
Reichert
Group 2 Moving Point of Contact;
These are rigs where the point of contact moves over both surfaces. This includes rigs using actual gears and cams as well as twin-disk machines.
FZG
IAE
Ryder
MIRA Cam and Follower
Group 3 Stationary Point of Contact/Minimal Energy Pulse/Independently Thermally Controlled;
These are test machines in which sliding velocities are maintained at low levels in order to minimize frictional heating and in order to promote boundary lubrication regimes. They are the short stroke reciprocation rigs and the two types most commonly available are as follows;
Optimol SRV
Plint TE 77
By comparison with Group 2 machines, the Group 3 machines (except in the case of the piston Ring on Cylinder Liner contact near stroke end) do not set out to emulate the mechanics of the real contact to be investigated, but aim to simulate the intimate contact conditions in a controllable and accessible way. In this respect, these machines fulfill the requirements of an effective bench test that is they are simulators of real contacts.
In his conclusion he said, "Group 1 machines (4-ball, Falex, Timken, Reichert) do not provide an adequate emulation or simulation of real contacts subject to boundary or mixed lubrication regimes. It is not necessary to emulate the mechanics of the contact in order to provide an adequate bench test simulation for assessment of lubricant/additive performance. A third generic group of bench test machines is identified. These machines are primarily simulators and not emulators. These machines provide better experimental control and more flexibility than the latter two Groups. This allows greater insight into the processes taking place within the contact zone. "
He further states that " The capabilities of the test machine groups can be summarized as follows;"
Machines---Real Contacts Emulated---Real Contacts Simulated
Group 1---------Nil ---------Nil
Group 2-----Gear Cam/Follower-----Nil
Group 3-----Ring/Liner-------Gear Cam/Follower
References;
1. Plint M A Alliston-Greiner A F: Extreme pressure and anti-wear properties of lubricants: A critical study of current test methods and suggestions for the future.
2. Bell J C: Critical physical conditions in the lubrication of automotive valve train systems: Tribology international Vol 24 No 2 1991
3. Mills T N and Cameron A: Basic studies on boundary, EP and piston-ring lubrication using a special apparatus: ASLE Transactions Vol 25 117-124.
4. Cooper D and Moore A J: The influence of boundary films on lubricant anti scuffing performance.
5. Alliston-Greiner A F: Testing extreme pressure and anti-wear performance of gear lubricants: ImechE Vol 205 June 1991
6. Cooper D and Moore A J: Wear control in automotive diesel engines: Austrib 94 Perth.
So as you can see the main focus, wear and EP findings are far from irrelevant and do show the difference between lubes as stated by the references I've listed above.
In addition to the above references I'll post a copy of an e-mail that I sent to an independent lab asking about the SRV test.
Hi Kevin!
The SRV is EXCELLENT for testing gear oils, greases, all sorts of lubes and materials... far more versatile and repeatable than any bench test around. Expensive, but WORTH IT!
For gear oils, I recommend you run both step and wear tests in oscillation mode. ASTM tests are a good starting point, but ideally you want to match an application's Temperature (C), Contact Pressures (psi), Stroke (mm) and Frequency (Hz). We can write a custom CAP (computer aided programming) to help you evaluate gear oil performance and optimize additive synergism's. You will receive charts showing coefficients of friction at each temp, load, or frequency range, plus we can measure wear scars and provide digital photos showing the results. SRV is a great sales tool, as well as product development tool.
Mark Adams
-----Original Message-----
From: Kevin Dinwiddie <KDinwiddie@socal. rr.com>
To: info@tribologytesting.com <info@tribologytesting.com>
Date: Monday, August 28, 2000 10:40 PM
Subject: Questions on the SRV for gear oils
Can the SRV be used for testing on gear oils for Wear, EP, and Coefficient of Friction? Is it as accurate as the 4-ball test? Would the test be called ASTM D-5707 and ASTM D-5706? Your expertise would be greatly helpful.
Sincerely,
Kevin Dinwiddie CLS
Lubrication Engineers Inc.
I believe that I've made my point that the SRV test is more accurate than any other bench test and is widely used for evaluating gear oils as well as other products and not just for greases. Given that the SRV test is accurate and used for gear oils, then the accuracy for the evaluation between the Amsoil and the LE gear oils stands as accurate and shows that the LE has many more times (30. 33) less wear than the Amsoil product. These test confermations are not an embarrassment but further affirms that LE uses the best tests and does not skimp on the quality of their products or the tests that they use.
Sincerely, Kevin
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