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3.1.3 Long-time tests
Long-time tests are performed to get an idea of the gradual wear and tear (abrasion) of
parts subjected to light wear with different lubricants used.
In long-time tests a lower load on the ball cup is preferable whereby the test may last for
several hours.
The loads are always less than 40kg.
Using a weight of 15kg over a 60-minute period has turned out ideal.
As the scale on the balance scale bar does not allow for setting a 15kg load with the lighter
jockey weights (2.5, 5, 7kg), you will need to use a special 1kg- or 2kg-weight which can
also be mounted in the detents of the balance scale bars.
The root mean squares (rms) of the 4 test balls are determined based on the top row of
numbers:
1kg jockey weight: divide by 10
2kg jockey weight: divide by 5
2.5kg jockey weight: divide by 4
5kg jockey weight: divide by 2
7kg jockey weight: divide by 1.4285
The test conditions for the tests above are not standardised.
Warning:
Only use weights that have the same centre of mass as the 10kg jockey weight. Weights
ranging from 1kg to10kg are available separately as accessory.
3.1.4 Testing materials
The four-ball tester can also be used to test materials.
You can, e.g., determine the behaviour of materials with regard to wear and tear, the
friction coefficient and corrosion susceptibility using the same type of lubricant
throughout.
Warning:
The four-ball tester only responds to the chemical composition of the lubricant. It does not
respond to the lubricant's viscosity as due to the low sliding velocities and the poor
engagement of the balls no hydrodynamic forces to speak of are generated.
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