Principles of Testing

Because of the important role tractors play in agricultural production, accurate information is a must for efficient management of the modern farm and ranch. Any information is usable, but the main objective of testing is to provide standardized results so that comparisons can be made between different models and different years. The primary purpose of tractor testing standards is to establish the test conditions and the rules of behavior for the manufacturer and the testing station.

It should be evident that engines are complex mechanisms with many different factors that influence the power produced and fuel efficiency. Because of the widespread use of the data, manufacturers want to be sure they get the best possible results. To provide standardized information, the testing environment must be consistent for every test, day after day, year after year, or changes must be thoroughly investigated so that the appropriate adjustments in the results can be made. In both tests, these factors are called test conditions.

Test conditions include the rules for the selection of the tractor and the control and/or recording of environmental conditions. During the PTO test, air temperature, barometric pressure, fuel type, fuel temperature, fuel measurement, lubricants, and accessory equipment on the tractor must be either controlled or recorded to ensure that they are within acceptable limits. Strict control of these factors is important because many tests measure the maximum power of the tractor. Each one of these factors will influence the power produced.

For the drawbar test all of the environmental factors in the PTO test must be accounted for, plus those that affect traction. The latter include tractor ballast, tires, and testing surface. The ballast, tires, and testing surface are critical because

1 OECD Standard Codes for the Official Testing of Agricultural Tractors, Organisation for Economic Cooperation and Development, 1988. 2, rue Andre-Pascal, 75775 Paris CEDEX 16, France.

2 Nebraska Test Station, Agricultural Engineering Department, University of NebraskaLincoln, Lincoln, Nebraska 68583.

the amount of pull a tractor can produce at the drawbar is greatly influenced by the amount of traction. Both the NTT station and the OECD station have strict standards on how all these factors are controlled and/or recorded.

In addition to the test conditions, the testing codes must establish rules governing such things as breakdowns, repeating tests, testing accessory systems such as hydraulic systems, safety standards, noise standards, and the method of reporting and publishing the results.

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