Date of this Version
NTTL. 2021. Nebraska Tractor Test 2085A for John Deere 7R 250.Lincoln, NE: Nebraska Tractor Test Laboratory. Retrieved from http://tractortestlab.unl.edu
ABOUT THE TEST REPORT AND USE OF THE DATA The test data contained in this report are a tabulation of the results of a series of tests. Due to the restricted format of these pages, only a limited amount of data and not all of the tractor specifications are included. The full OECD report contains usually about 30 pages of data and specifications. The test data were obtained for each tractor under similar conditions and therefore, provide a means of comparison of performance based on a limited set of reported data. EXPLANATION OF THE TEST PROCEDURES Purpose The purpose of the tests in this booklet, and available test reports is to provide users with data for comparisons of performance among tractor models. General Tractors are tested at the University of Nebraska according to test procedures of the OECD (Organization of Economic Cooperation and Development), the SAE (Society of Automotive Engineers) International and the ASABE (American Society of Agricultural and Biological Engineers). The three codes are technically equivalent, but do differ slightly. For the past 10 years, the majority of tests have been performed according to the OECD codes. The manufacturer selects the tractor to be tested from its production line, provides the specifications, and certifies that the tractor is a stock model. Each tractor is equipped with the common energy consuming accessories (power steering, PTO, implement lifts, etc.). Any power consuming accessory may be disconnected when the means for doing so can be reached from the operator position. A manufacturer's representative is present during the tests to as certain that the tractor gives its optimum performance. Weight can be added to the tractor to improve drawbar performance in certain tests. Static tire loads and inflation pressures must conform to the specifications of the Tire and Rim Association or to weight limits set by the manufacturer. Specifications All manufacturers provide the Laboratory with detailed specifications which are required for the tests. The Nebraska Tractor Test report provides only a limited amount of data due to space constraints. Preparation for Test The tractor is required to have been limbered up by the manufacturer for a sufficient number of hours; if this was not done, this limber- up is performed at the Tractor Test Lab. Adjustments are permitted during this period. After the start of the official test, no adjustments can be made. Any adjustments. repairs, alterations or replacements are mentioned in the final Nebraska Tractor Test report. At this time, instrumentation for measuring engine rpm, fan speed, temperatures and pressures is installed on the tractor. The tractor is also provided with connections to the Lab's fuel supply. PTO Performance The tractor PTO is connected to a dynamometer, which is a device for putting a load on the tractor and measuring the power generated by the tractor. During the preliminary runs, the manufacturer is allowed to make some adjustments to optimize the performance. These adjustments, which include the injection pump volume and timing and the high idle set within the specified range, will remain during the whole test program and must be settings guaranteed by the manufacturer. The tests are performed while maintaining an ambient temperature of 75°F (24°C) and at a barometer reading above 28.5 inches Hg (96.6 kPa). Data are taken at intervals after the tractor performance has stabilized. Inlet fuel temperatures are also maintained at a predetermined level. The throttle being set for maximum no-load rpm (High Idle), an increasing load is applied to the PTO by the dynamometer along the operating curve of the engine. The full test report will show the torque, rpm, power and fuel consumption data obtained at Rated Engine speed, Standard PTO speed (either 1000 or 540 rpm), the maximum power on the curve and the torque rise. Drawbar Performance Tests are performed in all gears between one gear below the one at Which 15% slip occurs and a maximum speed of 10 mph (16.1 km/h). In each gear, the throttle is set for maximum speed (High Idle) and the drawbar load increased until maximum drawbar power is obtained. The drawbar load is created by towing "load units" behind the test-and- measurement vehicle which, itself, is hitched to the tested tractor's drawbar. For each load, measurements and calculations are made to determine drawbar pull, speed, drawbar power, slip and fuel consumption. All measurements are recorded at intervals after the tractor's condition is stabilized. No operational limits set by the manufacturer can be exceeded. A second test series investigates the part loads at 75% and 50% of the drawbar load at Rated Engine Speed in a gear close to 4.6 mph (7.5 km/h) and in the gear where maximum drawbar power was obtained. Sound Measurement Sound measurement is made on the test track in two locations-at the driver's ear and in a location representing "bystander noise." The tests at the driver's ear are performed in several gears and under a number of conditions, but only the maximum level is reported. The "bystander sound" test is performed with the microphone located at 25 ft (7.5 m) from the centerline of the tractor which is accelerating from a lower speed to full speed in its top gear. The OECD procedure differs. The SAE/ASABE procedures and only the numbers for the same gears and same load conditions can be compared. The SAE/ASABE procedure measures sound in only one gear under different load conditions, whereas the GECD procedure measures sound in different gears between High Idle and Rated Engine speed. For tractors with Mechanical Front Wheel Drive, operator- ear measurements are made with the front-wheel drive engaged and disengaged. Hydraulic Lift Capacity and Flow Hydraulic lift capacity is measured in a special test stand. A frame is fitted to the three-point hitch lift links. Measurements of lift capacity are taken at the hitch points and at a point 24" (610 mm) behind the hitch points when the lower links are horizontal. The load is applied with a hydraulic cylinder and the arms move stepwise through the lift range. The number which is reported is 90% of the load which can be carried throughout the lift range. The booklet reports the lift capacity at 24" (610 mm) behind the hitch points. A second test determines the pressure/flow relationship and performance of the hydraulic system for supplying power to external hydraulic cylinders or hydraulic motors. The Nebraska report provides data on delivery rate, pressure and available power.
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