Tractors
Nebraska Tractor Tests – still the one

With a cash outlay in the six figures, a tractor purchase is a serious decision that warrants much analysis beyond the colour of the paint. Sure, dealer and brand are important, but the bottom line is that a tractor has to deliver the type of performance and dependability required for multiple tasks on the farm. 

While Western Canada used to test tractors at the Prairie Agricultural Machinery Institute, those tests are no longer conducted on the Prairies, leaving farmers to depend on the Nebraska Tractor Tests as their most reliable and unbiased testing facility. “The Nebraska Tractor Tests conform to OECD standards, and our laboratory is the officially designated tractor testing station for the United States”, says Dave Morgan, assistant director at the Nebraska Tractor Test Laboratory in Lincoln, Nebraska. 
OECD stands for the Organization for Economic Cooperation and Development, and its 29 member countries adhere to the tractor test codes with active tractor test stations in approximately 25 countries. The OECD codes require that the tractors be tested in the country of manufacture.

The OECD Tractor Test has compulsory tests that are performed. This includes verifying manufacturers’ specifications, performance of the tractor at the main power takeoff, the power lift and hydraulic pump and the drawbar. Included in the drawbar tests and PTO tests are fuel consumption measurements.

Snapshot of performance
The basics of tractor performance, including PTO performance, fuel consumption, hydraulic pump performance and drawbar power, are what most farmers are interested in, especially with high horsepower 4WD tractors. These tractors must be big enough to pull air drills and have a hydraulic pump capacity to drive air cart mechanics.

Drawbar tests are conducted on concrete at Nebraska so that the conditions are equal across tractors and so that comparisons can be made between different testing facilities. As a result, the test reports are not directly transferable to field conditions, but they give an approximate comparison. “The concrete test track gives the best tractive conditions, and is the same surface for everyone. If the tests were conducted on soil, the results would be useless as the conditions would be different for each test,” explains Morgan.

The standard test of drawbar performance is measured with unballasted tractors at rated engine speed and the maximum power engine speed in all gears between 15 percent slip and 13 km/hr plus partial loads of 75 percent and 50 percent of pull at maximum power in two separate gears.  The measurement most relevant to farmers is measured at 75 per cent of pull at maximum power, which reasonably reflects typical field work over a year of drawbar use. “Unballasted runs are the best to compare different tractors because they represent the basic tractor performance. Adding ballast increases pull and can increase drawbar power in some cases, but may cause increased fuel consumption from the added weight you carry around,“ says Morgan.

When diesel fuel prices spiked in 2008, many farmers turned a critical eye to fuel efficiency. The Nebraska Tractor Tests measure fuel consumption as a measure of power for a given amount of fuel, and the result is reported in horsepower-hours per gallon of fuel or Hp•hr/gal (Imperial), or in kilowatt hours per litre expressed as kW•h/L (metric). Higher numbers mean more work is being done for a given amount of fuel, but like automotive fuel efficiency ratings, the fuel consumption reported in the test will likely be better than achieved in the field because of varying soil and working conditions.

The most useful PTO measurement is maximum power at rated engine speed, which is the highest power level that a tractor can sustain, measured in horsepower. Tractors with a power bulge can produce more power at a slower engine speed, but there is no power reserve. “It is interesting to note that in some of the new engines, the only thing different between the tractor models is how the electronic chip controls the horsepower of the engine. A 190 horsepower engine and 250 horsepower engine are exactly the same, except for the electronic control,” says Morgan. 

The Nebraska Tractor Test Laboratory has reports for tractors from 1999 onward and they can be found online at www.tractor-testlab.unl.edu/testreports.htm in a pdf format at no charge. Individual reports are generally available within a few months of testing. A summary booklet can be ordered at a cost of $8 (US), and contains data on all tested models that are still on the market. An annual subscription of $35 per year will ensure delivery of all reports issued during the year, plus the summary booklet. 

Owner’s, parts and shop manuals can also be ordered online, as well as other materials such as advertising literature, blueprints and assembly drawings. Test reports going back as far as 1920 are also available, so if a grower is looking for a report on a 1920 Rumley Oil Pull K12 model, it is available.