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Taking a full measure of tractor performance

“Power mix” tests are latest in new evaluations conducted by the Nebraska Tractor Test Lab to keep pace with new technologies and evolving farmer demands

In 1920, staff at the then-newly-formed Nebraska Tractor Test Lab (NTTL) conducted the facility’s first official tractor test. The Lab was established along with a new state law in Nebraska, which subjected all tractors sold there to independent testing. At the time, too many tractor manufacturers made claims about horsepower and performance that were simply unrealistic. By providing farmers with reliable, unbiased information about each model, the NTTL helped keep manufacturers honest with their advertising. That benefit extended well beyond the state border to farmers all across the U.S. and Canada.

But the capability of tractors and their integrated systems 92 years ago bear little resemblance to what’s on the market today. So with more than 2,000 tractor tests under its belt so far, the Nebraska facility has had to evolve along with changes in technology to stay relevant and keep pace with farmer expectations. As part of that evolution, it’s now adding a new procedure, “power mix” tests, which simulate realistic field conditions.

Power mix tests

“Up to this point in Nebraska, we’ve typically tested just one power outlet at a time,” says Roger Hoy, director of the NTTL. “But a lot of implements today are using multiple power outlets at the same time. An air seeder is a good example. It might be using a couple of hydraulic ports and pulling a drawbar load. So we’re in the process of modifying our load car. We’re putting a device out front that will draw PTO power while we’re out on the track. We’re also putting on a load absorbing device to draw hydraulic power.”

Those new features will allow the NTTL to place power demands on a tractor using all three systems simultaneously, simulating real field conditions. “The idea is we’ll be able to simulate tractors pulling actual implements,” he adds. “We might have a load case for an air seeder, another for anhydrous ammonia spreaders and another for cultivators.”

That would significantly change the look of test reports created by the NTTL. Today, tractor evaluations include performance data based on stationary PTO tests and drawbar load-only tests at various RPM settings and load ratings. Power mix tests would add another element, providing even more information for farmers to consider.

“Maybe in the future our test report has a lot more sections to it,” Hoy goes on. “It could have six, eight or 10 load cases added to it to represent the most common applications (implement use) based on the particular tractor.”

Changing tests

This is far from the first time the NTTL has had to consider new test procedures and facility upgrades. “Of course, in the early days tractors didn’t even have PTOs,” Hoy notes. “We used to measure belt horsepower with the flat drive belts.”

Early drawbar tests were conducted on a track with a dirt surface. But to eliminate slippage from the equation, the centre upgraded to a concrete track in the middle of the last century. That original concrete surface, which was adequate for tractors of that time, eventually became too narrow for today’s high-horsepower giants. The current 22-feet-wide track, installed in 2007, uses high-density concrete and includes banked corners a little like a NASCAR track, which will allow for higher-speed tests of up to about 15 miles per hour in the future.

Over its life, the NTTL has added a variety of other tests in addition to its focus on measuring horsepower. “We added three-point hitch testing,” Hoy says. “We found out manufacturers weren’t being totally honest about what their hitches could pick up.”

Tests like that have managed to keep all the industry players honest when printing their brochures. But Hoy is particularly proud of the role the NTTL has played in spurring engineering improvements designed to protect operators.

“Something we’re really proud of is, about 1970, we told manufacturers we were going to start measuring how loud tractors were,” he explains. “Manufacturers were not at all enthusiastic about that. We did this in response to farmers that had helped advise us on what’s important.”

The first tractor tested for noise at the NTTL proved there was good reason for farmers to be concerned. That tractor roared at a very high 94 decibels when measurements were taken at the operator’s ear. “That’s going to cause hearing loss,” continues Hoy. “And kind of a funny thing happened, as soon as we started publishing sound numbers, manufacturers started competing on it. Today, a tractor can be as low as 68 decibels at full throttle. We sure don’t want to claim all the credit for this, but we think we may have caused this to happen a little earlier than it otherwise would have.”

NTTL’s future

Looking forward, Hoy thinks the NTTL’s future is pretty bright. There is interest from a variety of agencies hoping to make use of the expertise the Lab has to offer. For example, the U.S. Department of Energy has had discussions with him about partnering on research into fuel consumption rates in various types of off-road vehicles, and testing how emerging technologies will affect them.

With its core mandate to test ag tractor performance, there has been no shortage of work as new tractor models have been hitting the North American market fast and furiously in the last few years. “We’ve been a little busier than we’d like, but it’s better than not having enough to do,” Hoy says with a smile.

Those tests have to be crammed into only a few months out of each year. The NTTL can only evaluate tractors when the air temperature is moderate in order to get consistent engine performance. That means outside drawbar tests can only be done during the spring and fall. “When we do drawbar testing outdoors, the air temperature has to be between 40 and 80 degrees (Fahrenheit),” says Hoy. “That rules out Nebraska summers (and winters).”

There are many new technologies on the horizon today that could eventually make their way into the mainstream ag tractor market, and that could mean expanding the range of testing done at the NTTL yet again. “When I took over as director you’d have thought all the issues would have been taken care of in the 80-odd years the Lab had been in existence,” says Hoy. “But there are always new things popping up.”

NTTL now puts its tractor test reports online. To see them, go to For a video tour of the Nebraska Tractor Test Lab, watch the e-Quip TV video online at †

About the author


Scott Garvey

Scott Garvey is a freelance writer and video producer. He is also the former machinery editor at Grainews.

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