Inside PAMI’s magical mystery combine

BRANDON — It’s likely that every prairie farmer has heard about PAMI’s combine calibration machines, but few have ever seen one in person, much less in action.

Well here’s the scoop.

There are only about 20 such processor combines worldwide, the majority of which were designed and built by PAMI in Humboldt, Sask. Sooner or later, most units that originated elsewhere have had to be shipped to Humboldt to be made right. There’s no doubt that PAMI engineers are the renowned experts when it comes to combine calibrations.

Combines have been a main focus at PAMI since the organization was created in 1975. Over that time, PAMI engineers have developed a number of different systems and devices for measuring what happens within a combine. Their latest is based on a Challenger that has been stripped down and re-assembled with everything turned around the opposite direction from original, according to Joel McDonald, a retired PAMI combine engineer.

McDonald, keynote speaker at the Combine College in Brandon in mid-March, said PAMI’s test equipment has evolved to provide specific information on extracting the best performance from a combine.

“Testing was pretty primitive back in the mid-1970s. They mounted big tarp rollers on the back of combines to collect everything. They used collection bags and stationary processing units. It was very time-consuming,” says McDonald.

“Laziness often drives innovation. It took a lot of hard work and a lot of time and manpower to get a sample. As a result, our technology evolved to the point where a two-man crew can now get 20 to 30 data points in a day. It’s six or seven minutes per test, but then there’s the changeover time to consider.”

McDonald says the processor combine performs all the functions of a regular rotary or conventional combine, plus it documents everything. It’s made to clean out quickly, as close to 100 percent as possible. The ledges and sills are sealed, so no seeds are left behind. Augers are converted to conveyor belts so it cleans out quicker. And material is fed in slowly enough so nothing is lost.

Most farmers have heard about the mysterious PAMI combine calibration processors, but few people know what they’re all about. The engineers take a regular combine, disassemble it and then re-install all the components back-to-front so it becomes a data gathering machine. The data gives manufacturers answers to their questions and helps them design better combines. | PAMI illustration

To collect a representative sample, the 30-foot long green trailer with a yellow tarp is attached to the back of the combine. The trailer has an upper and lower collection belt. Material from the combine separator is conveyed on the top straw belt. Material from the cleaning shoe is conveyed on the lower chaff belt. The combine operator drives into a typical crop stand at his normal speed and normal settings. Once things have settled into normalcy, the trailer opens up to catch 30 feet of typical crop from the back of the combine.

The rear of the test combine is modified to allow collection of discharged material into the collector trailer. Crop residue spreaders are removed. A hitch is installed on the rear axle. Diverters and shielding are installed to deflect the discharge of straw, chaff and grain onto the collector belts. In conducting the test, the trailer collects all material discharged from the rear of the combine.

“We feed that 30-foot-long catch of material that came out the back of the combine. We feed it into our processor combine in about one minute. Now in the normal field operations, that catch would run through the combine in three to 10 seconds in real time. The processor combine does almost a perfect job.

“When we’re building one of these processors or fixing one somebody else built, our goal is to get 95 percent retrieval. We start by taking one kilogram of grain and dumping it in the front. We’d better get more than 950 grams back.”

The current Challenger processor has the threshing and separating sections inverted so all threshing elements are at the rear of the rotor. All the separating tines are at the front of the rotor. The concaves are at the back for tight clearance threshing. All the separator grates for separating free grain are at the front.

“The 30-foot crop sample comes in the front. The first section of the rotor has no threshing elements, just separating tines. Hopefully all your free grain falls out. Anything still attached to a head or a pod is carried through to the rear section.

“All that material that comes out goes over to the cleaning shoe. So now we’ve cleaned that free grain. The clean grain cross auger has been converted to a rubber belt, so it cleans out. We’ve installed a suction system that sucks that grain up into the cab into a settling plenum, so that’s our free grain.

“Meanwhile, the other stuff went on to the threshing portion of the rotor. We’ll have the concave clearance set pretty tight to try smashing out all those difficult kernels. Below that, where there’s an oscillating return pan on most combines, we have a conveyor belt that’s on its own control. During the first portion of the test, that conveyor belt is stopped. It’s just collecting the material. Once all our free grain is through and done, we turn the conveyor belt on and it runs forward, over the cleaning-shoe system. The cleaning shoe does its job, so now our unthreshed grain is threshed and it’s up in the cab.”

The process is run once for the upper belt from the rotor and once for the lower belt from the cleaning shoe.

The material other than grain (MOG) exits mostly through the rotor, with a lesser amount coming off the cleaning shoe. During the test, some clients want the combine to be fully equipped with sensors and video cameras to collect data on what happens within each chamber in the combine.

During his 10-year gig at PAMI, McDonald had a hand in designing and building a half dozen combine test processors. He says that each processor has a value of about $1.5 million, so it’s essential that they are accurate and sturdy.

“When testing prototypes, most manufacturers start combining in May and keep going until November. They’re hitting five to 10 different crops in five to 10 different locations, putting up to 30 different prototype combines in front of their test equipment. So it has to be efficient.”

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