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Developers of self-propelled rock picker conducting demonstrations in Sebeka area

Mel Aho, a native of Sebeka area, who lives near Vancouver, Wash., led development of a self-propelled rock picker that can dig field rock at about 3 mph and dump 10 yards of field rock in about 8 minutes. (Mikkel Pates/Forum Communications Co.)1 / 2
Perry Gilmour, left, Merf Aho and Mel Aho have been involved with the development of a self-propelled mechanical rock picker. (Mikkel Pates/Forum Communications Co.)2 / 2

SEBEKA -- On a field in northeast Otter Tail County, littered with field stones ranging from pebbles to volleyballs, the RP 1000 moves onward and then upward.

A curious, self-propelled contraption, it moves ahead at about 3 mph, unearthing rocks in a 20-foot width. Irregular rocks disappear into a cylindrical sieve that takes them to a conveyor and then onto a heavy-duty, high-lift box.

Eight minutes into a cycle, a standard dump truck comes alongside. The picker stops and the 10-yard trailing hopper is lifted up 10 feet and effortlessly dumps its contents into the truck.

"So ... what do you think?" asks Mel Aho, a primary developer of a machine he built for his own farm. He might predict the reaction from a visitor, a contemporary who, as a kid, also threw countless rocks onto a flatbed back home.

This rock picker, they agree, is like something they've never seen before -- "harvesting" rocks.

"I think of this like the first eight-row combine of the rock picking," Aho says.

Aho grew up in rural Sebeka but left home and made his career as a home building contractor in Washington state.

In the past 20 years, he has acquired property for hunting and eventually increased his farming as he added food plots.

"I'd buy a few pieces of farm equipment," Mel says of his farming.

Mel's Minnesota holdings have included some 38 parcels that were largely contiguous in his favorite deer hunting haunts. In past three years, he's hit a plateau of about 3,000 acres of land, including about 2,000 in farming. About 1,000 of those acres are leased, including about nine circle systems.

"Ag land and hunting land go well together," he says.

Much of the ground initially was in the Conservation Reserve Program, but he's since taken it out and farmed it. Some of the land was rocky.

He spends a total of about two months a year in the Sebeka area, between peak farming and hunting seasons.

Mel bought some of the existing rock pickers on the market, but they lacked the capacity and speed he wanted.

"I tried as many as I could find," he says. "I thought, to heck with those rocks, breaking everything," he says. "I wanted clean ground."

About four years ago, Mel and a friend, Perry Gilmour, started building their own rock picker in Washington.

Gilmour, a third-generation farmer in the Willamette Valley of northwest Oregon, supervises farming on some of Aho's long-term investment properties.

"Perry and I share an interest in tinkering," Mel says.

Initially, Mel and Gilmour thought about using a grain combine as a platform. They looked locally but eventually went online to find UNI 803C power unit with a Cummins engine. They flew to Iowa to look at it and had it shipped to Vancouver, Wash.

"We renovated and remodeled that, putting hydraulic pumps to make the machine hydraulically driven, rather than with the power take-off. That way it wouldn't have clutches slipping," he recalls.

After putting it together, Mel and Perry moved the machine to Sebeka.

"It was a good base to start our machine with," Mel says. "It worked pretty darn good."

One big advantage over most commercially available systems was that the operator looks forward rather than behind. The 20-foot-wide rake component is hydraulically driven, picking up rocks in the 4- to 8-inch depth.

"Essentially, the machine picks up rocks to whatever level the ground is tilled to," Mel says. "If you till it deep, it'll go down there deep. The better the soil is tilled, the better it's going to work."

The sieve screen is a cylindrical reel, spinning 300 RPM and counterclockwise, and is set at angle. The rock moves along a spiral, something like a cement mixer as the dirt vibrates through. Cleaned rocks go onto an elevator that throws them into a 10-yard capacity wagon. Heavy hydraulics lift them up for dumping -- often 15 tons of rock.

Mel says he has no "agenda" for the future of his machine, but has acquired both U.S. and international patents on the process. Additional machines could be built on a custom basis, probably for "north of $100,000," he thinks.

He built the prototype it for his own farming but acknowledges it probably has numerous commercial applications -- beach cleaning, road building, golf courses and other landscaping.

He's not in the machine manufacturing business, but others are.

"I'm open, OK?" Mel says of other possibilities.

Mel's brother, Merf, is doing some custom work. Merf has long been in the steel construction business in New Hampshire, but sold that business, and is in the Sebeka area with his family. Merf has been offering the machine on a custom rate, figured on a case-by-case basis, depending on the conditions and how clean the landowner wants it.

Once a field is clean, a farmer can increase speed of other farming operations with fewer breakdowns and lower maintenance costs.

Cleaned land is more valuable. Mel has seen how some rocky ground in Idaho and elsewhere could be cleaned to grow potatoes, adding to its value.

The first public demonstration of the machine was April 30. Other demonstrations are being scheduled. Go to to see more.

Mikkel Pates is a reporter at Agweek in Grand Forks, N.D., which is owned by Forum Communications Co.