Rugged Applicator

December 8, 2012 02:52 PM
Rugged Applicator

Farmer-built air boom reduces dry fertilizer drift

Around Burr Oak, Kan., Kelly McNichols is known for the creations that come out of his farm shop. So when his neighbor Joe Herz wanted a GPS-controlled air-delivery fertilizer applicator, he knew  who to turn to.

The applicator McNichols built won the Technology category of Farm Journal’s "I Built the Best" contest.

"Delivering fertilizer with outlets spaced across a boom lends itself to GPS control and variable-rate application," McNichols notes. "It’s well-suited for areas like ours. We have a lot of Farmer-built air boom reduces dry fertilizer drift By Darrell Smith Rugged Applicator wind, which can distort the pattern of a spinner applicator."

McNichols had a Gandy Orbit-Air delivery unit in his shed, waiting for a new mission. He had used it on a no-till air seeder that he built a few years ago.

Building Herz’s applicator involved constructing a caddy for the hopper and air delivery unit, fabricating a boom and setting up GPS controls.

For the center of the caddy’s triangular frame, McNichols used 4"×6", 3⁄8"-wall steel tubing. For the outer framework, he used 3"×3", ¼"-wall tubing. He set the frame on the axle and wheels from a Massey Ferguson 750 combine, confident they would be strong enough to support the weight of the hopper. For insurance, he reinforced the connection of the axle to the main frame with gussets.

McNichols framed the 48' boom’s center section with 4"×4", 1⁄4"-wall steel tubing. The lower bar of the wings is made from 3"×3", 3⁄16"-wall tubing. The upper diagonal framework is made from 1"×2", 11-gauge tubing. He mounted 24 fertilizer tubes on 24" spacings.

pD2 Rugged Applicator 2

The boom is anchored onto the quick attach frame by two 1" bolts.
"It goes on or off in five minutes,"
McNichols says.

Fertilizer leaves the applicator’s manifold through flex hose, which carries it to metal elbows on the center section of the boom. McNichols fabricated the elbows from 1" conduit. At the hinge point of the boom, the conduit is connected to flex hose, letting the boom pivot for folding. Past the hinge, the fertilizer completes its journey down the length of the boom through more 1" conduit.

McNichols used 1" conduit for the elbows because it’s readily available. "Elbows are the first thing to wear out, so I wanted to be able to replace them easily," he says.

To connect the elbows to the boom frame, McNichols used clamps made from plastic bearings and U-bolts from the pickup reel of a combine. "I staggered the clamps to fit them all in," he says. "The spacing had to be the same as on the original quick-attach manifolds on the other end, so the hose wouldn’t pull when the boom is raised or lowered."

Fit to the mold. It took ingenuity to connect the flex hose to the manifold’s rigid conduit air lines, since the diameters were different. "I built a little propane oven, where I heated short lengths of rigid plastic tubing and sized it to the diameter of either the conduit or the flex hose with a jig," McNichols says.

"After heating and sizing it, I had to cool it in ice water to fix the tubing size. I could only heat half of the tubing at a time because it got too flexible; I needed one side of the tubing to remain rigid to force it onto the die. It took quite a few rejects to develop the technique."

Folding the boom required raising it high enough to miss the tires and fertilizer tank, mounting saddles for the folded boom to rest on and designing a unique hinge. McNichols raises the boom into folding position with parallel linkage arms made from 4"×4", 3⁄8"–wall tubular steel. It folds to 15' wide.

Because he couldn’t get the entire machine in his shop, McNichols first constructed the center section and one wing. Then he built the second wing as a mirror image of the first, using the first wing as a jig. The wings include self-resetting breakaway end sections.

McNichols uses a tractor loader to mount the quick-attach boom on the caddy. The tapered design  of the caddy’s upper lift frame helps it slide into place. The design is similar to a combine feeder house and header attachment.

The boom is anchored onto the quick-attach frame by two 1" bolts. "It goes on or off in five minutes," McNichols says.

With the boom removed, the caddy and air delivery unit can be used with a planter or air seeder. The parallel arms are designed to lift a 12-row planter. Adding a coulter bar to the pull hitch on the caddy would make it possible for the operator to inject seed or fertilizer into the ground.

The boom alignment can be adjusted using a fabricated 1¼" all-thread rod. "Someone told me the boom looked factory-built," McNichols grins. "I told him it was a one-man factory."

For variable-rate capability, McNichols replaced the air delivery unit’s ground drive with a Rawson hydraulic drive. Gandy Company’s Gary Wolff helped him calculate the chain sprocket ratios and sizes to get the correct rpm and torque range with the hydraulic drive.

A Trimble CFX-750 display provides lightbar guidance and variablerate control. "For now, it controls each half of the boom individually," McNichols says. "I plan to set it to turn individual rows on and off by putting an air cylinder on each manifold."

Doug Langham, who was then  operating his own GPS company, wired the system and installed the Rawson hydraulic drive. When McNichols discovered that Herz’s tractor didn’t have enough hydraulic outlets, Langham suggested using the loader hydraulics. "So the boom is operated with the loader’s joystick control," McNichols says.

He expects it will last a long time. "I built it heavy, reinforced areas likely to break and installed grease zerks at every pivot point," he says. "I hate repairing things after they break."

To view more photos of McNichols’ GPS-controlled applicator, go to

You can e-mail Darrell Smith at

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