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Rx for harvester hazards

Combines are remarkable machines, says Earl Knuth. With the most complicated mechanisms on a farm, they are a myriad of parts agitating in unison in what seems to be an effortless manner – until they break down. “Then they become hundreds of thousands of dollars of machinery,” he says.

Knuth should know. During his 30-plus-year career, this master mechanic has worked on or has directed the maintenance for thousands of combines. That experience has taught him volumes on discovering looming parts failures.

See Knuth's considerable experience in a 30-minute inspection guide that airs on the Machinery Show (on RFD-TV) August 9 at 8 p.m.; August 10 at 10:00 a.m., and August 12 at 9 p.m. (all times are Central).

The boiled-down version of Knuth's guide is offered here and highlights six often-overlooked parts. Combine Doctor Knuth has one overriding bit of advice: “You can never spend too much time cleaning a combine. It is absolutely crucial to its performance.”

1. Cleaning shoe inspection is one of the dirtiest jobs on the farm. “But there is no other way to go about it,” Knuth says. “Remove the chaffer and sieve assemblies, and crawl inside. Inspect the pan area for cracks, holes, and rust that retard crop flow going down to the clean grain augers. Look over cleaning fans for any damage to their vanes. Examine the augers for rolled back or sharp edges (a sign of wear) and level operation. (Augers that are bowed move significantly less grain.)


2. Chaffer and sieve assembly inspection involves looking for missing elements, cracks in side frames and frame corners, and flopping deflectors (missing rivets). “When a frame breaks from cracks and wear, a corner of the frame often drops down,” Knuth says. “The shaking mechanism starts pounding the frame, which causes it to self-destruct in a short time.”


3. Belts throughout the entire harvester should be examined. There are no exceptions to this rule. “A damaged belt vibrates, and that hammers away at the pulley bearings and related parts causing premature failure,” Knuth explains. “Examine the entire length and all belt surfaces. Pay close attention to belts powering the feeder house and residue management system because they transfer a lot of power.” Look for cracks, missing pieces, separation, and burned spots (indicating excessive slip and wear). Rotate the belts by hand, listening and feeling for roughness in the operation of the pulleys they work with.


4. Concave sections must be examined for foreign objects, broken wires, or any damaged sections. “They must be removed from the combine,” Knuth says. “Clean them thoroughly, repair broken wires or damaged sections, and then reinstall them, making sure they are leveled properly.”


5. The clean grain elevator and vertical auger (to the grain tank) get little respect. They are simple mechanisms with long lives. “But when they fail, everything stops. And they are difficult to work on,” Knuth says. The most common failure with the clean grain elevator is chain breaking, and the most common reason for this is too much tension. “A chain that has too much tension will get tighter as the chain conveys material, and this could cause shaft and bearing failures,” Knuth explains. “Also, look for wear on rubber paddles (rounded corners and edges) and the vertical auger. Worn material-handling components reduce harvest capacity, increase power requirements, and damage grain.”


6. The residue management system, the chopper, needs a complete examination. But distribution vanes on the tailboard section are often overlooked. “They are crucial to evenly distributing chopped material,” Knuth explains. “Look for cracks in the vanes that can catch and hold residue. This can cause residue to shoot out in bunches.”

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