There's one bell and whistle on forage harvesters that custom operators have put to good use: the knife-sharpening apparatus.

Yet, as fuel costs increase, university experts continue to remind operators to sharpen knives daily and keep shearbars in good order.

“The biggest power consumer in the forage harvester is turning that cutterhead, and anything you can do to reduce that power is money in the bank,” says Jim Garthe, Penn State University ag engineer.

Garthe used to find creative ways to show custom operators the importance of keeping knives and shearbars in shape. Fifteen years ago, he put together a bicycle-powered forage harvester demonstration unit to show how power consumption increased when comparing sharp knives to dull. The bicycle ran a small cutterhead

The demonstration drew crowds, Garthe says, and helped remind operators that regular knife maintenance, a pain though it was, increased productivity and fuel economy.

“Years ago with the old forage harvesters, you had to do quite a bit to sharpen the knives. Now the self-sharpening knives are one of those value-added things that machinery folks have put in,” Garthe says. “If they are not self-sharpening, they have a system where they run a grinder over the knives very rapidly before the start of the day.”

It only takes a flip of a switch to sharpen most knives and a number of dealers say they think custom operators, in general, are making use of it.

Yet Garthe stresses just how important it is to make knife sharpening a daily habit during the harvest season.

“I've seen some knives on forage harvesters that have a very, very, blunt rounded edge,” he says. “And if you had that blade in your hand, you wouldn't have to worry about getting cut on it. When they get that dull, it will take considerably more horsepower and more fuel. It's tearing the plant material rather than severing it.”

If once a day seems too often, Garthe says, refer to your machine's operator manual. “It will probably tell you how often to sharpen them depending on the type of crop you're in and the hours you have gone. It will also tell you when to sharpen or rotate your shearbar.”

Three maintenance steps or adjustments that can significantly impact fuel consumption are theoretical length of cut, knife sharpness and knife-shearbar clearance, says Ron Schuler, recently retired University of Wisconsin extension ag engineer.

A well-adjusted forage harvester burns about 1.5 gallons of fuel per acre, he says. The pickup and feed rolls account for 20% of the fuel; the cutterhead, 40%; and the blower, 40%.

In tests, worn knives doubled the cutterhead's fuel requirement, Schuler says. The estimated 0.6 gallon per acre (1.5 gallons × 0.4) requirement increased to 1.2 gallons with worn knives. At $3/gallon, fuel costs would increase by $1.80/acre.

Watch knife-shearbar clearance, too, Schuler says. Increasing clearance from 0.01" to 0.02" can double the cutterhead's power requirement, also increasing the fuel cost by $1.80/acre. If clearance increased to 0.03", the fuel cost increase would be $3.60/acre. Add worn knives and the added fuel cost would be $5.40/acre.

Increasing the theoretical length of cut will reduce fuel consumption, but be sure it meets the needs of livestock and the storage system. If there is a choice, go with longer length of cut, Schuler says.

Additional maintenance can cut fuel consumption, adds Kevin Shinners, University of Wisconsin ag engineer. “Make sure they have good blower and paddle clearance,” he says. That includes adding water to the blower if there is gumming.

“And keep tire inflation right, make sure the air filters and the whole air-induction system are in good shape, and keep dust and crop off the engine and the machine so you get good cooling,” says Shinners.

“Producers want to pay attention to those things to not only lower fuel consumption, but to also provide the best possible capacity from the ma-chine and produce the best quality product for the customer,” he adds.