Building a Better Bale Slicer

During the last decade, large forage bales have gained tremendous popularity among farmers because they provide a low-cost, labor-efficient storage option. They make it easier for farmers to allocate forages to different classes of animals based on quality. More than half of the cows in the United States also are fed a total mixed ration (TMR), usually prepared with a mixer. A TMR provides a uniform feed, which helps producers monitor feed intake and improves the digestibility of the ration. But before a large bale can be put in a TMR mixer, the length of its forage particles must be reduced.

"Several machines process hay bales for TMR mixers, but they all use a grinding or shredding motion that requires large amounts of power," says Kevin Smith, who recently completed his master's degree in agricultural and biological engineering. "Existing machines also produce fine particles that result in hay losses of 2 to 9 percent, with the potential for much higher loss in windy conditions. Most of these losses are from the leaves, which are the most fragile and nutritious parts of forage."

Growing up on his family's dairy farm in Milton, Pennsylvania, Smith developed a passionate interest in science and nature, but he never dreamed he would someday build a better bale slicer. After earning a bachelor's degree in agricultural engineering at Penn State, he spent a summer interning with New Holland, a Pennsylvania-based farm equipment manufacturer. "I soon realized that I needed to know more before I started designing farm machines myself, so I went on to get a master's degree in design aspects of agricultural and biological engineering," Smith explains.

With adviser Dennis Buckmaster, Smith set out to develop a prototype machine that more efficiently slices large forage bales into material suitable for TMR mixers. He began building the prototype in May 1995, spending that summer working on the project with two undergraduates, Dan Fabin and Larry Hoover. "It took almost a year to come up with the design because Dr. Buckmaster and I considered many different options," he explains. "I also had to learn how to weld, and there were small setbacks along the way. The first time we tried to start the slicer, it wouldn't even run because of a flaw in the initial design of the platform system that holds the bale. But by November, we had the slicer running consistently."

Smith's bale slicer is made of steel and weighs about 1,000 pounds. A bale sits atop an adjustable deck and is cut from the bottom by a reciprocating knife made from serrated blades scavenged from a square bale cutting machine. "The machine is designed to be placed somewhere near a silo, and a conveyer belt could carry the chopped hay directly to a TMR mixer," Smith says. "Producers would use a front-end loader to place a bale onto the platform, and the machine would take care of the rest."

Round bales can weigh up to 1,500 pounds, so Smith designed a special dual-platform system to keep heavy bales from pressing on–and bending–the knife. "During processing, the bale remains stationary while the platforms and knife bar move across its bottom," he explains. "The platforms are connected to each other by see-saw brackets that we designed and made ourselves. These mechanical linkages keep the two platforms at a constant horizontal distance apart, but allow free vertical movement at the end of each slice. The leading platform will lift up at the end of a slice, while the weight of the bale pushes the trailing platform down to the plane below the knife. This allows the knife to slice the bale in both directions, while ensuring that the weight of the bale never rests on the knife. The mechanism allows for a 5-inch cut width–perfect for a TMR."

To try out the slicer, Smith processed 15 dry hay bales and recorded the results, testing three different knife stroke lengths at two oscillating speeds to determine the optimum setting. Then he tried this setting with high-moisture forage bales, which are more difficult to process than dry bales. "Hay processed by the machine was suitable for blending in most mixers," he says. "In fact, the bales used in our experiments were mixed in a TMR and fed to Penn State's dairy herd."

Smith also determined how much power the machine consumed to see if it used energy more efficiently. "The machine used a hydraulic power unit with a 15-horsepower capacity," he says. "Hydraulics cost a little more, but they operate more smoothly and require fewer moving parts. The most power we used in our tests was about 7 or 8 horsepower, compared to a 60-or 70-horsepower tractor that would be used to power a tub grinder."

Based on the experiments conducted with his prototype slicer, Smith believes that forage can be processed more efficiently by slicing than by grinding. "The machine processed a bale in ten to fifteen minutes," Smith says. "That's slower than a tub grinder, which takes about five minutes, but the slicer used about 95 percent less energy. That was far above our expectations."

After receiving his master's degree in June 1996, Smith returned to New Holland North America, Inc. in a new position–design engineer. Meanwhile, a patent application on the prototype bale slicer is pending, and future graduate students may further refine and fully automate his machine. "Right now, the operator must stop when the bale is half done to remove hay cuttings from beneath the machine," Smith explains. "Simply adding a conveyer belt underneath would carry the hay directly to a TMR mixer, and there are other improvements that could be made. Ultimately, I anticipate that a machine based on this design may cost nearly as much as a tub grinder, but it would have tremendous advantages in energy efficiency and animal performance."

–Eston Martz