Development and evaluation of a feederless fine chopper

A feederless chopper was developed to satisfy the fine chop requirement of materials used for silage, handmade paper, mulch or compost. The inclined-axis, flywheel-type chopper has a rotating steel disc. Welded to the top of the disc were four equidistant, upwardly inclined blade frames whose extensions function as a fan. A blade was bolted to each blade frame. A stationary counteredge was mounted below the housing cover. Length of introduced material was limited by a thin covering disc, from the slots of which the chopping blades protrude. Finely chopped materials pass through the slots of the limiting disc and are thrown out by the fan. Those not short enough are deposited on a circumferential screen for secondary chopping by two rechopper blades. The chopper was tested with napier grass, rice straw and corn stalks for capacity, power requirement, specific energy and fineness of chop at three speeds (1000, 1250, and 1500 rpm), and two designs of circumferential screen and limiting disc. For napier grass, clean fine chops without clogging were obtained at 1500 rpm, inclined U slot screen, and limiting disc with 20 mm slots. These settings gave a capacity, power requirement, specific energy and fineness of chop of 1095 kg/h, 1.683 kW, 1.559 kW-h/t and 88.6 percent, respectively. The round-hole screen was found appropriate for non-oriented rice straw. At 1500 rpm, the capacity, power requirement, specific energy and fineness of crop were 246 kg/h, 1.880 kW, 7.685 kW h/t and 77.4 percent, respectively. Supplementary tests with five forage grasses showed 65.78 percent of the chopped materials have lengths of 25 mm or less. Screen configuration was dependent on the type of material and its moisture content. Stiff-stemmed, large diameter material like corn stalks might not require a screen because of clogging and high power required. The use of a circumferential screen to improve fineness of cut is a low cost, but effective alternative to feed rolls