R ecently the chopping of straw in the field is looked at with more intent by farmers. The system of mulch and direct seeding, which goes along with a reduction in tillage, requires a short straw, which rots in a short time and is distributed evenly on the ground. On behalf of the machine, longer working periods and greater working widths result in harder working conditions and higher requirements concerning the straw chopper. The flail-type chopper is commonly used nowadays. In order to adapt

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... o the increasing throughput, the rotation speed of the chopper has been raised. The knives can reach speeds of over 100 m/s as they revolve at up to 4000 rpm. This results in the chop-per being one of the aggregates with the highest power consumption in the combine harvester. Research Goals The reduction of power consumption of the combine chopper is the main goal of the project , next to increasing the chopping quality and the ejection velocity, in order to achieve a better lateral distribution. One way to achieve these goals is to turn away from a "free cut" towards a cut by clamping the straw. The process of cutting and transporting the straw in a combine chopper is described by Kämmerer [1]. As was observed, the main part of the cutting process takes place at the inlet of the chop-per. A high relative velocity between flail knife and the straw is important at this point. In this project, the straw will be compac-ted and force fed to the chopper. The com-paction results from an increased support of the straw, causing a greater resistance towards the cutting flail knives. Preliminary Tests The test rig, as used by Kämmerer [2], was altered in such a way that the straw was fed to the chopper by a conveyor belt from the side (fig. 1). A feed roller was built above the conveyor belt. The roller was attached by an arm, which allowed it to move upwards, if required. The geometry of the roller as well as the position relative to the chopper were adjustable. The straw was moved across a table by the roller into the chopper. There were no counter knives or brake bars installed. The following tests were carried out using wheat and barley straw: • variation of the throughput • different moisture contents of the straw • different geometries of the feed roller • different sizes of the feed roller Results of Preliminary Tests The power consumption of the chopper was cut by approximately 10 % by using a feed Standards on combine straw chop-per are still rising. Good quality has only been achievable in conjunction with higher power requirements till now. The combine chopper is already one of the aggregates with the highest power requirements. This research project should show alternative ways of simultaneously reducing power requirements and improving chopping quality.