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Experiments made with a model helical chipper have shown that the infeed angle has a huge impact on chip quality parameters. Furthermore, it could be pointed out that the self feeding mechanism of the helical chipper was impeded with larger infeed angles and finally failed. This situation led to the hypothesis that the infeed angle must have an impact on power requirement during chipping. In the present investigation this conclusion was tested. Standardized preformed test rods were chipped with a helical chipper at seven different infeed angles while torque, rotational speed and chipping time were recorded. The experimentation was done using poplar wood with different moisture content. Based on the measurements power requirement and energy consumed was calculated for each test series. The results of the experiments show that power requirement and energy consumed are decreasing with increasing infeed angle. The results seem to be extraordinary since increasing infeed angles lead to decreasing chip sizes being produced. Based on theoretical deliberations and experimental data it can be assumed that besides the anisotropic character of wood geometrical settings of helical chipping could be a reason for the experimental findings. But, because the chipping time is also dependent on the infeed angle there still must be other reasons concerning the occurring forces during helical chipping, too. For this reason there is a need to have a closer look onto the different forces occurring during helical chipping. Against this background the Discrete Element Method (DEM) could be a simulation method for future research. [ABSTRACT FROM AUTHOR]

Abstract: Nowadays wood chips produced from raw material of inferior quality are mainly used to feed domestic and industrial boilers. For this use, a good chip size distribution and low manufacturing energy consumption are required. Cutting forces are still inaccurately measured during the wood chipping process, which implies the use of oversized chippers' motors. A test bench for chipping wood under reasonably realistic conditions of industrial production is improved by adding an indirect force measurement system with high bandwidth of 3 KHz. The dynamic experimentations give the data needed to compute the curve presenting the vertical component of the cutting force, which is composed of three sections; the first one presents the values of the impact force; the second one is relatively straight and it refers to shear stress in wood; the third section corresponds to the period between two crosscuts. [Copyright &y& Elsevier]

Abstract: The authors tested a 409 kW forager turned into an industrial chipper through a special conversion kit. Conversion was temporary, and the forager could be returned to its original occupation with one day of work. The converted forager proved as effective as a dedicated chipper of the same power. Net chipping productivity varied between 25 and 33 green t h−1. Productivity was highest with poplar tops and lowest with pine tops. Fuel consumption ranged from 1.6 to 1.8 l green t−1. Fuel consumption did not change with tree species, but increased significantly with knife wear. Temporary conversion allowed a better depreciation of the invested capital and resulted in a 25% reduction of unit chipping cost. The converted forager proved an ideal solution wherever the production of wood chips was a complementary business within the scope of a larger agricultural economy. In technical terms, this machine offered the combined advantages of road-capability and good off-road mobility, allowing low-cost independent relocation and effective in-field chipping. [Copyright &y& Elsevier]