chipper infeed chute which is incorporated herein by reference once the brush is grabbed by the feed system 18 the brush is moved into contact with the cutter drum 30 that is housed within the body 20 of the chipper 10 the cutter drum 30 spins cutting blades 80 at a high rate of speed which thereby reduces the brush and wood that contacts the drum 30 into small chips that are projected out the discharge chute 22 drum arrangements are described in greater detail in a related application filed on may 10 2007 titled chipper drum with integral blower which is incorporated herein by reference no 60 928 928 still referring to fig1 5 the feed system 18 of the chipper is described in greater detail below in the depicted embodiment the feed system 18 includes an upper feed roller 32 and a lower feed roller 34 in the depicted embodiment the upper feed roller 32 rotates counter clockwise and the lower feed roller 34 rotates clockwise to grab and pull material into the chipper 10 in the depicted embodiment the rotation is powered by a hydraulic drive motor not shown in the depicted embodiment the lower feed roller 34 is positioned closer to the chute 16.