to the t shaped guide rail 30 the joint 57 between adjacent lobes 25 on the roll 22 23 is located at the thinnest part of the lobes 25 to minimize the urethane to urethane contact a slight clearance between adjacent lobes at the joint 57 is desireable to further minimize this contact which during operation builds up significant amounts of heat through friction an optional bushing material 59 can be mounted on the guide rail 30 or bonded to the t shaped slot of the lobe 25 to further facilitate the sliding movement of the lobe 25 along the guide rail 30 furthermore the joint 57 could be provided with an optional bushing material bonded to one of the adjacent lobes 25 to facilitate relative movement therebetween in the alternative mounting embodiment shown in fig5 the t shaped guide rail 30 is located at the joint between adjacent lobes 25 with a half t shaped slot being formed in the opposing sides of the lobe 25 to accomodate the guide rail 30 this particular mounting configuration further minimizes any urethane to urethane contact but subjects the guide rail 30 to contact with juices from the conditioned crop material through the slight clearance between the adjacent lobes 25 immediately above the guide rails 30 as shown in fig4 and described above the guide rails 30 could be provided with a bushing material if desired it will be understood that changes in the details materials steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention the foregoing description illustrates the preferred embodiment.