From The Chairman’s Desk

    The work (presented in the paper printed in this issue from pages 22 to 34) is derived from a Masters Dissertation undertaken at the University of the Witwatersrand, and facilitated by the CMA, that was aimed at investigating the performance of unidirectional idlers under different inclined conveyor belt operating conditions.

    Up until now, very little work has been done in researching the performance of unidirectional idlers. As such, the CMA commissioned a
    test rig to be used to measure the resistance to motion between an inclined belt and a set of idler rolls locked in place.
    The experiments conducted on this rig varied a total of seven belt conveying factors in order to investigate the effects of these factors on the measured unidirectional idler resistive force. In order to plan and analyse the experiments, statistical Design Of Experiment (DOE) techniques were employed in the design of a series of experimental programmes.
    Overall, it was found that material load, troughing angle and idler pitch have the most significant effect on the braking ability of unidirectional rollers.
    Additionally it was identified that although contact friction affects unidirectional idler performance, the presence of non-friction resistances (such as belt sag) strongly influence resistive force at belt slip. Based on
    these findings, a conservative numerical method for specifying the required quantity of unidirectional idler rolls was derived through the separation of friction and non-friction effects and the use of experimental data.
    Jay Pillay, Chairman
    Acknowledgements from the authors
    The authors would like to express their deepest appreciation to all of those who contributed to the research presented in this paper. Special thanks to Simon Curry and the team at Flexco for their support in every stage of this research venture – from the initial stages of planning and equipment design, right through to commissioning and experimentation.
    Thanks also go to Dave Pitcher and everyone at Dunlop Belting Products for donating factory floor space for the UDR test rig and for the invaluable assistance of their maintenance team during commissioning and major experimental set-up changes, as well as for providing belt samples.
    Furthermore, thanks go to Bosworth for the construction of the UDR test rig, as well as Melco, Lorbrand, Megaroller and Dymot for the donation of idler frames, rolls, steel ropes and sheaves. Special thanks also to Beverly Claasens who vetted the structural design of the test rig. Last, but certainly not least, a very big shout-out to the CMA for funding the project in its entirety.