DESIGN OF SYNCHRONOUS BELT DRIVES IN IC ENGINES.

The adoption of toothed-belts for timing and ancillary drives of IC engines requires more understanding of design technique as the applications multiply. The essentials of this relatively undocumented field are set out in this article. Claimed advantages of synchronous drives by timing belts are: lightness, flexibility, high specific resistance, quietness, unstretchability, no lubrication required, high efficiency, simplicity and limited maintenance. Main factors to be considered in design are: type of engine, geometry of the drive (position and distance between the pulley shafts and the available space); number of revolutions of the engine and that of auxiliary components and the relative drive ratios; also power requirements of the components to be driven. On the basis of the above factors the following are to be calculated and determined: in relation to the synchronous belt, type, length and width. With regard to the other components of the drive, for pulleys, these are: diameter, width, material and design characteristics. For the tensioning device, factors are: type, diameter of the essential pulley and characteristics of the tensioning spring also configuration of protecting guards and other accessories of the drive. Some essential data and design recommendations necessary for calculations are given.