Conveyor Dynamics, Inc. (CDI) developed a reasonably accurate solution in the early 1990's. The work was based on Prof. Yonkers (Twente) when he was a student of Prof. Spaan (Delft). CDI have perfected this method and applied the technique to many overland conveyor designs. There are still many nay-sayers that do not wish to accept these methods, in part, because the methods are complex and require substantial investment in machines to measure the rubber properties, understanding the test machine quirks, and have identified the appropriate modeling schemes.

You can see many publications from Prof. Wheeler (Newcastle), Prof. Lodewijks (Delft), Prof. Rudolphi (Iowa), Dr. Qiu ( once a CDI employee and now with Metso), and many others who claim to solve most of the rolling indention loss modeling difficulty. These are all 2-D modeling schemes.

Today we also know the problem is not 2-dimensional. To be accurate, you need to include the squirm motion of the belt in contact with the rollers as the belt surface must move faster, and in 2 planes, than its internal tension member speed. In addition, you should consider the rubber heating, from internal hysteresis, and which is amplified by increased belt speed and short idler spacing. Associated with squirm is the idler surface texture and material properties. Formal tests are under way that compare different idler roll surface treatments. The second and third losses associated with the belt's energy consumption is belt flexure between every idler and ore turbulence as the belt deforms at the idler and between idlers.

Other tests have been conducted over the last two years on modified bottom cover constructions. Some already claim large improvements. I can say there are marked improvements with some treatments. This research is still under study. ■