We are planning to run troughed 1800 wide belts at 7 m/sec on coal. Designers have selected fairly large idler diameters - 178mm and 219mm - but it seems not too many manufacturers have experience in manufacturing these sizes and not many have 'runs on the board' for their life and performance. Anyone out there got experience with these diameters and anyone out there running belts at 7m/s or more with smaller idlers ? ■