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conveyors continued Figure 7—Herringbone Wing in underground quarry. of stress on the belt in an angled wing pulley. An end or radius crown provides good training action without over stressing the belt. The Herringbone Wing pulley crown is a combination of the end crown and the radius crown. The crown is only on the ends, similar to an end crown, and the crown is curved to ease the transi- tion between the flat center and the crowned edge. The different crowns are illustrated in Figure 6. This makes the Herringbone Wing crown effective on all locations. Putting the wings at an angle reduce the forces that cause wing fold-over. The force is caused by rocks getting caught between the end of the wing and the framework of the conveyor. This force is directed against the direction of rotation. With the wing at an angle, the fold-over force is at an angle to the wing, reducing the effect of this force. The Herringbone Wing height is between 3 and 6 inches, maximizing the lumps size and cleaning action, while minimizing air flow and fold-over bending moment. Figure 8—Herringbone Wing in load section tail for coal mine. Herringbone Wing pulleys were developed in 2010 and have been used in applications involving coal, potash, limestone, petroleum coke, grain, etc. (as shown in Figures 7 and 8) and have performed well in all. They have reduced maintenance, vibration, noise, and improved tracking over the pulleys they have replaced. Analysis has shown that they are stronger than the wings they replace, and have been used when conventional wings will not handle the load. Laughlin is the product engineering manager for Precision Pulley & Idler. This article is based on a presentation he made at the Coal Handling & Storage seminar, which took place in St. Louis during October. November 2012 www.coalage.com 49