The conveyor belt is driven around the helical track by drive sprockets at a single location outside the helical path. The maximum tension in the belt, which occurs just ahead of its engagement with the drive sprockets, can be quite high for such a long belt. To reduce the maximum belt tension, overdrive spiral conveyor systems are used. In these overdrive systems, the conveyor belt is driven by frictional contact between the inside edge of the belt and the faster-rotating outer surface of the rotating drum about which the belt is helically wrapped. And, because overdrive systems are sensitive to friction between the outside of the drum and the inside edge of the belt, the proper settings of tension and overdrive vary from installation to installation.

то есть, скорость шнека заведомо выше