Understanding Aspect Ratios for Enhanced Performance and Longevity
While some belts have covers of equal thickness on both sides, most belts are designed with a thinner (lighter in gauge) pulley-side cover compared to the carrying side. This difference is due to the varying wear resistance required for each side. The thickness difference between the top and bottom covers is known as the belt’s aspect ratio. However, the thickness disparity cannot be too significant, or the belt may cup.
Belts with poorly designed aspect ratios can have issues because the larger mass of rubber on one side will shrink more than the smaller mass on the other side. If a belt has an excessively large top-to-bottom cover ratio, the top cover may shrink due to age, UV exposure, or other factors, causing the belt to cup. This cupping reduces the contact area of the bottom cover with the idlers, making it harder to keep the belt aligned. This problem is more likely to occur when a plant orders a belt with an excessively thick top cover in an attempt to extend its service life.
To ensure consistent shrinkage and better tracking, it is recommended to use an aspect ratio of 1.5-to-1 for belts up to 900 millimeters (36 inches). For belts between 1000 and 1600 millimeters (42 to 60 inches), a 2-to-1 aspect ratio is recommended. For belts over 1600 millimeters (60 inches), a 3-to-1 aspect ratio is advised. Belts with a 3-to-1 aspect ratio are suitable for many applications and are the most commonly stocked by belting distributors.