The circumference of the inside diameter of a rotary drum tire is larger than the circumference of the outside diameter of the shell, and therefore the tire will not make a complete revolution at the same time as the shell. This difference per revolution between the tire and the shell is called tire creep.
Tires are originally set to creep around the rotary drum at a minimum rate, with the rate differing from “cold” to “hot” drums. The ideal creep is almost zero without having the drum shell expand and deform, though this is not an issue with cold drums.
When tire creep becomes excessive (say ¾” per revolution on a 9 ft drum), it is time to re-shim the tire blocks. Re-shimming is done by measuring the gap at the top 12 o’clock position of the drum, and dividing it by two to arrive at the approximate shim needed to get back to a “cold” drum setting. On a “hot” drum, you will need to contact FEECO for the proper gap recommended for the material application.
Proper inspection and maintenance is crucial to obtaining the maximum life of the rotary drum. For more in-depth information, contact our Customer Service Engineers today!