Why does the timing belt require one pulley to have a flange?

The requirement for one pulley to have a flange in a timing belt system is primarily to prevent the belt from "walking." The flanged design provides a physical barrier that keeps the belt aligned and ensures it remains seated on the pulley during operation. This alignment is crucial because if the belt were to move off the pulley, it could lead to misalignment, slippage, or even complete failure of the belt drive system.

The flange helps maintain the proper engagement between the timing belt and the pulley teeth, allowing for efficient power transmission without losing synchronization between the components it drives. This is particularly important in applications where precise timing is essential, such as in engine timing belts, where even slight deviations can result in significant operational issues.

While other factors can contribute to belt longevity and torque transmission, the specific role of a flange is to prevent lateral movement, or "walking," of the belt, ensuring stability and functionality in the mechanical drive system.