NEIEP Elevator Cab Assembly and Door Operators (530) Practice Exam

The correct answer is the compound idler. In a link-driven wing arm operator system, chain tension is crucial to ensure smooth operation and prevent any slippage or excessive wear. The compound idler sheave serves a specific function in the system by allowing for the necessary adjustments to be made to maintain proper tension in the drive chain.

Adjusting the position of the compound idler alters the effective length of the chain, which directly impacts the tension. This is important because maintaining the correct tension helps the operator function efficiently and prolongs the lifespan of the components involved.

While other sheaves like the primary idler, secondary sheave, and main sheave play roles in the overall operation of the system, they are not designed for direct tension adjustments in the same way that the compound idler is. This distinguishes the compound idler as the correct choice for adjusting chain tension in a link-driven wing arm operator.