A speed variance of ______ can be made using an adjustable pulley.

• A. 15%
• B. 30%
• C. 50%
• D. 75%

Answer: (B)

Using an adjustable pulley changes the drive ratio by moving the belt to different diameters on the pulleys, which directly alters the speed of the driven component without changing gears. In a typical belt-drive setup with an adjustable pulley, you can achieve about a thirty percent change in speed. This range is practical because it keeps belt tension and alignment reliable while avoiding excess wear or slippage. Larger variations would require more complex equipment or multiple pulleys, which isn’t standard for a single adjustable-pulley arrangement. Thus, thirty percent is the typical maximum for this setup.