The pitch circle of a belt drive is__________.

• A. The place in the belt which represents the center of the force being transmitted by the belt
• B. The outer edge of the belt
• C. The center of the shafts
• D. The belt midline length

Answer: (A)

The pitch circle is an imaginary circle that goes through the belt’s pitch line—the line along which the belt’s tensile force is effectively transmitted. This is the path used to measure belt length and to relate belt speed to pulley size, since the belt engages the pulleys along this line. It represents where the forces act within the belt, not the belt’s outer edge, not the centers of the shafts, and not simply the belt’s midline length. That makes the option describing the belt position that represents the center of transmitted force the correct description.