How To Measure Belt Size For Pulley. Measuring pulley size by hand is relatively easy. Overlap 4 inches of the nylon rope.
Begin by holding your pulley vertically to expose the flat side, and measure from outside edge to outside edge with a ruler. Cr = half the larger pulley circumference = π2⋅2r π 2 ⋅ 2 r , where 2r = larger pulley diameter. Set the flat outer edge of the v belt on a flat surface.
So a pulley measuring 10 inches in diameter from the edges might actually be smaller (9 inches:
This distance is measured from the center of the crankshaft to the center of the jackshaft. In order to determine the belt datum length, simply add the pulley circumference to twice the center distance between the pulleys. If the belt has turned to goo and is unmeasurable, measure the belt path in inches with a string pulled very taut (wrap the string around the pulleys just as the belt would go). The belt usually rides about 0.5 inch inside.