perancagan seabuk belt

Mate 4-inch-diameter sheave with 6-inch-diameter sheave. Their centerlines can range from 18 to 20 inches apart.
Select length of belt and determineactual centerline distance. If small sheave rotates 1800 rpm, determine ratio and surface speed. Find the angle of contact for the small sheave.
Answer : D1 = 4 inchi
D2 = 6 inchi
C    =  18 – 20 inchi
n    = 1800 rpm