D1 = Diameter of the driver
N1 = Speed of the driver in R.P.M.
D2 = Diameter of the driven or Follower
N2 = Speed of the driven or follower in R.P.M.
R1 = Radius of the driver
R2 = Radius of the driven or Follower
t = Belt thickness (if given)
X = Distance between the centers of two pulleys
α = Angle of lap (Generally less than 10º)
θ = Angle of contact (Generally greater than 150º) (always express in radian.)
µ = Coefficient of friction s = Total slip in percentage(%) L
= Total length of belt Formula For Open Belt Drive