Belts - Pulley Diameters vs. Speed

Pulleys - Speed vs. Pulley Diameters

Pulleys - Speed vs. Pulley Diameters

Pulley	Diameter (mm, in)	Speed (rpm)
1
2
3
4

Single Belt Transmission - one driving pulley and one driven pulley

For a system with two shafts and two pulleys - as indicated with pulley 1 and 2 in the figure above:

d₁ n₁= d₂ n₂                                   (1)

where

d₁ = driving pulley diameter (inch, mm)

n₁ = revolutions of driving pulley (rpm - rounds per minute)

d₂ = driven pulley diameter (inch, mm)

n₂ = revolutions of driven pulley (rpm - rounds per minute)

Equation (1) can be transformed to express the

Revolution of Driven Pulley 

n₂ = d₁ n₁ / d₂                          (2)

Revolution of Driver Pulley 

n₁ = d₂ n₂ / d₁                           (3)

Diameter of Driven Pulley 

d₂ = d₁ n₁ / n₂                          (4)

Diameter of Driver Pulley 

d₁ = d₂ n₂ / n₁                         (5)

Multiple Belt Transmission Systems

For a system a with three shafts and four pulleys - as indicated in the figure above:

n₂ = n₃                            (6)

n₄ = n₁ (d₁ d₃) / (d₂ d₄)                          (7)

Example - Multiple Belt Transmission System

The revolutions of shaft 4 in a multiple belt transmission like indicated in the figure above where

n₁ = 1000 rpm

d₁ = 100 mm

d₂ = 50 mm

d₃ = 110 mm

d₄ = 60 mm

can be calculated as

n₄ =(1000 rpm) (100 mm) (110 mm) / ((50 mm) (60 mm)) 

    = 3667 rpm

Temperature ^oC
K
^oF

Length m
km
in
ft
yards
miles
naut miles

Area m²
km²
in²
ft²
miles²
acres

Volume m³
liters
in³
ft³
us gal

Weight kg_f
N
lbf

Velocity m/s
km/h
ft/min
ft/s
mph
knots

Pressure Pa
bar
mm H₂O
kg/cm²
psi
inches H₂O

Flow m³/s
m³/h
US gpm
cfm