Belt Length Calculator
Here's a handy littly tool we wished was around a
long time ago. It will calculate the length of any fan belt for
you. Simply plug in diameters of the pulleys and the distance between
the centerline of each pulley and click the "Calculate"
button. The page will reload and your answer will appear at the
bottom of the new page.
NOTE: It does not matter what
units you enter your values in (i.e. inches vs. millimeters) so
long as you are consistent. If you enter inches your results will
be in inches. If you enter millimeters, your results will be in
millimeters. Never measure with a string, cord or other material
subject to stretch. ALWAYS use a steel tape drawn tightly around
pulleys. If there is a tolerance, pulleys should be nearly closed.
For V- or U-shaped pulleys, measure INSIDE pulley grooves. Include
take-up allowance.
Two Pulley Systems:
This setup is easy. Just measure the diameter of
each pulley and the center distance between them.
Here is the formula we use:
BL=(2 x SQRT(C12 + (.5 * D1 - .5 * D2))) + (0.5 x 3.1415 x (D1+D2))
Where:
C1 = Centerline
D1, D2 = Diameter of pulleys
Three Pulley Systems:
Three pulley systems require alittle more work on
your part (and alot more math on mine). It is no longer sufficient
to simply know the diameters and center distances of the pulleys,
but you must also calculate the angle of the triangle formed by
the center distances. Use a protractor (remember these from school?)
to determine the angles.
Here is the formula we use:
L=C1 + C2 + C3 +1/2[(R2-R1)2/C12
+ (R3-R1)2/C13 + (R3-R2)2/C23]
+ p ( R1 + R2 + R3) – (a 1R1 + a 2R2
+ a 3R3)
where:
R1, R2 , R3 = Radi of the three pulleys
C1, C2, C3= center distances
a 1, a 2, a 3 = angles (in radians) of the triangle formed by the
center distances
