How do you Calculate Belt Length?

[tkwetzel]

Originally Posted by JosephM

Use geometry...

Measure the distance between the two pulleys, write down and multiply it by 2. (56 * 2= 112 in).

Now, take one pulley (6 inches) then find the circumference of it (2*pi*r).

2*pi*r= 37.699 -> 38 in around.

Then divide that by 2 (the belt only contacts half the pulley) and you get 19 in. Repeat your steps for 2.

112in + 19in + 63in = 194 in will be needed. Of course, it's totally theoretical.

I thought of it that way, but with a small change that will be more accurate because it compensates for the extra length between the two pulleys along the line that the belt travels.

I looked at the line that the belt travels between the two pulleys as the hypotonuse of a right triangle. The longest side is 56" (the centerline bewtween the pulleys) and the shorter side is 14" (large radius minus the smaller radius). Then you use the pythagrean therom a^2+b^2=c^2
I included my math so anyone can check it.

56^2+14^2=c^2
3136+196=c^2
3332=c^2
c=57.72...

So you would multiply that number by two and add it to half the circumference of each of the pulleys. Using the numbers in JosephM's post...the distance would come out to roughly 197.5" of total belt length.