What Belt Length Do I Need?

One of the most common questions we get is: “What belt length do I need?” Well, there are a couple of ways to figure this out. First, lets do it the hard way. You can use the equation:

Lp = 2C + 1.57(D + d) + ((D – d)^2 / 4C)

Where:
Lp = belt pitch length, inches
D = diameter of large sprocket, inches
D = diameter of small sprocket, inches
C = center distance, inches

Now if doing the math isn’t for you, there are a couple of easier ways to get this figured out. I would recommend our free software. We offer both Design Flex (Web and Pro versions), and Design IQ. You can download either of these at www.gates.com/drivedesign Design Flex is a two point drive design program that is tailored to help you easily design drives, and find proper tension. Design IQ is a little more complex; it is designed to help with drives no matter how many sprockets or sheaves.

With Design Flex, you will need to enter in a load in order to get it to calculate a belt length. While this load doesn’t need to be accurate for calculating belt length, you do need proper loading for trying to design or find the correct tension for a given drive.

With Design IQ, you don’t need to enter a load to get a belt length, but you need to understand where you are placing the sprockets/sheaves. Starting with the driver at the coordinates (0,0), place the driven at the measured center distance in the X coordinate and 0 in the Y coordinate, you can easily find the two belt lengths that are closest (one shorter, and one longer) by selecting the belt length button. When you select one of the belt lengths, the program will then show you what your actual center distance will be in the driven sprockets/sheave’s X coordinate box.

As always, if you have any questions, or would like us to walk you through an example of how to do this, you can call us at 303-744-5800.