First Time Belt Drive

Our team has ran chain drives for multiple years, we are now wanting to switch to belt drive for weight reduction, and ease of maintenance. Are there any considerations we need to take on manufacturing it, fitting it, or running it? How do we find the right belt size and right thickness and right pulley for said belt?

Basically you wanna use htd timing belts and pulleys sold by vex here. You can use 9mm wide or 15. I suggest 15 because its the same as the KoP chassis. Make sure to use the same size driving and driven pulley to not break anything. Using this calculator you can figure out how many teeth you need on the belt for the distance you need.

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Holding the center-to-center distances between pulleys gets a lot more important with belts. I would recommend getting a few test bars and trying a few different variations on the center-to-center distance and find one that has good tooth engagement while spinning freely. 0.005" is the difference between a killer drivetrain and a drivetrain killer. For short belt runs, we have a little measurement jig to help dial those dimensions in.

What is meant by “desired Center” on the calculator? more so as in how can I measure it.

“Desired center” is the approximate distance you want between the centers of the two pulleys. From there the calculator will find the belts that give the nearest C-C distances above and below your desired value.

I have a similar calculator with a few other helpful tools as part of my design spreadsheet.

Watch the WCP tutorials on belts and pulleys. They have everything you need to know and probably some stuff you didn’t need to know.

https://www.youtube.com/channel/UC98W6C_j1yR8SzDi1ws5Jyw/videos

This is also a great piece of paper with a ton of information.

2 Quick suggestions:

(1) Use the VexPro bearing blocks instead of just drilling bearing holes into your tubing. The bearing blocks allow you to make small adjustments to the pulley location.

(2) https://sdp-si.com/ has timing belts in odd-number sizes. If the 60-tooth belt you bought from Vex is just a little too loose, they have a 59-tooth belt that may work better.

We’ve run 9mm belts on our drivetrain for the past two years. No issues with the belts, but we have had the sides on a few Vex pulleys come off.

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