Error with Belt Length Calculator

[PaulV]

I used the Belt Length Calculator that is part of the pulley subroutine to come up for the center distances for a belt drive. When checking the results against the work of another person who did the same calculation using the belt length calculator on the Westcoast Products website, we came up with substantially different answers. We did a simple calculation by hand using two 30 tooth HTD pulleys and a 160 tooth HTD belt having 5mm pitch and came up with 11.811 inches, whereas the Belt Length Calculator came up with 11.694 inches, which is almost exactly 99% of the hand calculated distance. When comparing results with the Westcoast Products calculator, the Gearotic center distances are 99% to 99.5% shorter with the difference being greater with longer belts. Is this intentional?

[ArtF]

Hi Paul:

  It can be a matter of manufacturers spec. They may better know the actual thickness of a particular
belt they use. I will check the calculations though, as I recall I  use a generic formula for the calculation
based on the pitch distance, but as a safety Ill take another look to see why they may differ. Ive
only made things with XL style pulleys and the distance worked well, so Ill check that HTD arent missing
something .

Thx
Art