Gear Center to Center question (and discrepancy)

[TheHolyHades1]

Hello.

I was looking at designing a custom gearbox and came across the WCP center to center distance calculator. After playing with a couple values, I wanted to check if they were accurate. I downloaded the cad model for the VexPro 2 CIM ball shifter and discovered a problem; the distances calculated by the WCP calculator were significantly larger than those on the shifter. Namely, the distance between 40-44 gears should be 2.1020 inches. The shifter, upon inspection in solidworks, shows only a distance of 1.9882 inches center to center.

Could someone please explain this discrepancy? I fear that it may be me simply not using one of the two tools incorrectly, so I'd love if someone could clear up the issue.

Thanks,
Hades

http://www.wcproducts.net/how-to-gears/
http://www.vexrobotics.com/ball-shifter.html