Here's an Excel based timing belt calculato
r.
http://www.davall.co.uk/downloadlibrary/BELT%20CENTRES.xls I really needed this as I'm making and using non-standard pulleys, (80 tooth).
No instructi
ons, I had to play a few minutes, but it works.
After you designate the wanted distance between pulley centers, you get a non-integer belt.
Use the whole number to then get an exact center distance.
Ozzie