1 HP 2" Belt Sander

[tekcraft]

My wheels were both grooved to the same dia of 3.75". The circumference of that dia =3.75 x 3.1416 (Pi) = 12.81" So a 48" belt - 12.81 = 35.19" That divided by 2 = 17.6" the center-to-center distance.
I used a 1" OD x 4" long spring inside the 1.25 sq tube to get the proper belt tension. For a 2" wide belt 3M recommends 40-50 lbs of force. If you know the spring rate, you can then determine how much it must be compressed to get the right belt tension. I designed around this compressed spring length but also put an adjusting screw under it so someday as the spring ages my grandkids can tighten it up.

Another option if you already have your wheels & belt is to have someone hold the belt tight with the wheels and then measure the center-to-center distance.

Happy building !