Hi Shotgun12 - welcome to HomemadeTools.net

Sounds like you'll fit in well here. We have a great belt sander page here: Homemade Belt Sander

There are many treadmill belt sander builds out there. Another trick is to use the treadmill incline motor (that simulates running "uphill") as a belt tensioner. And the metal from the treadmill frame becomes the belt sander frame.