There are a bunch of books out there. But it isn't that complicated especially one of that small size. It is a pretty elementary structural design challenge. The only aspects that are at all different is the belt tension loads and the dynamic loads (both probably not governing the design).
But honestly. If you are unfamiliar with the relevant structural codes and standards, then pay engage a local structural engineer to get it done.
(There is certainly strong cross over in some areas of mechanical and structural engineering, but I wouldn't say this is one. Sure I'm not going to tell you not to learn all you can to be a structural engineer as well, but sometimes it is probably better to stick to your expertise. (I recently got handed as simple mechanical shaft design (probably 1st year college stuff) by somebody within my organisation to 'check over and approve' the design. I did look briefly but refused. Better to pay somebody who knows what they are doing for 3hrs of their time than to waste my time trying to teach myself the basics and the having to triple check everything.)
This is a reverse example. Do you really want to spend your time learning about wind and seismic loads. LTB and effective lengths of structural members if you don't know it already? If you DO know it all then go nuts.
