If you need a basic overview of conveyor, the Hytrol ABC of conveyor is good. I found this link that has it.
http://www.hytrol.com/brandinfo/hcctraining/abc.html
The books from CEMA are very good, and give a lot of detailed information about each style of conveyor. The booklets are priced a...
You can also look at the Conveyor Equipment Manufacturers Association website. Look in the "MA" section for a list of companies and their websites.
http://www.cemanet.org/
Conveyor weight may vary depending on who manufacture's the unit, but they are probably all pretty close. If possible, when someone gets ready to buy a scale, if they could tell you who is making the conveyor, the model, length, and width, you can go to their website and look through a catalog...
Based on the small diameter rollers and close roller centers, there are only a few common ways to power the rollers.
The most common method is to use a flat belt, maybe about 12" wide, with a second set of "pressure" rollers under the belt, maybe on 3" centers, to drive the tread rollers. This...